Gas-Phase Synthesis of Nanoparticles E-Book
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- Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
The first overview of this topic begins with some historical aspects and a survey of the principles of the gas aggregation method. The second part covers modifications of this method resulting in different specialized techniques, while the third discusses the post-growth treatment that can be applied to the nanoparticles. The whole is rounded off by a review of future perspectives and the challenges facing the scientific and industrial communities.
An excellent resource for anyone working with the synthesis of nanoparticles, both in academia and industry.
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Veröffentlichungsjahr: 2017
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Table of Contents
Cover
Title Page
Copyright
List of Contributors
Preface
Part I: Introduction to Gas Phase Aggregation Sources
Chapter 1: History, Some Basics, and an Outlook
1.1 Introduction
1.2 Three Types of Gas Aggregation Sources
1.3 Development of the Magnetron Cluster Source
1.4 Deposition Machine and Mass Spectra
1.5 Some Experimental Questions
1.6 Deposition of Clusters with Variable Kinetic Energy
1.7 Outlook and Future Development
Acknowledgments
References
Chapter 2: Principles of Gas Phase Aggregation
2.1 The Landscape
2.2 Step 2: Nucleation
2.3 Kinetic Nucleation Theory
2.4 Clusters in Real Gases
2.5 : Adiabatic Expansion
2.6 : Supersonic Beam with Buffer Gas
2.7 Size Distribution
2.8 Conclusion
References
Chapter 3: Types of Cluster Sources
3.1 High-Vacuum Free Beam Sources
3.2 Generic Aspects of Design
3.3 Seeded Supersonic Nozzle Source (SSNS)
3.4 Thermal Gas Aggregation Source (TGAS)
3.5 Sputter Gas Aggregation Source (SGAS)
3.6 Laser Ablation Source (LAS)
3.7 Pulsed-Arc Cluster Ion Source (PACIS)
3.8 Pulsed Microplasma Cluster Source (PMCS)
3.9 Comparison and Specialization of Sources
References
Part II: Modifications of Gas Phase Aggregation Sources
Chapter 4: The Double-Laser Ablation Source Approach
4.1 Introduction
4.2 Source Description
4.3 Studies on Bimetallic Clusters
4.4 Conclusions
Acknowledgments
References
Chapter 5: In-Plane Multimagnetron Approach
5.1 Introduction
5.2 The Multitarget Single-Magnetron Approach
5.3 The Multimagnetron Approach
5.4 Summary
Acknowledgments
References
Chapter 6: Adjustable Multimagnetron Approach
6.1 Introduction
6.2 Design and New Parameters of Multimagnetron Gas Aggregation Sources
6.3 Possibilities in the Fabrication of Nanoparticles with Multimagnetron Approach
6.4 Summary, Perspectives, and Applications
Acknowledgments
References
Chapter 7: Hollow Cylindrical Magnetron
7.1 Introduction
7.2 Project Design and Implementation
7.3 Characterization
7.4 Cluster Production
7.5 Alternative Cylindrical Geometries for Magnetron Sputtering
7.6 Concluding Remarks
References
Chapter 8: High-Flux DC Magnetron Sputtering
8.1 Introduction
8.2 Gas Flow
8.3 Oxygen-Assisted Synthesis
8.4 Ion Beams
8.5 Conclusions
References
Chapter 9: High-Flux Metal Vapor Cell
9.1 Introduction
9.2 Vapor Cell Components
9.3 Vapor Pressure
9.4 Methods and Techniques
9.5 Devices Using Metal Vapor Cells
9.6 Summary
References
Chapter 10: Microwave Plasma Synthesis of Nanoparticles
10.1 Introduction
10.2 Basic Design of Microwave Plasma Systems and Resulting Products
10.3 Realization of Microwave Plasma Systems for Synthesis of Coated Nanoparticles
10.4 Conclusions
References
Chapter 11: Enhanced Synthesis of Aggregates by Reduced Temperature, Pulsed Magnetron Sputtering, and Pulsed Buffer Gas Delivery
11.1 Introduction to Nanoparticle Aggregation
11.2 Experiment
11.3 Kinetic Phenomena during Cluster Growth
11.4 Pulsed Sputtering of Metal Target
11.5 Pulsed Delivery of Buffer Gas
11.6 Cluster Mass Flux in a Gas Dynamic System
11.7 Conclusions
Acknowledgments
References
Chapter 12: High-Power Pulsed Plasmas
12.1 Background: High-Power Impulse Magnetron Sputtering
12.2 Synthesis of Nanoparticles Using High-Power Pulsed Plasmas
12.3 Summary and Outlook
References
Chapter 13: High-Pressure and Reactive Gas Magnetron Sputtering
13.1 Introduction
13.2 Types of Reactive Sputtering
13.3 Hysteresis Effect in DC Reactive Sputtering
13.4 Methods to Overcome Hysteresis
13.5 Arcing in Reactive Sputter Deposition
13.6 Methods to Overcome Arcing Problem
13.7 Modeling of Reactive Sputtering
13.8 Implementation of High-Pressure and Reactive Gas Sputtering in Gas Aggregation Sources (GASs)
13.9 Conclusion
Acknowledgment
References
Part III: In-Flight Post-Growth Manipulation of Nanoparticles
Chapter 14: Coating
14.1 Core/Shell Nanoparticles
14.2 Fabrication Methods
14.3 Structural Modification via In-flight Coating
14.4 Summary
Acknowledgments
References
Chapter 15: Nanostructuring, Orientation, and Annealing
15.1 Introduction and Scope
15.2 Control of Crystal Structures
15.3 Nanostructuring
15.4 Conclusions
Acknowledgments
References
Chapter 16: Deflection and Mass Filtering
16.1 Introduction
16.2 Magnetic Deflection
16.3 The Time-of-Flight Mass Filter
16.4 The Reflectron TOF Mass Filter
16.5 The Quadrupole Mass Filter
16.6 Aerodynamic Lenses
16.7 The Wien Filter
16.8 Magnetic Sector
16.9 Cluster Ion Traps
16.10 Matter-Wave Interferometry
16.11 Comparison of Mass Filters
16.12 Mass Filtering Requirements for Applications
16.13 Conclusions
References
Chapter 17: In-Flight and Postdeposition Manipulation of Mass-Filtered Nanoparticles under Soft-Landing Conditions
17.1 Introduction
17.2 In-Flight Manipulation of Cluster Beams
17.3 Soft Landing
17.4 Summary
Acknowledgments
References
Chapter 18: In-Flight Analysis
18.1 Introduction
18.2 Electron Diffraction and X-ray Scattering Analysis of Clusters and Nanoparticles
18.3 Photoelectron and X-ray Absorption Spectroscopy
18.4 Magnetic Deflection Experiments
18.5 X-ray Magnetic Circular Dichroism Experiments
18.6 Conclusions
References
Part IV: Perspectives
Chapter 19: Nano- and Micromanufacturing with Nanoparticles Produced in the Gas Phase: An Emerging Tool for Functional and Length-Scale Integration
19.1 Introduction
19.2
Site
-Selected Nanoparticle Deposition
19.3 Supersonic Cluster Beam Deposition
19.4 System Integration Approach by SCBD
19.5 Conclusions
References
Index
End User License Agreement
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Guide
Cover
Table of Contents
Preface
Begin Reading
List of Illustrations
Chapter 1: History, Some Basics, and an Outlook
Figure 1.1 Gas aggregation is a well-known natural process: air, containing some moisture, flows over a high mountain. As the gas moves to higher altitudes, the air pressure decreases. This leads to a decrease in gas temperature; see Eq. (1.1). If the temperature is low enough, water will condense, forming a cloud. Often, a vertical oscillation of the air stream is induced by the mountain, leading to a series of stationary clouds that are produced by a moving wind.
1
Figure 1.2 Principle of a supersonic source. Gas expands from a high pressure (say, helium at 10
6
Pa) through a small hole of diameter
D
into vacuum. The velocities of the He atoms are indicated by arrows. They are random in size and direction prior to the expansion. Afterward, they equalize rapidly. Temperature and pressure on the center of the beam line are given. Note the extreme cooling already close to the nozzle. A large variety of clusters have been produced using this type of “auto-gas-aggregation” source.
Figure 1.3 Two types of gas aggregation sources are used by the Freiburg group. Either atoms or molecules are evaporated (a) into a stream of gas; a glow discharge (indicated by the arrow) is used to produce charged clusters of both polarities. (b) The evaporator is exchanged for a magnetron sputter discharge, which does not need additional ionization.
Figure 1.4 The magnetron sputter head in more detail. A cylindrical magnetic field is used. Charge production and surface erosion are maximal in the region where the magnetic field is parallel to the surface, as indicated by the two inserts. Note that the argon gas is introduced in two different regions, (i) around the source and (ii) it is blown directly into the region where sputtering is maximal. The intensity and mass distribution of clusters can be optimized, by playing with these two gas flows. The sputter head has to be water-cooled.
Figure 1.5 Sketch of the experimental setup. A magnetron sputter head (
K
) is sitting in the aggregation tube (1). Clusters are formed (2) in the flowing afterglow of the discharge and traverse two small holes. The beam is electrically separated into its neutral (
n
) and charged (
c
) components. Charged clusters of one polarity can be accelerated up to 20 keV and impinge in the main chamber 8 on the substrate holder (3), which can be moved horizontally by a small motor. The cluster ion beam can be swept perpendicularly to the motion of the substrate holder. A TOF-MS (time-of-flight mass spectrometer, not shown) is used for the analysis of the cluster size distribution. A load-lock chamber (4) allows rapid sample exchange. Differential pumping (5) is necessary to reach the good vacuum of the X-ray photoelectron spectrometer (XPS) chamber (6) used for
in situ
elemental analysis by an electron energy analyzer (7). Note the large pumps necessary to cope with the gas flow necessary for a gas aggregation source.
Figure 1.6 Mass spectra of large copper clusters are plotted as a function of mass (a) or as a function of diameter (b). The relative widths at FWHM (full width at half maximum) are 0.5 and 0.2, respectively. The resolving power of the mass spectrometer is not sufficient to resolve single masses for these large cluster sizes.
Figure 1.7 Mass spectra of small cobalt clusters taken with similar source condition used for Figure 1.6. A lot of small clusters – even atomic ions of Ar and Co – are seen, although Figure 1.6 suggests that there are no small clusters present.
Figure 1.8 Molecular dynamics simulations of structures obtained by impact of clusters, containing 1043 molybdenum atoms each, with three different kinetic energies onto a Mo(001) substrate. At low kinetic energy, the clusters stay more or less intact after landing and form porous structures. At the highest energy, a very smooth and compact film is obtained. These results are in excellent agreement with the experimental ones.
Figure 1.9 Magnetron cluster source with three stages of aerodynamic focusing. A large increase in intensity is measured for large particle sizes. The loss of intensity after the exit hole can thus be partially compensated for.
Chapter 2: Principles of Gas Phase Aggregation
Figure 2.1 Schematic view of the nucleation process in three regimes discussed subsequently. in real gases with the formation of unstable -mer according to virial expansion, with nucleation and growth above the critical radius as observed in adiabatic expansion, in adiabatic expansion assisted by a buffer gas with a small critical radius (Step 2), rapid growth (Step 3), coalescence of clusters between (Step 4) them, and rearrangement of the inner structure (Step 5).
Figure 2.2 Phase transition in the van der Waals EOS and analogy with phase order transition in the Ginzburg–Landau formalism.
Figure 2.3 Left panel: competition between the increase of the surface energy when particles grow and the decrease of the volume free energy. Below the maximum , the particle growth is not thermodynamically favorable; most of the particles dissolve back to liquid phase. When particles reach the size of and pass the barrier of , further growth of particles will lead to decrease in , a tendency favorable for the continuous solidification (Step 3). Right panel: inverse stabilization time versus size (-mer) for nucleation at = 2000 K with Pa of atmosphere; the surface tension is 350 dyn cm and the viscosity = 100 poises (other parameters are given in Ref. [17]). The correspondence between the classical and the microscopical views of the critical nucleus is shown.
Figure 2.4 Cluster populations for water at a subcritical temperature of 373 K.
Figure 2.5 Expansion with condensation in the diagram: nucleation takes place when the isentrope line crosses the equilibrium phase coexistence curve. Dry isentrope corresponds to Eq. (2.32) without nucleation.
Figure 2.6 Mass size distribution of sodium clusters obtained in a supersonic beam without gas (a) (Knight
et al.
1984 [24]. Reproduced with permission of American Physical Society.) and with additional buffer gas (b) showing the more efficient growth with buffer gas.
Figure 2.7 (a) C clusters produced in laser vaporization source with helium buffer gas showing a perfect sticking coefficient. (Mélinon
et al.
1998 [28]. Reproduced with permission of American Physical Society.) (b) Bismuth and selenium clusters produced in a seeded beam (helium) showing the partial sticking. The blue line, which is the envelope of the “second” nucleation, is not taken into account in the simulation (Smoluchowski). (Tribollet
et al.
1992 [27]. Reproduced with permission of Springer.) The best fits are and for bismuth and selenium, respectively. The low value for selenium is due to the molecular character where nascent clusters , , and in the vapor form molecular complexes with a low number of channels (Eq. (2.16)).
Figure 2.8 Qualitative changes in the cluster morphology from small to large sizes in the case of indium, gold, and platinum. The clusters are mass-selected prior to deposition. Each cluster with ramified structures has the same number of atoms. The width of the branch gives qualitatively the diameter of the cluster prior to coagulation. The melting temperature governs the coagulation in the gas phase. (Alayan
et al.
2006 [29]. Reproduced with permission of American Physical Society.)
Chapter 3: Types of Cluster Sources
Figure 3.1 Basic layout of sources using rare gases to produce supersaturated vapors. (a) Seeded supersonic nozzle source, (b) thermal gas aggregation source, (c) sputter gas aggregation source, (d) pulsed-arc cluster ion source, (e) laser ablation source, and (f) pulsed microplasma cluster source.
Figure 3.2 Micrographs of nanoparticles synthesized with sputtering gas aggregation sources: (a) transmission electron microscope (TEM) image of unfiltered 5 nm cobalt nanoparticles. (De Toro
et al
. 2015 [46]. Reproduced with permission of American Physical Society.) (b) Scanning tunneling microscope (STM) image (300 × 300 nm) of size-selected Au
70
clusters deposited on graphite. (Xirouchaki and Palmer 2004 [47]. Reproduced with permission of Elsevier.) (c) Alumina nanoparticles synthesized using the same source as in (a), but replacing the DC source with an RF power supply (the larger particles are agglomerates of smaller nanoparticles).
Figure 3.3 Schematic of a sputtering gas aggregation source coupled to a quadrupole filter and a deposition chamber.
Figure 3.4 Schematics of the operating principle and cluster formation dynamics in a pulsed microplasma cluster source. (Molecular Beams and Nano-Crystalline Materials Laboratory, Physics Department and CIMaINa, Università degli Studi di Milano.)
Chapter 4: The Double-Laser Ablation Source Approach
Figure 4.1 Schematic overview of the dual-target dual-laser ablation source design used in Leuven.
Figure 4.2 Schematic overview of the dual-target dual-laser cluster source used at the Fritz Haber Institute of the Max Planck Society in Berlin, Germany.
Figure 4.3 Intensity of Au
n
+
(
n
= 1–20) clusters in the mass spectrum for different laser energy densities. The intensity axis is plotted on a logarithmic scale.
Figure 4.4 Mass spectra of Pd
m
Au
n
+
(
m
= 0−3,
n
= 1−20) clusters at different laser energy densities used to ablate the Pd target: (a)
E
Pd
=
0.4 mJ/mm
2
, (b)
E
Pd
=
1.2 mJ/mm
2
, and (c)
E
Pd
=
3.5 mJ/mm
2
.
Figure 4.5 Mass spectrum of Pd
m
Au
n
+
(
m =
0−1,
n =
1−20) clusters at different extraction timings: (a)
t
vi
=
1270 µs, (b)
t
vi
=
1290 µs, (c)
t
vi
=
1350 µs, and (d)
t
vi
=
1370 µs.
Figure 4.6 Au
n
+
cluster production for different carrier gas (He) backing pressures.
Figure 4.7 Schematic drawing of the Leuven cluster apparatus equipped with a collinear reflectron TOF.
Figure 4.8 Mass spectra of photofragmented (a) Au
n
+
, (b) Au
n
Y
+
, (c) Au
n
Er
+
, and (d) Au
n
Nb
+
(
n
= 1–30) clusters under the excitation of 193 nm laser light. In (b–d), peaks corresponding to Au
n
X
+
, X = Y, Er, Nb, respectively, are connected by solid lines in order to visualize the relative abundances.
Figure 4.9 (a) Reaction probabilities of CO adsorption for Au
n
(black), Au
n
−1
Ag (red), and Au
n
−2
Ag
2
(dark yellow). (De Haeck
et al
. 2011 [3]. Reproduced with permission of American Chemical Society.) (b) Ratio of forward and backward reaction rates for Au
n
(black), Au
n
V (red), and Au
n
V
2
(blue) clusters measured at 124 K.
Figure 4.10 Comparison of experimental absorption cross sections of Au
4
+
, PdAu
3
+
, and CuAu
3
+
clusters (a, c, and e, respectively) with electronic excitation spectra calculated for the minimum energy structures, shown as insets in the Figure (b, d, and f, respectively).
Figure 4.11 (a) Mass abundance spectrum of mixed AlPb
n
+
clusters, showing the enhanced stability of AlPb
10
+
and AlPb
12
+
. Inset: DFT calculated minimum energy structures of AlPb
10
+
and AlPb
12
+
. (Neukermans
et al
. 2004 [15]. Reproduced with permission of American Physical Society.) (b) Fragmentation of AlPb
n
+
(
n
=10–12) with 70 mJ/cm
2
laser light (355 nm). The dissociation channels are indicated by arrows. Labels m (monomer) and d (dimer) correspond to neutral Pb and Pb
2
loss, respectively.
Figure 4.12 (a) IR-MPD spectra (upper traces) of Si
n
Co
+
·Xe (
n
= 5–7) and IR spectra and geometries of the computed lowest energy isomers for the corresponding bare clusters (lower traces). (b) Typical mass spectrum of Si
n
Co·Xe
p
clusters produced with the cluster source at 115 K and using a carrier gas mixture of 2.5%
129
Xe in He.
Figure 4.13 Mass spectra of Au–Ag bimetallic clusters produced by ablation of (a), a 35%Au–65%Ag (50–50 weight percent) alloy target, and (b,c) independent Au and Ag targets with different respective laser energies. (d) RBS spectra of the deposited bimetallic clusters. The cluster composition is labeled according to a detailed analysis of the mass spectra. The average composition as deduced from RBS is given in the legend of panel d.
Chapter 5: In-Plane Multimagnetron Approach
Figure 5.1 Schematic representation of possible mixing patterns for bimetallic NPs: core–shell (a), subcluster segregated (b), mixed (c), and three-shell (d). The pictures show cross sections of the NPs.
Figure 5.2 (a) Schematic illustration of the sectioned target of Mo–Cu. (Krishnan
et al
. 2013 [74]. Reproduced with permission of Royal Society f Chemistry.) (b) Sm–Co composite target used for the production of mixed metal NPs.
Figure 5.3 (a) Photographic image and schematic illustration (b) of the Nanogen-Trio multimagnetron sputter gas aggregation source from Mantis Deposition Ltd used for the deposition of bi- and trimetallic NPs.
Figure 5.4 Representative mass distributions of Si, Ag, and mixed Ag–Si NPs obtained using a quadrupole mass filter after the gas aggregation region.
Figure 5.5 HAADF-STEM micrographs of representative Si–Ag NPs prepared with a Si/Ag sputtering power ratio of 2.25 (a) and 1.8 (b).
Figure 5.6 (a) TEM micrograph and (b) HAADF-STEM image of a representative NP revealing a distinct core–shell structure. (c) EELS line profiles acquired along the representative NP showing the content of Fe, Al, and O.
Figure 5.7 Proposed mechanism of the formation of mixed NPs. Step 1 shows the nucleation and growth in the plasma zone near the surface of the sputtered targets. Step 2 depicts cluster–cluster collisions. The Fe and Ag nanoclusters (NCs) juxtapose forming dumbbell-like NPs. Then the Si particles cover the surface of the FeAg particles resulting in a core–shell structure. The resulting core–shell NPs coalesce with each other in-flight and form mixed species (Step 3).
Figure 5.8 HAADF-STEM images (a,b) of representative Pt/V NPs revealing a distinct core–shell structure. EELS line profiles (c) acquired along the representative Pt/V NP showing the content of Pt (black) and V (blue).
Figure 5.9 (a) HAADF-STEM image and (b) TEM micrograph of representative PtRu NPs. (c) TOF-MEIS spectra confirming the presence of Pt in Ru-rich NPs. (d) Cyclic voltammograms showing the activity and stability of the PtRu NPs toward the O
2
reduction reaction.
Figure 5.10 (a) Schematic diagram of Pd and Pd–MgO catalytic NPs on glassy carbon electrodes. (b) Cyclic voltammograms of room temperature methanol oxidation on the Pd/GC and P–MgO/GC catalysts.
Chapter 6: Adjustable Multimagnetron Approach
Figure 6.1 Cs-corrected STEM image of (from left to right) homogeneous Au; heterogeneous Au–Ag alloy; Ag core–Au shell; Au core–Ag shell; and Au–Ag Janus nanoparticles. In all cases, the scale bar represents 5 nm.
Figure 6.2 Scheme of an adjustable multimagnetron gas aggregation source in different configurations.
Figure 6.3 Evolution of the average nanoparticle size as a function of the sputtering Ar flux on the active magnetron (a); the Ar flux on one of the inactive magnetrons (b); and the total Ar flux introduced in the aggregation zone (c).
Figure 6.4 (a) Ag 3d and (b) Au 4f core level XPS spectra of Au–Ag alloyed NPs. (c) Low-magnification TEM of an assembly of Ag
55
Au
45
alloyed NPs. (d) HRTEM image of a representative Ag
55
Au
45
alloyed NP. (e) Corresponding EDS profile performed at the Ag and Au L edges along the line depicted in (d).
Figure 6.5 Cs-corrected STEM images of (a) an Ag–Au nanoparticle. (b) Confirmation of the CS structure directly given by the EDS line scans performed along the line displayed in (a). (c) A nanoparticle with the inverse Au–Ag structure. (d) A Co–Au nanoparticle. (e) EDS line scans performed along the line displayed in (d). (f) A nanoparticle with the inverse Au–Co structure.
Figure 6.6 (a) Atomic resolution image of a Co icosahedron coated by fcc Au facets. (b) EELS spectrum of the core (note the absence of oxygen). (c) Scheme of a sliced icosahedral Co core (dark spheres) with a shell formed by 10 fcc Au projected domains (bright spheres). (d) Aberration-corrected STEM-HAADF image of the corresponding Co–Au nanoparticle. In (c) and (d), the 10 Au fcc domains are numbered.
Figure 6.7 Core–shell–shell Co–Ag–Au nanoparticles. (a) Representation of the complex Co–Ag–Au structure together with the expected EDS intensity profiles. (b) Cs-corrected STEM representative image of a Co–Ag–Au NP. (c) EDS line scan performed at the Co, Ag, and Au, along the line depicted in (b). (d) EELS compositional analysis for the Co L
3,2
edge. The dashed line represents the outer limit of the NP. (e) EELS map for the Ag M
4,5
edge. (f) STEM image together with the corresponding Co and Ag EELS concentration maps superimposed.
Chapter 7: Hollow Cylindrical Magnetron
Figure 7.1 Scheme illustrating the homemade hollow cylindrical magnetron sputtering. The target (cathode) is placed in the center, and the anode corresponds to the whole cylindrical structure around it. At the cylindrical walls, one finds the magnets and the cooling system. The gas inlet is placed at the bottom as illustrated. The soft iron at the magnet's extremities is used to ensure the magnetic lines' closure.
Figure 7.2 (a) Homemade hollow cylindrical magnetron with the sliding cover retracted to show the silver target. (b) Front view. (c) Front view with open plasma. Note the greenish color around the target, typically seen in silver plasma formation.
Figure 7.3 Finite element method magnetics (FEMM) simulation of the magnetic field lines for the hollow cylindrical magnetron. The field's profile was obtained for a Cu target and NdFeB magnets.
Figure 7.4 – curves obtained for the (a) hollow cylindrical magnetron sputter and for (b) a homemade planar 1 in. magnetron sputter.
Figure 7.5 Pictures of the same target made of two wires of identical diameter, one of silver and the other of gold before (a) and after (b) sputtering. After 8.5 h, target consumption was . As predicted by simulations, there is a gradient of erosion on the target surface caused by the concentration of magnetic field in that region.
Figure 7.6 Scheme illustrating the cluster source with the orthogonal time-of-flight mass spectrometer.
Figure 7.7 Mass spectra indicating the formation of silver (a) and cobalt (b) clusters.
Figure 7.8 Mass spectra obtained for two different targets of silver–gold alloys, one made of one silver and one gold wire (dashed line) and the other made of two silver wires and one gold wire (red). In the inset, a picture of the actual targets is shown.
Chapter 8: High-Flux DC Magnetron Sputtering
Figure 8.1 Haberland's original design of a gas aggregation cluster source. Maximum deposition rate was in the range of several hundred Å/min.
Figure 8.2 Radial thickness profile of a nanostructured film through atomic force microscopy (AFM) with (dotted) and without (solid) a graded exposure screen for the compensation of radial intensity variation. The graded exposure variation is achieved with either single or multiple leaflet radial thickness screens such as those shown in the inset.
Figure 8.3 Cluster source with no differential pumping, (a) carrier gas flux lines when exiting the aggregation chamber, (b) typical deposit at intermediate working pressures (0.6 mbar), and early stage of deposits at (c) low (0.3 mbar), (d) medium (0.6 mbar), and (e) large (1 mbar) working pressures.
Figure 8.4 Deposits of nanoparticles: (a) homogeneous edges correspond to the shadow of the sample holder where the substrate was placed. (Martínez
et al.
2012 [7]. Reproduced with permission of American Chemical Society.) (b) Highly focused (no shadowing).
Figure 8.5 Simulated carrier gas flow streamlines (a) and particle trajectories (b) in an aerodynamic lens assembly (20 nm nanoparticles, 2.26 mm orifice diameter, and 1.85 mm exit nozzle).
Figure 8.6 Scanning electron micrograph of a silicon-carbide “tower” deposited on a stationary substrate (1.3 mm deposit height).
Figure 8.7 Nanoparticle source with a pulsed gas delivery setup (3″ magnetron sources, 3 mm exit orifice). The diagram on the left-hand side shows the control procedure for pulsed gas delivery and time-resolved measurement of mass spectra (1, HV chamber; 2, QMF; 3, cluster source; 4, magnetron; 5, pressure sensor; 6, valve).
Figure 8.8 The dependence of cluster mass flux and total cluster current per second on gas pulse repetition frequency. Continual gas delivery is shown for comparison.
Figure 8.9 Cluster deposition rate as a function of the oxygen admixture (Cu target, 160 Pa Ar pressure, 124 sccm Ar flow, 100 W discharge power, and 160 mm aggregation length).
Figure 8.10 (a) Cluster size as a function of the magnetron power and (b) deposition rate as a function of magnetron power for various flows. A quartz crystal monitor (at a distance of 100 mm from the source aperture) was used to measure the deposition rate of the clusters (Cu, 1 Hz = 0.11 Å).
Figure 8.11 Deposition rate of nanoparticles generated by a gas aggregation cluster source in combination with continuous DC magnetron sputtering (solid fill) or pulsed DC magnetron sputtering (textured fill) systems. Measurements were performed for different powers (50 and 100 W), argon aggregation pressure 200 Pa, orifice 3 mm, 18 cm target–orifice distance, 108 sccm Ar flow, and optimal low amount of oxygen admixture.
Figure 8.12 Diagram of the (1a) initial collection cross section of neutrals , (1b) collection cross section of ions (active OML collection), (1c) growth zones and the growth mechanisms. In zone I, nucleation takes place and clusters grow to a size after which they become negatively charged. In zone II, clusters are negatively charged and the effective collection cross section is much larger. (2) Nanoparticle source setup [2, 17].
Figure 8.13 Conical RF-driven octopole ion guide; A, eight cone-shaped rods (3 to 0.5 mm) arranged in a conical geometry; B, Teflon plates; C, carriage bolts; and D, metal collars. Inset shows the three possible ion trajectories: R, reflected; A, absorbed; and T, transmitted. A reduction of beam diameter from 9 to 2 mm is achieved.
Chapter 9: High-Flux Metal Vapor Cell
Figure 9.1 Different types of metal vapor cells sold commercially by Megatech [14]. (a) Boats (can be ordered with alumina coating), (b) tungsten/alumina crucibles, and (c) tungsten baskets.
Figure 9.2 Diagram identifying transitions of forms of matter from one type into another.
Figure 9.3 Boltzmann distribution for an Fe atom at different temperatures.
Figure 9.4 Vapor pressure of iron (blue), cobalt (red), and manganese (green).
Figure 9.5 Phase diagram of water. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. Attributed to Matthieumarechal [15].
Figure 9.6 Molecular beam epitaxy chamber showing effusion cells typically manufactured of boron nitride. Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license. Attributed to EI.vegaro [18].
Figure 9.7 MBE-Komponenten [20] effusion cells for use in molecular beam epitaxy chambers. (a) Standard effusion cell (WEZ model), (b) HTEZ model including various crucible inserts, and (c) schematic of main components within the HTEZ cell.
Figure 9.8 Schematic layout of an EBE metal vapor cell.
Figure 9.9 Leicester University Mesoscopic Particle Source used for manufacturing magnetic nanoparticles.
Figure 9.10 Evaporation device for nanoparticle growth in microgravity.
Figure 9.11 Wet-wire evaporation device used for nanoparticle growth in a sounding rocket experiment.
Chapter 10: Microwave Plasma Synthesis of Nanoparticles
Figure 10.1 Energy transferred in a microwave plasma to a charged particle as a function of the collision frequency in the plasma for three different microwave frequencies.
Figure 10.2 In this graph, the three ranges with different electrical charges of the particles are indicated. In Range I, the particles carry positive electrical charges; in Range III, the charges of the particles are negative; in Range II, different types of electrically charged particles coexist.
Figure 10.3 Temperature of the plasma gas measured at the exit of the reaction zone as a function of the gas pressure. These data were obtained using a system powered with 2.45 GHz microwaves. The course of the temperature resembles the course of the energy transfer as a function of the collision frequency, which is proportional to the gas pressure.
Figure 10.4 Number of charges of one particle according to Matsui. For these calculations, conditions where the particles carry negative charges (Range III) were assumed. As unit for the electrical charges, the charge of one electron was selected. The average energy of the electrons was set to 3 eV.
Figure 10.5 Probability of collision of two particles as a function of the size of the collision partners. Plate (a) displays the relation for uncharged particles and plate (b) for charged particles. In the latter plate, the different behavior of the system for small particles, where the electrical charge is particle size independent, and the range, where the electrical charges increase linearly with the particle diameter, are well visible [13].
Figure 10.6 Particle size distribution function calculated by Schweigert and Schweigert [12] for three different times. The starting size of the particles was 2 nm, and particle density .
Figure 10.7 Temporal evolution of the particle size distribution for different conditions. For these Monte Carlo calculations, atoms were used. In these graphs, the
z
axis, representing the number of particles, has a logarithmic scale. As on such a scale the value 0 is impossible, 0.1 was selected, instead. Plate (a) displays the result of the synthesis for electrically neutral particles. In total, collisions were considered. Using the same parameters, plate (b) shows the evolution of the particle size distribution for electrically charged particles. Plate (c) is an extension of plate (b) calculated for collisions.
Figure 10.8 Particle size distribution for a product with an average size of 10. This graph shows two important features: using charged particles, the particle size distribution is significantly narrower as compared to the product synthesized with neutral particles. Furthermore, in the case of charged particles, there is no residue of the precursor left. For the calculation of this graph, collisions for charged particles and collisions for neutral particles were necessary.
Figure 10.9 Silicon nanoparticles obtained by microwave synthesis. During synthesis, the experimental conditions were selected in such a way as to obtain only particles carrying electrical charges of equal sign. Plate (a) displays an electron micrograph of the product. Plate (b) displays the experimentally determined particle size distribution. It is remarkable, as expected, except for a few larger particles, that this size distribution can be approximated using the symmetric normal distribution.
Figure 10.10 Average particle size of the product as a function of the number of collisions. It is obvious that the experimental conditions are, in case of particles carrying electrical charges of only one sign, not that critical as compared to the application of neutral particles.
Figure 10.11 Comparison of two products, synthesized under nearly identical conditions in a microwave plasma. The only difference was the addition of water in one case, which led to neutral particles.
Figure 10.12 Setup of a device for plasma synthesis powered with microwaves. Microwaves are generated in a magnetron, which is protected against back-streaming power by a circulator combined with a water load. The reflection of the microwave power, not consumed in the plasma, is measured by a power meter connected to a directional coupler. The flow of energy to the plasma located in the applicator is optimized using a tri-stub tuner. Depending on the design of the applicator, a sliding short may be necessary to obtain maximal microwave power at the location of the plasma.
Figure 10.13 Arrangement for synthesis of particles using microwaves. In this device, the reaction tube passes a resonant microwave cavity. To avoid leaking of the microwaves, cut-off tubes are necessary. This design is applicable for cavities using and the rotating mode. Directly in the plasma, for safety reasons, temperature measurement using thermocouples is not possible [3, 11, 16].
Figure 10.14 Example of a product synthesized using equipment as shown in Figure 10.13. This product, ZrO
2
, was synthesized using the water-free chloride ZrCl
4
as precursor.
Figure 10.15 WS
2
particles produced in a system according to Figure 10.13. As reaction gas, diluted with argon was used. The lattice fringes represent the position of lattice planes incorporating the heavy tungsten atoms. The kinks in the lattice fringes indicate lattice defects.
Figure 10.16 Basic design of a mode cavity for plasma synthesis. As in the design depicted in Figure 10.13, cut-off tubes are necessary to avoid leaking of the microwaves. The “nose” is necessary to obtain a high E-field for plasma ignition [17].
Figure 10.17 Gallium nitride, GaN [17], synthesized in a system according to Figure 10.16. As precursor for gallium, trimethyl gallium, , was selected. As reaction and carrier gas, a mixture of ammonia, , and nitrogen was selected. (Reproduced with permission of Japan Society of Applied Physics.)
Figure 10.18 Schematic drawing of the design of a plasma torch working under ambient pressure. The geometry of the whole system is selected in such a way that microwave leaking is avoided.
Figure 10.19 Metallic cobalt particles synthesized in a plasma torch. As precursor, was used. As carrier and reaction gas, hydrogen was applied.
Figure 10.20 Metallic iron particles synthesized in a microwave plasma torch using as precursor.
Figure 10.21 Size distribution of iron particles stemming from the same series of experiments as the particles shown in Figure 10.20 [36]. It is remarkable that there are only a few large particles. This indicated the possibility of particles carrying electrical charges of only one sign.
Figure 10.22 System working with pulsed plasma. The average size of the product depends on the duration of the pulses [8, 37].
Figure 10.23 Hard magnetic FePt particles produced in a system according to Figure 10.22. It is remarkable that all particles are of nearly the same size.
Figure 10.24 Dependency of the particle size of the plasma pulse duration for magnetic FePt particles using a system according to Figure 10.22 [8].
Figure 10.25 System for the production of ceramically coated ceramic nanoparticles [38, 39]. This system consists of two cascaded plasma sources for synthesis. At the entry of the plasma sources, the precursor for the particle or the coating is added.
Figure 10.26 Zirconia, , particle coated with alumina, . The lattice fringes indicate that the zirconia core is crystallized, whereas the coating is amorphous [26]. (Reproduced with permission of Imperial College.)
Figure 10.27 Setup for a microwave torch system for the synthesis of coated particles [24]. It is an essential feature of this system that both processes, synthesis of the particles and coating, occur in one plasma reaction zone consecutively.
Figure 10.28 Silicon-carbide-coated cobalt particles synthesized in a system according to Figure 10.27 [24]. It is typical for this material that the cobalt cores are bound together with the silicon carbide coating. As determined by X-ray diffraction, both kernel and coating are crystallized. (Chau 2006 [24]. Reproduced with permission of Elsevier.)
Figure 10.29 System to synthesize ceramic nanoparticles with an organic layer, for example, a polymer or lumophor. This setup consists of a reaction zone with a microwave plasma (Figure 10.13) and. following this, a second reaction zone heated with a tubular furnace for coating with an organic compound [40].
Figure 10.30 Polymer (PMMA)-coated maghemite, , particles [40]. Plate (a) displays a few particles where the coating is very well visible. The whole ensemble is depicted in plate (b). At the temperature of synthesis, the polymer coating is quite sticky; therefore, the particles are clotted. (Vollath 1999 [40]. Reproduced with permission of Elsevier.)
Chapter 11: Enhanced Synthesis of Aggregates by Reduced Temperature, Pulsed Magnetron Sputtering, and Pulsed Buffer Gas Delivery
Figure 11.1 Schematics of the nanocluster source. 1, 2, 3 – Pressure gauges. Magnetron section: 4 – magnetron, 5 – aggregation region, 6 – variable orifice, 7 – inlets for cooling of the aggregation chamber walls, 8 – interfaces for magnetron power and cooling water, 9 – orifice. Quadrupole mass filter (QMF): 10 – quadrupole rods, 11 – detection plate. Deposition chamber: 12 – substrate holder.
Figure 11.2 Cluster size (number of atoms) distribution as measured with the quadrupole mass filter for different magnetron discharge powers (argon gas flow 12.5 sccm, gas pressure 12 Pa, wall temperature 173 K).
Figure 11.3 (a) AFM picture of deposited clusters. Deposition time 15 s, wall temperature 148 K. (b) Height histograms with log-normal fits for the indicated wall temperatures of the magnetron chamber.
Figure 11.4 The surface coverage of deposited clusters () and the extracted mean heights () versus wall temperature inside the cluster source. Deposition time 15 s.
Figure 11.5 Measured velocity distribution of negative cluster ions composed of copper atoms. The thick solid line corresponds to a fit of these points employing a Gaussian distribution. Thin lines indicate the fit error. Experimental conditions: Ar flow rate 15 sccm, pressure 19 Pa, discharge power 120 W.
Figure 11.6 Most probable cluster velocity versus gas flow. Experimental results () for negatively charged copper clusters of size [36] are compared with the predictions from Eq. (11.12) [36]. Dashed line shows the dependence ; see text.
Figure 11.7 Most probable cluster velocity versus cluster mass for positively () and negatively () charged cluster ions. The dashed curve represents Eq. (11.12) with the same fit coefficients as in Figure 11.6 [36], see text.
Figure 11.8 Ratio of positively and negatively charged cluster ions () versus cluster mass . Lines show the theoretical dependence (11.13) with and (dashed line) and and (solid line).
Figure 11.9 Cluster mass of Cu nanoparticles as a function of discharge current. Dependencies for DC discharge or DC-pulsed modulated discharge are marked by dashed and solid lines, respectively.
Figure 11.10 Cluster mass as a function of discharge repetition frequency for the indicated buffer gas pressures. The mean discharge current was kept constant for all experiments.
Figure 11.11 Cluster mass as a function of duty cycle for different repetition discharge frequencies.
Figure 11.12 Cluster mass and FWHM of mass spectra as a function of duty cycle. Circles (red color) denote mass and FWHM of appropriate spectra.
Figure 11.13 Time-resolved measurement of pressure for different gas-pulse frequencies . The pulse active width was varied to keep the same mean pressure for all experiments.
Figure 11.14 AFM tapping mode images of deposited Cu clusters: (a) deposited in pulsed regime for , (b) deposited with continuous gas delivery for . The cluster diameter distributions are compared in the graph (c). The mean pressure in the aggregation tube and the discharge current were kept constant.
Figure 11.15 Cluster mass and pressure evolution during the gas pulse. The color bar represents the cluster current , which corresponds with the cluster production. Highlighted stages I–IV are discussed in the text. Mean pressure 80 Pa, discharge current 500 mA.
Figure 11.16 Time evolution of cluster mass distributions with normalized signal intensity for different gas-pulse frequencies . The false color bar represents the cluster current proportional to the number of clusters formed: blue color indicates while red denotes .
Figure 11.17 Cluster mass spectra time-averaged, from larger amount of measurements presented in Figure 11.16, for different gas-pulse frequencies . The data measured are approximated by log-normal distribution function.
Figure 11.18 The dependence of cluster mass flux on gas-pulse repetition frequency. The limit for the cluster mass flux typically observed during continual gas delivery () at the same experimental condition is also shown.
Chapter 12: High-Power Pulsed Plasmas
Figure 12.1 (a) Sketch of a magnetron setup. Material is sputtered from the cathode (i.e., target) and deposited on a substrate. The operation mode of a magnetron can easily be changed by changing the power supply. (b) Example of a pulse applied to the cathode using HiPIMS. The black curve shows the applied voltage pulse and the red curve the discharge current.
Figure 12.2 Overview on pulsed plasmas. An upper limit for the applied power was chosen at to avoid overheating and melting of the target. Pulsed discharges are divided into DC magnetron sputtering (DCMS) and high-power magnetron sputtering (HPPS), which is further divided into modulated pulse power (MPP) and high power impulse magnetron sputtering (HiPIMS).
Figure 12.3 Estimation of (a) the floating potential and (b) the charge of a nanoparticle using Eq. (12.1). The red dashed lines are calculated using Eq. (12.5), and the black solid lines are calculated by solving the implicit equation for the floating potential using Eqs. (12.4a) and (12.4b).
Figure 12.4 Sketch of nanoparticle growth. Nucleation takes place by collisions of source atoms and ions until stable nuclei are formed. Coagulation occurs when the density of clusters is high enough and surface growth dominates when nanoparticles become negatively charged and repel each other.
Figure 12.5 (a) Sketch of a setup for synthesizing nanoparticles with a pulsed hollow cathode. (Pilch
et al.
2013 [38]. Reproduced with permission of American Institute of Physics.) (b) Photograph of a discharge generated by a pulsed hollow cathode (frequency , pulse width , peak current , and pulse voltage ).
Figure 12.6 Illustration of the pulse dynamics. (a) Situation before a subsequent pulse is applied. Sputtered material from the cathode moves downward together with the gas flow and expands due to diffusion. When the next pulse is applied (b), a plasma between the anode ring and the hollow cathode as well as inside the hollow cathode is generated, which leads to sputtering. At the end of the pulse (c), the plasma decays, but the material is ejected from the hollow cathode with a time delay (d).
Figure 12.7 Total ion current of Ag clusters measured with time-resolved mass spectroscopy at different frequencies: (a) 7, (b) 10, and (c) . At higher frequencies, the total current does not vanish between pulses, indicating an overlap.
Figure 12.8 (a) SEM images (top) and size distributions (bottom) for nanoparticles synthesized with the anode ring position at (left) and (right). (b) Growth rate calculated as a function of the electron temperature according to Eq. (12.9) for ions.
Chapter 13: High-Pressure and Reactive Gas Magnetron Sputtering
Figure 13.1 Typical hysteresis curve in DC reactive magnetron sputtering – hysteresis curve for the sputtering of TiO
x
using mass flow control of the reactive gas.
Figure 13.2 The cycle that leads to instability in reactive sputtering.
Figure 13.3 Typical hysteresis curve using partial pressure control of reactive gas.
Figure 13.4 Schematic of plasma emission monitoring system.
Figure 13.5 Schematic of a baffled system.
Figure 13.6 Schematic drawing of the dual magnetron sputtering arrangement.
Figure 13.7 (a) Berg's model depicting the mathematical equivalent of a simple sputtering system. (b) Flux distribution during reactive gas sputtering.
Figure 13.8 An example – target erosion rate and deposition rate versus partial pressure as calculated from the Berg's model. (For the reactive deposition of AlN.)
Figure 13.9 Calculated partial pressure,
P
, versus supply rate of the reactive gas,
Q
tot
.
Figure 13.10 Schematic of a gas aggregation source.
Figure 13.11 TEM images of (a) chromium oxide nanoclusters deposited on an amorphous carbon film of TEM grid. (Chen
et al.
2008 [64]. Reproduced with permission of American Institute of Physics.) (b) Lead sulfide (PbS) nanocomposites deposited onto a titanyl phthalocyanine (TiOPc) film at a H
2
S/Ar ratio of 1 : 1. Inset: higher magnification image of an individual NC ∼2.5 nm in size, showing PbS lattice fringes. (Zachary
et al.
2009 [76]. Reproduced with permission of American Chemical Society.) (c) Titanium oxide (TiO
x
) nanoparticles deposited onto carbon-coated copper grids.
Figure 13.12 AFM images of deposited nanoclusters: (a) tungsten oxide clusters deposited on silicon wafer. Gas flows during the deposition were 100 sccm of argon and 0.45 sccm of oxygen (O
2
/Ar: 0.0045) and (b) 1600 × 1600 nm
2
AFM image of a heavily deposited chromium oxide film sampled on a flat silica glass sheet.
Figure 13.13 High-resolution XPS spectra of Ti 2p peak. (a) Pure Ar or (b) Ar/O
2
mixture with 1.4% of O
2
. SEM images and corresponding size histograms of NPs deposited using (c) pure Ar and (d) Ar/O
2
mixture with 1.4% of O
2
. Magnetron current was 300 mA, and pressure in the aggregation chamber was 28 Pa. Ar flow was 1.5 sccm.
Figure 13.14 Dependence of cluster deposition rate on the reactive gas flow in reactive sputtering of cobalt target with nitrogen reactive gas (carrier gas argon flux 100 sccm, 178 Pa). 0.2 sccm of nitrogen corresponds to a partial pressure of 0.54 Pa.
Chapter 14: Coating
Figure 14.1 Schematic representation of simultaneous versus sequential growth of core–shell NPs by gas aggregation sources. Common characteristics of various methods are categorized and summarized from [15, 16, 26, 28, 30, 36, 42, 44, 45, 49].
Figure 14.2 (a) Commercial magnetron-sputter shell-coating device from Mantis Deposition Ltd, UK. (b) Decomposition of the apparatus into its main components.
Figure 14.3 Schematic representation of shell-coating device and method: the core nanoclusters are coated with shell material atoms, sputtered from linear magnetron sputter sources, forming hybrid NPs.
Figure 14.4 (a) Schematic configuration of the integrated nanocluster deposition system for fabrication of core/shell NPs. (b) Bright-field transmission electron microscopy (TEM) image of (i) (iron–cobalt)
core
–gold
shell
nanostructures and (ii) iron–cobalt NPs. (c) High-resolution TEM image of (iron–cobalt)
core
–silver
shell
NP consisting of a 14 nm iron–cobalt core and a 0.8 nm silver shell.
Figure 14.5 Schematic comparison between pure silicon sputtering (a), simultaneous silicon and silver co-sputtering (b), and postgrowth, in-flight inoculation of silicon clusters with silver atoms (c). Fabrication methods and resultant NP structures can be seen in the top and middle row, respectively. In the bottom row, bright-field high-resolution transmission electron microscopy (HRTEM) micrographs are presented, showing the equivalent experimentally observed microstructures. In (c), a silver-coated silicon NP, decorated with several silver nanoclusters (appearing as dark spots and marked by blue numerals 1–4), can be seen. Three crystal grains are indicated by red arrows. A fourth crystal grain is confirmed by tilting the sample by −15° relative to the incident electron beam. Qualitative correlation between the number of silver satellites and the number of grains in the silicon core is evident. No silver nanoclusters were observed in control depositions without a silicon cluster flow, as schematically indicated in (d).
Figure 14.6 (a) Evolution of temperature and fraction of disordered atoms of a silicon NP containing 1000 atoms, in the center of a molecular dynamics (MD) cell surrounded by a randomly dispersed silver gas containing 243 atoms. Snapshots depict characteristic instants of MD simulation run. The process is decomposed in stages, denoted by Latin numerals. (b) Evolution of the local bonding environment of silver atoms.
Chapter 15: Nanostructuring, Orientation, and Annealing
Figure 15.1 A schematic of the cluster deposition process used for fabricating Co-rich intermetallic compound nanoparticles.
Figure 15.2 (a) XRD patterns of Y–Co nanoparticles deposited using different DC magnetron sputtering powers
P
dc
. The standard peak positions and relative intensities for the YCo
5
phase having hexagonal CaCu
5
and Y
2
Co
17
phase having rhombohedral Th
2
Zn
17
structures are shown as vertical lines below the XRD patterns of YCo
5
and Y
2
Co
11
nanoparticles, respectively. (b) Sputtering-power-dependent crystal structures and room-temperature coercivities (
H
c
) of Y–Co nanoparticles.
Figure 15.3 (a) TEM image of the cluster-deposited YCo
5
nanoparticles. The corresponding particle-size histogram (top) and a high-resolution HRTEM image of nanoparticle (bottom) are shown as insets.
d
and are the average particle size and rms standard deviation, respectively. (b) HRTEM images showing single-crystalline nature of HfCo
7
, Zr
2
Co
11
, Co
2
Si, and MnSi nanoparticles.
Figure 15.4 (a) A schematic of the cluster deposition process used for producing FePt nanoparticles. A sintering oven is employed between the cluster formation and deposition chambers to anneal the FePt nanoparticles in the gas phase, prior to deposition. (b) TEM image of FePt nanoparticles annealed at 1.0 mbar and 1000 °C. (c,d) HRTEM images of L1
0
-ordered FePt nanoparticles annealed at 1.0 mbar and 1000 °C as seen along [100] and [110] zone axes, respectively. (e,f) Diffractograms as obtained from the Fourier transformation of the marked areas in the images (c) and (d), respectively.
Figure 15.5 (a) XRD patterns for Ti, TiO, and TiO
2
nanoparticles prepared at oxygen flow rates of 0, 6.7, and 50 sccm, respectively. The X-ray diffraction peaks corresponding to the anatase and rutile structures are labeled as A and R, respectively. (b) XRD patterns showing the dependence of oxygen flow rates on the anatase and rutile phases in TiO
2
nanoparticles.
Figure 15.6 (a) A schematic of the easy-axis alignment by applying a magnetic field (
H
al
≈ 5 kOe) along the
x
-axis using a set of permanent magnets (N–S). (b) Geometric configuration, where
H
x
is the magnetic field applied along the
x
direction (direction of
H
al
) during the measurement and is the angle between the easy axis and
H
x
. (c) The normalized texture function
p
() for aligned Zr
2
Co
11
nanoparticles.
Figure 15.7 (a) A schematic of the cluster deposition process used for the formation of TiO
2
–organic material core–shell structures. (b) The deposition rate of TiO
2
nanoparticles (
R
c
) as a function of the evaporation temperature of paraffin. The chemical structure of the paraffin is also schematically given in the inset, where the black and gray spheres represent carbon and hydrogen atoms, respectively. (c) XRD patterns of TiO
2
–paraffin core–shell nanoparticles prepared at different
T
e
is given from = 20.5–24.5°. The higher angle region having the intense diffraction patterns of TiO
2
nanoparticles is not shown in the figure.
Figure 15.8 (a) A schematic of the fabrication method showing the fabrication of exchange-coupled nanocomposites. (b) HAADF image and the corresponding energy dispersive x-ray spectroscopy (EDS) color maps for aligned Hf–Co:Fe–Co nanocomposite thin films having Fe–Co contents of 22 vol%. The color distributions for Hf (blue), Co (red), Fe (green), combined Hf and Co, and combined Hf, Co, and Fe are shown.
Chapter 16: Deflection and Mass Filtering
Figure 16.1 Schematic of second-stage separator unit. ORNL Drawing 42951. Note that the magnets have a size of the order of 4 m.
Figure 16.2 Stern–Gerlach experiment: silver atoms from a source (1) travel (2) through an inhomogeneous magnetic field (3) and are deflected up or down depending on their spin (4, 5). By Tatoute – Own work, CC BY-SA 4.0,
Figure 16.3 Basic geometry of the TOF mass spectrometer.
Figure 16.4 Example of a typical TOF mass spectrum (antimony clusters), produced by condensation in He atmosphere. Clusters have been detected up to 820 µs
Figure 16.5 Schematic of the mass selector. Short high voltage pulses applied to plates 1 and 4 are used to displace a preaccelerated convergent ion beam laterally.
l
, length of the ion beam package displacement;
x
, total displacement;
a
, beam offset traversed during the high voltage pulse;
b
, length of the field-free region;
d
1/
d
2, plate separations;
s
, length of the portion of the ion beam that cannot be used due to field distortion; and
L
, total length.
Figure 16.6 Schematic diagram of a quadrupole mass filter, the most common mass spectrometer used in ICP-MS. Voltages applied to the rods cause the ions entering the quadrupole to oscillate. Extreme oscillations cause the ions to be ejected from the stable transmission region, striking the rods or the inside of the quadrupole housing. Only ions of a single
m
/
z
have a stable path and exit the quadrupole.
Figure 16.7 The
x
axis gives the direction of the incoming cluster beam. The
z
axis is parallel to the quadrupole electrodes. The
y
axis is parallel to the outcoming bent cluster beam. The
x–z
and
y–z
planes are both symmetry planes of the quadrupole deviator.
Figure 16.8 Basic principle of aerodynamic size selection and focusing. The inertia of large particles (St ≫ 1) exceeds the drag action of the gas, separating the particle trajectories from the gas stream lines and leading to wall deposition. Very small particles (St ≪ 1) closely follow the original beam direction. Intermediate-size particles have trajectories only slightly deviating from the stream lines, which can be exploited to concentrate them at the given positions in the flow field.
Figure 16.9 Wien filter.
Figure 16.10 Magnetic sector mass filter.
Figure 16.11 Diagram of the experimental setup (not to scale). Hot, neutral C60 molecules leave the oven through a nozzle, pass through two collimating slits separated by 1.04 m, traverse a SiN
x
grating (period 100 nm) 0.1 m after the second slit, and are detected via thermal ionization by a laser 1.25 m behind the grating. The ions are then accelerated and directed toward a conversion electrode. The ejected electrons are subsequently counted by a Channeltron electron multiplier. The laser focus can be reproducibly scanned transversely to the beam with 1 mm resolution.
Chapter 17: In-Flight and Postdeposition Manipulation of Mass-Filtered Nanoparticles under Soft-Landing Conditions
Figure 17.1 Schematic view of the arc cluster ion source ACIS. Left part: hollow cathode made of the target material; right part: electrostatic quadrupole deflector acting as mass-filtering unit.
Figure 17.2 Size-dependent Fe nanoparticle diffraction patterns. Larger particles (a,b) give rise to a Debye–Scherrer powder pattern (arrows denoting intense 200 and 1 reflexes). Smaller particles show weak (c) or no (d) diffraction rings and altered spot patterns, indicating the onset of spontaneous alignment relative to the substrate.
Figure 17.3 FeCo (a) and Fe nanoparticles (b) deposited onto W(110) at room temperature and afterward annealed to 1023 K (FeCo: 1 h) and 640 K (Fe: 10 min). STM images: (a) .
Chapter 18: In-Flight Analysis
Figure 18.1 (a) Sketch of the experimental apparatus used for in-flight electron diffraction measurements of free Ag NPs. (Hall
et al.
1991 [25]. Reproduced with permission of American Physical Society.) (b) Series of diffracted intensity curves for Ag NPs obtained at different temperatures of the crucible. Reported on the peaks are the Miller indexes of the relative diffraction planes. (Reinhard
et al.
1997 [26]. Reproduced with permission of American Physical Society.)
Figure 18.2 (a) Experimental apparatus for electron diffraction experiments on trapped ion clusters. (Schooss
et al.
2005 [30]. Reproduced with permission of American Chemical Society.) (b) Experimental and simulated molecular scattering functions
sM
(
s
) for different ion metal clusters, together with sketches depicting the relative best-fit atomic arrangements. (Rapps
et al.
2013 [31]. Reproduced with permission of Wiley.)
Figure 18.3 Experimental and simulated wide-angle X-ray scattering patterns from selected NPs. (Barke
et al.
2015 [38]. Reproduced with permission of Nature Publishing Group.)
Figure 18.4 (a) Field lines and helical trajectories of electrons in a magnetic bottle analyzer. (Kruit and Read 1983 [55]. Reproduced with permission of Institute of Physics.) (b) Sketch of a PES experiment on ion cluster beam. (Senz
et al.
2009 [57]. Reproduced with permission of American Physical Society.) In this case, the photons used for PES were produced by the free-electron laser FLASH.
Figure 18.5 Photoelectron spectra of Na
N
+
(
N
= 31–60) taken at
h
ν = 6.42 eV. The peak labels give the quantum numbers of the corresponding electron shells. The arrows for
N
= 36, 42, and 60 indicate the peak corresponding to the new electronic shell, which starts to be filled. (Wrigge
et al.
2002 [50]. Reproduced with permission of American Physical Society.)
Figure 18.6 (a) Representation in color scale of the partial ion yield XAS spectra from Ti L
2,3
edges taken for different ion mass values. Each row is an XAS spectrum taken at a given ion mass, each column is a TOF mass spectrum recorded at a given photon energy. (b) Partial ion yield spectra for different cluster mass ranges. (Piseri
et al.
2006 [63]. Reproduced with permission of Institute of Physics.)
Figure 18.7 (a) Sketch of the experimental apparatus used to detect magnetic moments of Co and Gd clusters [68]. (b) Laser vaporization cluster source. (Douglass
et al.
1993 [68]. Reproduced with permission of American Physical Society.)
Figure 18.8 (a) Position-sensitive TOFS mass peak of Co
20
showing the field-off (dashes) and the field-on (
B
= 2 T, solid) deflections. Note the single-sided deflections. (Xu
et al.
2008 [76]. Reproduced with permission of American Physical Society.) (b) Magnetic moments per atom, μ
exp
, for Co clusters consisting of 13–200 atoms. E1 and E2 are two different experiments described in [75]. The dashed line is the average value of μ reported in [68]. (Payne
et al.
2007 [75]. Reproduced with permission of American Physical Society.)
Figure 18.9 Sketch of the experimental arrangement used for XMCD experiments on metal clusters. (Peredkov
et al.
2011 [8]. Reproduced with permission of Elsevier.)
Figure 18.10 (a) L
2,3
XAS spectra taken from Co
22
+
clusters with right-handed (σ
+
, open circles) and left-handed (σ
−
, open triangles) circularly polarized light, showing dichroism effect. (Peredkov
et al.
2011 [8]. Reproduced with permission of Elsevier.) (b) Magnetic moments as revealed from XMCD using sum-rule analysis, for Co clusters of different size values. (Peredkov
et al.
2011 [95]. Reproduced with permission of American Physical Society.)
Chapter 19: Nano- and Micromanufacturing with Nanoparticles Produced in the Gas Phase: An Emerging Tool for Functional and Length-Scale Integration
Figure 19.1 (a) Indium nanoparticles assembled by nanoxerography onto positively charged 100 nm wide lines. (Barry
et al
. 2003 [36]. Reproduced with permission of American Institute of Physics.) (b) 80-nm-wide line pattern of silver nanoparticles obtained via an ion-induced focusing mask. (You
et al
. 2010 [37]. Reproduced with permission of Wiley.)
Figure 19.2 Sketch of (a) the supersonic cluster beam deposition (SCBD) apparatus, (b) the pulsed microplasma cluster source (PMCS) coupled to the aerodynamic focusing system, and (c) the working principle of the PMCS.
Figure 19.3 (a) Schematic representation of SCBD through non-contact stencil masks, (b,c) nanoparticle-assembled patterns of (b) carbon (Barborini
et al
. 2000 [47]. Reproduced with permission of American Institute of Physics), and (c) tungsten (Barborini
et al
. 2008 [24]. Reproduced with permission of Institute of Physics) clusters deposited by SCBD using stencil masks.
Figure 19.4 (a) Metal-oxide sensor obtained by SCBD of nanoparticle-assembled films onto the μHP wafers. (Barborini
et al
. 2008 [24]. Reproduced with permission of Institute of Physics.) (b, c) Sensor array (14 × 15) fabricated by SCBD of metal oxide nanoparticles on interdigitated gold electrodes.
Figure 19.5 Microfluidic device for FISH fabricated by SCBD. (Zanardi
et al.
, 2010 [22]. Reproduced with permission of BioTechniques.)
Figure 19.6 Schematic pictures of the microsupercapacitor fabricated by SCBD on Mylar substrate. (Bettini
et al
. 2015 [70]. Reproduced with permission of Elsevier.)
List of Tables
Chapter 3: Types of Cluster Sources
Table 3.1 Comparison of different types of cluster sources
Chapter 6: Adjustable Multimagnetron Approach
Table 6.1 Working parameters of a standard and an adjusTable multimagnetron gas aggregation source
Chapter 8: High-Flux DC Magnetron Sputtering
Table 8.1 Several reported maximum deposition rates
Chapter 9: High-Flux Metal Vapor Cell
Table 9.1 Elements with the highest melting points
Table 9.2 Elements commonly used as crucible materials [13]
Table 9.3 Heating procedure for high-flux metal cell utilizing an alumina crucible
