Growth Of Metal Films Research Articles

Surface science using radioactive ions at ISOLDE: from metal surfaces to two-dimensional materials

We review the research carried out using the apparatus for surface physics and interfaces (ASPIC), at ISOLDE, CERN. We give an overview of the research highlights since 2000, focusing on magnetic and non-magnetic metallic surfaces, and introduce the scientific program that will follow the upgrade which is currently underway, focusing on two-dimensional materials. ASPIC was formerly used for the growth of ultrathin metallic films and their characterization by means of perturbed angular correlation spectroscopy. Past research has mainly focused on the determination of the magnetic hyperfine field at the probe atom located on different sites at the surface such as terraces, kinks, steps as well as on the investigation of the static magnetic polarization at the interface between ferromagnetic and paramagnetic layers. Future research on two-dimensional materials using ASPIC is foreseen to focus on the investigation of structural and electronic properties of adatoms (adsorption sites, hybridization effects, intra-atomic charge transfer, magnetic moments, etc). We emphasize, in this context, the exceptional capabilities of ASPIC in terms of broad applicability, high precision and low detection limits.

Effect of Pulse Frequency on Structural and Thermoelectric Properties of Bismuth Telluride Thin Films By Electrodeposition

Recently, thin film materials for environmental energy harvesting such as solar cells and thermoelectric generators have been growing the interest. In particular, thin film thermoelectric generators are promising devices with applications in sensor nodes for the internet of things (IoT). To justify a wider range of practical applications for these devices, higher performance thermoelectric materials are needed. Thermoelectric performance is defined by a figure of merit, ZT = s S2T/ k, where S is the Seebeck coefficient, s is the electrical conductivity, and k is the thermal conductivity. The figure of merit depends on the temperature, and its maximum value is different for different kinds of thermoelectric materials. Among thermoelectric materials, bismuth telluride (Bi2Te3) and alloys based on it are especially favorable because they exhibit a high figure of merit near room temperature (RT), and can be produced in both n-type and p-type. Electrodeposition is one of the most important methods of film fabrication, offering low-cost growth of high-quality metal, alloy, and semiconductor films. This is because it involves operation at low temperature with no requirement for vacuum conditions. However, the thin films prepared by electrodeposition generally obtained relatively low thermoelectric performance compared with that by other deposition methods. Therefore, in this study, we performed a pulse-electrodeposition method to improve the thermoelectric performance. We used bismuth telluride (Bi2Te3) as a thermoelectric material because this material exhibits high performance near room temperature (RT). For the electrodeposition, we used a standard three-electrode cell with a potentiostat and a function generator. The working electrode was a stainless steel (SUS304) substrate, chosen because of its excellent corrosion resistance. A platinum-coated titanium mesh on a titanium plate was used as the counter electrode. A Ag/AgCl (saturated KCl) electrode was used as the reference electrode. The pulse frequency was varied from 1 Hz to 10 kHz whereas the mixing ratio (Te/[Te+Bi]) of Bi(NO3)3, and TeO2was constant through all the experiments. To avoid complications in analysis due to the electrical conduction of the stainless steel substrate, the film was fixed on a glass plate using an epoxy resin, followed by thin film removal from the substrate. The structural properties were evaluated by means of scanning electron microscopy (SEM) and XRD (X-ray diffraction) analysis. The thermoelectric properties, which were electrical conductivity, Seebeck coefficient and power factor, were measured at RT. The most apparent changes between the thin films with the pulse-electrodeposition and that with the potential constant electrodeposition were the electrical conductivity. The thin films prepared by the potential constant electrodeposition obtained the electrical conductivity and the other properties as follows; s = 135.6 S/cm, S = −57.3 µV/K, and P.F. = 0.44 µW/(cm·K2). The thin films prepared by the pulse-frequency electrodeposition at 10 Hz obtained the electrical conductivity and the other properties as follows; s = 211.8 S/cm, S = −52.9 µV/K, and P.F. = 0.59 µW/(cm·K2). Therefore, we observed that the thermoelectric properties were improved by applying pulse potential to the electrodeposition. To further investigate the effect of pulse frequency of electrodeposition, we plan to analyze the surface morphology and crystallographic properties.

Ultramicroelectrode Studies of Self-Terminated Electrodeposited Ultrathin Ni Electrocatalysts

Metal hydroxides, oxides, and related compounds, particularly those containing Ni and Fe, have received much attention for oxygen evolution reaction (OER) catalysts because they have produced some of the highest reported OER rates and are chemically stability in alkaline media. Electrode platforms based on Ni and Fe are attractive because they exclude expensive precious metals, and thin films of these metals can be coupled with light-absorbing materials in photoelectrochemical energy conversion devices used in water electrolysis. Our group has been investigating growth of thin metal films through self-terminated deposition reactions, i.e., wet atomic layer deposition. These reactions can be coupled with potential modulation to deposit films of any desired thickness [1]. Similarly, self-termination behavior has been recently uncovered for iron-group metals albeit through a different mechanism than that reported for Pt. Ni growth stops upon the onset of H2O reduction whereas formation of a saturated Hupd monolayer is responsible for termination of Pt deposition. Possible explanations for Ni growth termination include formation of a passivating surface-bound OH– species formed upon H2O reduction or cross reactions between the egress of OH– and the incoming Ni2+ species to form Ni(OH)2 and related products. Here, we employed ultramicroelectrodes (UME’s) and scanning electrochemical microscopy (SECM) to further probe electrodeposition of thin metal films of Ni on Au electrodes and elucidate possible mechanisms for self-termination. Benefits of using UME’s include minimized solution resistance and well-controlled mass transport. Voltammetry of Au UME’s in electrolytes containing Ni2+ revealed a sharp, current spike at the onset of H2O reduction, demonstrating the first observed electrochemical signal corresponding to a metal self-termination process. The sharpness of this feature is reminiscent of a phase change or the initiation of a catalytic process. One explanation is that a highly-active species for the HER is generated upon H2O reduction in the presence of Ni2+; it is well-known that hydroxy-nickel species form during Ni2+ reduction due to a rise in pH, and Ni(OH)2catalyzes the HER. Generation/collection SECM, where a second Pt UME was used as the collector electrode, indicated that H2is generated during the process giving rise to this cathodic spike. Electrochemical results will be compared with optical characterization as well as SEM, EDX, and Raman spectroscopy to characterize electrodeposited films. Ni films deposited with only concurrent proton reduction were silvery, bright, and continuous; however, at potentials near the onset of H2O reduction, the Au was covered with a patchy, thin metallic film. These results agree with those at larger, cm-sized electrodes. At sufficiently negative potentials under H2O reduction, a thick, dull gray ring formed on the glass sheath surrounding the Au disk electrode, suggesting a transport-dependent phenomenon in the diffusion layer, e.g., precipitation of hydroxy-nickel species, surrounding the UME disk. At even higher overpotentials, hydrogen bubbles formed, destroying the Ni films. [1] Y. Liu et al,. Science, 338, 1327 (2012) N.L.R. acknowledges a National Research Council (NRC) Postdoctoral Research Assistantship.

The Coupled Photothermal Reaction and Transport in a Laser Additive Metal Nanolayer Simultaneous Synthesis and Pattering for Flexible Electronics.

The Laser Direct Synthesis and Patterning (LDSP) technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively deposits target material in a preselected pattern on the substrate. In this study, we experimentally investigated the effect of the processing parameters and type and concentration of the additive solvent on the properties and growth rate of the resulting metal film fabricated by this LDSP technology. It was shown that reactive metal ion solutions with substantial viscosity yield metal films with superior physical properties. A numerical analysis was also carried out the first time to investigate the coupled opto-thermo-fluidic transport phenomena and the effects on the metal film growth rate. To complete the simulation, the optical properties of the LDSP deposited metal film with a variety of thicknesses were measured. The characteristics of the temperature field and the thermally induced flow associated with the moving heat source are discussed. It was shown that the processing temperature range of the LDSP is from 330 to 390 K. A semi-empirical model for estimating the metal film growth rate using this process was developed based on these results. From the experimental and numerical results, it is seen that, owing to the increased reflectivity of the silver film as its thickness increases, the growth rate decreases gradually from about 40 nm at initial to 10 nm per laser scan after ten scans. This self-controlling effect of LDSP process controls the thickness and improves the uniformity of the fabricated metal film. The growth rate and resulting thickness of the metal film can also be regulated by adjustment of the processing parameters, and thus can be utilized for controllable additive nano/microfabrication.

Inverted Wedding Cake Growth Operated by the Ehrlich–Schwoebel Barrier in Two‐Dimensional Nanocrystal Evolution

AbstractWedding cake growth is a layer‐by‐layer growth model commonly observed in epitaxial growth of metal films, featured by repeated nucleation of new atomic layers on the topmost surface owing to the confinement of the Ehrlich–Schwoebel (ES) barrier. Herein, we report an inverted wedding cake growth phenomenon observed in two‐dimensional nanostructure evolution. Through a dynamically controlled vapor–solid deposition process of ZnO, a unique basin‐shaped crown was formed on the tip of each nanowire, featured with concentric steps. The atomic steps were nucleated along the edge and propagated toward the center. This is an opposite growth behavior compared to the conventional wedding cake growth, and is thus denoted as inverted wedding cake growth. Through the relation between the crown expansion rate and the temperature, the ES barrier of ZnO was determined to be 0.88 eV. The discovery of inverted wedding cake growth provided insight into the developing nanostructure growth mechanisms.

Inverted Wedding Cake Growth Operated by the Ehrlich-Schwoebel Barrier in Two-Dimensional Nanocrystal Evolution.

Wedding cake growth is a layer-by-layer growth model commonly observed in epitaxial growth of metal films, featured by repeated nucleation of new atomic layers on the topmost surface owing to the confinement of the Ehrlich-Schwoebel (ES) barrier. Herein, we report an inverted wedding cake growth phenomenon observed in two-dimensional nanostructure evolution. Through a dynamically controlled vapor-solid deposition process of ZnO, a unique basin-shaped crown was formed on the tip of each nanowire, featured with concentric steps. The atomic steps were nucleated along the edge and propagated toward the center. This is an opposite growth behavior compared to the conventional wedding cake growth, and is thus denoted as inverted wedding cake growth. Through the relation between the crown expansion rate and the temperature, the ES barrier of ZnO was determined to be 0.88 eV. The discovery of inverted wedding cake growth provided insight into the developing nanostructure growth mechanisms.

Porous Gold Films Fabricated by Wet-Chemistry Processes

Porous gold films presented in this paper are formed by combining gold electroless deposition and polystyrene beads templating methods. This original approach allows the formation of conductive films (2 × 106 (Ω·cm)−1) with tailored and interconnected porosity. The porous gold film was deposited up to 1.2 μm on the silicon substrate without delamination. An original zirconia gel matrix containing gold nanoparticles deposited on the substrate acts both as an adhesion layer through the creation of covalent bonds and as a seed layer for the metallic gold film growth. Dip-coating parameters and gold electroless deposition kinetics have been optimized in order to create a three-dimensional network of 20 nm wide pores separated by 20 nm thick continuous gold layers. The resulting porous gold films were characterized by GIXRD, SEM, krypton adsorption-desorption, and 4-point probes method. The process is adaptable to different pore sizes and based on wet-chemistry. Consequently, the porous gold films presented in this paper can be used in a wide range of applications such as sensing, catalysis, optics, or electronics.

Influence of Water on Chemical Vapor Deposition of Ni and Co thin films from ethanol solutions of acetylacetonate precursors.

In chemical vapor deposition experiments with pulsed spray evaporation (PSE-CVD) of liquid solutions of Ni and Co acetylacetonate in ethanol as precursors, the influence of water in the feedstock on the composition and growth kinetics of deposited Ni and Co metal films was systematically studied. Varying the water concentration in the precursor solutions, beneficial as well as detrimental effects of water on the metal film growth, strongly depending on the concentration of water and the β-diketonate in the precursor, were identified. For 2.5 mM Ni(acac)2 precursor solutions, addition of 0.5 vol% water improves growth of a metallic Ni film and reduces carbon contamination, while addition of 1.0 vol% water and more leads to significant oxidation of deposited Ni. By tuning the concentration of both, Ni(acac)2 and water in the precursor solution, the fraction of Ni metal and Ni oxide in the film or the film morphology can be adjusted. In the case of Co(acac)2, even smallest amounts of water promote complete oxidation of the deposited film. All deposited films were analyzed with respect to chemical composition quasi in situ by XPS, their morphology was evaluated after deposition by SEM.

Volmer-Weber growth stages of polycrystalline metal films probed by in situ and real-time optical diagnostics

The Volmer-Weber growth of high-mobility metal films is associated with the development of a complex compressive-tensile-compressive stress behavior as the film deposition proceeds through nucleation of islands, coalescence, and formation of a continuous layer. The tensile force maximum has been attributed to the end of the islands coalescence stage, based on ex situ morphological observations. However, microstructural rearrangements are likely to occur in such films during post-deposition, somewhat biasing interpretations solely based on ex situ analysis. Here, by combining two simultaneous in situ and real-time optical sensing techniques, based on surface differential reflectance spectroscopy (SDRS) and change in wafer curvature probed by multibeam optical stress sensor (MOSS), we provide direct evidence that film continuity does coincide with tensile stress maximum during sputter deposition of a series of metal (Ag, Au, and Pd) films on amorphous SiOx. Stress relaxation after growth interruption was testified from MOSS, whose magnitude scaled with adatom mobility, while no change in SDRS signal could be revealed, ruling out possible changes of the surface roughness at the micron scale.

Using Scanning Electrochemical Microscopy to Control Boundary Layer Chemistry during Nickel Electrodeposition

Thin films of iron-group metals, e.g., Ni, Fe, and Co, and their alloys and oxides are of interest to a wide range of technical endeavors from microelectronics to low cost energy storage and conversion devices. For example, Ni is a well-known component of rechargeable battery cathodes and has demonstrated superior oxygen evolution kinetics in alkaline media, making it a popular catalyst for photoelectrochemical cells. Our group has been investigating growth of thin metal films through self-terminated deposition, i.e., wet atomic layer deposition, where film thickness is controlled by potential modulation (Y. Liu et al., Science, 338, 1327 (2012) ). Thin Ni films can be deposited in a similar, self-terminated manner as reported for Pt by reduction of Ni2+ albeit through a different mechanism. Ni growth stops upon H2O reduction whereas H+ reduction is sufficient to terminate Pt growth through adsorbed H. However, bulk Ni deposition proceeds at H+ reduction potentials. Possible explanations for Ni termination include formation of surface-bound species that block further deposition or outward flux of OH– generated during the simultaneous H2O reduction, hindering transport of Ni2+ species to the electrode surface and/or reacting with Ni2+, e.g., to form Ni(OH)2, as the pH increases. Here, we used scanning electrochemical microscopy (SECM) to better understand the effect of boundary layer chemistry at the electrode-electrolyte interface during Ni electrodeposition with µm-sized spatial resolution. Our focus was on differentiating between effects of species adsorbed/bound to the electrode surface and changes in solution chemistry, i.e., pH, on termination as well as using the SECM probe to perturb the solution adjacent to the electrode surface and therefore control Ni deposition. In our studies at planar, cm-sized Au substrate electrodes, the SECM tip probe blocked diffusion of Ni2+ species in the probe-substrate gap, precluding meaningful measurements. Therefore, we adopted a tip-to-tip configuration, where two disk ultramicroelectrodes (UME’s) are aligned, to enhance flux in the gap. Because the edge-effect dominates the behavior of UME’s, we first considered Ni deposition at Au UME’s, comparing deposition under two regimes: H+ reduction and H2O reduction. Ni films deposited with only H+ reduction were silvery, bright, and continuous. With concurrent H2O reduction, the Au was covered with a patchy, thin metallic film. These results agree with those at the larger, cm-sized electrode. At sufficiently negative potentials under H2O reduction, a thick, dull gray ring formed on the glass sheath surrounding the Au disk electrode, suggesting a transport-dependent phenomenon in the diffusion layer surrounding the UME disk. Pt probe and Au substrate UME’s were used for SECM measurements. The potential of the Pt, acting as a local buffering agent, was poised to generate H+ via H2 oxidation, and Ni deposition occurred at Au. Under buffering conditions during H2O reduction, a thicker metallic layer formed on the Au and the ring was absent, indicating that pH buffering may lift the termination process. On-going experiments include surface analysis, e.g., SEM, EDX, and in situ Raman spectroscopy to characterize the morphology and composition of the electrodeposited films, and fabricating pH probes for the SECM. N.L.R. acknowledges a National Research Council (NRC) Postdoctoral Research Assistantship.

Growth and photoemission spectroscopic studies of ultrathin noble metal films on graphite

Growth of Cu, Ag and Au thin films on graphite(0 0 0 1) surface and possible formation of quantum well (QW) states originating due to the confinement of thin film sp electrons within the band gap of graphite along ΓM symmetry direction are investigated using low-energy electron diffraction (LEED) and angle-resolved photoemission spectroscopy (ARPES). Higher surface diffusivity and surface energy of Cu on graphite surface led to cluster growth and does not reveal any quantum size effect, while Ag and Au films grow epitaxially in spite of large lattice mismatch. However, better surface ordering has been achieved by growing Ag and Au at low temperature (LT), followed by room-temperature (RT) annealing which are evident from LEED and the presence of sharp Shockley-type surface state (SS) at Fermi level (EF). ARPES study of Ag films on graphite does not show any QW states, whereas Au films demonstrate a very sharp SS, Au bulk bands and well-resolved QW states or resonances. The observed low in-plane dispersions of these Au QW states or resonances are compared with the dispersions obtained in the previous Au QW state studies as well as for free-standing Au films.

Direct growth of metallic TiH2 thin films by pulsed laser deposition

We report the layer-by-layer growth and electronic properties of (111)-oriented, nearly stoichiometric TiH2 films (δ-phase) pulsed-laser-deposited on α-Al2O3(0001) using a TiH2 ceramic target. The content of the δ-phase increased as the decomposition to the Ti metal was suppressed at low temperatures. Moreover, long-lasting oscillations of reflection high-energy electron diffraction intensity were observed during the initial growth of the δ-phase film. The film showed metallic conductivity down to low temperatures. The results of Ti 2p–3d resonant photoemission spectroscopy and Hall measurement were consistent with those of the conducting electrons residing in the Ti 3d states.

Suppression of copper thin film loss during graphene synthesis.

Thin metal films can be used to catalyze the growth of nanomaterials in place of the bulk metal, while greatly reducing the amount of material used. A big drawback of copper thin films (0.5-1.5 μm thick) is that, under high temperature/vacuum synthesis, the mass loss of films severely reduces the process time due to discontinuities in the metal film, thereby limiting the time scale for controlling metal grain and film growth. In this work, we have developed a facile method, namely "covered growth" to extend the time copper thin films can be exposed to high temperature/vacuum environment for graphene synthesis. The key to preventing severe mass loss of copper film during the high temperature chemical vapor deposition (CVD) process is to have a cover piece on top of the growth substrate. This new "covered growth" method enables the high-temperature annealing of the copper film upward of 4 h with minimal mass loss, while increasing copper film grain and graphene domain size. Graphene was then successfully grown on the capped copper film with subsequent transfer for device fabrication. Device characterization indicated equivalent physical, chemical, and electrical properties to conventional CVD graphene. Our "covered growth" provides a convenient and effective solution to the mass loss issue of thin films that serve as catalysts for a variety of 2D material syntheses.

Metallic Nanofilms on Single Crystal Silicon: Growth, Properties and Applications

The metal–silicon thin−film system is not isostructural and furthermore exhibits pronounced interdiffusion and chemical reactions. Therefore the growth of metallic films on silicon leads to a high concentration of defects in the film, especially at its substrate interface. The material also contains stress and a transition layer consisting of melts or compounds (silicides). We have considered theoretical viewpoints and reviewed experimental data on the growth and properties of metallic nanofilms (including multilayered ones) on silicon, and also provided a brief review of their applications. The films consist either of atomic−sized, quabquantum sized and quantum sized layers. We have suggested a low temperature film growth technology based on freezing growing layers during deposition by maintaining a low temperature of the substrate and using an atomic beam with a reduced heat power. The technology uses a specially shaped deposition system in which the distance between the source and the substrate is comparable to their size or smaller. Furthermore, we use a special time sequence of deposition that provides for a reduced substrate surface temperature due to greater intervals between deposition pulses. This growth method of atomically thin films and multilayered nanofilms excludes interdiffusion between the layers, reduces three−dimensional growth rate and relatively increases lateral layer growth rate.

Manganese Precursor Selection and the Thermal Atomic Layer Deposition of Copper/Manganese Alloy Films

Our laboratory seeks to develop the growth of metallic first row transition metal thin films using atomic layer deposition (ALD). The microelectronics industry is calling for the growth of metallic first row transition metal films by the ALD method for a variety of applications, including copper metallization, seed layers for copper metallization, copper/manganese alloys for self-forming copper diffusion barriers, and magnetic alloys. The ALD growth of noble metal thin films has been explored extensively in the past ten years, due to the positive electrochemical potentials of these metal ions and relative ease of reduction to the metallic state. The low temperature ALD of high purity, low resistivity Cu films has been described, but ALD routes to the other metallic first row transition metal films remain poorly developed, largely because of the negative electrochemical potentials of most of the ions and a corresponding lack of powerful reducing co-reagents that can convert precursors in positive oxidation states to the metals. We will describe the synthesis, structure, and properties of a large series of new first row transition metal ALD precursors that combine high volatilities, high thermal stabilities, and high reactivities toward reducing agents. We will also report borane and other reducing agents that can react with the metal precursors to afford metallic films. Additionally, we will overview the thermal growth of metallic copper, nickel, cobalt, iron, manganese, and chromium thin films from these new precursors. Key advances include development of optimized ALD precursors with very similar ligands and chemistry, and identification of new reducing co-reagents that can rapidly reduce the positive oxidation state precursors to the metals.

Time-domain and energetic bombardment effects on the nucleation and coalescence of thin metal films on amorphous substrates

Pulsed, ionized vapour fluxes, generated from high power impulse magnetron sputtering (HiPIMS) discharges, are employed to study the effects of time-domain and energetic bombardment on the nucleation and coalescence characteristics during Volmer–Weber growth of metal (Ag) films on amorphous (SiO2) substrates. In situ monitoring of the film growth, by means of wafer curvature measurements and spectroscopic ellipsometry, is used to determine the film thickness where a continuous film is formed. This thickness decreases from ∼210 to ∼140 Å when increasing the pulsing frequency for a constant amount of material deposited per pulse or when increasing the amount of material deposited per pulse and the energy of the film forming species for a constant pulsing frequency. Estimations of adatom lifetimes and the coalescence times show that there are conditions at which these times are within the range of the modulation of the vapour flux. Thus, nucleation and coalescence processes can be manipulated by changing the temporal profile of the vapour flux. We suggest that other than for elucidating the atomistic mechanisms that control pulsed growth processes, the interplay between the time scales for diffusion, coalescence and vapour flux pulsing can be used as a tool to determine characteristic surface diffusion and island coalescence parameters.

Temperature-dependent 2-D to 3-D growth transition of ultra-thin Pt films deposited by PLD

During the growth of thin metal films on dielectric substrates at a given deposition temperature Td, the film’s morphology is conditioned by the magnitude and asymmetry of up- and downhill diffusion. Any severe change of this mechanism leads to a growth instability, which induces an alteration of the thin film morphology. In order to study this mechanism, ultrathin Pt films were deposited via pulsed laser deposition onto yttria-stabilized zirconia single crystals at different deposition temperatures. The morphological evolution of Pt thin films has been investigated by means of scanning electron microscopy, atomic force microscopy and standard image analysis techniques. The experimentally obtained morphologies are compared to simulated thin film structures resulting from a two-dimensional kinetic Monte Carlo approach. Two main observations have been made: (i) thin Pt films deposited onto ZrO2 undergo a growth transition from two-dimensional to three-dimensional growth at Td>573K. The growth transition and related morphological changes are a function of the deposition temperature; and (ii) a critical cluster size of i∗=4 in combination with an asymmetric Ehrlich–Schwoebel barrier favoring the uphill diffusion of atoms allows for a computational reproduction of the experimentally obtained film morphologies.

Smallest Metallic Nanorods Using Physical Vapor Deposition

Physical vapor deposition provides a controllable means of growing two-dimensional metallic thin films and one-dimensional metallic nanorods. While theories exist for the growth of metallic thin films, their counterpart for the growth of metallic nanorods is absent. Because of this absence, the lower limit of the nanorod diameter is theoretically unknown; consequently the experimental pursuit of the smallest nanorods has no clear target. This Letter reports a closed-form theory that defines the diameter of the smallest metallic nanorods using physical vapor deposition. Further, the authors verify the theory using lattice kinetic MonteCarlo simulations and validate the theory using published experimental data. Finally, the authors carry out a series of theory-guided experiments to grow well-separated metallic nanorods of ∼10 nm in diameter, which are the smallest ever reported using physical vapor deposition.

Molecular dynamic simulation of binary ZrxCu100−x metallic glass thin film growth

In this work, we employed classical molecular dynamics simulations model to study ZrxCu100−x (3≤x≤95) metallic glass films deposited on a silicon (100) substrate. Input data were chosen to fit with the experimental operating conditions of a magnetron sputtering deposition system. The growth evolution is monitored with variable compositions of the incoming atom vapor. The Zr–Zr, Cu–Cu and Zr–Cu interactions are modeled with the Embedded Atom Method (EAM), the Si–Si interaction with Tersoff potential, the Zr–Si and Cu–Si interactions with Lennard-Jones (12-6) potential. Different film morphology and structure were detected and analyzed when the Zr to Cu ratio is varied. The results are compared with X-ray diffraction and scanning electron microscopy analyses of experimentally deposited thin films by magnetron sputter deposition process. Both simulation and experiment results show that the structure of the ZrxCu100−x film varies from crystalline to amorphous depending on the elemental composition.

Atomic Layer Electrodeposition

An electrochemical process provides a cheap and simple route to layer-by-layer growth of metal films.