Formation energies of two-dimensional nuclei randomly-generated on (001), (110), and (111) planes of a face-centered-cubic crystal

Monte-Carlo simulations of the two-dimensional crystal nucleus growth on (001), (110) and (111) crystal planes of a face-centeredcubic lattice have been conducted considering: (1) the adsorption of an atom from the surrounding gases, (2) its surface diffusion, (3) its annihilation, and (4) its being incorporated into the crystal nucleus. The energy of the formed nucleus was calculated using the bond-splitting model with reference to the energy of atoms at the half-crystal position and its dependence on the nucleus size were evaluated. The results implies that Pangarov's theory to explain the dependence of preferred orientation on the supersaturation might have to be amended in case above dynamic processes have a vital effect on the shape of nucleus of deposited thin films.     

Comparison of growth mechanisms of silicon thin films prepared by HWCVD with PECVD

Hot-wire chemical vapor deposition (HWCVD) and plasma-enhanced chemical vapor deposition (PECVD) of Si thin films show different growth kinetic processes. According to the fractal analysis, the root-mean-square surface roughness δ and the film thickness d have the relation of δ ∼ d^β, where β is the dynamic scaling exponent related to the film growth mechanism. It was found that β is 0.44 for Si films prepared by HWCVD and 0.24 by PECVD. The former refers to a stochastic deposition while the latter corresponds to the finite diffusion of the radicals. Monte Carlo simulations indicate that the sticking process of growth radicals play an important role in determining the morphology of Si films.     

Crystallographic properties of four-fold grain K3Li2Nb5O15 thin films

The structural properties of a potassium lithium niobate (KLN; K₃Li₂Nb₅O₁₅) thin film deposited by rf-magnetron sputtering on a Pt/Ti/SiO₂/Si(100) substrate were investigated. The crystalline structures of the Pt under layer and KLN thin films were examined using θ-2θ, θ-rocking, and mesh scan X-ray diffraction (XRD). The XRD results revealed that the Pt under layer was a strong (111) direction orientated poly crystal. Unlike the Pt under layer film, the KLN(001) peak was found to consist of two separate peaks, one with a broad full width half maximum (FWHM) and the other with a narrow FWHM, indicating that the KLN film had a single crystalline structure. The surface and cross-section morphology were investigated using a scanning electron microscope (SEM). Accordingly, from the results of the SEM and XRD experiments, it was concluded that the KLN film was composed of small single crystals, which had a four-fold symmetry morphology with a c-axis normal to the substrate.     

Effects of oxygen pressure on the growth of pulsed laser deposited ZnO films on Si(0 0 1)

ZnO thin films were prepared on Si(0 0 1) substrates using a pulsed laser deposition (PLD) technique and then their growth and properties were investigated particularly as a function of ambient O₂ pressure during film growth. It was found that the microstructure, crystallinity, orientation and optical properties of the films grown are strongly dependent on the O₂ pressures used. Completely c-axis oriented ZnO films are grown in a low O₂ pressure regime (5×10⁻⁴-5×10⁻² Torr), whereas a randomly oriented film with a much lower crystallinity and a rougher grained-surface is grown at an O₂ pressure of 5×10⁻¹ Torr. This deterioration in film quality may be associated with the kinetics of atomic arrangements during deposition. Our results suggest that ambient O₂ pressure is an important processing parameter and should be optimized in a narrow regime in order to grow a ZnO film of good properties in PLD process.     

Three-dimensional deposition topography simulation based on new combinations of flux distribution and surface representation algorithms

The development of a full three-dimensional (3-D) deposition topography simulator is indispensable to the precise estimation of thin film deposition topography on asymmetric deposition geometries. In this study, we expand the application range of the equi-volume rate model (EVRM), a cell-based surface representation algorithm for full 3-D topography simulation, into rigorous flux distribution algorithms such as the Monte Carlo method (MCM) and the ballistic transport and reaction model (BTRM). A new full 3-D deposition topography simulation is conducted based on the new combinations of flux distribution and surface representation algorithms. To ensure the effectiveness of our simulation, we conduct numerous simulations for various deposition geometries with varying sticking coefficients and directionality factors. We also compare the simulation results of MCM-EVRM and BTRM-EVRM versions. From the viewpoint of precise simulated topography, a particle-based MCM has better suitability to a cell-based EVRM than a flux-based BTRM. In addition, from the viewpoint of computational time, the MCM-EVRM method is apt for the complex geometries and for the deposition processes of high sticking coefficient; such as physical vapor deposition and plasma enhanced chemical vapor deposition. In the other hand, the BTRM-EVRM method is suitable for the simple geometries and for the processes of low sticking coefficient such as chemical vapor deposition.     

四配位非晶碳薄膜的研究进展

四配位非碳薄膜是近年来发展的一种新型宽带隙半导体材料,具有独特的物理化学特性,本文对四配位非晶碳薄膜的研究意义,制备方法,形成机理,结构和性能表征及应用前景作较全面的介绍。     

Electrodeposition of CuInS2 from aqueous solution Part I. Electrodeposition of Cu---S film

As the first stage for thin film preparation of copper indium disulfide (CuInS₂), an electrodeposition technique of thin films in the Cu---S system was investigated from a new viewpoint. Deposition was carried out potentiostatically on a Ti substrate from acidic aqueous solution containing CuSO₄ and Na₂S₂O₃. Tartaric acid was found to be effective as a buffer for stabilizing the hydrogen ion concentration. Thin films of Cu₂S were obtained at −0.7 V vs. Ag/AgCl with good reproducibility from a solution containing 10 mM CuSO₄, 400 mM Na₂S₂O₃ and 100 mM tartaric acid. Scanning electron microscopy and energy dispersive X-ray analyses revealed that the film deposited had a crack-free surface and uniform stoichiometry of Cu₂S. Film thickness was estimated to be 0.6−0.8×10⁻⁶m after 3600 s deposition. The mechanism of Cu₂S formation was supposed to be that S₂O₃²⁻ ion reduces Cu(II) ion to make complex with Cu(I) ion. Probably it is this complex that contributes to the Cu₂S formation.     

Sputter deposition of NiTi thin film shape memory alloy using a heated target

In this paper we present a novel method for depositing NiTi thin film by DC sputtering. The film has transformation temperatures very close to that of the target. The new process involves heating the target and does not require compositional modification of the NiTi target. Results from X-ray diffraction, differential scanning calorimeter, four-point probe, Rutherford backscattering, and transmission electron microscopy are presented. These results indicate that compositional modification can be produced by varying the target temperature. Films produced from hot targets have compositions similar to the target while films produced from cold targets were Ti deficient. Films that were produced by gradual heating of the target have compositional gradation through the film thickness. The gradated films exhibit the two-way shape memory effect.     

Pulsed ion beam characterization of CVD diamond surfaces under thin film deposition conditions

Diamond and diamond-like carbon have properties which in principle make them ideally suited to a wide variety of thin-film applications. The widespread use of diamond thin films, however, has been limited for a number of reasons related largely to the lack of understanding and control of the nucleation and growth processes. Real-time, in-situ studies of the surface of the growing diamond film are experimentally difficult because these films are normally grown under a relatively high pressure of hydrogen, and conventional surface analytical methods require an ultrahigh vacuum environment. Pulsed ion beam based analytical methods with differentially pumped ion sources and particle detectors are able to characterize the uppermost atomic layer of a film during growth at ambient pressures in the range 0.7–27 Pa (4–6 orders of magnitude higher than other surface-specific analytical methods). We describe here a system which has been developed for the purpose of determining the hydrogen concentration and bonding sites on diamond surfaces as a function of sample temperature and ambient hydrogen pressure under hot-filament chemical vapor deposition (CVD) growth conditions. It is demonstrated that as the hydrogen partial pressure increases the saturation hydrogen coverage of the surface of a CVD diamond film increases, but that the saturation level depends on the atomic hydrogen concentration and substrate temperature. At the highest temperatures studied (700 °C), it was found that the surface hydrogen concentration did not exceed 1/4 monolayer.     

Micromechanical properties of amorphous carbon coatings deposited by different deposition techniques

Amorphous carbon coatings about 20 nm thick are commonly used as an overcoat on magnetic thin-film rigid disks and tape and disk head surfaces to improve their wear performance. In this study, we deposited amorphous carbon coatings with thicknesses ranging from 20 to 400 nm on single-crystal silicon substrates by four deposition processes: cathodic arc, ion beam deposition, r.f.-plasma-enhanced chemical vapor deposition, and r.f. sputtering. R.f.-sputtered SiC coatings were also deposited for comparison. The hardness, elastic modulus, and scratch resistance of these coatings were measured by nanoindentation and microscratching using a nanoindenter. The cathodic arc carbon coatings followed by sputtered SiC coatings exhibited the highest hardness, elastic modulus, scratch resistance/adhesion, and residual compressive stresses. The critical load, a measure of the scratch resistance/adhesion of the coating, increases with thickness. The cathodic arc coatings of lower thicknesses (˜ 30 nm) exhibited instant damage when the normal load exceeded the critical load, whereas thick coatings (greater than or equal to 100 nm) exhibited gradual damage through the formation of tensile cracks. The sputtered carbon coatings exhibited damage to the coating at very low loads and ploughing of the tip into the coating occurred right from the beginning of the scratch.     

Pd-Ni-P metallic glass film fabricated by electroless alloy plating

In the present study a Pd-Ni-P film has been fabricated by electroless alloy plating. The fabricated Pd-Ni-P film was found to be a metallic glass on the basis of two features, namely, an amorphous structure and a glass transition followed by crystallization during heating. The thermal stability of the supercooled liquid region, however, was lower than that of bulk Pd-Ni-P metallic glass. And unlike the conventional metallic glasses, the fabricated Pd-Ni-P film did not have a uniform microstructure. The non-uniform microstructure of this film resulted from the inhomogeneous distribution of the free volume accompanying the electroless alloy plating reaction.     

Crystallinity properties of parylene-n affecting its use as an ILD in submicron integrated circuit technology

Parylene-n (Poly-p-xylylene) (PA-n) [1–3] has a long history of use as a moisture barrier for printed circuit boards and hybrids. This paper evaluates this compound as a candidate vapor-depositable polymer interlayer dielectric for submicron integrated circuit technology due to its low dielectric constant, good step coverage, and high etch selectivity. To apply PA-n on high-density very large scale integrated circuits, its properties, such as deposition rate, deposition yield, and Crystallinity, are investigated as a function of deposition pressure and annealing temperature. The deposition rate was found in the range of 2.66 Pa to 13.3 Pa to be a linearly increasing function of pressure. Good-quality films were obtained when pressure was controlled below 10.64 Pa. Cloudy films, however, were found at 13.3 Pa. The deposition rate could be as high as 3.33 × 10⁻¹⁰ m s⁻¹ when deposited at 10.64 Pa. The plot of PA-n yield vs. pressure showed a constant plateau of 1 × 10⁻⁴ m kg⁻¹ from 2.66 Pa to 10.64 Pa. The optimum deposition rate was hence obtained at 10.64 Pa without compromising the deposition yield. The crystallinity-associated properties examined were hardness, dielectric constant, and water permeability. A lower deposition pressure was observed to produce higher Crystallinity that could be further enhanced by thermal annealing. A 5 × 10⁻⁸ m hard surface layer was detected with hardness 3.5 GPa, that was 3˜7 times larger than that of bulk hardness which was 0.4˜0.7 GPa. The bulk hardness was found to increase as Crystallinity increased. The dielectric constant tended to increase when the deposition pressure decreased. Furthermore, the dielectric constant was nearly constant when the polymer was heated up to temperatures as high as 698 K. This behavior, together with the formation of the hard layer and a higher Crystallinity, was believed to result from the improved film organization of the deposited films. The competition between the film build-up in the surface region and the monomer diffusion into the bulk region (penetration) was theorized to be responsible for the film organization. The water permeability, which was measured to be as low as 1.2 × 10⁻¹⁵ kg m⁻¹ s⁻¹ Pa⁻¹ and was found to increase as the deposition pressure was increased, further strengthened the film organization claim.     

Submonolayer and single crystal film from ligand-stabilized silver nanoparticles

Ligand-stabilized silver nanoparticles were synthesized by a method of ultraviolet light irradiation reduction from a parent solution containing inorganic silver salt, then deposited on carbon coated copper microscope grid by electrophoretic technique. All samples were examined on transmission electron microscope. The results indicate that when the parent solution was irradiated for 5 min a submonolayer of silver nanoparticles was obtained; however, when the parent solution was irradiated for 10 min single crystal silver films were formed. The mechanisms about formation of the submonolayer of nanoparticles and the single crystal silver films were discussed.     

Modeling and visualization of polycrystalline thin film growth

A novel polycrystalline thin film growth simulator, FACET, has been developed. FACET is a multi-scale model with two major components: an atomic level one-dimensional kinetic lattice Monte Carlo (1D KLMC) model and a real time feature scale two-dimensional facet nucleation and growth model.

The 1D KLMC model has been developed to calculate inter-facet diffusion rates. By inputting the diffusion activation energies, the model will calculate the inter-facet atomic flux between {1 0 0}, {1 1 0}, and {1 1 1} facets of FCC materials at any temperature. The results of the 1D KLMC model have been verified by comparison with a full three-dimensional kinetic lattice Monte Carlo (3D KLMC) model.

The feature scale polycrystalline thin film nucleation and growth model is based on describing grains in terms of two-dimensional faceted surfaces and grain boundaries. The profile of the nuclei are described by crystallographically appropriate facets. The position and orientation of the nuclei can be randomly selected or preferred textures can be created. Growth rates are determined from different deposition fluxes and surface diffusion effects. Quantitative microstructural characterization tools, including roughness analysis, average grain size analysis, and orientation distribution analysis, were incorporated into the model, which allows the users to design, conduct and analyze the virtual experiments within one integrated graphical user interface. Users can also visualize the nucleation and growth process of the film and obtain the final film microstructure. The effects of thickness, temperature, and deposition flux on thin film microstructures have been studied by FACET.     

The influence of film structure on In2O3 gas response

This paper reports the influence of In₂O₃ film structure on gas-sensing characteristics measured in steady state and transient modes. Films were deposited by spray pyrolysis from InCl₃–water solutions. Correlation between gas-sensing parameters and structural parameters such as film thickness (20–400 nm), grain size (10–70 nm), refractive index and film texture (I(400)/I(222)) were established. It was shown that grain size and porosity are the parameters of In₂O₃ films that best control gas response to ozone. In the detection of reducing gases, the influence of film structure is less important. Decreases in film thickness, grain size and degree of texture are the best way to decrease time constants of the gas response of In₂O₃-based gas sensors.     

Electronic properties of low temperature epitaxial silicon thin film photovoltaic devices grown by HWCVD

This study addresses the correlation of the electrical, surface, and structural evolution of HWCVD crystalline Si thin films with temperature, thickness, and hydrogen dilution. Scanning electron microscopy and atomic force microscopy reveal an increase with surface roughness with hydrogen dilution, as expected, while showing increasing surface roughness with substrate temperature, in contrast to previous studies of crystalline Si growth. This suggests that H desorption enables more contaminant absorption of the growing surface with increasing temperature, in turn increasing roughness. The open-circuit voltage of these films is shown to increase significantly over time, ∼ 50 mV over one week, due to the decrease in surface recombination velocity associated with the growth of a native oxide layer. This indicates the importance of post-deposition treatments for surface passivation.     

Structure, morphology and magnetic properties of Fe-B-Si-Nb glassy alloy thin film prepared by a pulsed laser deposition method

With the aim of applying to a soft magnetic underlayer of the double-layered perpendicular magnetic recording media, an Fe_74.9B_17.5Si_2.5Nb_5.1 alloy thin film was fabricated on Si substrate by a pulsed laser deposition method. The Fe-based alloy thin film of 200 nm in thickness was confirmed as a glassy structure. The thermal properties of the thin film have similar features to those for the melt-spun glassy alloy ribbon. The glassy alloy thin film exhibits good soft magnetic properties, i.e., high B_s of 1.2 T and in-plane low H_c of 134 A/m. The Fe-B-Si-Nb glassy alloy thin film is expected to be suitable for the soft magnetic underlayer material in the double-layered perpendicular magnetic recording media.     

Microstructural study of titanium–palladium–nickel base thin film shape memory alloys

A new generation of thin film shape memory alloys has been developed with 1.65 μm thickness for micro-actuator applications. In this work, the microstructure of thin film Titanium–Palladium–Nickel (TiPdNi) shape memory alloys deposited using ion beam assisted deposition from a Ti₅₀Pd₃₀Ni₂₀ target is studied. The TiPdNi thin films were deposited with and without substrate heating during deposition. As-deposited films without substrate heating were found to be amorphous. Deposition on heated substrate produced a dense, columnar crystalline structure. Microstructures of bulk TiPdNi thin films as well as the interfacial region between the film and substrate were characterized by various techniques including transmission electron microscope, scanning transmission electron microscope, scanning electron microscope-energy dispersive X-ray spectroscopy and scanning transmission electron microscope-energy dispersive X-ray spectroscopy. A transition layer with 70 nm thickness is observed at the interface between the bulk film and silicon substrate. It is composed of three layers; two amorphous layers above the silicon substrate and a 50 nm thick twin absent layer, which was identified as B2 austenite phase by Fourier spectra analysis. In the bulk film, nano-scale grains in the range of 80–200 nm were observed. The width of twin band of the film was very narrower in the range of 5 nm.     

Influence of processing variables on the structure and properties of ZnO films

Zinc oxide films of high optical quality have been deposited onto both silica and silicon substrates using reactive sputtering, pulsed laser deposition, and an aqueous solution based technique. Films have been characterized with respect to crystalline phase and phase stability, surface morphology, and optical response by means of X-ray diffraction, Raman spectroscopy, atomic force microscopy, optical transmission and ellipsometry measurements. All films studied were of the wurtzite phase, fine-grained, and exhibited varying degrees of c-axis orientation with respect to the substrate normal depending upon deposition conditions. Films showed some degree of residual tensile stress which was inferred from the E₂ Raman line shift relative to the single-crystal frequency. The wurtzite phase was found to be stable to temperatures near 800 °C, but at higher temperatures, reaction with silica led to evolution of Zn₂SiO₄ at the interface. Variations in Raman line intensities upon post-deposition annealing have been correlated with oxidation of excess zinc in the lattice.     

溅射与沉积过程的计算机模拟

应用TRIM和TRIDYN程序模拟氮化硼材料的溅射率与Ar 入射角的关系，Ar 辅助沉积氮化础薄膜与硅基片的界面结构，铜基片溅射率与入射能量的关系，以及Ar 以垂直于表面方向轰击非晶硅产生的溅射速率。铜基片溅射率的计算结果与已有的实验数据相比较表明，两者吻合得很好。硅片的溅射速率与应用38－cm宽束离子源设备的实验结果之间也吻合比较好。