The effect of the electron bombardment of NaCl substrates on the epitaxial growth of gold and silver films

The effect of the electron bombardment of NaCl substrates on the epitaxial growth of gold and silver films was investigated by transmission electron microscopy and Auger electron spectroscopy. The results indicate that anion surface vacancies are created during low energy electron bombardment; these vacancies, in turn, promote nucleation and subsequent epitaxial growth of vapor-deposited films. Nucleation is interpreted in terms of the attraction of metal atoms to the surface vacancies and the subsequent formation of a rigid cluster in an epitaxial orientation. These clusters then grow by the accretion of deposited atoms to form epitaxial islands which eventually coalesce with near-perfect register to form a continuous film characterized by a high degree of epitaxy and low defect densities.     

Effect of carbon additive on microstructure evolution and magnetic properties of epitaxial FePt (001) thin films

FePt:C thin films were deposited on CrRu underlayers by DC magnetron co-sputtering. The effects of C content, FePt:C film thickness and substrate temperature on the microstructural and magnetic properties of the epitaxial FePt (001) films were studied. Experimental results showed that even with 30 vol.% C doping, the FePt films could keep a (001) preferred orientation at 350 °C. When a FePt:C film was very thin (< 5 nm), the film had a continuous microstructure instead of a granual structure with C diffused onto the film surface. With further increased film thickness, the film started to nucleate and formed a column microstructure over continuous FePt films. A strong exchange coupling in the FePt:C films was believed to be due to the presence of a thin continuous FePt layer attributed to the carbon diffusion during the initial stage of the FePt:C film growth. Despite the presence of a strong exchange coupling in the FePt:C (20 vol.% C) film, the SNR ratio of the FePt:C media was about 10 dB better than that of the pure FePt media. The epitaxial growth of the FePt:C films on the Pt layers was observed from high resolution TEM cross sectional images even for the films grown at about 200 °C. The TEM images did not show an obvious change in the morphology of the FePt:C films deposited at different temperatures (from 200 °C to 350 °C), though the ordering degree and coercivity of the films increased with increased substrate temperature.     

The effect of amorphous intermediate layers on the epitaxial growth of gold evaporated onto silver single crystals

Amorphous layers of carbon and silicon monoxide have been evaporated onto silver substrates at temperatures of 150°, 270° and 400°C. Gold was subsequently evaporated onto the specimens without changing the temperature. The gold films were examined by electron microscopy in order to determine whether or not epitaxy had occurred. Three “phases” were observed: complete epitaxy for amorphous films less than 4 Å (carbon) or 5 Å (silicon monoxide); completely disordered structures for amorphous films greater than 10 Å (carbon) or 11 Å (silicon monoxide); and a partially oriented structure (partial epitaxy) for intermediate thicknesses.     

Epitaxial growth of the Au/C/Ag system in ultrahigh vacuum

Carbon layers were evaporated onto silver single crystals (that had been previously exposed to air) at room temperature in an ultrahigh vacuum (UHV), and a gold film was subsequently evaporated onto the specimens without change of temperature. The gold films were examined by transmission electron microscopy to determine whether or not epitaxy had occurred. Three cases were observed: complete epitaxy when the average carbon film thickness was 1 Å or less; completely disordered structures for amorphous films 3 Å thick or more; and a partially oriented structure in the intermediate range. The fact that epitaxy is destroyed before the coalescence stage of the carbon film is reached suggests that the carbon islands block the mobility of the nuclei that are growing epitaxially; there is no need for carbon to cover the silver crystal completely for epitaxy to be destroyed. The experimental results obtained also indicate that not only is direct contact between substrate and evaporated film necessary for epitaxy but that the substrate surface must be “suitably” contaminated.     

Epitaxial growth of thin gold films onto pure and doped NaCl and KCl substrates

The influence of impurities such as calcium, strontium or silver ions present in the substrates on the structural growth features of continuous gold thin films, vacuum evaporated at constant deposition rates onto NaCl and KCl substrates heated in the temperature range from 90 to 300 °C, was studied by transmission electron microscopy and transmission electron diffraction. The epitaxial growth of gold thin films is inhibited by the presence of 5 × 10^-1 mol.% strontium or calcium ions in the KCl and NaCl substrates. The presence of 1.7 × 10^-1 mol.% silver ions in the NaCl substrates enhances the epitaxial growth of the gold thin films even at a substrate temperature of 120 °C. An enhancement of the gold thin film epitaxial growth is also obtained with NaCl-2 × 10^-2mol.%Ag-5 × 10^-1mol.%Ca and NaCl-1.7 × 10^-1mol.%Ag-5 × 10^-1mol.%Ca substrates.     

Electron diffraction from periodic arrays of misfit dislocations formed during epitaxial growth

Changes in transmission electron diffraction patterns were examined during the epitaxial growth of copper and palladium on (111) gold substrates. Bicrystal patterns contain discrete reflections which can be explained by diffraction from uniformly strained deposit and substrate layers or by double diffraction between these two layers. Extra reflections are also observed, which vary markedly in intensity with increasing deposit thickness. It is shown that the extra reflections may be ascribed to periodic arrays of perfect edge misfit dislocations which are observed directly in both Cu/(111)Au and Pd/(111)Au films. The interpretation of these results is discussed and their significance for more general studies of epitaxial growth is briefly considered.     

Formation of thin β-FeSi2 template layer for the epitaxial growth of thick film on Si (111) substrate

For the epitaxial growth of thick β-FeSi₂ films, we fabricated ultrathin β-FeSi₂ template layers (thinner than 20 nm) on Si (111) substrates with different methods. Surface morphology and crystallinity of the template layers were found to be dependent on the surface conditions of the substrate and the fabrication method. It was revealed that to form a smooth and continuous template, a hydrogen-terminated surface was better than that covered with a several-nanometer oxide layer. Using this surface, continuous (110)/(101)-oriented epitaxial template was obtained by depositing 6-nm iron at 400 °C and subsequent in situ annealing at 600 °C in MBE chamber, namely, a reaction deposition epitaxy (RDE) method. Co-deposition of iron and silicon with atomic ratio of Fe/Si=1/2 allowed the forming of template layers at further low temperature. Co-deposited template layers exhibited better crystallinity and morphology than those prepared by RDE. By using the optimized template layer, we succeeded in growing high-quality thick β-FeSi₂ films on Si (111) substrates with sharp β-FeSi₂/Si interface.     

Solid phase epitaxy of silicon thin films by diode laser irradiation for photovoltaic applications

High temperature solid phase epitaxial crystallization of amorphous silicon layers prepared by electron beam evaporation is investigated. By using a continuous wave diode laser for heating the films rapidly (in milliseconds to seconds) this method is suitable on glass substrates with low temperature resistance. Therefore, the method is an economically advantageous technique of producing absorber layers for thin film solar cells. For the experiments 500 nm of amorphous silicon was deposited on two different configurations of substrates. In the first one monocrystalline wafers of three different crystallographic orientations were used. In the second one a polycrystalline seed layer prepared on borosilicate glass served as substrate. The crystallization process was monitored in situ by time resolved reflectivity measurements. Depending on the crystal orientation 2 s to 3 s was needed for complete solid phase epitaxial crystallization of the amorphous films. The evolution of temperature during crystallization was simulated numerically.     

Growth and structure of heteroepitaxial thin films of homologous compounds RAO3(MO)m by reactive solid-phase epitaxy: Applicability to a variety of materials and epitaxial template layers

A reactive solid-phase epitaxy (R-SPE) method combines deposition of a thick amorphous or polycrystalline layer with a desired chemical composition and post-deposition solid-phase epitaxial growth. The solid-phase epitaxial growth is invoked by thermal annealing with an assistance of a sacrificial layer working as an epitaxial template. Thereby it enables us to grow high-quality epitaxial films of complex oxides whose epitaxial films are not grown by conventional high-temperature growth techniques. It was reported that 2-nm-thick ZnO layers worked as template for growing InGaO₃(ZnO)_m (m = integer) epitaxial films. The present study extended the R-SPE technique to growth of various complex oxides with chemical compositions of RAO₃(MO)_m and to use of various epitaxial template layers. We found that mono oxide epitaxial layers such as In₂O₃ and Ga₂O₃ work as template layers as well. Alternatively, a ZnO epitaxial layer is also applicable to ZnO-free compounds. The films obtained were grown heteroepitaxially on YSZ(111) and single-crystalline when the fabrication conditions are optimized.     

Epitaxial growth of nanostructured gold films on germanium via galvanic displacement

This work focuses on the synthesis and characterization of gold films grown via galvanic displacement on Ge(111) substrates. The synthetic approach uses galvanic displacement, a type of electroless deposition that takes place in an efficient manner under aqueous, room temperature conditions. Investigations involving X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were performed to study the crystallinity and orientation of the resulting gold-on-germanium films. A profound effect of HF(aq) concentration was noted, and although the SEM images did not show significant differences in the resulting gold films, a host of X-ray diffraction studies demonstrated that higher concentrations of HF(aq) led to epitaxial gold-on-germanium, whereas in the absence of HF(aq), lower degrees of order (fiber texture) resulted. Cross-sectional nanobeam diffraction analyses of the Au-Ge interface confirmed the epitaxial nature of the gold-on-germanium film. This epitaxial behavior can be attributed to the simultaneous etching of the germanium oxides, formed during the galvanic displacement process, in the presence of HF. High-resolution TEM analyses showed the coincident site lattice (CSL) interface of gold-on-germanium, which results in a small 3.8% lattice mismatch due to the coincidence of four gold lattices with three of germanium.     

Effects of diffusion on interfacial fracture of gold-chromium hybrid microcircuit films

In this study, the effects of diffusion on gold-chromium film durability was determined from interfacial fracture energy measurements on laboratory samples aged to simulate long term service. The samples were prepared by sputter deposition of gold films and chromium adhesive layers on sapphire substrates. Some films were left in the as-deposited condition while others were given an accelerated age to drive the chromium off the interface and into the gold film. Stressed overlayers and nanoindentation were then used to induce interfacial delamination and blister formation from which interfacial fracture energies were determined using mechanics-based models. These tests showed that the fracture energies for interfacial failure of the as-deposited and annealed films occurred near 1.3 J m^–2 even when diffusion had driven all chromium into solution. These results clearly demonstrate that chromium in solution is as effective in promoting adhesion as continuous chromium adhesive layers.     

Unstrained epitaxial InxGa1−x As films obtained on porous GaAs

Epitaxial layers of InGaAs solid solutions were grown on porous GaAs(100) substrates by liquid-phase epitaxy. A comparison between the compositions and thicknesses of these epitaxial layers with those of layers obtained under the same conditions on normal monolithic GaAs substrates suggests that the crystallization of epitaxial layers on porous substrates may be considered as the growth of free unstrained films. Pis’ma Zh. Tekh. Fiz. 25, 15–20 (November 12, 1999)     

通过制备Ti/TiC和Si/SixNy过渡层在铜基体上沉积类金刚石膜的研究

将磁控溅射物理气相沉积（MS-PVD）和电子回旋共振-微波等离子体增强化学气相沉积（ECR—PECVD）技术相结合，在铜基体上通过制备两种不同的过渡层，成功地沉积了类金刚石膜。拉曼光谱结果分析表明，所制备的碳膜都具有典型的类金刚石结构特征。通过原子力显微镜对薄膜的微观形貌进行分析，采用纳米压痕测量薄膜的硬度和模量。并对Ti／TiC过渡层和Si／SixNy过渡层上沉积的类金刚石薄膜进行了研究对比。     

Single-crystalline GaAs, AlGaAs, and InGaAs layers grown by metalorganic VPE on porous GaAs substrates

Conditions for the growth of single-crystalline GaAs, AlGaAs, and InGaAs layers by metalorganic VPE were established and the corresponding semiconductor films were obtained on porous GaAs substrates. Comparative data on the morphology, structure, and electrical homogeneity of the epitaxial layers grown on the porous and monolithic substrates are presented. It was found that passage to the porous substrates leads to changes in the film growth rate and morphology, the concentration of electrically active defects, and their distribution in depth of the epitaxial structures.     

Sol-Gel法制备PZT铁电薄膜新进展

从底电极的选择、过渡层的引入、外延膜的生长、取代阳离子的改性四个方面介绍了Sol-Gel法制备PZT铁电薄膜的研究进展,简述了PZT的Sol-Gel机理研究现状和引起PZT铁电薄膜极化疲劳的原因,分析了Sol-Gel法制备PZT铁电薄膜研究中存在的问题,并提出展望。     

Electrodeposition and characterization of CdSe semiconductor thin films

The electrodeposition of cadmium selenide alloy on glassy carbon and gold electrodes has been studied by electrochemical techniques. Potentiostatic I-t transients were recorded to obtain the nucleation mechanism, while cyclic voltammetry was used to characterize the system. Structural information on the electrodeposited layers was obtained by X-ray diffraction. The experimental results clearly show that the deposition of cadmium selenide alloy on glassy carbon and gold electrodes is a diffusion-controlled process. The nucleation is progressive, and the number of nucleation sites decreases with increasing bath temperature. The deposition of CdSe alloy results in well-defined crystals with hexagonal shape. The films were characterized by optical absorption and electrical resistivity measurements. Films showed a direct band gap of 3.56 eV.     

The influence of ordered surface point defect arrays on the epitaxial deposition of gold upon (100) surfaces of sodium chloride

The effect of an ordered array of sodium ion vacancies (incorporated into a (100) surface of sodium chloride) upon the epitaxial temperature associated with gold being deposited onto that (100) surface has been investigated. A dramatic reduction in the epitaxial temperature has been observed, and single-crystal correctly oriented gold films have been achieved at - 30 °C upon those areas of the sodium chloride surface containing the point defects.     

High quality epitaxial ZnO films grown on solid-phase crystallized buffer layers

High quality epitaxial ZnO films on sapphire (110) plane have been fabricated on ZnO homo-buffer layers crystallized via solid-phase epitaxially (SPE). The SPE-ZnO films are fabricated by annealing of amorphous ZnON (a-ZnON) films deposited by RF magnetron sputtering. During annealing, the a-ZnON films are oxidized and converted to ZnO crystal. X-ray diffraction (XRD) analysis shows that the resultant films are epitaxially grown on the sapphire substrates. By using the SPE-ZnO films as homo-buffer layers, the ZnO films with high crystallinity, which are deposited by RF magnetron sputtering, are fabricated. The full width at half-maximum of XRD patterns for 2θ-ω and ω scan of (002) plane are 0.094° and 0.12°, respectively, being significantly small compared with 0.24° and 0.55° for the films without buffer layers. Thus utilizing SPE buffer layers is very promising to obtain epitaxial ZnO films with high crystallinity.     

Relation between the hue and composition of TiCxNy films prepared using multiple hollow cathode discharge ion plating

There is a distinct colour difference between electroplated gold layers and gold-like TiN films deposited by ion plating. In order to improve the hue of TiN coatings we have added carbon atoms to the Ti---N matrix and studied the influence of the carbon content on the hue of Ti---C---N complex films.

The films were prepared by means of the reactive ion-plating method using an in-line system composed of three chambers. The film composition was controlled by regulating the throughput of each reactant gas, i.e. nitrogen, acetylene, methane and hydrogen.

The colour of materials is dependent on the optical reflectivity and its dependence on the wavelength and on the lightness. It was found that a colour close to that of electroplated gold could be obtained with an appropriate TiC_xN_y composition, although the lightness of the film surface decreased as the reactant gas throughput increased.     

Effect of carrier concentration on the microhardness of GaN layers

The paper presents a microhardness study of thick crack-free hydride vapor phase epitaxial GaN layers (not intentionally doped), and of thin metal-organic vapor phase epitaxial (MOVPE) GaN layers (undoped and Si-doped), grown on sapphire. A Vickers indentation method was used to determine the microhardness under applied loads up to 2 N. An increase in the microhardness was observed with decreasing carrier concentration and increasing mobility. A dip at an indentation depth of about 0.75 μm is observed in the microhardness profile in the MOVPE films, and is correlated with peculiarities in the spatially resolved cathodoluminescence spectra. The relationship between the mechanical and electrophysical parameters is discussed.