Interfacial reactions of rf-sputtered TiNi thin films on (100) silicon with a SiN diffusion barrier

Silicon nitride (SiN) with a 50?nm thickness on Si(100) as a thermal barrier was obtained by plasma-enhanced chemical vapour deposition (PECVD). TiNi thin films were rf sputtered on a SiN/Si substrate and then annealed at 400–700°C for 30?min. Their interfacial reactions were studied using transmission electron microscopy, X-ray diffraction and Auger electron spectroscopy analyses. Experimental results show that the thickness of reaction layer in TiNi/SiN/Si specimens is clearly reduced, compared with that in TiNi/Si specimens under the same annealing conditions. The significant effect of the SiN layer as a diffusion barrier in TiNi/SiN/Si can be recognized. N and Si atoms diffuse from the SiN layer to react with TiNi films at 500°C and 600°C respectively. The TiN_{1 ? x} phase is formed in specimens annealed at 500°C, and mixed Ti₂Ni₃Si and Ti₄Ni₂O compounds are found at 600°C. In the specimen annealed at 700°C, the reaction layer has sublayers in the sequence TiNi/Ti₄Ni₂O/Ti₂Ni₃Si/TiN_{1 ? x} /SiN/Si. The SiN thermal barrier obtained by PECVD caused quite different diffusion species to cross the interfaces between TiNi/SiN/Si and TiNi/Si specimens during the annealing.     

Electrical and optical properties of vacuum deposited MnPc thin films

Sandwich and planar structures were fabricated using manganese phthalocyanine (MnPc) as active layer and gold (Au) as electrodes by thermal evaporation method. The permittivity ε of MnPc was determined from the dependence of capacitance on film thickness. J-V characteristics of Au/MnPc/Au structure at room temperature were performed. Thermally generated hole concentration p₀, hole mobility μ_p, total trap concentration N_t and depth of the trap level were estimated. The activation energies of MnPc films were determined from the Arrhenius plots of ln σ versus 1000/T. The absorption and reflectance spectra of MnPc thin film deposited at room temperature were recorded in the spectral range 300–900 nm. The optical band gap of MnPc thin film was determined from the α² versus hν graph. The optical constants n and k were found. The real and imaginary parts of the optical dielectric constant ε₁ and ε₂ were calculated.     

Full X-ray pattern analysis of vacuum deposited pentacene thin films

Pentacene thin films with thicknesses ranging from 10 nm to 180 nm are investigated by specular X-ray diffraction in the reflectivity regime and in the wide angular regime. The results of the reflectivity measurements show a clear shift of the 001 reflection of the thin film phase depending on the layer thickness. It is shown that this shift can be explained by the dynamical scattering theory. The wide angular regime measurements show the 00L of the thin film phase. Williams-Hall plots are used to extract information on the crystallite size and mean micro strain of the thin film phase. The crystallite size is in good agreement with the results obtained by the reflectivity measurements. From this it can be concluded that the thin film phase crystallites are extended over the entire film thickness down to the substrate. Additionally an increase of the micro strain with increasing film thickness is observed.     

Physical properties of ZnSe thin films deposited on glass and silicon substrates

ZnSe thin films were deposited onto Corning glass and silicon substrates using thermal evaporation. The samples were prepared at different substrate temperatures. The thin films’ surface chemical composition was determined through Auger electron spectroscopy (AES). AES signals corresponding to Zn and Se were only detected in AES spectra. The samples’ crystallographic structure was studied through X-ray diffraction. The material crystallised in the cubic structure with preferential orientation (111). Optical properties of the ZnSe films were studied over two energy ranges via electron energy loss spectroscopy (10–90 eV) and spectral transmittance measurements (0.4–4 eV). In both cases, the spectral variation of the refractive index and the absorption coefficient were determined by fitting the experimental results with well-established theoretical models. Experimental values for the material’s gap were also found, and photoconductivity (PC) measurements were carried out. Transitions between bands, usually labelled Γ^V₈ → Γ^C₆ and Γ^V₇ → Γ^C₆, were found in the optical and PC responses. A wide spectral photoconductive response between 300 and 850 nm was found in the ZnSe/Si samples prepared at 250 °C substrate temperature.     

Hafnium oxide thin films deposited from a filtered cathodic vacuum arc

The electrical and structural characteristics of hafnium oxide thin films reactively deposited from a filtered cathodic vacuum arc have been investigated. X-ray photoelectron spectroscopy was used to determine the deposition conditions (Ar/O₂ ratio) which produced stoichiometric HfO₂ films. Cross-sectional transmission electron microscopy showed that the micro-structure of the films was highly disordered with electron-diffraction analysis providing evidence for the presence of sub-nano-metre crystallites of the monoclinic HfO₂ (P2₁/c) phase. Further evidence for the presence of this phase was provided by measuring the O k-edge using electron energy loss spectroscopy and comparing it with calculations performed using FEFF8.2, a multiple scattering code. Surface imaging revealed that local film damage occurred in films deposited with substrate bias voltages exceeding −200 V. The current-leakage characteristics of the HfO₂ films deposited with a bias of approximately −100 V suggest that device grade HfO₂ films can be produced from a filtered cathodic vacuum arc.     

Low-temperature deposited ZnO thin films on the flexible substrate by cathodic vacuum arc technology

In this paper, un-doped zinc oxide (ZnO) films with various thicknesses (150, 250, 350, 450 and 550 nm) were successfully prepared onto PET substrates using cathodic vacuum arc technique at low-temperature (<40 °C). Their microstructure, optical and electrical properties were investigated and discussed. The films showed (0 0 2) peaks, an average transmittance over 80% in the visible region. Calculated values of the band gap are around 3.29-3.33 eV when the film thickness increased, indicating a slight blue shift of optical transmission spectra. The lowest resistivity about 5.26 × 10⁻³ Ω cm could be achieved for the un-doped ZnO film with thickness of 550 nm.     

离子束反应溅射沉积SiO2薄膜的光学特性

 主要研究采用离子束反应溅射（RIBS）制备SiO2薄膜的折射率、消光系数、化学计量比与氧气在氩氧混合工作气体中含量及其沉积速率的关系。研究结果表明：RIBS制备的SiO2薄膜在0.63 μm处折射率n= 1.48,消光系数小于10-5;随着沉积速率的增加,薄膜的折射率和消光系数随之变大,当沉积速率超过0.3 nm/s,即使是在纯氧环境溅射,折射率值也不低于1.5;通过对红外透射光谱的主吸收峰位置研究得到沉积的SiO2薄膜为缺氧型,化学计量比不超过1.8,且红外吸收峰位置和SiO2折射率存在对应关系,因此在不加热衬底情况下使用RIBS制备SiO2薄膜时,会限制沉积速率的提高。     

Laser deposited YBaCuO thin films

YBa₂Cu₃O_7-x thin films were deposited by laser ablation using KrF excimer laser. In deposition on polycrystalline ZrO₂/(1–102) sapphire substrates influence of deposition conditions on film properties were studied. Zero resistance temperatureT _z of 83 K of epitaxially grown YBaCuO films on poly-ZrO₂/sapphire substrates was reached. Epitaxially grown yttria stabilized zirconia (YSZ) buffer layers were deposited by laser ablation on (1–102) sapphire substrates. On YSZ/sapphire, SrTiO₃ and NdGaO₃ substrates, temperatures T_z between 89–90 K were measured. Results of X-ray diffraction and SEM are also presented.We would like to express our thanks to L. Cibulka, L. and L. Rouek, and J. Stránský for their efficient help during the solution of technological problems connected with the construction of experimental apparatus.     

Optical characterization of thin silicon films deposited by CVD and annealed by pulsed laser

Polycrystalline Si layers 100 to 800 nm thick have been deposited on Si single crystal substrates by CVD and annealed with a Q-switched ruby laser at energies up to 1.5 J/cm². The optical characteristics of these layers have been measured by SEM and ellipsometry. The results can be attributed to a change in surface roughness with film thickness and laser energy.     

Analysis of thin thermal silicon nitride films on silicon

We have investigated the chemical and electrical properties of very thin (<32 Å thick) silicon nitride films grown by rapid thermal nitridation of silicon. These films were of interest as a possible means of tailoring the barrier heights of silicon Schottky barrier diodes. Auger and XPS analysis showed that the level of oxygen contamination in the films was very low ([N]/[N]+[O]) =0.85 to 0.95). The oxygen is located primarily at the surface and interface of the films. Metal-nitride-silicon devices were characterized by I-V and C-V techniques. These measurements indicated an increase in barrier heights to p-type substrates and a decrease in barrier heights to n-type substrates compared to values measured in the absence of the nitride layers. The magnitude of the change in barrier height increases with increasing nitride thickness. The barrier height can be varied reproducibly over a wide range. For molybdenum on p-type, this range is greater than half the bandgap. For titanium and molybdenum on p-type diodes, barrier heights higher than 1.0 V can be achieved. These measurements could be explained by a reduction in the density of silicon interface states with increasing nitride thickness or by the presence of positive fixed charge in the nitride layer.     

Characteristics of filtered vacuum arc deposited ZnO-SnO2 thin films on room temperature substrates

ZnO, SnO₂ and zinc stannate thin films were deposited using filtered vacuum arc deposition (FVAD) system on commercial microscope glass and UV fused silica substrates (UVFS) at room temperature (RT). The structural and morphological analyses were performed using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM), respectively. XRD patterns of ZnO films deposited at RT had strongly c-axis orientation, whereas SnO₂ and zinc stannate films had amorphous structure as they did not have any defined patterns. Average crystalline size and surface grain size of ZnO films were ∼16 nm, as determined from diffraction line broadening and AFM images, respectively. Optical constants in the 250-1100 nm wavelength range were determined by variable angle spectroscopic ellipsometry and transmission measurements. The transmission of the deposited films in the VIS was 80-90%, affected by interference. The refractive indices and the extinction coefficients of deposited ZnO, SnO₂ and zinc stannate films were in the range 1.87-2.15 and 0.02-0.04, depending on wavelengths and deposition parameters. The optical band gap (E_g) was determined by the dependence of the absorption coefficient on the photon energy at short wavelengths. Its values for ZnO, SnO₂ and zinc stannate were in the range 3.25-3.30 eV, 3.60-3.98 eV and 3.43-3.52 eV, respectively, depending on the deposition pressure.     

Electrochemically deposited bismuth telluride thin films

Thin films of bismuth telluride grown by electrochemical deposition technique on conducting glass and Mo sheet substrates, were characterized for their structural, morphological, optical and compositional analysis. These studies revealed polycrystalline anisotropic and layered structure of these films with different compositional stoichiometry. In the present work electrochemical deposition of bismuth telluride thin films is studied as a dopant material in II–VI group absorber materials for photovoltaic application since it has a narrow optical energy band gap of 0.13 eV. In this deposition process different film growth parameters were optimized to get good quality of compositionally uniform bismuth telluride thin film. XRD analysis revealed a hexagonal symmetry with large c-axis lattice constants (Bi₂Te₃, Bi_2+XTe_3−X).     

Analysis of the composition of Ti-based thin films deposited on silicon by means of self-ion assisted deposition

The composition of Ti-based thin films deposited on silicon using a self-ion assisted deposition (SIAD) method was investigated by utilising the Rutherford backscattering spectrometry technique and RUMP simulation code. The hydrogen affinity of the coatings produced by means of SIAD was investigated using the ¹H(¹⁵N, αγ)¹²C nuclear resonance reaction. The titanium–based films on silicon were found to have a high content of oxygen, carbon, hydrogen and substantial concentration of the substrate. Near 10% H content enrichment was found at the surface of coatings but no hydrogen enrichment at the coating–substrate interfaces was observed.     

单室沉积p-i-n型微晶硅薄膜太阳电池性能优化的研究

采用原位的氢等离子体处理技术和微晶覆盖技术来降低单室沉积p-i-n型微晶硅薄膜太阳电池中的硼污染问题.通过对不同处理技术所制备电池的电流密度-电压和量子效率测试结果的比较发现,一定的氢处理时间和合适的覆盖层技术都可以在一定程度上提高电池的性能,但每种方法的影响程度各异、文中对此异同进行了分析.通过对电池陷光结构和氢等离子体处理时间的优化,在单室中获得了效率为6.39%的单结微晶硅太阳电池.     

Preparation of p-type CdS thin films and in situ dark conductivity in vacuum deposited CdS:Cu films

CdS:Cu thin films were prepared using a vacuum co-evaporation technique. The Hall measurements indicate that the conductivity characteristic of CdS thin films transformed from highly compensated in as-grown or weakly annealed materials to p-type conductive in strongly annealed materials. X-ray diffraction spectra show that as-deposited thin films were the hexagonal phase of CdS except the presence of copper for high Cu doping and the diffraction peaks of Cu disappeared after annealing. From the X-ray photoelectron spectroscopy we found the ionization of Cu atoms and the formation of an acceptor level. In situ dark conductivity in vacuum as-deposited CdS:Cu was performed in the temperature range between 27 and 250 °C. An abnormal temperature dependence of conductivity was observed in medium and heavily Cu-doped films. The formation of a p-type material at a certain temperature was also studied by the hot probe measurements, which indicates a complex compensation process in the Cu-doped CdS films.     

Photoluminescence of thin amorphous-nanocrystalline silicon films

Photoluminescence spectra of thin hydrogenated-silicon films having mixed amorphous-nanocrystalline phase composition have been studied. Fabry-Perot interference was found to affect strongly the shape of the spectra. An analysis of the spectra made with inclusion of interference corrections shows that only one emission band forms in the 0.6–1.0 μm region due to carrier recombination at centers of the same type. Fiz. Tverd. Tela (St. Petersburg) 41, 153–158 (January 1999)     

Strains and rotations in thin deposited films

Thin films deposited on misfitting substrates exhibit distortions produced by the superposition of coherency strains and the elastic fields of interfacial defects. These distortions become homogeneous strains, ?, and rotations, φ, beyond a characteristic distance from the interface, z, and are partitioned between the film and substrate. Residual strain arises when the density of interfacial defects is insufficient to compensate the intrinsic coherency strain, and is partitioned in a manner depending on the relative thicknesses of the two layers, d. However, rotations are not partitioned in this way. Expressions for the magnitude and partitioning of ? and φ are derived for the case of elastically isotropic materials. Calculated values are shown to be in excellent agreement with experimental measurements for a variety of technologically relevant cases.     

Composition of the sputter deposited W-Ti thin films

Tungsten-titanium (W-Ti) thin film was deposited by dc Ar⁺ sputtering of W(70 at.%)-Ti(30 at.%) target. The thin film composition, determined by X-ray photoelectron spectroscopy (XPS) depth profiling, is W_(0.77±0.07)Ti_(0.08±0.03)O_(0.15±0.03). The presence of oxygen in the deposit is due to the rather poor vacuum conditions during the deposition, while significant deficiency of Ti, as compared to the sputtering target composition cannot be explained straightforwardly. Monte Carlo simulations of both, transport of sputtered particles from target to the substrate through the background gas (SRIM 2003 program) and thin film sputtering during the XPS depth profiling (program TRIDYN_FZR) are presented. The simulations show that the particle transport through the background gas is mainly responsible for the Ti depletion: the estimated composition of the thin film is W_0.61Ti_0.16O_0.23. Additional apparent Ti depletion occurs due to the preferential sputtering during the thin film composition analysis. The simulation of the sputtering process show that the surface concentration measured by XPS should be about W_0.74Ti_0.11O_0.15. The discrepancy between the estimated surface composition and the actual experimental result is in the range of the experimental error.