Epitaxial growth of titanium oxide thin films on MgO(100) single-crystal substrates by reactive deposition methods

We synthesized titanium oxide thin films on MgO(100) single-crystal substrates by two reactive deposition methods and compared the structures of the thin films formed by these methods. In one method (pulsed-molecular-beam deposition method), molecular oxygen is supplied to the substrates by using a pulsed-molecular-oxygen beam source and deposition of one unit layer of titanium and subsequent supply of molecular oxygen are repeatedly performed. In the other method (radical beam deposition method), atomic oxygen is irradiated to the substrates by using an atomic oxygen beam generated by the radical beam source and irradiation of the atomic oxygen and deposition of titanium are simultaneously performed. In the case of the pulsed-molecular-beam deposition method, the crystal structure was changed by increasing the number of oxygen pulses supplied from the beam source. We found that the crystal structure of titanium oxide depended on the composition ratio of O:Ti in the film. The maximum ratio of O:Ti attainable by this method was 1.85, and at this ratio, (100)-oriented pseudorutile was formed. In the case of the radical beam deposition method, (100)-oriented anatase was formed below the titanium deposition rate of 0.10 nm/s and pseudorutile (TiO_2−δ) was formed above 0.15 nm/s. The pseudorutile structure synthesized on this experiment was very stable in air. We concluded that the crystal structure of the pseudorutile is a new crystal structure of titanium oxide.     

Relaxation of extrinsic and intrinsic stresses in germanium substrates with silicon films

Si films were deposited on Ge substrates at 400°C by two different Physical Vapor Deposition techniques: (A) ion beam sputtering and (B) magnetron sputtering. The intrinsic stresses in the as-deposited films were measured to be compressive and much greater in samples (A), about −1500 to −2000 MPa than in samples (B), about −300 to −500 MPa. The substrates were subsequently exposed to thermal treatments for varying times at 800°C. In the lower stressed (B) samples, the films had relaxed and reduced the overall curvature of the structure whereas in the high stresses (A) samples, an irreversible large increase in the substrate curvature was found to occur. This indicated that plastic deformation in the Ge substrates itself had occurred.     

Effects of applied substrate bias during reactive sputter deposition of nanocomposite tantalum carbide/amorphous hydrocarbon thin films

Nanocomposite tantalum carbide/amorphous hydrocarbon (TaC/a-C:H) thin film composition, structure, and mechanical properties depend on the direct current bias voltage (V_b) level applied to the substrate during reactive sputter deposition. A set of TaC/a-C:H films was deposited across the range V_b = 0 to − 300 V with all other deposition parameters held constant except substrate temperature, which was allowed to reach its steady state during the depositions. Effects of V_b on film composition and structure were explored, including TaC crystallite size and dispersion using X-ray diffraction and high resolution transmission electron microscopy. In addition, the dependency of stress and hardness on V_b was studied with an emphasis on relationships to a-C:H phase structure.     

Influence of substrate temperature on structural,optical, and electrical properties of flash evaporated CuIn0.81Al0.19Se2 thin films

Chalcopyrite copper indium aluminum diselenide (CuIn_0.81Al_0.19Se₂) compound is prepared by direct reaction of high purity elemental copper, indium, aluminum and selenium in their stoichiometric proportion. Structural and compositional characterizations of pulverized material confirm the formation of a single phase, polycrystalline nature. CuInAlSe₂ (CIAS) thin films are deposited on organically cleaned soda lime glass substrates using flash evaporation technique by varying the substrate temperatures in the range from 423 K to 573 K. Influence of substrate temperature observed by X-ray diffraction (XRD), scanning electron microscope (SEM), optical and electrical measurement. CIAS Films grown at different substrate temperatures are polycrystalline in nature, exhibiting a chalcopyrite structure with lattice parameters a = ∼0.576 nm and c = ∼1.151 nm. The crystallinity in the films increases with increasing substrate temperature up to 473 K, and tend to degrade at higher substrate temperatures. Optical band gap is in the range of 1.20 eV–1.38 eV and the absorption coefficient is close to 10⁵ cm⁻¹. Electrical characterization reveals p-type conductivity and the structural, morphological and optical properties indicate potential use of CIAS thin films as an absorber layer for thin film solar cell applications.     

Growth of C60 single crystal films on metal substrates

High-quality C₆₀(111) single crystal films have been grown on Ni₃Fe(111), Ni₃Co(111) and Ni₃Fe(110) surfaces using hot-wall diffusion method. X-ray diffraction results show that well-ordered films can be obtained near 150°C on these substrates. The high quality of the films could be attributed to the perfect lattice match between C₆₀ film and substrates, low growth rate of C₆₀, and the suitable substrate temperature.     

Process and characterisation of chemical bath deposited manganese sulphide (MnS) thin films

Manganese sulphide (MnS) thin films have been deposited by a simple and inexpensive chemical bath deposition (CBD) method using thioacetamide as a sulphide ion source from an aqueous medium. The effect of preparative parameters on the film growth and quality has been studied. The MnS films have been characterised by XRD, TEM, SEM, EDAX, RBS, optical absorption and (time resolved microwave conductivity) TRMC techniques for their structural, compositional, and optical properties. The as-deposited MnS film on glass substrate consists of nanocrystalline grains. The film consists of mixed (cubic and hexagonal) phases. The optical band gap of the film is estimated to be 3.02 eV.     

Excimer laser deposition and characteristics of tin oxide thin films

ArF excimer laser assisted chemical vapor deposition of tin oxide thin films on Si was obtained using SnCl₄ and O₂ as precursors. Experimental measurements revealed that the deposition rate increases with incident laser energy density. The composition, structure and ultraviolet-to-visible spectra of the thin films were investigated by means of XPS, SEM, XRD and a UV–Vis techniques. It was shown that SnO₂ and SnOCl₂ coexisted in the thin films, and SnOCl₂ was almost completely converted into SnO₂ after annealing. The SnO₂ thin films deposited at room temperature were amorphous in structure and the grain size of the films became larger after annealing. The transmittance of the SnO₂ thin films is above 90%, the absorption edge is 355 nm and the energy gap is 3.49 eV.     

Orientation of B-C-N hybrid films deposited on Ni (111) and polycrystalline Ti substrates explored by X-ray absorption spectroscopy

Orientation of sp²-bonded boron carbonitride (BCN) hybrid films has been investigated. The films were synthesized on Ni (111) and polycrystalline Ti substrates by radio frequency plasma enhanced chemical vapor deposition using tris-dimethylamino borane as a single-source molecular precursor. The deposition was performed at the radiofrequency power 400-800 W at the working pressure 2.6 Pa. Formation of sp²-BCN hybrids in the samples was confirmed by X-ray diffraction (XRD). In the XRD profile, the peak at 26.3° revealed formation of crystalline phase in the samples in which the lattice planes are separated from each other by around 3.5 Å. The D band at ~ 1350 cm^− 1 and the G band at ~ 1570 cm^− 1 in Raman spectra also suggested presence of graphite-like sp²-B-C-N hybrid bonds. The films were composed of different B-N, B-C, and C-N bonds to form sp²-BCN atomic hybrids confirmed by X-ray photoelectron spectra. Orientation and local structures of the films were studied by near-edge X-ray absorption fine structure (NEXAFS) measurements. The dominant presence of π* and σ* resonance peaks of the sp² hybrid orbitals in B K-edge NEXAFS spectra revealed preferred formation of sp²-BCN atomic hybrids around B atoms like-BN₃ configuration in respect to the plane of Ni (111) substrate. Different orientations were suggested on the basis of polarization dependence of B K-edge and N K-edge of the NEXAFS spectra.     

Preparation and character of textured ZnO:Al thin films deposited on flexible substrates by RF magnetron sputtering

ZnO:Al thin films deposited on transparent TPT substrates by magnetron sputtering were etched in acetic acid solution. The effects of etching solution concentration and etching time on the structure and properties of ZnO:Al films were investigated. The obtained films had a hexagonal structure and a highly preferred orientation with the c-axis perpendicular to the substrate. The ZAO film etched in 1% acetic acid solution for 10 s had a pyramidal structure and an enhanced light scattering ability, the average transmittance and reflectance in the visible region were 72% and 26% respectively, the sheet resistance was 260 Ω/□. Both transmittance and reflectance of the films decreased as the etching solution concentration and etching time increasing. Etching had a negative effect on the conductive properties of ZAO films. The lowest sheet resistance was 120 Ω/□ for the ZAO film without etching.     

Pulsed laser deposition of NiTi shape memory alloy thin films with optimum parameters

A series of experiments was carried out to optimize the pulsed laser deposition parameters for the fabrication of high quality NiTi shape memory alloy thin films. Smooth NiTi shape memory alloy thin films were deposited at high growth rate with optimum deposition parameters based on the analysis of the relationships among the morphology of the target surface and the deposited thin film, the laser energy, the target–substrate distance, the thin film composition and its growth rate. Crystal structures and phase transformation temperatures of the annealed Ni_49.7Ti_50.3 thin film were characterized by using X-ray diffraction and differential scanning calorimetry, respectively. The martensitic transformation temperature of the crystallized Ni_49.7Ti_50.3 thin film is found to be lower than room temperature and 27°C lower than that of the NiTi target material. These results are attributed to the refined grain size of the thin film and its composition, which deviates slightly from Ni₅₀Ti₅₀.     

Polishing of polycrystalline diamond by hot nickel surface

A microwave plasma technique has been employed to deposit polycrystalline diamond film over a molybdenum substrate button using a gas mixture of hydrogen and methane at a substrate temperature of 851°C. A CVD diamond coated molybdenum substrate button was mounted with a load against hot nickel plate and rotated for 3.45 h in a hydrogen ambient. Hot tungsten filament was used as a heat source to maintain the temperature of the nickel block and CVD diamond coated molybdenum button at 848°C. This experiment has reproducibly shown the successful polishing of polycrystalline CVD diamond by hot nickel. A Tencor profilometer and scanning electron microscope have been used to evaluate the surface smoothness and morphology before and after polishing the polycrystalline diamond thin films.