Structural and mechanical characterization of BCxNy thin films deposited by pulsed reactive magnetron sputtering

BC_xN_y thin films deposited at 250 °C by pulsed reactive magnetron sputtering of a B₄C target in an Ar/N₂ plasma were studied by elastic recoil detection analysis, Fourier transform infrared, Raman, and photoelectron spectroscopy, electron microscopy, and nanoindentation. In the concentration range of 6% to 100% N₂ in the sputter plasma the segregation into nanocrystalline hexagonal boron nitride and amorphous sp² carbon is the dominant process during the film growth. The stoichiometric ratio and structural details of the major phases depend on the N₂ concentration in the plasma and have significant influence on the Young′s modulus and the elastic recovery of the BC_xN_y thin films.     

Effect of sputtering power on the properties of Cd1 − xZnxTe films deposited by radio frequency magnetron sputtering

Cd_1 − xZn_xTe films were prepared by radio frequency (r.f.) magnetron sputtering from Cd_0.9Zn_0.1Te slices target with different sputtering power (60-120 W). The effects of sputtering power on the properties of Cd_1 − xZn_xTe films were studied using X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscopy (AFM), ultraviolet spectrophotometer and Hall effect measurements. The composition of the deposited films was determined by EDX. The Cd content was found always to be higher than the Te content, regardless of sputtering power. This behavior may be explained by the preferential sputtering of cadmium atoms in the target. XRD studies suggest that ZnTe secondary phases were coexisted in Cd_1 − xZn_xTe films. The origin of the secondary phase is ascribed to the lowest sticking coefficient of Zn atom. AFM micrographs show that the grain size increases with the sputtering power. The optical transmission data indicate that shallow absorption edge occurs in the range of 750-850 nm, and the sputtering power does not have a clear effect on the optical absorption coefficient. In Hall Effect measurements, the sheet resistivities of the deposited films are 1.988 × 10⁸, 8.134 × 10⁷, 8.088 × 10⁷ and 3.069 × 10⁷ Ω/sq, respectively, which increase with the increasing of sputtering power.     

Fabrication of YbAl3 film via annealing amorphous Yb-Al film deposited by RF magnetron sputtering

YbAl₃ single-phase bulk alloy was synthesized by melting at 1258 K using raw Yb and Al metals in the ratio of 1:2.2. A sputtering YbAl₃ target was prepared using the precursor YbAl₃ bulk alloy with the spark plasma sintering process. An amorphous Yb-Al film was fabricated by RF magnetron sputtering using the YbAl₃ target, and a single-phase crystalline YbAl₃ film was fabricated by annealing the amorphous Yb-Al film at temperatures higher than 923 K in Ar atmosphere.     

Ambient temperature stabilization of crystalline zirconia thin films deposited by direct current magnetron sputtering

Nanocrystalline zirconia thin films have been deposited on borosilicate glass substrates at ambient temperature by direct current (dc) magnetron sputtering. The present study demonstrates the possibility of growing zirconium oxide films in 100% pure oxygen dc plasma. Films of thickness of the order of 500 nm have been grown using a metallic Zr target in pure oxygen plasma. Interestingly, the presence of high temperature polymorphs of ZrO₂ is observed in films deposited with 40, 60 and 80% oxygen in the sputtering gas, while only the monoclinic phase is observed at lower and higher oxygen percentages. The refractive index in this range of oxygen percentages peaks at 1.85 in the dispersion free region. The crystallite size in the films varies between 11-25 nm, as calculated from X-ray diffraction patterns and is dependent on oxygen percentage in the sputtering gas. The grain sizes observed in atomic force microscope images are in the range 38 to 45 nm. The dielectric constants of the films, measured at microwave frequencies [8-12 GHz] ranged between 13-19.2.     

Tungsten-doped ZnO transparent conducting films deposited by direct current magnetron sputtering

Highly conducting and transparent thin films of tungsten-doped ZnO (ZnO:W) were prepared on glass substrates by direct current (DC) magnetron sputtering at low temperature. The effect of film thickness on the structural, electrical and optical properties of ZnO:W films was investigated. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The electrical resistivity first decreases with film thickness, and then increases with further increase in film thickness. The lowest resistivity achieved was 6.97 × 10⁻⁴ Ω cm for a thickness of 332 nm with a Hall mobility of 6.7 cm² V⁻¹ s⁻¹ and a carrier concentration of 1.35 × 10²¹ cm⁻³. However, the average transmittance of the films does not change much with an increase in film thickness, and all the deposited films show a high transmittance of approximately 90% in the visible range.     

Mechanical and deformation behaviour of titanium diboride thin films deposited by magnetron sputtering

Nanoindentation studies have been carried out for TiB₂ films deposited on Si, glass and steel by sputtering for studying the influence of the substrates. It was observed that the modulus of the film was influenced by the substrates from 30 nm onwards. Plastic energy analysis has shown that as load increases more energy is absorbed by the substrate. Quantitative indentation depth limits for obtaining film only hardness, using a combination of log-log plot of load vs displacement and load vs (displacement)² functions, have shown the dependence on the threshold load for crack formation. Comparison of the hardness data with composite hardness models has been performed. Fracture toughness of the coatings was also evaluated using two methods which resulted in comparable results.     

Photo-fixation of SO2 in nanocrystalline TiO2 films prepared by reactive DC magnetron sputtering

We report on photo-fixation of SO₂ onto nanostructured TiO₂ thin films prepared by reactive DC magnetron sputtering. The films were exposed to 50 ppm SO₂ gas mixed in synthetic air and illuminated with UV light at 298 and 473 K. The evolution of the adsorbed SO_x species was monitored by in situ Fourier transform infrared specular reflection spectroscopy. Significant photo-fixation occurred only in the presence of UV illumination. The SO₂ uptake was dramatically enhanced at elevated temperatures and then produced strongly bonded surface-coordinated SO_x complexes. The total SO_x uptake is consistent with Langmuir adsorption kinetics. The sulfur doping at saturation was estimated from X-ray photoelectron spectroscopy to be ~ 2.2 at.% at 473 K. These films were pale yellowish and had an optical absorption coefficient being ~ 3 times higher than in undoped film. The S-doped films exhibit interesting oleophobic properties, exemplified by the poor adherence of stearic acid. Our results suggest a new method for sulfur doping of TiO₂ to achieve combined anti-grease and photocatalytic properties.     

Structural,electrical and photoluminescence properties of ZnO:Al network films grown on nanochannel Al2O3 substrates by direct current magnetron sputtering with an oblique target

ZnO:Al network films were grown on nanochannel Al₂O₃ substrates at 300 K by direct current magnetron sputtering with an oblique target. The film thicknesses are 60 nm, 160 nm and 190 nm. The holes of the network films diminish with increasing film thickness. For the 60-nm thick film, the network is formed by connecting grains. For the 160-nm and 190-nm thick films, however, the network is formed by connecting granules. The granules consist of many small grains. All the network films have a wurtzite structure. The 60-nm and 160-nm thick network films mainly have a [1 0 1] orientation in the film growth direction while the 190-nm thick network film grows with a random crystallographic orientation. A temperature dependence of the resistance within 160–300 K reveals that the network films exhibit a semiconducting behavior and their carrier transport mechanism is thermally activated band conduction. Room temperature photoluminescence spectra for wavelengths between 300 nm and 700 nm reveal a violet emission centered at 405 nm for the 60-nm thick network film and a blue emission centered at 470 nm for both the 160-nm and the 190-nm thick network films. Annealing decreases the resistivity of the network film.     

Properties of Al heavy-doped ZnO thin films by RF magnetron sputtering

Al-doped ZnO films were deposited by RF magnetron sputtering. From the X-ray diffraction and scanning electron spectrometer studies, wurtzite structure with (0 0 2) orientation ZnO thin films were obtained at Al concentration below 15 atomic percent (at.%). As the Al concentration above 15 at.%, the thin films did not fully crystallize. Two new emission peaks occurred at 351 nm and 313 nm when the Al doping above 15 at.% from the photoluminescence spectrum, and the peaks shift towards the shorter wavelengths with increasing the Al concentration. X-ray photonic spectra of O 1s conformed the amount of oxygen captured by Al³⁺ increasing as the Al³⁺ concentration increasing due to the dominant Al³⁺ possess high charge in competition with Zn²⁺ in the matrix of ZnO.     

Scaling behavior and structure transition of ZrO2 films deposited by RF magnetron sputtering

ZrO₂ thin films were deposited onto Si wafers and glass slides by reactive rf magnetron sputtering with varying conditions of substrate temperature (T_s). Structural analysis was carried out using high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The scaling behavior of the AFM topographical profiles was analyzed using one-dimensional power spectral density method (1DPSD). Morphological and structural evolution of ZrO₂ films have been studied in relation to T_s. With substrate temperatures ranging from RT to 550 °C, the structural transition of the films is a-ZrO₂ (below 250 °C) → m-ZrO₂ with a little a-ZrO₂ (450 °C) → m-ZrO₂ with a little t-ZrO₂ (550 °C). The roughness exponent α is 1.53 ± 0.02, 1.04 ± 0.01, 1.06 ± 0.05, 1.20 ± 0.03 for ZrO₂ thin films deposited at RT, 250 °C, 450 °C, and 550 °C, respectively. Quantitative surface characterization by spatially resolved 1DPSD analyses identified three different growth mechanisms of surface morphology for ZrO₂ thin films deposited at RT, 250∼450 °C and 550 °C. The evolution and interactions of surface roughness and microstructure are discussed in terms of surface diffusion, grain growth, and flux shadowing mechanisms.     

Cu2O thin films deposited by reactive direct current magnetron sputtering

The Cu₂O thin films were prepared on quartz substrate by reactive direct current magnetron sputtering. The influences of oxygen partial pressure and gas flow rate on the structures and properties of deposited films were investigated. Varying oxygen partial pressure leads to the synthesis of Cu₂O, Cu₄O₃ and CuO with different microstructures. At a constant oxygen partial pressure of 6.6 × 10^− 2 Pa, the single Cu₂O films can be obtained when the gas flow rate is below 80 sccm. The as-deposited Cu₂O thin films have a very high absorption in the visible region resulting in the visible-light induced photocatalytic activity.     

Structure and optical properties of nanocrystalline BiFeO3 films prepared by chemical solution deposition

Bismuth ferric oxide (BiFeO₃) films grown on quartz substrate were prepared by a simple chemical solution deposition. Phase constitution characterization of the films were obtained by X-ray diffraction, surface morphology and transmittance of the films were studied by atomic force microscopy and ultraviolet-visible-infrared light spectrophotometer. The optical constants (refractive index n, extinction coefficient k) were calculated by straightforward method proposed by Swanepoel [Swanepoel R, J. Phys., E J. Sci. Instrum. 1983; 16: 1214-1222. [1]]. The influence of the processing parameters on microstructure and optical properties, especially band gap, were studied.     

Nanocrystalline SnO2 and Au:SnO2 thin films prepared by direct current magnetron reactive sputtering

Nanocrystalline pure and gold doped SnO₂(Au:SnO₂) films were prepared on unheated glass substrates by dc magnetron reactive sputtering and, subsequently, the as deposited films were annealed in air. The films structure, surface morphology, photoluminescence, electrical and optical properties were investigated. After annealing the as deposited SnO₂ films, crystallinity increased and the surface roughness decreased. The intensity of PL peaks increases sharply with the annealing temperature. The optical transmittance of the films was around 89% after annealing the as deposited SnO₂ films at 450 °C. The as deposited Au:SnO₂ films show better crystallinity than the as deposited SnO₂ films, the average grain size was around 4.4 nm. The emission peaks of Au:SnO₂ films are slightly blue shifted as compare to undoped SnO₂ films. The Au:SnO₂ films show the lowest electrical resistivity of 0.001 Ωcm with optical transmittance of 76%, after annealing at 450 °C.     

Structure and properties of ternary manganese nitride Mn3CuNy thin films fabricated by facing target magnetron sputtering

Deposition of Mn₃CuN_y thin films on single crystal Si (1 0 0) at various substrate temperatures (T_sub) by facing target magnetron sputtering is reported. The crystal structure and composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results confirmed that the crystalline antiperovskite Mn₃CuN_y thin film with (2 0 0) highly preferred texture had been obtained at T_sub = 180 °C. Furthermore, for the resulting Mn₃CuN_y thin film, it showed different properties compared with the bulk counterpart. There was a paramagnetic to ferrimagnetic transition at 225 K with decreasing temperature. The change of the lattice constant with temperature presented positive thermal expansion behavior and no structural transition was observed. The average linear thermal expansion coefficient (α) is 2.49 × 10⁻⁵ K⁻¹ from 123 K to 298 K. More interestingly, the temperature dependence of resistivity displayed a semiconductor-like behavior, i.e. an obvious monotonous decrease of resistivity with increasing temperature.     

磁控反应溅射制备的Ta2O5薄膜的光学与介电性能

采用直流磁控反应溅射技术，在不同的Ar/O2比条件下制备了系列Ta2O5薄膜样品，采用紫外．可见光透射光谱和椭偏光谱测试分析技术，研究了Ta2O5薄膜在可见光范围内的透射率、折射率和消光系数；同时还采用HP 4192A阻抗分析仪测试分析了样品在500Hz～13MHz频段的介电谱，结果表明在300～700nm的可见光波长范围内，氧化钽薄膜的消光系数k→0，折射率＞2．0，透射率大约80％。500Hz下的低频介电常数5的典型值为20.1。损耗角正切tgδ为19.9。     

Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering

Effects of deposition parameters on tantalum films deposited by direct current magnetron sputtering were studied. The results indicated that the electrical properties were relative to the oxygen and other impurities rather than to growth orientation. As the sputtering power increases from 25 to 100 W, the preferred-growth orientation of Ta films changes from (200) to (202) and the oxygen and impurities content in the films decrease. The temperature coefficient of resistance also reduces from −289.79 to −116.65 ppm/°C. The O/Ta ratio decrease and grain size reduction related to a change of electrical resistivity were observed at substrate temperatures in the range 300-500 °C. At 650 °C, partial stable α-Ta associated with a sharp decrease of the electrical resistivity was also found.     

Influence of annealing temperature on the properties of ZnO:Zr films deposited by direct current magnetron sputtering

Transparent conducting zirconium-doped zinc oxide (ZnO:Zr) films were deposited on quartz substrates by direct current (DC) magnetron sputtering at room temperature. The influence of post-annealing temperature on the structural, morphological, electrical and optical properties of ZnO:Zr films were investigated. When annealing temperature increases from room temperature to 573 K, the resistivity decreases obviously due to an improvement of the crystallinity. However, with further increase in annealing temperature, the crystallinity deteriorates leading to an increase in resistivity. The films annealed at the optimum annealing temperature of 573 K in vacuum have the lowest resistivity of 9.8 × 10⁻⁴ Ω cm and a high transmittance of above 92% in the visible range.     

Structure and mechanical properties of ZrO2 films deposited by gas flow sputtering

ZrO₂ films were deposited by reactive gas flow sputtering (GFS) where voltage is applied to a cyindrical hollow-cathode target from a DC source, the discharge being produced at relatively high sputtering pressure. In this system, secondary electrons form a major component of the total current flow and lead to heating of the substrate which in turn has an effect on the properties of deposited films. The present experiments were carried out under the following conditions: Ar gas flow rate of 200 sccm, O₂ flow rate FO₂ in the range between 0.003 and 1 sccm, and sputtering power (P_S) in the range of 50-800 W. The reults showed that the crystal structure of the films deposited for P_S below 200 W was monoclinic but for P_S above 400 W, the films included tetragonal cystals of stable structure formed at high temperature by the electron bombardment. The films were formed with grains of 20-100 nm in diameter in a porous structure. The mechanical properties of the films were determined by a nanoindentation technique. Martens hardness (H_M) of the porous films was found to be in the range between 220 and 330 MPa which is substantially less than that of films typically deposited by rf magnetron sputtering.     

High dielectric tunability of Ba0.6Sr0.4TiO3 thin film deposited by radio-frequency magnetron sputtering

In microwave tunable devices, one of the major challenges encountered is the simultaneous minimization of the material's dielectric loss and maximization of dielectric tunability. In this work, Ba_0.6Sr_0.4TiO₃ thin film with the thickness of 300 nm was deposited on Pt/SiO₂/Si substrates using radio-frequency magnetron sputtering technique, and its dielectric properties were investigated. Due to the high temperature annealing process at substrate temperature of 600 °C, well-crystallized Ba_0.6Sr_0.4TiO₃ film was deposited. The dielectric constant and dielectric loss of the film at 100 kHz are 300 and 0.033, respectively. Due to the good crystallinity of the Ba_0.6Sr_0.4TiO₃ films deposited by radio-frequency magnetron sputtering, high dielectric tunability up to 38.3% is achieved at a low voltage of 4.5 V.     

Self-buffered BaxSr1−xTiO3 films by sol-gel and RF magnetron sputtering method

Ba_xSr_1−xTiO₃ (BST) films are fabricated by sol-gel and RF (radio frequency) magnetron sputtering method. A buffer layer with columnar grains by sol-gel method is introduced to improve the dielectric anomaly in BST films. We find that the presence of buffer layer can increase the differential dielectric constant against temperature in sol-gel derived BST films while not so with sputtered films. We explain this by an ‘expanded layer thickness model’ and an unstable crystallized surface, respectively. The obtained (dε/ε) dT is up to 6% around 11 °C by the sol-gel method.