Structural and optical properties of tellurium films obtained by chemical vapor deposition（CVD）

1 Introduction Te thin films have been extensively used in various technological areas, especially in microelectronic devices such as gas sensor [1?3], optical information storage [4] and other applications [5?7]. All these applications are due to remark…     

Synthesis and structural characterization of undoped and Co doped zinc oxide thin films obtained by aerosol assisted chemical vapour deposition

Dilute magnetic oxides are transparent, wide-bandgap materials that behave ferromagnetically when doped with a few percent of a magnetic 3d cation. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material, that is a prerequisite for successful fabrication of useful devices for the emerging technologies of spintronics. Here we report a study of growth characteristics and microstructural properties of undoped and Co doped ZnO films grown onto borosilicate glass substrates, using aerosol assisted chemical vapour deposition method. The obtained films are single phase, of Wurtzite type, some of them with a strong c-axis orientation, i.e. with the c-axis normal to the substrate surface.     

Ion-assisted vapor deposition of acryl polymer thin films

Polymer thin films were prepared by an ion-assisted vapor deposition polymerization method that involves physical vapor deposition of monomer combined with low-energy ion irradiation. In a high vacuum environment, zinc diacrylate monomer was evaporated at a rate of 0.8 nm/min on gold-coated glass substrates under simultaneous irradiation by nitrogen ions of 20 nA/cm² at ion energy ranging from 500 to 2000 eV. The ion irradiation remarkably reduced the surface roughness of the deposited films. Infrared spectroscopy showed that the absorption bands of the vinyl group diminish with increasing ion energy. Formation of polymer molecules was confirmed by gel permeation chromatograph. Moreover, the film became insoluble to organic solvents when the ion energy was increased. These results indicate that polymer thin films can be prepared by vapor deposition of monomers under ion irradiation. The ion-assisted vapor deposition polymerization was also possible on insulating substrates.     

Nanocrystalline p-type-cuprous oxide thin films by room temperature chemical bath deposition method

Nanocrystalline cuprous oxide (Cu₂O) thin films were synthesized on amorphous glass substrate by using simple room temperature chemical route namely, chemical bath deposition (CBD) method. The deposition kinetics played important role to get good quality nanocrystalline films with uniform thickness. The structural, surface morphological, optical and electrical properties of the films were investigated. Crystallization and growth processes obtained micro-spherical shaped grains of Cu₂O due to agglomeration of smaller nanoparticles. An optical and electrical characterization was performed to study the optical band gap and type of electrical conductivity of the film.     

Novel low temperature atmospheric pressure plasma jet systems for silicon dioxide and poly-ethylene thin film deposition

In this study, both low-density plasma quartz tube (QT) and high-density plasma metallic tube (MT) jet-electrodes with pulsed-type alternating-voltage (AC) generator were used to investigate the influences of the process parameters and electrode types on the microstructures and the corrosion behaviors of silicon dioxide (SiO₂) or poly-ethylene (PE, (CH₂CH₂)n) thin films. Tetraethoxysilane (TEOS) and ethylene (C₂H₄) were used as precursors for SiO₂ and PE thin film deposition. The TEOS precursor was vaporized by an ultrasonic oscillator and introduced into the AP plasma systems by argon (Ar) carrier gas. The main plasma working gas was Ar gas mixed with or without oxygen gas. The pulsed-type AC generator, with a frequency of 30 kHz, a voltage of 10 kV and a wattage of 300 W, was used to deposit SiO₂ and PE thin films on the silicon and AISI 1005 low carbon steel substrates at the room temperature, respectively. The high-density plasma MT jet-electrode with an Ar gas flow rate of 6 slm, a precursor flow rate of 40 sccm and an oxygen flow rate of 40 sccm revealed optimal plasma dissociation and chemical reaction efficiencies to synthesize effective atomic stoichiometry of SiO₂ (in-organic films) thin films. However, the low-density plasma QT jet-electrode with an Ar gas flow rate of 6 slm and an ethylene flow rate of 15 sccm appeared optimal plasma-induced polymerization efficiency to exhibit reasonable atomic stoichiometry of PE (organic films) thin films. Moreover, the optimal SiO₂ thin films deposited by MT jet-electrode possessed better corrosion resistant integrity than the optimal PE thin films synthesized by QT jet-electrode. It was also found that SiO₂ and PE thin films synthesized by the AP plasma method possess effective corrosion barrier characteristics like other deposition techniques.     

Characterization of cobalt oxide thin films prepared by a facile spray pyrolysis technique using perfume atomizer

Cobalt oxide (Co₃O₄) thin films were prepared by a facile spray pyrolysis technique using perfume atomizer from aqueous solution of hydrated cobalt chloride salt (CoCl₂·6H₂O) as source of cobalt. The films were deposited onto the amorphous glass substrates kept at different temperatures (300-500 °C). The influences of molar concentration of the starting solution and substrate temperature on the structural, morphological and optical properties of (Co₃O₄) thin films were studied. It was found from X-ray diffraction (XRD) analysis that the films prepared with molar concentration greater than 0.025 M/L were polycrystalline spinel type cubic structure. The preferred orientation of the crystallites of these films changes gradually from (6 2 2) to (1 1 1) when the substrate temperature increases. By Raman spectroscopy, five Raman active modes characteristic of Co₃O₄ spinel type cubic structure were found and identified at 194, 484, 522, 620 and 691 cm⁻¹. The scanning electron microscopy (SEM) images showed micro porous structure with very fine grains less than 50 nm in diameter. These films exhibited also a transmittance value of about 70% in the visible and infra red range.     

Physical properties of tin oxide thin films improved by vapour chopping

The vapour chopping technique has been successfully used to lower the ambient air ageing effect on the tin oxide thin films. The films were prepared by thermal oxidation (in air) of vacuum evaporated vapour chopped and nonchopped tin thin films. The films showed SnO and SnO₂ phases with tetragonal and orthorhombic structure. All the films showed increase in optical transmittance with increase in oxidation temperature and duration. The vapour chopped films showed higher refractive index and band gap than those of nonchopped films. The refractive index was found to increase with the thickness. Due to air ageing, the refractive index of both the films was found to increase. The ageing effect was found lower on the vapour chopped (0.008) than those on nonchopped (0.02) tin oxide thin films. These films can have potential use in optical waveguides.     

Deposition of SDC and NiO-SDC thin films and their surface morphology control by electrostatic spray deposition

The deposition of samaria-doped ceria (SDC, Sm_0.2Ce_0.8O_x) and NiO-SDC thin films on a SDC substrate was studied using the electrostatic spray deposition (ESD) technique. The precursor solution was prepared by dissolving the correct amount of Sm(NO₃)₃·6H₂O, Ce(NO₃)₃·6H₂O and Ni(NO₃)₂·6H₂O into a mixture of ethanol (C₂H₅OH) and butyl carbitol (C₄H₉OC₂H₄OC₂H₄OH). The surface microstructure of as-deposited thin films was strongly influenced by the substrate temperature, solvent composition and precursor solution. The reticular film of SDC with high porosity could be successfully prepared at the deposition temperature ranging from 300 to 350 °C, a precursor solution of 0.005 mol/dm³ and a 50 vol.% of butyl carbital. The correlations between the surface morphology of as-deposited thin films and the physical properties of precursor solution could be approximately explained by the following equation [21]:

where d is the size of sprayed droplet, Q the flow rate of liquid pushed through the jet, the dielectric constant of liquid, ₀ the electrical permittivity of vacuum, and G() is the function of .The as-deposited thin films were amorphous at the used deposition temperature (350 °C). Subsequently, the thermal treatments were done for ranging from 700 to 900 °C in air. As the result, the crystal structure transformed into the desired cubic fluorite one after the sample was annealed over 700 °C in the as-deposited SDC thin films and 900 °C in the as-deposited NiO-SDC thin films, respectively. To confirm the composition of the as-sintered SDC thin films, ICP-OES analysis was studied for the films annealed at 900 °C in air for 2 h. The observed chemical composition was found to be close to that of the precursor solution within experimental errors.     

Approaching the limits of dielectric breakdown for SiO2 films deposited by plasma-enhanced atomic layer deposition

This study explores the ultimate limit in dielectric breakdown of SiO₂ thin films deposited by gas-phase, plasma-enhanced atomic layer deposition. Thickness-dependent breakdown behaviors similar to conventional, thermally grown SiO₂ thin films were observed for the first time on ALD films, where the dominant breakdown mechanisms were impact ionization, trap creation and anode hole injection, respectively. By suppressing these mechanisms, we show a reversible degradation in SiO₂ after the onset of Fowler–Nordheim tunneling before permanent dielectric damage occurs. The reversible window was only observable in films thinner than 10 nm. The SiO₂ thin films ultimately reached irreversible breakdown at a field strength of 2.7 V nm^?1, where Si–O bonds were destroyed due to impact ionization and accelerated electrons.     

脉冲激光沉积及硒化法制备Cu(In,Ga)Se2薄膜研究

采用脉冲激光沉积和硒化后热处理的方法在石英衬底上制备Cu(In,Ga)Se2（简写为CIGS）薄膜,研究脉冲激光沉积（PLD）技术在制备CIGS薄膜太阳能电池材料上的应用,分析了不同预制层沉积顺序及厚度对CIGS薄膜组织结构、表面形貌、成分以及光学性能的影响。实验结果表明：(1)利用PLD技术及后硒化处理的工艺,制得的CIGS太阳能电池吸收层具有纯相和高结晶度等特性;(2)CuGa/In金属预制层的叠层顺序和叠层数、硒化退火温度对薄膜的结晶质量、晶粒尺寸、成分都具有重要的影响,其中叠层顺序影响最为明显;(3)样品均表现出对可见光区具有透射率低和吸收系数高的光学特性。本工作为制备性能优良的CIGS太阳能电池吸收层,提供了一个新颖的工艺手段。     

Room-temperature high radio-frequency source power effects on silicon nitride films deposited by using a plasma-enhanced chemical vapor deposition

Silicon nitride films were deposited at room temperature using a plasma-enhanced chemical vapor deposition system. In this study, the effects of radio frequency (RF) source power ranging from 200 W to 800 W on the deposition rate, the refractive index, and the surface roughness were examined. The surface roughness measured by atomic force microscopy is detailed in terms of the typical mean surface roughness, major pixel density, and non-uniformity (NU) of the pixel density. Ion energy distribution (IED) collected with an ion energy analyzer was correlated to the film characteristics. The deposition rate increased as the RF source power decreased. Interestingly, the variation of the deposition rate was strongly correlated to an energy difference in IED. A decrease in the refractive index in the power range of 400 W to 800 W was attributed mainly to an increased N content. An analysis of the major pixel density clarified the formation of denser films at lower powers. This was further supported by the NU variation. The NU variation contrasted with the variation of the energy difference. In consequence, higher deposition rates and denser films at lower powers could be achieved.     

Deposition of nanocomposite thin films by a hybrid cathodic arc and chemical vapour technique

A hybrid technique is described for the synthesis of nanocomposite Ti-Si-N thin films based on the reactive deposition of Ti produced from a cathodic arc source and silicon from a liquid tetramethylsilane (TMS), precursor. The influence of the TMS flow rate on the structure and mechanical properties has been investigated. The film structure was found to comprise TiN crystallites and amorphous Si₃N₄. The X-ray diffraction data showed that with increasing TMS flow there is a decrease in the TiN crystalline size from 33 nm to 4 nm. The hardness of the films was found to be strongly dependent on the Si content and reached a maximum value of 41 GPa at ∼ 5% Si content at a total pressure of nitrogen and TMS of 0.8 Pa. Hardness enhancement was found to arise from the nanostructural change induced due to the addition of an amorphous Si₃N₄ phase into the film. Transmission electron microscopy (TEM) analysis confirmed the structure of the Ti-Si-N composites.     

氮气对DC-PCVD法制备金刚石薄膜影响的研究

采用直流热阴极等离子体化学气相沉积方法,用甲烷、氢气、氮气的混合气体在Mo基底上成功制备了金刚石薄膜.分别采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、拉曼光谱仪(Raman)对不同流量氮气氛下生长金刚石薄膜的形貌、取向、质量进行了表征.结果表明:适量氮气的加入,不仅可以促进金刚石薄膜的生长速率,还可以促进金刚...     

Characterization of CuInS2 thin films prepared by sulfurization of Cu-In precursor

CuInS2 thin films were prepared by sulfurization of Cu-In precursors. The influences of the deposition sequence of Cu and In layers, such as Cu/In, Cu/In/In, and In/Cu/In, on structure, topography, and optical properties of CuInS2 thin films were investigated. X-ray diffraction results show that the deposition sequence of Cu and In layers affects the crystalline quality of CuInS2 films. Atomic force microstructure images reveal that the grain size and surface roughness are related to the deposition sequence used. When the deposition sequence of precursor is In/Cu/In, the CuInS2 thin films show a single-phase chalcopyrite structure with （112） preferred orientation. The surface morphology of CIS films is uniform and compacted. The absorption coefficient is larger than 10^4 cm^-1 with optical band gap Egclose to 1.4 eV.     

Advanced methods for titanium (IV) oxide thin functional coatings

The paper reports on preparation of titanium (IV) oxide thin films by a series of chemical, physico-chemical and physical methods including the sol-gel process carried out in the environment of lyotropic liquid crystals, Barrier-torch Discharge deposition, Magnetron Sputtering and the Modulated Hollow Cathode Plasma Jet Sputtering. The produced layers have been thoroughly described by means of a series of characterization techniques including atomic force microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, Fourier transformed infrared spectroscopy, Raman spectroscopy, ellipsometry, profilometry and surface wettability. The films were then used as photoactive species in catalytic oxidation tests based on photoinduced decomposition of methylester of stearic acid.     

Influence of substrate pre-treatments on the growth of SixNyHz thin films by plasma enhanced chemical vapor deposition

A two-step plasma enhanced chemical vapor deposition procedure has been developed to produce high quality Si_xN_yH_z films for quantum cascade laser applications. The procedure consists in exposing the GaAs substrate to a controlled N₂ plasma previous to the silicon nitride film deposition. The pre-treatment causes the formation of a thin GaN film that passivates the GaAs wafer. The method has been optimized varying RF power, N₂ flow rate and process time of the pre-treatments and monitoring their effects on the resulting chemical composition and dielectric properties of the nitride overlayers, by means of infrared spectroscopy, X-ray photoelectron spectroscopy and electric characterizations. A narrow window in the pre-treatment RF power, N₂ flux and time values, improves the composition, structural and dielectric properties of the silicon nitride overlayers. The best result has been found depositing the silicon nitride films on GaAs wafer after 2 min of N₂ plasma treatment with a power of 20 W and a 50 cm³/min flow rate.     

Chemical deposition of CuInSe2 thin films by photoelectrochemical applications

Copper indium diselenide films have been synthesized by chemical bath deposition method. The configuration of fabricated cell is n-CuInSe₂|NaOH (1 M) + S (1 M) + Na₂S (1 M)|C_(graphite). The photoelectrochemical cell characterization of the films is carried out by studying current-voltage characteristics in dark, capacitance-voltage in dark, barrier height measurements, power output, photoresponse and spectral response. The study shows that CuInSe₂ thin films are n-type conductivity. The junction ideality factor is found to be 3.81. The flat band potential is found to be 0.763 V. The barrier height value is found to be 0.232 eV. The study of power output characteristic shows open circuit voltage, short circuit current, fill factor and efficiency are found to be 310 mV, 20 μA, 42.12% and 0.82%, respectively. Photoresponse shows lighted ideality factor which is 2.92. Spectral response shows the maximum current observed at 650 nm.     

Properties of multilayer gallium and aluminum doped ZnO(GZO/AZO) transparent thin films deposited by pulsed laser deposition process

Multilayer gallium and aluminum doped ZnO (GZO/AZO) films were fabricated by alternative deposition of Ga-doped zinc oxide(GZO) and Al-doped zinc oxide(AZO) thin film by using pulsed laser deposition(PLD) process. The electrical and optical properties of these GZO/AZO thin films were investigated and compared with those of GZO and AZO thin films. The GZO/AZO (1:1) thin film deposited at 400 °C shows the electrical resistivity of 4.18×10-4 Ω·cm, an electron concentration of 7.5×1020 /cm3, and carrier mobility of 25.4 cm2/(V·s). The optical transmittances of GZO/AZO thin films are over 85%. The optical band gap energy of GZO/AZO thin films linearly decreases with increasing the Al ratio.     

Enhanced piezoelectric properties of Ta substituted-(K0.5Na0.5)NbO3 films: A candidate for lead-free piezoelectric thin films

Piezoelectric (K_0.5Na_0.5)NbO₃ (KNN) and (K_0.5Na_0.5)(Nb_0.7Ta_0.3)O₃ (KNNT) thin films were prepared via chemical solution deposition. An analysis of X-ray diffraction revealed that Ta⁵⁺ diffuses into the KNN to form a single perovskite structure. Compared to KNN films, KNNT films exhibited a low leakage current density due to their fine-grain nonporous structures. The partial substitution of Ta⁵⁺ for the B-site ion Nb⁵⁺ in the KNNT films decreased the Curie temperature (T_C). This in turn led to the existence of a polymorphic phase transition near room temperature and further improvement in the piezoelectric properties. Lead-free KNNT films exhibited a well-saturated piezoelectric hysteresis loop with a effective piezoelectric coefficient (d_33,eff) value of 61 pm/V, comparable to that of PZT thin films.     

Electron beam deposition and characterization of thin film Ti-Ni for shape memory applications

Thin film of Ti-Ni alloy has a potential to perform the microactuation functions required in the microelectromechanical system (MEMS).It is essential, however, to have good uniformity in both chemical composition and thickness to realize its full potential as an active component of MEMS devices.Electron beam evaporation technique was employed in this study to fabricate the thin films of Ti-Ni alloy on different substrates.The targets used for the evaporation were first prepared by electron beam melting.The uniformity of composition and microstructure of the thin films were characterized by electron probe microanalysis (EPMA), Auger electron spectroscopy (AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM).The mechanical property of the thin films was evaluated by the nano-indentation test.The martensitic transformation temperature was measured by differential scanning calorimetry (DSC).It is confirmed that the chemical composition of deposited thin films is identical to that of the target materials.Furthermore, results from depth profiling of the chemical composition variation reveal that the electron beam evaporation process yields better compositional homogeneity than other conventional methods such as sputtering and thermal evaporation.Microstructural observation by TEM shows that nanometer size precipitates are preferentially distributed along the grain boundaries of a few micron size grains.The hardness and elastic modulus of thin films decreases with an increase in Ti contents.