Inductively coupled plasma assisted physical vapor deposition of titanium nitride coatings

Beneficial effects of increased low energy ion bombardment during physical vapor deposition of ceramic thin films and coatings have been amply documented recently. We have constructed a small laboratory scale high density inductively coupled plasma (ICP) assisted magnetron sputtering system. Such a system offers higher plasma densities as compared to conventional magnetron sputtering. We describe the synthesis of titanium nitride coatings at relatively low temperatures by ICP assisted reactive magnetron sputter deposition.     

Effects of silver substrates on the visible light photocatalytic activities of copper-doped titanium dioxide thin films

Novel copper-doped titanium dioxide (Cu-doped TiO₂) thin films on silver (Ag) substrates with different thicknesses were prepared by sol–gel and magnetron sputtering methods. The influences of the Ag substrate thickness on the morphology and performance of the films were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, UV–visible spectroscopy, and photocatalytic degradation testing with methylene blue aqueous solution under visible light irradiation. The results indicated that Ag substrates with an optimal thickness of 30 nm not only maintained the tiny nanocrystals but also greatly improved dispersion of the nanoparticles on the surface of the nanofilms. Furthermore, during the calcination process, part of the Ag atoms diffused from the substrates into the Cu–TiO₂ films and substituted for the Cu ions to form Ag–TiO₂. A proper Ag substrate thickness (30 nm) greatly improved the photocatalytic properties of TiO₂ with photocatalytic efficiency, reaching approximately 86% in 300 minutes under visible light irradiation. However, an excess of Ag substrate not only led to the Cu ion separating out in the form of CuO but also resulted in the agglomeration of TiO₂ particles on the surface, which were detrimental to photocatalytic activities.     

The effects of substrate bias,substrate temperature,and pulse frequency on the microstructures of chromium nitride coatings deposited by pulsed direct current reactive magnetron sputtering

Recently, great attention has been devoted to the pulsed direct current (DC) reactive magnetron sputtering technique, due to its ability to reduce arcing and target poisoning, and its capability of producing insulating thin films. In this study, chromium nitride (CrN) coatings were deposited by the bipolar symmetric pulsed DC magnetron reactive sputtering process at different pulse frequency, substrate bias voltage, and the substrate temperature. It was observed that the texture of CrN changed from (111) to (200) as substrate temperature increased to 300°C as deposited at 2 kHz without substrate bias. With increasing pulsing bias and pulse frequency of target, predominated (200) orientation of CrN film was shown due to the ion bombardment/channeling effect to preferentially sputter those unaligned planes. For the CrN coatings deposited with pulsed biasing, the grain size decreased with increasing pulse frequency and substrate bias, whereas the surface roughness showed a reverse trend. The deposition rate of the CrN films decreased with increasing pulse frequency. It was concluded that the pulse frequency, substrate bias, and substrate temperature played important role in the texture, microstructure, and surface roughness of the CrN coatings deposited by the pulsed DC magnetron sputtering process.     

Characterizations of high resistivity TiNxOy thin films for applications in thin film resistors

We report about developing high resistivity thin film resistors using titanium oxy-nitride. Titanium nitride films of different thicknesses ranging from 50 to 300 nm were deposited on SiO₂/Si substrates using the reactive magnetron sputtering method. After deposition, these films were annealed in the air ambient. The structural and electrical properties of the films were examined as a function of annealing temperature. The samples with various thicknesses show TiN(1 1 1) phase. The sheet resistance increases from 150 up to 420 Ω/□ when the film thickness decreases from 300 to 50 nm. Temperature coefficience of resistance (TCR) of the films significantly decreased with decreasing the film thickness. The TCR of 50-nm thick film is quite low, about 49 ppm/K.     

Effects of deposition pressure on the properties of transparent conductive ZnO:Ga films prepared by DC reactive magnetron sputtering

Gallium (Ga)-doped zinc oxide (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. Effects of deposition pressure on the structural, electrical and optical properties of ZnO:Ga films were investigated. X-ray diffraction (XRD) studies show that the films are highly oriented with their crystallographic c-axis perpendicular to the substrate almost independent of the deposition pressure. The morphology of the film is sensitive to the deposition pressure. The transmittance of the ZnO:Ga thin films is over 90% in the visible range and the lowest resistivity of ZnO:Ga films is 4.48×10⁻⁴ Ω cm.     

Effects of annealing temperature on the photoluminescence of RF sputtered Barium titanate thin films

BaTiO₃ thin films were deposited onto quartz substrates by an RF magnetron sputtering method. The films deposited at room temperature and annealed at 773–1173 K were characterized using X-ray diffraction (XRD)Scanning electron microscopy (SEM), UV–vis spectroscopy and Photoluminescence spectroscopy (PL). X-ray diffraction studies revealed that the film is amorphous in nature at 773 K and that the crystallinity increases with increase in annealing temperature. The average crystallite size of the films increased from 13–18 nm and the optical band gap decreased in the range of 4.33–3.43 eV, with increase in annealing temperature. The films exhibited good adherence to the substrates and the SEM images showed smooth surface morphology. Energy dispersive X-ray (EDX) analysis confirmed the presence of barium, titanium and oxygen in the film. The red-shifts of excitonic UV emission peaks were observed in all samples which can be attributed to the stress produced due to lattice distortions. The visible PL emission intensity showed appreciable enhancement with post-deposition annealing.     

Composition,structure and electrical properties of DC reactive magnetron sputtered Al2O3 thin films

Thin films of alumina (Al₂O₃) were deposited over Si 〈1 0 0〉 substrates at room temperature at an oxygen gas pressure of 0.03 Pa and sputtering power of 60 W using DC reactive magnetron sputtering. The composition of the as-deposited film was analyzed by X-ray photoelectron spectroscopy and the O/Al atomic ratio was found to be 1.72. The films were then annealed in vacuum to 350, 550 and 750 °C and X-ray diffraction results revealed that both as-deposited and post deposition annealed films were amorphous. The surface morphology and topography of the films was studied using scanning electron microscopy and atomic force microscopy, respectively. A progressive decrease in the root mean square (RMS) roughness of the films from 1.53 nm to 0.7 nm was observed with increase in the annealing temperature. Al–Al₂O₃–Al thin film capacitors were then fabricated on p-type Si 〈1 0 0〉 substrate to study the effect of temperature and frequency on the dielectric property of the films and the results are discussed.     

Thin stoichiometric silicon nitride prepared by r.f. reactive sputtering

Thin silicon nitride films were prepared on silicon wafers at deposition rates of 4 nm/min to 56 nm/min by r.f. reactive sputtering. Various mechanical, chemical and optical properties were investigated as a function of r.f. power, gas composition and temperature by means of AFM, RBS, XPS and an ellipsometer. Chemical stoichiometric films, with N-to-Si atomic ratio of 4:3 and refractive index of 2.0 were achieved even at room temperature. An interference filter for a UV detector with central wavelength of 254 nm was manufactured based on sputtered nitride, aluminum and silicon dioxide.     

氧分压对ZnO薄膜结构与光学性能的影响

采用直流磁控溅射法在不同氧分压下制备了ZnO薄膜.用原子力显微镜(AFM)、X射线衍射(XRD)仪、荧光分光光度计、紫外-可见分光光度计对样品进行检测.实验表明,氧分压对ZnO薄膜的结构与光学性能影响很大.在样品的光致发光谱中,均只发现了520 nm附近的绿色发光峰,该峰随着氧分压的增大而增强.不同氧分压制备的ZnO薄膜中,氧分压为0.25Pa的样品结晶性能最好,透过率最高.     

Preparation and characterization of transparent conducting ZnO:W films by DC magnetron sputtering

Tungsten-doped zinc oxide（ZnO:W） films with low resistivity and high transmittance were successfully deposited on glass substrates by direct current magnetron sputtering at low temperature.The deposition pressure is varied from 12 to 21 Pa.The X-ray diffraction results show that all of the deposited films are polycrystalline and have a hexagonal structure with a preferred c-axis orientation.The crystallinity,morphologies and resistivity of ZnO:W films greatly depend on deposition pressure while the optical properties including optical transmittance, optical band gap as well as refractive index are not sensitive to deposition pressure.The deposited films with an electrical resistivity as low as 1.5×10^-4Ω·cm,sheet resistance of 6.8Ω/□and an average transmittance of 91.3% in the visible range were obtained at a deposition pressure of 21 Pa and sputtering power of 130 W.     

反应溅射法制备氮化铝薄膜及工作气压对其场发射性能的影响

采用反应磁控溅射法在不同工作气压(0.5～2.0Pa)下沉积了一系列氮化铝(AlN)薄膜。研究发现,在保持其他工艺参数不变的条件下,工作气压对薄膜厚度的影响很小。场发射性能测试表明,在较低的工作气压(0.5Pa和0.7Pa)下制备的AlN薄膜具有一定的场发射性能。扫描电子显微镜(SEM)图像显示,在较高的工作气压(2.0Pa)下制备的薄膜易产生空位及微空洞等缺陷,使薄膜致密性下降。电子在薄膜中的输运因受到缺陷的散射而不能隧穿表面势垒进行发射。研究表明,为获得具有良好场发射性能的AlN薄膜,若采用反应磁控溅射法,应选取较低的工作气压;同时,对于薄膜型阴极,具有紧密晶粒结构及较小缺陷的薄膜可能具有更优异的场发射性能。     

直流磁控溅射制备非晶硅薄膜的研究

非晶硅薄膜（a-Si）是目前重要的光敏材料,在很多领域得到广泛应用。直流磁控溅射具有工艺简单．沉积温度低等优点,是制备薄膜的一种重要技术。采用直流磁控溅射工艺在玻璃基板上沉积薄膜,并对样品进行了退火处理。研究了沉积速率与溅射功率的关系。结果表明薄膜的沉积速率与溅射功率近似有线性关系。利用X射线衍射（XRD）对薄膜进行了分析鉴定,结果表明溅射的薄膜是非晶硅薄膜。利用扫描电子显微镜（SEM）对非晶硅薄膜的表面形貌进行了观察和分析,与X射线衍射测试的结果一致。所以．利用直流磁控溅射工艺能在常温下能快速制备出良好的非晶硅薄膜。     

Absorption spectra of TiO2 thin films synthesized by the reactive radio-frequency magnetron sputtering of titanium

The optical absorption spectra of TiO₂ thin films with different phase compositions (anatase, rutile-brookite, anatase-rutile-brookite) are studied. The films are produced by the reactive radio-frequency magnetron sputtering of titanium in different atmospheres. It is shown that, on the assumption of the additivity of the contributions of each phase to the general spectrum with the fraction of the phase in the layer known, it is possible to use the method of subtraction of the spectra of individual phases. The fundamental absorption spectra of all of the crystal modifications detected in the multiphase films by structural studies are separated out, and the edges of the optical transitions in all of the phase components are established.     

直流磁控溅射ZnO薄膜的结构特性

通过改变工作气压、溅射电流、氩氧比等工艺参数,较为系统地探索了用反应式直流磁控溅射法制备ＺｎＯ薄膜的工艺条件,并采用ＸＲＤ和ＡＥＳ对这些薄膜的结构特性进行测试分析,成功地得到了具有ｃ轴择优取向、结晶度高的ＺｎＯ薄膜。     

High photosensitivity with enhanced photoelectrical contribution in hybrid nanocomposite flexible UV photodetector

To devise a reliable strategy to develop an ultraviolet (UV) sensitive hybrid photodetector, plasma process is utilized as a single step method for production of large area nanocomposite films based on plasma polymerized aniline–titanium dioxide (PPani–TiO₂). The synthesis of PPani–TiO₂ nanocomposite films are made using reactive magnetron sputtering in combination with plasma polymerization. The deposited PPani–TiO₂ nanocomposite films are characterized and discussed in terms of structural, optical and electrochemical properties. A hybrid flexible nanostructured UV photodetector is constructed from PPani–TiO₂ nanocomposite and its optoelectronic properties are evaluated which exhibits a greatly enhanced photosensitivity resulting in high photoconductive gain (G = 4.56 × 10⁴) and high responsivity (R = 9.36 × 10³ AW⁻¹) under UV illumination of 254 nm. The flexible devices are successfully operated under bending up to 170° (bending radius, R = 8 mm) and showed a good folding strength and stability. The proposed plasma based method provides a green technology where the self-assembly of molecules, that is, the spontaneous association of atomic or molecular building blocks under plasma environment, emerge as a successful strategy to form well-defined structural and morphological units of nanometer dimensions.     

Preparation and characterization of TiO2 thin film by thermal oxidation of sputtered Ti film

Titanium dioxide (TiO₂) thin films were successfully prepared on quartz substrate by thermal oxidation of sputtered titanium film in air. The structure, composition, morphology and optical properties of oxidized TiO₂ films were characterized by Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and UV-visible spectroscopy. Meanwhile, the photocatalytic activity of the films was evaluated on the basis of the degradation of methyl orange solution under UV irradiation. Ti films after oxidation present mainly in TiO₂ form with a larger amount of adsorbed O₂, and oxidation temperature has a strong impact on the crystal structure and properties of the films. A phase transformation of anatase to rutile for oxidized TiO₂ films occurred in the temperature range of 700–800 °C. The energy band gap of oxidized TiO₂ films decreased first and then increased with annealing temperature. Furthermore, TiO₂ film oxidized at 600 °C exhibited the best photocatalytic activity due to suitable crystal phase and size. These results might contribute to the synthesis of metal oxide thin films with expectant structural morphology and properties by thermal oxidation methods.     

Preparation of in-plane textured buffer layers for YBa2Cu3Oy film growth by modified bias sputtering

A modified bias sputtering technique has been proposed to grow in-plane textured yttria-stabilized zirconia buffer layers on polycrystalline metallic substrates for deposition of YBa₂Cu₃O_y films. The principle of developing an in-plane texturing by this technique is basically the same as that of ion beam assisted deposition; an in-plane texturing occurs by off-normal ion beam bombardment because of the higher sputtering yields of all orientations other than the channelling direction. In our process, however, a flux of energetic particles impinging on the growing film is generated using specially devised negatively biased electrodes installed in a magnetron sputtering system instead of a separate ion-source in IBAD. So far an X-ray phi-scan width of 18° was attained for YSZ films on Hastelloy tapes. Epitaxial YBCO films grown on these buffer layers using pulsed laser deposition showed the J_c’s exceeding 10⁵ A cm⁻² (77 K, 0 T). In this paper, we present variation of the bias sputtering technique also used to obtain the textured films on large area substrates. Although the proposed process offers a very convenient method to grow textured films, more efforts must be made to increase growth rates of the films (currently ∽0.1 nm s⁻¹) for large-scale applications of YBCO films.     

氧化锌薄膜紫外光电导机理研究

分别采用反应磁控溅射和金属锌膜空气中热氧化两种方法,制备了两种氧化锌薄膜.X射线衍射实验发现,反应磁控溅射法制备的氧化锌薄膜结晶性能好,具有很高的c轴取向性,而金属锌膜热氧化法制备的氧化锌薄膜结晶性能相对较差,晶粒取向呈随机分布.对上述两种氧化锌薄膜进行了光电导测试,结果表明,反应磁控溅射制备的氧化锌薄膜的电阻率很高,没有明显的光电导,而金属锌膜氧化法制得的氧化锌薄膜电阻率较小,光电导现象非常明显.进一步分析结果表明,金属锌膜热氧化制备的氧化锌薄膜的光电导主要来自于表面吸附气体的吸附与解吸.     

DC Magnetron-Sputtered Mo Thin Films with High Adhesion,Conductivity and Reflectance

The main challenge in the deposition of molybdenum thin films for high efficiency in copper indium gallium selenide (CIGS) modules lies in gaining an adherent coating without compromising conductivity and reflectance characteristics. In this study, Mo thin films were deposited on soda-lime glass by DC magnetron sputtering at different deposition power (55, 100, 200 and 300 W) and with high working gas pressure (2 and 4 Pa). Analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect were employed to analyze the structure, morphology and electrical resistivity of the deposited films. Ultraviolet–visible (UV–Vis) spectrometry was performed to measure the reflectance and a cross-hatch adhesion tape test was employed to determine the adhesion behavior of deposited films. With higher sputtering power and reduced gas pressure, an increase in the crystallite size of the deposited films was observed. Films deposited at higher gas pressure were found with tensile stresses and higher adhesion with the substrate. The van der Pauw method reveals an increase in conductivity at high power and low gas pressure. Improved reflectance was achieved at moderate sputtering power and low gas pressure.     

Structural characterization of DC magnetron-sputtered TiO2 thin films using XRD and Raman scattering studies

Titanium dioxide films have been deposited using DC magnetron sputtering technique onto well-cleaned p-silicon substrates at an oxygen partial pressure of 7×10^–5 mbar and at a sputtering pressure (Ar+O₂) of 1×10^–3 mbar. The deposited films were calcinated at 673 and 773 K. The composition of the films as analyzed using Auger electron spectroscopy reveals the stoichiometry with an O and Ti ratio 2.08. The influence of post-deposition annealing at 673 and 773 K on the structural properties of the titanium dioxide thin films have been studied using XRD and Raman scattering. The structure of the films deposited at the ambient was found to be amorphous and the films annealed at temperature 673 K and above were crystalline with anatase structure. The lattice constants, grain size, microstrain and the dislocation density of the film are calculated and correlated with annealing temperature. The Raman scattering study was performed on the as-deposited and annealed samples and the existence of Raman active modes A_1g, B_1g and E_g corresponding to the Raman shifts are studied and reported. The improvement of crystallinity of the TiO₂ films was also studied using Raman scattering studies.