Surface characterization of the SiOx films prepared by a remote atmospheric pressure plasma jet

The deposition rate and surface properties of SiO_x films were prepared and investigated using remote atmospheric pressure plasma (APP) jet. The APP, generated with low frequency power at 16 kHz, was fed with tetraethoxysilane (TEOS)/air gas mixture. After deposition, the SiO_x films were analyzed for chemical characteristics, elemental composition, surface morphology, and hardness. It was found that the deposition substrate temperature is the key factor to affect the deposition rate of remote APP chemical vapor deposition process. Fourier transform infrared (FTIR) spectra indicated that APP deposited SiO_x films are an inorganic feature. XPS examination revealed that the SiO_x films contained approximately 30% silicon, 58% oxygen and 12% carbon. Atomic forced microscopy (AFM) analysis results indicated a smooth surface of SiO_x films in deposition under higher substrate temperature. Also, pencil hardness tests indicated that the hardness of APP deposited SiO_x films was greatly improved with increasing substrate temperatures. Copyright © 2008 John Wiley & Sons, Ltd.     

Initiated chemical vapor deposition of poly(1H,1H,2H,2H-perfluorodecyl acrylate) thin films

A solvent-free initiated chemical vapor deposition (iCVD) process was used to create low surface energy poly(1H,1H,2H,2H-perfluorodecyl acrylate) (PPFDA) thin films at deposition rates as high as 375 nm/min. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy showed full retention of the fluorine moieties, and no measurable cross-linking was detected. Additionally, the FTIR studies support the hypothesis that film deposition results from vinyl polymerization. For all iCVD PPFDA films, the static contact angle was found to be 120.8 +/- 1.2 degrees. The roughness of the films was found to be between 14.9 and 19.8 nm RMS, and the refractive index of the films was found to be between 1.36 and 1.37. The deposition rate was studied as a function of the substrate temperature and the partial pressure of the monomer. It was found that the deposition rate increases with decreasing substrate temperature and increasing monomer partial pressure. It was also found that the molecular weight increases with decreasing substrate temperature and increases with increasing monomer partial pressure. The highest molecular weight measured was 177 300 with a polydispersity of 2.27. Quartz crystal microbalance (QCM) measurements showed that these effects correlated with an increased monomer concentration at the surface. The deposition rate data and the QCM data were quantitatively analyzed to find the rate constants of the process using a previously published model for the iCVD process involving nonfluorinated monomers. The determined values of the rate constants of the surface polymerization were found to be similar to the rate constants measured in liquid-phase free radical polymerization. The kinetic data found in this paper can now be used to study iCVD deposition onto substrates with more complex geometries.     

Plasma deposition of silicon nitride-like thin films from organosilicon precursors

Plasmas containing hexamethyldisilazane or hexamethylcyclotrisilazane and nitrogen or ammonia were used to deposit silicon nitride-like films at low substrate temperature (T<60°C). Optical properties (refractive index and absorption coefficient), chemical composition of the deposit and film growth rate were examined with respect to the deposition parameters (rf power, pressure and feed composition). As deposited films from ammonia containing mixtures were silicon nitride-like, contained carbon, and were nearly oxygen free. Furthermore, only Si−N, Si−H, and N−H bonds were identified in as-deposited films. The reactive Si−H bonds progressively transformed into Si−O bonds as the films were exposed to air. Films deposited from highly ammonia-diluted mixtures, high RF power and low pressure showed the highest stability with refractive indices as high as 1.8.     

Preparation of epitaxial La0.6Ca0.4Mn1−xFexO3 (x = 0, 0.2) thin films: Variation of the oxygen content

Perovskite thin films with a nominal composition of La_0.6Ca_0.4Mn_1−xFe_xO₃ (x = 0, 0.2) were deposited by pulsed reactive crossed beam laser ablation. The film properties, such as electrical conductivity and magnetoresistance are studied as a function of the oxygen content and substrate type. The oxygen content of the thin films was determined by Rutherford Backscattering and controlled by varying the background gas pressure, pressure of the gas pulse and by using alternatively O₂ and N₂O as the gas pulse.

LaAlO₃ and SrTiO₃ were used as substrates at deposition temperature of 650 °C. The grown films were analyzed by X-ray diffraction in order to optimize the growth conditions, i.e. to obtain epitaxial thin films. Thin films doped with 20% Fe were grown under the same experimental conditions as the undoped LCMO films and the effect of the doping on the structural and transport properties of the thin films has been investigated.

The temperature of the metal–insulator transition was measured as a function of the oxygen content and substrate type.     

Titanium arsenide films from the atmospheric pressure chemical vapour deposition of tetrakisdimethylamidotitanium and tert-butylarsine

Thin films of titanium arsenide have been deposited from the atmospheric pressure chemical vapour deposition (APCVD) of [Ti(NMe(2))(4)] and (t)BuAsH(2) at substrate temperatures between 350-550 °C. Highly reflective, silver coloured films were obtained which showed borderline metallic-semiconductor resistivities. The titanium arsenide films were analyzed by scanning electron microscopy (SEM), Raman spectroscopy, wavelength dispersive analysis of X-rays (WDX), powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The films showed variable titanium to arsenic ratios but at substrate temperatures of 500 and 550 °C films with a 1 : 1 ratio of Ti : As, consistent with the composition TiAs, were deposited. Powder XRD showed that all of the films were crystalline and consistent with the formation of TiAs. Both nitrogen and carbon contamination of the films were negligible.     

Deposition of SiOx Films from Hexamethyldisiloxane/Oxygen Radiofrequency Glow Discharges: Process Optimization by Plasma Diagnostics

Optical emission and Fourier transform infrared absorption diagnostics have been carried out in hexamethyldisiloxane/oxygen RF discharges for studying the effects of the feed composition and the power on the deposition of SiO₂—like thin films. Ex situ FTIR absorption has been utilized to monitor organic moieties and silanol groups in the film. It is shown that carbon-free films can be obtained by highly diluting the monomer in oxygen, while medium-to-high power is necessary to abate silanol groups. These two conditions represent the optimization criterion to obtain excellent barrier films for food packaging applications.     

CO gas sensing by ultrathin tin oxide films grown by atomic layer deposition using transmission FTIR spectroscopy

Ultrathin tin oxide films were deposited on SiO2 nanoparticles using atomic layer deposition (ALD) techniques with SnCl4 and H2O2 as the reactants. These SnO(x) films were then exposed to O2 and CO gas pressure at 300 degrees C to measure and understand their ability to serve as CO gas sensors. In situ transmission Fourier transform infrared (FTIR) spectroscopy was used to monitor both the charge conduction in the SnO(x) films and the gas-phase species. The background infrared absorbance measured the electrical conductivity of the SnO(x) films based on Drude-Zener theory. O2 pressure was observed to decrease the SnO(x) film conductivity. Addition of CO pressure then increased the SnO(x) film conductivity. Static experiments also monitored the buildup of gas-phase CO2 reaction products as the CO reacted with oxygen species. These results were consistent with both ionosorption and oxygen-vacancy models for chemiresistant semiconductor gas sensors. Additional experiments demonstrated that O2 pressure was not necessary for the SnO(x) films to detect CO pressure. The background infrared absorbance increased with CO pressure in the absence of O2 pressure. These results indicate that CO can produce oxygen vacancies on the SnO(x) surface that ionize and release electrons that increase the SnO(x) film conductivity, as suggested by the oxygen-vacancy model. The time scale of the response of the SnO(x) films to O2 and CO pressure was also measured by using transient experiments. The ultrathin SnO(x) ALD films with a thickness of approximately 10 A were able to respond to O2 within approximately 100 s and to CO within approximately 10 s. These in situ transmission FTIR spectroscopy help confirm the mechanisms for chemiresistant semiconductor gas sensors.     

Composition of plasma-chemical silicon dioxide films as studied by IR spectroscopy

The results of a comparative analysis of the compositions of silicon dioxide films prepared by the decomposition of tetraethoxysilane vapor in a glow discharge and the deposition of the products onto a substrate are presented. The compositions of films prepared in gas mixtures containing argon, oxygen, tetraethoxysilane vapor, and NaCl were compared using IR spectroscopy. The electric discharge was excited at a frequency of 19 kHz and in a radiofrequency range at 81.36 MHz. It was found that the additives of oxygen and sodium-containing vapors exerted a noticeable effect on the composition of the films. The compositions of the films prepared at the low-frequency and high-frequency discharge excitation were also different.     

Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

Perovskite thin films deposited by pulsed laser ablation as model systems for electrochemical applications

Thin films of a bifunctional electrocatalyst with the compositions La_0.6Ca_0.4CoO_3−δ and La_0.7Ca_0.3CoO_3−δ have been deposited by a variation of pulsed laser deposition, i.e. pulsed reactive crossed-beam laser ablation. These perovskite phases have been used as catalysts for oxygen reduction and evolution in re-chargeable Zn/air batteries. The utilization of a synchronized reactive gas pulse with N₂O or O₂ allows the preparation of perovskite films with almost ideal oxygen content without additional annealing steps and to control the oxygen content of the films. The films with higher oxygen content reveal a lower resistivity. These compositions have been selected to study the influence of the texture on the electrocatalytical activity for oxygen reduction and evolution of the films. Amorphous films, or films with mixed or single orientation can be obtained by varying the target–substrate distance and substrate temperature without changing the composition of the films. A clear influence of the crystallinity on the catalytic activity, i.e. smaller overpotential for the two oxygen reactions, is observed. The amorphous films reveal the largest overpotential, followed by the polycrystalline films with one or more orientations, and the single crystalline films with (100) orientation.     

Role of reaction atmosphere in preparation of potassium tantalate through sol–gel method

Potassium tantalate (KT) thin films and powders of both K₂Ta₂O₆ (KT pyrochlore) and KTaO₃ (KT perovskite) structures were prepared by means of chemical solution deposition method using Si(111) with ZnO and MgO buffer layers as a substrate. The influence of reaction atmosphere on reaction pathway and phase composition for both KT powders, and KT thin films has been studied mainly by means of powder diffraction and infrared spectroscopy. When an oxygen flow instead of static air atmosphere has been used the process of pyrolysis in oxygen runs over much narrower temperature interval (200–300 °C), relatively to air atmosphere (200–600 °C) and almost no (in case of powders), or no (in case of thin films) pyrochlore intermediate phase has been detected in comparison with treatment in air, where the pyrochlore phase is stable at temperatures 500–600 °C (powders). KT perovskite phase starts to crystallize at temperatures 50° and 150 °C lower compared to air atmosphere in case of powders and thin films, respectively. Microstructure formed by near-columnar grains and small grains of equiaxed shape was observed in films treated in oxygen and air atmosphere, respectively.     

等离子化学气相沉积硅-硼-氮复合薄膜的组成和结构

利用X射线衍射（XRD）和X光电子能谱（XPS）等技术对射频－直流－等离子化学气相沉积（RF－DC－PVCD）在钢基本上Si-B-N复合薄膜的组成和结构进行分析和研究；结果表明，通过给试样基体加一适当的直流负偏压，得到含有显著六方氮化硼（h-BN)，立方氮化硼（c-BN)结晶相的Si-B-N薄膜。     

脉冲激光沉积具有锂离子储存能力的CeO2薄膜

锂电池具有比能量高,循环性能好的优点,已成为二次电池研究的热点．锂离子电极材料的电致变色性能也引起了人们的广泛兴趣．最近一项日本专利报导了水热法合成的氧化铈粉末,属单斜晶系,作为锂离子电池阳极时,其体积比容量达５３０ｍＡｈ·ｃｍ－３,高于通常用的石墨阳极．该专利还指出,以ＣｅＯ２为阳极,ＬｉＣｏＯ２为阴极,与非水电解质组成的锂电池平均放电电压为３．５Ｖ左右［１］．近年来,全固态薄膜锂离子微电池为适应电子器件的微型化而受到重视,它可以采用不同的二维形状直接构织到集成电路上．例如,可作为动态随机存储…     

Effect of deposition temperature on the growth mechanism of chemically prepared CZTGeS thin films

The Cu₂ZnSnGeS₄ (CZTGeS) thin films were deposited by the spray pyrolysis method at different substrate temperatures without further sulfurization. The influence of various deposition temperatures on the surface morphology, microstructure, optical properties, chemical, and phase composition were investigated. The substitution mechanism of Sn/Ge in the crystal lattice of CZTGeS depending on deposition temperatures was studied. It was shown that a variation in substrate temperature has a strong effect on the surface morphology of the films. The X-ray diffractometer (XRD), transmission electron microscope (TEM), and Raman spectroscopy (RS) analysis showed that CZTGeS films were polycrystalline with a kesterite-type single-phase structure and a preferential orientation of (112). The RS-mapping analysis showed the distribution of intensities on the surfaces of the films. Optical measurements showed that CZTGeS films are highly absorbing in the visible region, and the optical band gap is shifted from 1.89 to 1.84 eV.     

Microstructure and infrared reflectance modulation properties in DC-sputtered tungsten oxide films

Tungsten oxide (WO₃) films were deposited on indium tin oxide glass by reactive DC magnetron sputtering of a tungsten target in an oxygen and argon atmosphere at different substrate temperatures. Infrared reflectance modulation properties of the films were investigated in the wavelength range of 2.5–25 μm. The morphology and structure of the films are strongly dependent on the substrate temperature, and therefore have a great influence on infrared reflectance modulation properties. The charge capacity and diffusion coefficient of H⁺ ions in WO₃ films decrease, and the infrared reflectance modulation and color efficiency first increase and then decrease with increasing the deposition temperature. The values achieve a maximum of 40% and 18.5 cm² C⁻¹, respectively, at 9 μm and 250 °C.     

Chemical Investigation on Various Aromatic Compounds Polymerization in Low Pressure Helium Plasma

Remarkable properties of plasma polymer films are greatly dependent not only on the chemical structure of precursor but also on the reactor design and the deposition conditions. In many industrial applications it is a challenge to control the plasma polymer structure. In this paper we investigate the chemical transformation of various aromatic compounds, such as activation and fragmentation of substituent-part, aromatic ring opening, during plasma polymerization process. Polymerized films are deposited in a low-frequency capacitively coupled plasma-enhanced chemical vapour deposition reactor, working at low pressure. The chemical composition of plasma-polymerized films is elucidated by Fourier-transform infrared spectroscopy, solid-state carbon-13 nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy. Based on spectroscopic measurements, the intermediary reactions during film growth may be presumed.     

Substrate temperature influenced physical properties of silicon MOS devices with TiO2 gate dielectric

DC reactive magnetron sputtering technique was employed for deposition of titanium dioxide (TiO₂) films. The films were formed on Corning glass and p‐Si (100) substrates by sputtering of titanium target in an oxygen partial pressure of 6×10^?2 Pa and at different substrate temperatures in the range 303 – 673 K. The films formed at 303 K were X‐ray amorphous whereas those deposited at substrate temperatures ≥ 473 K were transformed into polycrystalline nature with anatase phase of TiO₂. Fourier transform infrared spectroscopic studies confirmed the presence of characteristic bonding configuration of TiO₂. The surface morphology of the films was significantly influenced by the substrate temperature. MOS capacitor with Al/TiO₂/p‐Si sandwich structure was fabricated and performed current–voltage and capacitance–voltage characteristics. At an applied gate voltage of 1.5 V, the leakage current density of the device decreased from 1.8 × 10^?6 to 5.4 × 10^?8 A/cm² with the increase of substrate temperature from 303 to 673 K. The electrical conduction in the MOS structure was more predominant with Schottky emission and Fowler‐Nordheim conduction. The dielectric constant (at 1 MHz) of the films increased from 6 to 20 with increase of substrate temperature. The optical band gap of the films increased from 3.50 to 3.56 eV and refractive index from 2.20 to 2.37 with the increase of substrate temperature from 303 to 673 K. Copyright © 2012 John Wiley & Sons, Ltd.     

Structure and optical properties of CVD molybdenum oxide films for electrochromic application

Vibrational and optical properties of MoO₃ thin films have been studied by Raman and infrared spectroscopy. The films were deposited onto Si substrates at a temperature of 150 °C by chemical vapor deposition of Mo(CO)₆ at atmospheric pressure and different amounts of oxygen in the reactor. The Raman and IR spectral analyses show that the as-deposited films are in general amorphous. Post-deposition annealing at 300 and 400 °C leads to crystallization and the MoO₃ film structure is a mixture of orthorhombic and monoclinic MoO₃ modifications. Transformation of the monoclinic crystallographic modification to a thoroughly orthorhombic layered structure is observed for films heated at temperatures above 400 °C. Electronic Publication     

Influence of Pressure on SiNx:H Film by LF-PECVD

Hydrogenated silicon nitride films as an effective antireflection and passivation coating of silicon solar cell were prepared on p-type polished silicon substrate (1.0 Ωcm) by direct LF-PECVD (low frequency plasma enhanced chemical vapor deposition) of Centrotherm. The preferable passivation effect was obtained and the refractive index was in the range of 2.017-2.082. The refractive index of the hydrogenated silicon nitride films became larger with the increase of the pressure. Fourier transform infrared spectroscopy was used to study the pressure influence on the film structural properties. The results highlighted highhydrogen bond and high Si-N bonds density in the film, which were greatly influenced by the pressure. The passivation effect of the films was influenced by the Si dangling bonds density. Finally the effective minority liftetime degradation with time was shown and discussed by considering the relationship between the structural properties and passivation.     

Precise Control of Metal Oxide Thin Films Deposition in Magnetron Sputtering Plasmas for High Performance Sensing Devices Fabrication

Magnetron sputtering deposition is a widely used technique to deposit thin film precisely at nanoscale level. During the deposition of metal oxide thin films, reactive oxygen gas is introduced into the deposition chamber. Pure metal and metal oxide materials can be used as sputter target, although the simplest way is by using a pure metal target. In such reactive process, the effect of target poisoning significantly influence the deposition process and the growth mechanisms of metal oxide thin films became very complex. In general, external parameters such as discharge power, working pressure, reactive gases ratio and substrate temperature are used to optimize the properties of deposited thin films. Then, ex-situ analyses such as scanning electron microscope and X-ray diffraction analysis are performed to obtain the optimized parameter. Sample depositions and ex-situ analyses consume time to achieve the goal through try and error. In this article, in-situ plasma diagnostics are reviewed focusing on an optical emission spectroscopy to precisely control and investigate the sputter target poisoning effect during the deposition of metal oxide thin films. The emission of atomic lines from several metal and oxygen atoms were used to discuss the deposition mechanisms and their correlation with the deposited thin films was observed. Finally, the deposited metal oxide thin films were proposed and tested for several applications such as gas sensor and frequency selective surface glass.