Structure and electrical properties of ITO thin films deposited at high rate by facing target sputtering

High rate deposition of ITO thin films at a low substrate temperature was attempted by using a facing target sputtering (FTS) system. Deposition rate as high as 53 nm/min was realized on polycarbonate film substrate of 80-μm thickness. When the film was deposited at a deposition rate above 80 nm/min, polycarbonate film substrate was thermally damaged. The film deposited by FTS has much smaller compressive film stress than the film deposited by conventional magnetron sputtering. The film stress was reduced significantly by increasing the sputtering gas pressure and stress-free films can be obtained by adjusting the sputtering gas pressure. This may be mainly caused by the fact that bombardment by high energy negative oxygen ions to substrate surface during deposition can be completely suppressed in the FTS. Film structure and electrical properties changed little with substrate position, and uniform films were obtained by the FTS.     

Peculiarities of film growth in glow discharge with runaway electrons

We have studied the properties of films deposited in gas discharge with a beam of runaway electrons and observed for the first time an anomalous behavior of the intensity of a probing light beam reflected from a film on substrate upon switching off of the discharge. The observed phenomenon is interpreted in the framework of a two-layer model of the film growth on a substrate, according to which an optically homogeneous surface layer of unknown nature appears on the film during growth in discharge and fully decomposes when the discharge is switched off.     

Simple recurrence matrix relations for multilayer anisotropic thin films

Generalized Abelès relations for one anisotropic thin film [E. Cojocaru, Appl. Opt. 36, 2825-2829 (1997)] are developed for light propagation from an isotropic medium of incidence (with refractive index n(0)) within a multilayer anisotropic thin film coated onto an anisotropic substrate. An immersion model is used for which it is assumed that each layer is imaginatively embedded between isotropic gaps of zero thickness and refractive index n(0). This model leads to simple expressions for the resultant transmitted and reflected electric field amplitudes at interfaces. They parallel the Abelès recurrence relations for layered isotropic media. These matrix relations include multiple reflections while they deal with total fields. They can be applied directly to complex stacks of isotropic and anisotropic thin films.     

The effect of substrate temperature on the oxidation behavior of erbium thick films

The effect of substrate temperature on the oxidation behavior of erbium thick films, fabricated by electron-beam vapor deposition (EBVD), was investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The erbium thick film is black when it is deposited at substrate temperature below 450 °C and turns gray at higher substrate temperature in a vacuum pressure of approximately 1.5 × 10⁻⁶ Torr, which indicates that the thickness of erbium oxide layer formed on the surface of erbium films increases with the decreasing substrate temperature. XPS depth profile results demonstrate that the thickness of the surface erbium oxide layer of erbium film deposited at substrate temperature of 550 and 350 °C are about 50 and 75 nm, respectively. The thicker oxide layer at lower substrate temperatures may be attributed to grain size and the dynamic vacuum condition around the substrates. Other possible factors involved in the oxidation behavior are also discussed.     

Inhomogeneous character of the initial stage of ion beam deposition of ultrathin gold films

Gold films with thicknesses ranging from below 1 nm to 3 nm have been simultaneously deposited by the ion beam sputter technique onto the surface of glass substrates smooth on a subnanometer level and onto Si(001) substrates with nanodimensional inhomogeneities in the form of germanium atomic islands. Irrespective of the substrate surface nature, gold deposition initially leads to the formation of a stable layer with a thickness of several atomic monolayers. The gold films with thicknesses above 2 nm are continuous and homogeneous. Terminated in an intermediate stage, the sputter deposition of gold may result in the formation of an inhomogeneous layer of the island type. The results are interpreted taking into account the well-known fact that a high-energy component is present in the flux of the ion beam sputtered target material.     

化学溶液方法制备涂层导体Ce_xLa_(1-x)O_2薄膜的研究

获得多功能单一过渡层是简化涂层导体多层结构的主要课题之一. 采用化学溶液方法制备La掺杂CeO₂过渡层,研究La掺杂量对CeO₂薄膜表面形貌和双轴取向生长的影响. 结果表明La掺杂量为10mol％的薄膜表面平整致密,且能保持锐利的双轴织构. 通过多次涂敷工艺,获得具有120nm厚的Ce_0.9La_0.1O₂过渡层. 采用脉冲激光沉积方法在Ce_0.9La_0.1O₂/NiW结构模板层上沉积了YBCO超导薄膜,其起始临界转变温度达到90.5K. 这表明采用化学溶液方法制备Ce_0.9La_0.1O₂薄膜是一种有前景的简化涂层导体多层结构的方法.     

A study of titanium thin films in transmission laser micro-joining of titanium-coated glass to polyimide

Electron beam evaporation (EB-PVD) and cathodic arc physical vapor deposition (CA-PVD) techniques were used for the preparation of titanium (Ti) thin films onto Pyrex borosilicate 7740 glass wafers and the deposited films were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The microstructure and surface morphology of the films were studied as a function of the film deposition techniques. Film properties such as, adherence, microstructure and roughness were interconnected to the laser joint strength between Ti coated glass wafers and polyimide films. Ti thin films on glass had a natural oxide layer on the surface as found from XPS. AFM study showed the formation of a uniform Ti coating consisted of packed crystallites with average size of 35 nm by EB-PVD. The root-mean-square surface roughness of the films was 1-2 nm. Whereas, films prepared by CA-PVD had crystallites with an average size of 120 nm and defects in the form of macro-particles which is a common attribute of this deposition system. The surface roughness of the film was 125 nm. The laser joint strength was found to be influenced by the Ti film quality on the glass substrate.     

The stability of thin tellurium and tellurium alloy films for optical data storage: II

The chemical and physical degradation and the effects of the substrate and a low surface energy subbing layer on the stability of thin tellurium and tellurium alloy films for optical data storage are reported. Chemically, thin tellurium films degrade mainly through the uniform oxidation of tellurium to TeO₂. In addition, localized degradation occurs at regions where initial defects on the substrate are present. Thin tellurium and tellurium alloy films can also degrade physically through crystal growth for an initially polycrystalline film and phase transformation for an initially amorphous film. While no significant difference in the uniform degradation rate is observed between films deposited onto poly(methyl methacrylate) (PMMA) and those deposited onto glass substrates, more localized degradation is detected for the films deposited onto PMMA substrates because of the higher initial defects of the substrate. The presence of a low surface energy subbing layer tends to degrade both the chemical and physical stability of these films. The degradation in the chemical stability is attributed to the change in the microstructure or thickness of the film due to the presence of the low surface energy subbing layer.     

Brillouin scattering by surface acoustic modes for elastic characterization of ZnO films

Brillouin scattering from surface phonons was used for determining the dispersion curves of guided acoustic modes propagating along piezoelectric ZnO films. Measurements were performed on films of different thicknesses in the range between 20 and 320 nm, deposited by RF magnetron sputtering on Si and SiO(2) substrates. Brillouin spectra from Rayleigh acoustic modes are taken in the backscattering geometry at different incidence angles between 30 degrees and 70 degrees . The experimental data for the ZnO/Si films fit the expected theoretical dispersion curves fairly well for film thicknesses greater than 150 nm, while they appreciably depart from the same curves for smaller thicknesses. This behavior is interpreted in terms of a reduction of the effective elastic constants of the film in a layer near the interface, due to the lattice misfit between the film and the substrate. This effect was not observed in the case of ZnO films deposited on fused quartz substrates.     

热循环退火对InAs/Si(211)薄膜结构和电学性能的影响

InAs作为III-V族化合物半导体材料,可以应用于磁阻和霍尔元器件、量子点激光器元件、太阳能电池和红外探测器元件等方面,具有广泛的研究和应用前景.本文以Si(211)为衬底,采用热壁外延(hot wall epitaxy,HWE)技术制备了InAs薄膜,研究热循环退火(thermal cycle annealing,TCA)次数对InAs/Si(211)薄膜结构及电学性能的影响.热壁外延制备InAs薄膜的衬底温度为400℃,生长时间为4 h,不同的热循环退火次数为2、4、6、8、10.X射线衍射(XRD)测试表明:利用HWE技术在Si(211)衬底表面成功制备了闪锌矿结构的InAs薄膜,且沿(111)取向择优生长;TCA能够明显增强Si(211)衬底表面生长的InAs薄膜的择优取向.扫描电子显微镜(SEM)及原子力显微镜(AFM)测试分析表明:随着TCA次数增加到6次,InAs/Si(211)薄膜表面由于晶粒细化作用变得均匀平整,表面粗糙度从69.63 nm降低到56.43 nm,此时霍尔迁移率达到2.67×10~3cm~2/(V·s);过多的退火次数(≥8次)又会使薄膜表面的晶粒过大、缺陷增多,导致薄膜性能下降.     

Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.     

Microstructural study of titanium–palladium–nickel base thin film shape memory alloys

A new generation of thin film shape memory alloys has been developed with 1.65 μm thickness for micro-actuator applications. In this work, the microstructure of thin film Titanium–Palladium–Nickel (TiPdNi) shape memory alloys deposited using ion beam assisted deposition from a Ti₅₀Pd₃₀Ni₂₀ target is studied. The TiPdNi thin films were deposited with and without substrate heating during deposition. As-deposited films without substrate heating were found to be amorphous. Deposition on heated substrate produced a dense, columnar crystalline structure. Microstructures of bulk TiPdNi thin films as well as the interfacial region between the film and substrate were characterized by various techniques including transmission electron microscope, scanning transmission electron microscope, scanning electron microscope-energy dispersive X-ray spectroscopy and scanning transmission electron microscope-energy dispersive X-ray spectroscopy. A transition layer with 70 nm thickness is observed at the interface between the bulk film and silicon substrate. It is composed of three layers; two amorphous layers above the silicon substrate and a 50 nm thick twin absent layer, which was identified as B2 austenite phase by Fourier spectra analysis. In the bulk film, nano-scale grains in the range of 80–200 nm were observed. The width of twin band of the film was very narrower in the range of 5 nm.     

射频磁控溅射 Ba0.6Sr0.4TiO3薄膜表层的XPS研究

用射频磁控溅射在Pt／Ti／SiO2／Si基体上沉积Ba0．6Sr0．4TiO3（BST）薄膜，用X射线光电子能谱（XPS）研究BST薄膜表层在常规晶化和快速晶化条件下的结构特征．结果表明，常规晶化时，BST薄膜表层约3-5nm厚度内含有非钙钛矿结构的BST，随着温度的升高该厚度增加；快速晶化时，该厚度减薄至1nm内，随着温度的升高没有明显增加．元素的化学态分析结果表明，非钙钛矿结构的BST并非来自薄膜表面吸附的CO和CO2等污染物，而与表面吸附的其他元素（如吸附氧）对表层结构的影响有关．GXRD和AFM表明，致密的表面结构能有效的阻止表面吸附元素在BST膜体中的扩散，从而减薄含非钙钛矿结构层的厚度．     

pH-sensing properties of poly(aniline) ultrathin films self-assembled on indium-tin oxide

The structural and functional properties of ultrathin (<5 nm) poly(aniline) (PANI) films deposited on indium-tin oxide (ITO) have been investigated using electrochemical and attenuated total reflection (ATR) spectroscopy methods. Layer-by-layer (LbL) self-assembly was used to form films composed of one and two bilayers of PANI and poly(acrylic acid) (PAA), as well as single PANI layers of approximately monolayer thickness. PANI deposited on an ITO electrode is electroactive at neutral pH, both with and without codeposition of an acid dopant such as PAA. In the absence of PAA, it is hypothesized that the acidic surface groups on ITO can function as the counterion. The pH response of PANI single layer, (PANI/PAA)(1), and (PANI/PAA)(2) films was examined using both potentiometry and ATR spectroscopy. Near-Nernstian potentiometric responses over pH 3-9 were observed for all three types of films, consistent with the weak acid-base behavior expected of polymers assembled in a LbL film. The ATR spectral sensitivity to pH increases as the number of layers in the film increases, with the highest sensitivity achieved by monitoring the absorbance at 800 nm (predominately due to the emeraldine salt form) of (PANI/PAA)(2) films. Codeposition of PANI and PAA appears to produce a wide distribution of strengths of acidic and basic sites in the film and thus a large linear dynamic range, up to six pH units. The water contact angle of (PANI/PAA)(2) is approximately 16 degrees, which is considerably more hydrophilic than either the PANI single layer or (PANI/PAA)(1) films ( approximately 40 degrees ). This film is shown to be a suitable substrate for deposition of a planar supported phospholipid bilayer. The supported membrane is highly impermeable to protons, which makes this architecture useful for monitoring transmembrane charge transport.     

Nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition

Nano-polycrystalline vanadium oxide thin films have been successfully produced by pulsed laser deposition on Si(100) substrates using a pure vanadium target in an oxygen atmosphere. The vanadium oxide thin film is amorphous when deposited at relatively low substrate temperature (500 degrees C) and enhancing substrate temperature (600-800 degrees C) appears to be efficient in crystallizing VOx thin films. Nano-polycrystalline V3O7 thin film has been achieved when deposited at oxygen pressure of 8 Pa and substrate temperature of 600 degrees C. Nano-polycrystalline VO2 thin films with a preferred (011) orientation have been obtained when deposited at oxygen pressure of 0.8 Pa and substrate temperatures of 600-800 degrees C. The vanadium oxide thin films deposited at high oxygen pressure (8 Pa) reveal a mix-valence of V5+ and V4+, while the VOx thin films deposited at low oxygen pressure (0.8 Pa) display a valence of V4+. The nano-polycrystalline vanadium oxide thin films prepared by pulsed laser deposition have smooth surface with high qualities of mean crystallite size ranging from 30 to 230 nm and Ra ranging from 1.5 to 22.2 nm. Relative low substrate temperature and oxygen pressure are benifit to aquire nano-polycrystalline VOx thin films with small grain size and low surface roughness.     

The effect of ion irradiation on the adherence of germanium films

Germanium films deposited under simultaneous argon ion irradiation show substantially better adherence on glass and other substrate materials than conventionally produced films.The ion bombardment leads to a strengthening of the interfacial bonding, an effect believed to be associated with a thin layer of intermediate composition produced at the substrate surface by ion knock-on processes. In addition irradiation causes a significant reduction in film stress.     

Molecular ordering in monolayers of an alkyl-substituted perylene-bisimide dye by attenuated total reflectance ultraviolet-visible spectroscopy

Surface-relative orientational parameters were determined for monolayer films of N, N'-ditridecylperylenetetracarboxylic dianhydridediimide (C13-PTCDI) in terms of the relative electronic transition dipole strengths, providing a three-dimensional view of the absorption dipole distribution. In order to obtain a macroscopically ordered film, C13-PTCDI was deposited by (1) horizontal Lang-muir-Blodgett (LB) transfer onto methyl- and phenyl-silanized glass, and (2) vapor deposition onto oriented films of poly(tetrafluoroethylene) (PTFE) on glass. Films of LB-deposited C13-PTCDI were found to be completely isotropic prior to annealing. After annealing, these films remained isotropic in the plane of the substrate while the out-of-plane anisotropy was significantly enhanced. In contrast, films of C13-PTCDI vapor deposited onto oriented poly(tetrafluoroethylene) (PTFE)-modified substrates yielded films with a high degree of both in- and out-of-plane anisotropy. Atomic force microscopy (AFM) images of both the LB- and vapor-deposited films show substantial differences in film morphology and long-range order. These results demonstrate that molecular orientation in C13-PTCDI films can be controlled by varying substrate surface chemistry and post-deposition processing.     

Microstructural enhancement of high coercivity L1(0)-FePt films for next-generation magnetic recording media

The effects of substrate Ar-ion milling and Ta adhesion layer on the microstructural and magnetic properties of L1(0)-FePt films prepared on Si, SiO2, and glass substrates were investigated. It was discovered that the relatively large in-plane surface roughness of CrRu/MgO/FePt films deposited on Si substrates was due to the deformation of the CrRu layer when the composition was heated to 550 degrees C. More than an order of magnitude improvement for the in-plane surface roughness was achieved when substrate Ar-ion milling or Ta adhesion layer was incorporated into the process. While the Ta adhesion layer proved to be detrimental to the (200) growth of the CrRu layer, optimal FePt film properties with coercivity values larger than 2 Tesla and out-of-plane roughness less than 1 nm were achieved when only substrate Ar-ion milling was implemented.     

基底温度对直流溅射Nb掺杂TiO2薄膜性能的影响

采用陶瓷靶直流磁控溅射,以玻璃为基底制备2.5wt%Nb掺杂TiO2薄膜,控制薄膜厚度在300~350 nm,研究了不同基底温度下所制得薄膜的结构、形貌和光学特性.XRD分析表明,基底温度为150℃、250℃和350℃时,薄膜分别为非晶态、锐钛矿(101)和金红石相(110)结构.基底温度250℃时,锐钛矿相薄膜的晶粒尺寸最大,约为32 nm.薄膜表面形貌的SEM分析显示,薄膜粗糙度和致密度随基底温度升高得到改善.薄膜的平均可见光透过率在基底温度为250℃以内约为70%,随基底温度升高至350℃,平均透过率下降为59%,金红石相的存在不利于可见光透过.Nb掺杂TiO2薄膜的光学带宽在3.68~3.78 eV之间变化.基底温度为250℃时,锐钛矿相薄膜的禁带宽度最大,为3.78 eV.     

Tribological properties of multilayer DLC/W-DLC films on Si

Multilayer films of diamond-like carbon (DLC) and tungsten-containing diamond-like carbon (W-DLC) films were deposited onto silicon wafers using radio frequency chemical vapor deposition (RFCVD) and a magnetron sputtering method. The W-DLC layer was deposited on the silicon wafer with less than 60 W magnetron output. The DLC layer was then deposited on the W-DLC layer.Surface morphology was investigated by atomic force microscopy and the film structure by transmission electron microscopy. Friction tests for multilayered films were performed in a nitrogen atmosphere at room temperature using a ball-on-disk tribometer. A conventional stainless steel ball was used for the test.The surface profiles seen by atomic force microscopy showed that round-shaped clusters of around 100 nm were observed in just the single W-DLC layer. These clusters were considered to be tungsten or tungsten-carbon composites. In the case of the DLC/W-DLC multilayered structure, the top DLC layer covered the W-DLC single layer and smoothed the surface of the W-DLC film.Friction tests demonstrated that the friction coefficient of the W-DLC single layer was above 0.6 and increased gradually as the number of cycle increased. The W-DLC films partially broke down during our measurements. However the DLC/W-DLC multilayer films showed stable friction properties and were observed for up to 100,000 cycles. Their friction coefficient was typically less than 0.1 at 10 cm/s rotating speed. The DLC/W-DLC multilayer films exhibited stable low friction properties in a long term test under a nitrogen atmosphere.