TiC coatings deposited onto carbon and molybdenum surfaces by electron beam evaporation

TiC coatings were deposited onto graphite and molybdenum substrates by an electron beam evaporation method. A titanium film 1000–10000 Å thick was evaporated onto the graphite substrate which was then heated at 1000 °C for 5 min to form the TiC film by an interdiffusion process. In the case of the molybdenum substrate, a double-layer film consisting of titanium and carbon (Ti/C/Mo) was prepared by evaporation and the subsequent heat treatment was performed at 700 °C or at 1000 °C for 5 min. The properties of the coatings were examined by various surface analysis techniques including Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Rutherford backscattering (RBS). The atomic ratio of carbon to titanium in these coatings was found to be 0.9. The in-depth profiles obtained by XPS examination showed that the coating prepared at 700 °C had a carbon layer between the TiC layer and the molybdenum substrate, while that prepared at 1000 °C had an Mo₂C layer between the coating and the substrate.     

Influence of substrate properties on the growth of titanium films: part III

The growth of thin Ti-oxide films (12 nm) on alumina substrate films formed by reactive evaporation of Ti in an oxygen atmosphere was studied by in situ internal stress measurements under ultra high vacuum conditions and transmission electron microscopy. Oxygen pressure and substrate temperatures were the varied parameters of the reactive evaporation. These Ti-oxide-films with different oxygen content (O₂/Ti-films) were then used as substrate films for the deposition of a clean titanium film. The growth stress of the titanium film on the as-deposited O₂/Ti-substrate films is comparable with that previously found for H₂O/Ti-substrates and indicates island growth and the formation of polycrystalline titanium films. Annealing (400°C, 20 min) of the as-deposited – amorphous – O₂/Ti-films gives rise to the formation of crystalline TiO₂. The amount of TiO₂ formed during annealing is strongly dependent on the oxygen content of the O₂/Ti-film. The oxygen content, in return, is dependent on oxygen partial pressure and substrate temperature during O₂/Ti-film deposition. The corresponding changes in the substrate film properties (oxygen content, crystallinity, etc.) are reflected in significant changes in the growth stress of the titanium film. The stress vs. thickness curve of these titanium films appears to indicate a superposition of the growth stress of two different growth modes, i.e. growth of a polycrystalline film with island growth on the as-deposited, amorphous oxide substrate and epitaxial growth of a quasi single crystalline film on the crystalline TiO₂-substrate.     

Influence of substrate properties on the growth of titanium films: Part II

In situ internal stress measurements were used to investigate the influence of the chemical properties of the substrate on the growth of a titanium film deposited under UHV conditions. The substrate films used were titanium films evaporated at different water partial pressures. When the titanium film is evaporated at substrate temperatures of 130 °C and higher the shape of the stress vs thickness curve is interpreted to indicate island growth. Comparing the internal stress curve of titanium on Al₂O₃ and Ti/H₂O substrates it is seen that the initial tensile stress is significantly larger on the Ti/H₂O substrate film. This larger tensile stress is interpreted to originate from a redistribution of oxygen at the substrate interface during the early growth stage of the clean titanium film. A compressive stress contribution at higher thickness of the titanium film is interpreted to be due to hydrogen interdiffusion from the substrate into the titanium film. Annealing of the Ti/H₂O substrate films at 350 °C for 20 min reduces the concentration of the surface oxygen species and the amount of hydrogen incorporated in the films.

Dosing of previously annealed Ti/H₂O substrate films with water affects both the oxygen concentration on the surface of these substrate films and the amount of hydrogen incorporated in the films. Oxygen dosing of these films only increases the concentration of the oxygen species on the substrate surface; thus only the initial tensile stress built up in the titanium film is affected. Dosing the films with hydrogen, on the other hand, only increases the amount of hydrogen incorporated in the substrate film, which by way of interdiffusion into the growing titanium film gives rise to a larger compressive stress at higher film thickness     

具有光透性的超长TiO_2纳米管阵列/FTO的制备及表征

采用电子束蒸发方法在透明导电玻璃FTO上沉积Ti金属薄膜,室温条件下在C2H6O2+NH4F中通过恒压阳极氧化法制备出超长TiO2纳米管阵列/FTO电极,并通过场发射扫描电子显微镜(FESEM),透射电子显微镜(TEM),X光电子能谱(XPS),X射线衍射(XRD)及光谱分析等方法对纳米管阵列/FTO电极进行了表征.研究表明,制备出的TiO2纳米管阵列内径43nm,管长5.4μm,经退火处理后得到长度为5μm锐钛矿相TiO2纳米管阵列/FTO透明电极,在可见光波长段的透射率为45%,在400nm波长处有一明显吸收峰.     

Evaluation of the oxidation of TiO2 films during reactive evaporation of Ti3O5 and during exposure of the films to the atmosphere

A surplus amount of oxygen is needed to produce titanium dioxide film by reactive electron-beam evaporation of Ti3O5. We investigated the ratio of the rates at which oxygen molecules and TiO(x) molecules impinge upon substrates at 25 degrees and 250 degrees C to produce TiO2 filmsthat show no optical absorption in the visible spectral region. On unheated substrates the ratio was 49, and at 250 degrees C it was 26, provided that the substrates had been exposed to air after being coated at the given substrate temperature. Higher ratios were required if the TiOs film was covered with a SiO2 film, which impeded further oxidation. Furthermore, the postdeposition oxidation behavior of these films was studied.     

Ion beam based composition and texture control of titanium nitride

Titanium nitride was formed by electron beam evaporation of titanium in an atmosphere of backfilled nitrogen. The growing film was simultaneously irradiated with argon ions. From of a single-aperture ion source, a Gaussian-shaped ion beam was extracted. Each position on the sample was correlated with a particular ion beam current density. With this method, on a single substrate a large variation in ion irradiation intensity could be obtained. Since the titanium evaporation rate was uniform over this area, the parameter varied over the sample surface was only the ion-to-atom arrival ratio. It turns out that with a constant Ti condensation rate and nitrogen impact rate, the Ti:N ratio in the film is a strong function of the argon ion impact rate. Ion-beam induced nitrogen sorption saturates at a certain ion irradiation intensity. While under all conditions the TiN (mono)phase is obtained, it shows different preferred crystal orientations in dependence on ion bombardment intensity. At low level, the film grows in (111)-orientation, at high levels in (100)-orientation. In a small transition zone, (110)-orientation prevails. Thus, the orientation can be selected by the ion beam intensity, which is relevant for application.     

Properties of TiO(x) films prepared by electron-beam evaporation of titanium and titanium suboxides

The titanium suboxides TiO, Ti2O, and Ti3O5 are widely used to produce films of titanium dioxide by reactive evaporation. If they are evaporated in high vacuum, however, they yield absorbing TiO(x) films with a transmission color varying between blue and gray. We investigated the specific properties of these TiO(x) film. TiO, Ti2O3, Ti3O5, and titanium metal were evaporated in high vacuum upon glass substrates at 25 degrees and 250 degrees C. Differences in chemical composition, transmission and reflection, color, stress, and abrasion resistance of these fims, depending on the starting material and the substrate temperature, were evaluated.     

Indentation induced film fracture in hard film – soft substrate systems

Nanoindentations were made into oxide films on aluminum and titanium substrates for two cases; one where the metal was a bulk (effectively single crystal) material and the other where the metal was a 1 m thick film grown on a silica or silicon substrate. In both cases indentation was used to produce discontinuous loading curves, which indicate film fracture after plastic deformation of the metal. The oxides on bulk metals fractures occurred at reproducible loads, and the tensile stresses in the films at fracture were approximately 10 and 15 GPa for the aluminum and titanium oxides, respectively. Fine grained films only exhibited discontinuous loading under cyclic indentations, and demonstrated decreased load at catastrophic film fracture as the amplitude of cycling was decreased. A hypothesis regarding film fracture in these film systems is presented based on plastic deformation in the substrate and the superposition of the load carried by the elastic stretching of the film and the plastic deformation of the substrate.     

Two-step growth of high-quality nano-diamond films using CH4/H2 gas mixture

Diamond films with fine grain size and good quality were successfully deposited on pure titanium substrate using a novel two-step growth technique in microwave plasma-assisted chemical vapor deposition (MWPCVD) system. The films were grown with varying the methane (CH₄) concentration at the stage of bias-enhanced nucleation (BEN) and nano-diamond film deposition. It was found that nano-diamond nuclei were formed at a relatively high methane concentration, causing a secondary nucleation at the accompanying growth step. Nano-diamond film deposition on pure titanium was always very hard due to the high diffusion coefficient of carbon in Ti, the big difference between thermal expansion coefficients of diamond and Ti, the complex nature of the interlayer created during diamond deposition, and the difficulty in achieving very high nucleation density. A smooth and well-adhered nano-diamond film was successfully obtained on pure Ti substrate. Detailed experimental results on the synthesis, characterization and successful deposition of the nano-diamond film on pure Ti are discussed.     

蒸发速率对ZnS薄膜性能的影响

为了研究蒸发速率对ZnS薄膜的折射率、表面形貌和应力等性能的影响,本文采用电子束蒸发技术进行了ZnS薄膜的制备。首先在K9玻璃基片上镀制薄膜,采用分光光度计进行透射率曲线的测试,利用光谱反演法得出薄膜的折射率,采用原子力显微镜表征了样品的表面形貌。最后在聚酰亚胺基底上镀制薄膜,利用Stoney公式计算出薄膜的应力。结果表明,随着蒸发速率的增加,薄膜折射率先增大后减小,在2000nm波长处薄膜的折射率最大值为2.21,最小值为2.07。蒸发速率越大,薄膜样品表面结构越疏松。不同蒸发速率下制备的薄膜均呈现压应力,增大蒸发速率可以显著降低薄膜应力。ZnS薄膜的性能受蒸发速率影响显著,蒸发速率为1.5nm/s时折射率可达到最大值,蒸发速率为2.5nm/s时薄膜应力最小。     

Low temperature interdiffusion in Au/In thin film couples

Interdiffusion in Au/In thin film couples was studied by in situ backscattering spectrometry. The substrate temperature was varied in the range from -170 to +50 °C. It was found that a uniform layer of AuIn₂ grows at the same rate as that at which gold condenses onto an indium film for substrate temperatures down to -50 °C. This is the fastest formation of intermetallic phases that has been reported. By lowering the substrate temperature the formation of an AuIn₂ layer during evaporation is suppressed. In this case the temperature of the thin film couple has to be raised considerably (to about 20 °C) to obtain interdiffusion within a reasonable time, and the final state of the thin film couple is different from that obtained when the phase formation is completed during evaporation. A possible explanation for this behaviour is discussed. The formation and growth of AuIn₂ after evaporation may be characterized by an activation energy of 0.23 eV.     

高场发射性能碳纳米管薄膜的沉积与表征

利用电泳法将碳纳米管（CNTs）沉积在表面镀覆了50～150 nm Ti薄膜的Si基底表面,900℃真空退火后形成了具有良好场发射性能的Ti-CNTs薄膜阴极.利用X射线衍射和扫描电子显微镜对制备的Ti-CNTs薄膜进行了表征.结果表明,高温退火过程中,CNTs的C原子和基底表面的Ti原子发生化学反应,在CNTs与基底之间形成了导电性钛碳化物,明显改善了CNTs与基底之间的电导性和附着力等界面接触性能;与Si基底表面直接电泳沉积的CNTs薄膜相比,制备的Ti-CNTs薄膜的开启电场从1.31 V/μm降低到1.19 V/μm;当电场强度为2.50 V/μm时,Ti-CNTs薄膜的场发射电流密度可达13.91 mA/cm^2;制备的Ti-CNTs薄膜显示出改善的发射稳定性.     

Evaluation of uniformity for organic film evaporation using two dimensional different apertures

We have demonstrated an evaporation method to obtain a uniform organic thin-films with designed evaporation source which have array of two dimensional apertures of different sizes above an evaporation source optimized the distance between evaporation source and substrate, a uniform film was formed. Experimental results varying with position of the substrate are fitted to the theory of evaporation and the simulation of film uniformity using the uniform evaporation method was examined. In the simulation, different diameters of each apertures and distance between the evaporation source and the substrate were investigated. When the distance between the evaporation source and the substrate was 7 mm, adjusting the diameters of each apertures, the simulation uniform of film thickness of ±3.9 and ±1.0% at array of 3 × 3 and 9 × 9 apertures of different sizes was achieved in simulation, respectively. Moreover, in the evaporation experiment using array of 3 × 3 apertures, the uniformity of ±6.5% was obtained by photoluminescence measurement.     

共蒸发制备GaSb多晶薄膜的研究

GaSb的禁带宽度为0.72eV,是热光伏电池的理想材料。采用共蒸发的方法,在普通玻璃衬底上生长GaSb多晶薄膜。通过XRD谱、Hall及透射反射谱测试,研究了Ga、Sb源的蒸发温度、衬底温度以及薄膜厚度对薄膜的结构特性和光电特性的影响。研究表明,随衬底温度的升高、薄膜厚度的增加,晶粒尺寸逐渐增大;随衬底温度的升高、Ga源温度的降低以及厚度的增加,迁移率逐渐上升,迁移率最高可达172cm2/(V.s);随衬底温度的降低、Ga源温度的提高以及厚度的增加,载流子浓度逐渐增加。     

A functionally graded titanium/hydroxyapatite film obtained by sputtering

A functionally graded film of titanium/hydroxyapatite (HA) was prepared on a titanium substrate using a radio frequency magnetron sputtering. The ratio of titanium to HA was controlled by moving the target shutter. The film was composed of five layers, with overall film thickness of 1 m. The HA was concentrated close to the surface, while the titanium concentration increased with proximity to the substrate. The bonding strength between the film and the substrate was 15.2 MPa in a pull-out test and the critical load from a scratch test was 58.85 mN. The corresponding values of a pure HA sputtered film were 8.0 MPa and 38.47 mN, respectively. The bonding strength of a pure HA plasma spray coating was 10.4 MPa in the pull-out test. The graded film and the pure HA film were sputter-coated to a thickness of 1 m on titanium columns (10 mm in length and 4 mm in diameter). These columns were implanted in diaphyses of the femora of six adult dogs and a push-out test was carried out after 2, 4, and 12 weeks. After 12 weeks, the push-out strengths of the graded film, the pure HA film and the non-coated columns were 3.7, 3.5, and 1.0 MPa.     

Growth of polycrystalline and nanocrystalline diamond films on pure titanium by microwave plasma assisted CVD process

Well-faceted polycrystalline diamond (PCD) films were deposited along with nanocrystalline diamond (NCD) films on the pure titanium substrate by a microwave plasma assisted chemical vapor deposition (MWPCVD) system in the environment of CH₄ and H₂ gases at a moderate temperature. Diamond film deposition on pure titanium and Ti alloys is always extremely hard due to the high diffusion coefficient of carbon in Ti, the big mismatch in their thermal expansion coefficients, the complex nature of the interlayer formed during diamond deposition, and the difficulty of attaining very high nucleation density. A well-faceted PCD film and a smooth NCD film were successfully deposited on pure Ti substrate by using a simple two-step deposition technique. Both films adhered well. Detailed experimental results on the preparation, characterization and successful deposition of the diamond coatings on pure Ti are discussed. Lastly, it is shown that smooth NCD film can be deposited at moderate temperature with sufficient diamond quality for mechanical and tribological applications.     

Characterization of titanium dioxide atomic layer growth from titanium ethoxide and water

Atomic layer growth of titanium dioxide from titanium ethoxide and water was studied. Real-time quartz crystal microbalance measurements revealed that adsorption of titanium ethoxide is a self-limited process at substrate temperatures 100–250°C. A relatively small amount of precursor ligands was released during titanium ethoxide adsorption while most of them was exchanged during the following water pulse. At temperatures 100–150°C, incomplete reaction between surface intermediates and water hindered the film growth. Nevertheless, the deposition rate reached 0.06 nm per cycle at optimized precursor doses. At substrate temperatures above 250°C, the thermal decomposition of titanium ethoxide markedly influenced the growth process. The growth rate increased with the reactor temperature and titanium ethoxide pulse time but it insignificantly depended on the titanium ethoxide pressure. Therefore reproducible deposition of thin films with uniform thickness was still possible at substrate temperatures up to 350°C. The films grown at 100–150°C were amorphous while those grown at 180°C and higher substrate temperature, contained polycrystalline anatase. The refractive index of polycrystalline films reached 2.5 at the wavelength 580 nm.     

Effects of temperature on columnar microstructure and recrystallization of TiO2 film produced by ion-assisted deposition

Titanium oxide thin films were deposited by electron-beam evaporation with ion-beam-assisted deposition. The effect of the substrate temperature and annealing temperature on the columnar microstructure and recrystallization of titanium oxide was studied. The values of the refractive index varied from 2.26 to 2.4, indicating that the different substrate temperatures affected the film density. X-ray diffraction revealed that all films were amorphous as deposited. At annealing temperatures from 100 degrees C to 300 degrees C, only the anatase phase was formed. As the substrate temperature increased from 150 degrees C to 200 degrees C to 250 degrees C, the recrystallization temperature fell from 300 degrees C through 250 degrees C to 200 degrees C. Changing the substrate temperature resulted in the formation of various types of columnar microstructure, as determined by scanning-electron microscopy. Different columnar structures resulted in different surface morphologies, as measured by atomic-force microscopy.     

Simultaneous determination of the optical indices of an absorbant film and its metallic substrate by statistical analysis of spectroreflectometric data: Application to the oxide/titanium system

A method to compute the optical indices of a thin absorbant film, together with those of its metallic substrate, from a statistical analysis of the reflectance changes with film thickness d of the metal-film system is given. The results are applied to anodic oxide films grown on titanium. The accuracy of the indices of the titanium substrate is shown to be a function of the ratio of the film thickness to the wavelength. By using films with thicknesses ranging between 10 and 2500 Å, the optical indices in a wavelength range 0.25–2.5 μm were obtained. The titanium indices are compared with results recently cited in the literature; the accuracy of our result, for instance in the determination of the bulk plasmon frequency, is demonstrated.     

Simulation of the creep damage behavior of thin film/substrate systems by bending creep tests

The purpose of this paper is to understand the creep damage properties of thin film/substrate systems by bending creep tests. To this aim, a numerical study has been performed on the creep damage development of the thin film/substrate systems by implementing the Kachanov–Rabothov damage law into finite element models. The work may shed some light on the influence of the modulus ratio of the substrate to the thin film, the thickness of the thin film and the bending load. Finite element method (FEM) results show that three obviously damaged zones are found. The first is at the edge of the loading pin, the second is at the interface between the film and the substrate ahead of the loading pin edge, the last is at the edge of the supporting pin A. The influence of the modulus ratio of the substrate to the thin film on the bending creep damage is not obvious at the preliminary stage of creep time. However, with the lapse of time, the damage rate decreases with the increase of modulus ratio of the substrate to the thin film. The change of the thickness of the thin film and the bending load also influence the creep damage behavior of the thin film/substrate systems.