Studies using AFM and STM of the correlated effects of the deposition parameters on the topography of gold on mica

A systematic study of the correlated effects of deposition temperature, film thickness and deposition rate on the morphology of gold films on mica was carried out using atomic force microscopy and scanning tunnelling microscopy. For the range of thicknesses, rates and temperatures concerned, a variety of surface structures, mainly in the form of rounded mounds, islands, long channel and short channel plateaux topographical features were formed under various combinations of these three parameters. The rounded mounds and islands formed, respectively, on the mica substrate at room temperature and at 150°C were found to be essentially independent of the film thickness and deposition rate selected. When deposited at higher temperatures (300°C and 440°C), a change from islands to channelled features, via the growth and coalescence of the islands, was observed either on increasing the film thickness for a given deposition rate (≈ 1.0 Å s⁻¹) or on increasing the deposition rate to a given film thickness (400 Å). It is evident from the results presented that, whereas the film thickness and the deposition rate at a given temperature determine to what extent the film has coalesced, the growth temperature influences the lateral size of the surface features formed. In consequence, conducting films were found when the gold coverage was ≥ ≈0.9. Investigation of the vertical characteristics of the films was also conducted. The origin of all the phenomena observed can be attributed to competition between secondary nucleation and thermally enhanced diffusion processes occurring on the gold surface during deposition and film formation.     

Mechanical and thermal properties of physical vapour deposited alumina films Part I Thermal stability

Thermal stability of non-reactive physical vapour deposited alumina films of varying thickness on Al₂O₃-TiC and Si substrates, deposited at two different substrate biases, is examined. Substrate curvature measurements were used to determine the deposition stress and stress development during thermal cycling and annealing. Thermal cycling experiments revealed that the films deposited on Al₂O₃-TiC substrates become irreversibly more compressive on heating and annealing while films deposited on Si substrates become irreversibly more tensile. The deposition stress was found to be independent of film thickness, substrate material, and substrate bias during deposition. The thermal stability was independent of film thickness and substrate bias during deposition.     

Abscheidung optisch,elektrisch und akustisch wirksamer Schichten mit dem Doppel‐Ring‐Magnetron

Numerous applications in optics, electronics and sensor technology require thin dielectric films. Conventionally they are deposited by evaporation, activated evaporation, rf‐sputtering or CVD‐techniques. This paper describes the deposition of such films using reactive Pulse Magnetron Sputtering. This technology not only enables a tenfold deposition rate compared to the conventional techniques but also offers new possibilities for influencing film growth. For example it is possible to alter film composition during deposition and hence to deposit complete optical systems without interruption of the plasma process. Furthermore the energetic bombardment of the growing film can be controlled in a wide range by the pulse mode and the pulse parameters. This can be used to either deposit very dense films by strong energetic bombardment or to deposit films at low thermal load onto temperature sensitive substrates. Examples of film deposition for laser optics, electrical insulation applications and surface acoustic wave devices show how these new technological possibilities advantageously can be used for creating innovative layer systems. Film deposition is carried out in stationary mode using a Double Ring Magnetron. This type of magnetron ensures film thickness uniformity better than ± 1 % on 8” substrates by the superposition of the thickness distributions of two concentric discharges.     

Compositional analysis of polycrystalline hafnium oxide thin films by heavy-ion elastic recoil detection analysis

The composition of polycrystalline hafnium oxide thin films has been measured by heavy-ion elastic recoil detection analysis (HI-ERDA). The films were deposited by high-pressure reactive sputtering (HPRS) on silicon wafers using an oxygen plasma at pressures between 0.8 and 1.6 mbar and during deposition times between 0.5 and 3.0 h. Hydrogen was found to be the main impurity and its concentration increased with deposition pressure. The composition was always slightly oxygen-rich, which is attributed to the oxygen plasma. Additionally, an interfacial silicon oxide thin layer was detected and taken into account. The thickness of the hafnium oxide film was found to increase linearly with deposition time and to decrease exponentially with deposition pressure, whereas the thickness of the silicon oxide interfacial layer has a minimum as a function of pressure at around 1.2 mbar and increases slightly as a function of time. The measurements confirmed that this interfacial layer is formed mainly during the early stages of the deposition process.     

Application of in situ ellipsometry in the fabrication of thin-film optical coatings on semiconductors

Thin-film interference filters, suitable for use on GaAs- and InP-based lasers, have been fabricated by use of the electron-cyclotron resonance plasma-enhanced chemical vapor deposition technique. Multilayer film structures composed of silicon oxynitride material have been deposited at low temperatures with an in situ rotating compensator ellipsometer for monitoring the index of refraction and thickness of the deposited layers. Individual layers with an index of refraction from 3.3 to 1.46 at 633 nm have been produced with a run-to-run reproducibility of 0.005 and a thickness control of 10 A. Several filter designs have been implemented, including high-reflection filters, one- and two-layer anitreflection filters, and narrow-band high-reflection filters. It is shown that an accurate measurement of the filter optical properties during deposition is possible and that controlled reflectance spectra can be obtained.     

Ion-beam etching for the precise manufacture of optical coatings

We propose using ion-beam etching as an additional tool for the accurate control of the thickness of thin films during the manufacture of sensitive optical multilayer coatings. We use a dual ion-beam sputtering system in the deposition and etch modes. In the deposition mode both the assist and sputtering ion beams are used to produce dense films at deposition rates in the range of 0.1-0.3 nm/s. In the etch mode, only the assist ion beam is used to remove material at a rate of less than 0.1 nm/s. A very high precision in the layer thicknesses can be obtained by alternating between deposition and etch modes. We observed that etching did not significantly affect the surface quality and the uniformity of the coatings. We introduced etching into our current manufacturing process and demonstrated its potential for the fabrication of several optical multilayer systems with performances that are very sensitive to the thickness of their layers.     

大气等离子喷涂NiCrBSi-Mo/Ni涂层中黏结层对NiCrBSi-Mo复合工作层性能的影响

利用大气等离子喷涂系统在叶片钢材料FV520B上依次制备镍基黏结层和NiCrBSi-Mo复合工作层,并对NiCrBSi-Mo粉末的沉积率、涂层孔隙率、结合强度及表面硬度进行测试。结果表明:在NiCrBSi-Mo/Ni涂层中,厚度为180~220μm的黏结层在提高NiCrBSi-Mo粉末沉积率的同时可制备较低孔隙率、较高结合强度和硬度的表层涂层;黏结层厚度的增大导致工作层起始沉积位置的孔隙率增大,且加快了工作层在垂直方向上孔隙率的衰减过程。SEM分析发现,黏结层厚度的增大引起黏结层与工作层结合界面处熔滴沉积堆叠形貌的变化,黏结层中的缺陷对工作层产生"遗传性"的影响;胶结拉伸实验表明,黏结层厚度过大会导致拉伸过程中黏结层与工作层结合面处的断裂;在不同的抛磨面,一定黏结层厚度的试样块在垂直方向上的维氏硬度衰减较为缓慢,NiCrBSi-Mo/Ni涂层不仅保持了涂层表面高的硬度,且增大了涂层的厚度,以修复材料表面的损伤。     

On-line reoptimization of filter designs for multivariate optical elements

An automated method for producing multivariate optical element (MOE) interference filters that are robust to errors in the reactive magnetron sputtering process is described. Reactive magnetron sputtering produces films of excellent thickness and uniformity. However, small changes in the thickness of individual layers can have severe adverse effects on the predictive ability of the MOE. Adaptive reoptimization of the filter design during the deposition process can maintain the predictive ability of the final filter by changing the thickness of the undeposited layers to compensate for the errors in deposition. The merit function used, the standard error of calibration, is fundamentally different from the standard spectrum matching. This new merit function allows large changes in the transmission spectrum of the filter to maintain performance.     

Using fence post designs to speed the atomic layer deposition of optical thin films

Atomic layer deposition (ALD) at this time is much slower than conventional optical thin-film deposition techniques. A more rapid ALD process for SiO(2) has been developed than for other ALD materials. A fence post design for optical thin films has thin layers of high-index posts standing above a broad low-index ground. If a design for ALD can be predominantly composed of SiO(2) layers with thin high-index layers, the deposition times can be correspondingly shortened, and it is shown that the required performance can still be nearly that of more conventional designs with high- and low-index layers of equal thickness. This combination makes the ALD benefits of conformal coating and precise thickness control more practical for optical thin-film applications.     

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.     

Study of the sensitivity of the acoustic waveguide sensor

The sensitivity of the acoustic waveguide sensor to mass deposition in the presence of liquid was optimized as a function of the over-layer thickness. The waveguide geometry consisted of a 0.2-2.2-microm poly(methyl)methacrylate (PMMA) over-layer deposited on the surface of a shear acoustic wave device and supported a Love wave. The response of each polymer-coated waveguide was initially assessed by monitoring the frequency and insertion loss of the device in the presence of air. Sensitivity to viscous and mass loading was studied by recording the amplitude and phase of the wave during the application of water and of a supported lipid bilayer, respectively, on the device surface. Supported bilayers are a versatile system for mass calibration in the presence of liquid because they can be formed spontaneously on a hydrophilic surface, resulting in a layer of reproducible mass density. Results clearly showed that the response of both amplitude and phase depends on the over-layer thickness and increases with the thickness of the polymer layer. Phase was generally found to be more sensitive than amplitude to both viscous water and mass loading. The maximum sensitivity to vesicles deposition was measured at 250 cm2 g(-1) and was detected when 1.3 microm of PMMA was used as a waveguide layer. Results showed that the sensitivity of the acoustic wave sensor can be improved by simply increasing the thickness of the PMMA and that supported phospholipid layers can form an ideal system for both mass calibration and interfacial modification.     

Preparation of highly oriented titania nanosheet thin films by electrophoretic deposition

Highly oriented titania nanosheet thin films on Pt substrate were fabricated by electrophoretic deposition. The structure and morphology of thin films formed under a variety of conditions are characterized by X-ray diffraction and field-emission scanning electron microscopy. It was found that the quality of titania nanosheet precursor suspension and electrode potential play crucial roles in the film morphology. After the colloidal suspension is optimized by settling for 2 months, the surface of the deposited film is smooth, and the layered structure is dense and well-organized. Film thickness increases with increasing electrode potential, deposition temperature and deposition time. The delicate balance among the above factors that govern the film quality and thickness should be discerned. The films can exhibit a smooth surface and well-organized layered structure under the optimal deposition conditions.     

Measurement of foil thickness in transmission electron microscopy

Methods for the measurement of the thickness of thin-foil specimens used in transmission electron microscopy are either difficult to carry out or have been subject to criticism. In particular, the contamination spot method is said to overestimate the thickness because the region of rapidly changing contrast marking the apparent edge of the spot is not on the foil surface but is on a broad contamination deposit whose thickness is changing much more slowly. A new method for measuring foil thickness is proposed, based on contamination deposits on the foil surfaces. The problems of the contamination spot method, in which the deposit is of circular form, are avoided by using one of the condenser lenses to focus the electron beam in a thin line on the foil during deposition. Adequate contrast can be obtained with a line whose width is one-third to one-fifth of the foil thickness and having a height equal to or less than its width. The error, being a fraction of the line width, is then very small. After rotation of the foil, the lines separate into two and the corresponding edges of the lines provide distinct features whose separation can be measured to determine thickness. The axis of rotation, perpendicular to which the separation of the lines has to be measured to calculate foil thickness, is determined by depositing two contamination lines at right angles. The method allows a number of measurements of thickness covering a relatively large area of foil to be made per contamination experiment. Near the edge of the foil, the upper and lower lines of contamination can join around the foil edge to form a U shape which can be used to measure thickness profile of the foil right up to the edge.     

Cathodic electrophoretic deposition of barium titanate films from aqueous solution

Cathodic electrophoretic deposition (EPD) of barium titanate from aqueous suspensions was performed on nickel substrate. Cathodic deposition allows preparation of thin layers from aqueous solution on base metal electrodes, such as Ni or Cu, without creating an intermediate oxide layer during the deposition. This opens the opportunity to prepare complex shapes of dielectric layers onto base metals for co-firing, using relatively cheap and environmentally benign aqueous EPD. Stable barium titanate colloidal suspension with a concentration of 10 g/100 mL at pH of 9.2 has been prepared for the deposition. The characteristics of electrophoretic deposition of those positively charged particles onto cathode were investigated. A uniform and dense layer was obtained for films deposited at 3 V for 2 min. The calculated film thickness for the sintered layer at these conditions was ∼1 μm. The morphology can be controlled, and in particular the pore size and distribution can be controlled via the applied voltage. At low voltage a uniform layer can be obtained whereas at high voltage a large number of macropores appears in the deposit and their size increase with the increasing of the voltage due to gas bubble formation.     

Process parameters for diamond synthesis assisted by DC plasma using a water-ethylene glycol solution

Influence of the liquid composition, concentration of the potassium acetate, substrate-liquid distance and liquid layer thickness on the diamond formation were surveyed under a constant current for deposition during 1 h. Optimum deposition conditions were found to be 0.1 mol % potassium acetate, 8 mm substrate-liquid distance and 10–20 mm liquid layer thickness. Diamond forming liquid composition was then examined under a constant substrate temperature. It ranged from 60 to 99.9 mol % ethylene glycol; end compositions showed a poor yield. A constant substrate temperature was maintained under a constant current for temperatures lower than 900 °C. However, an important current reduction was required during the deposition to keep the substrate temperature higher than 1000 °C.     

Studies of the optical properties of metal-pliable polymer composite materials

Polymer-nano-metallic-particle composites have demonstrated technological potential due to their unique optical and electrical properties. Herein, we report on composites prepared via physical vapor deposition of silver metal onto pliable poly(dimethylsiloxane) (PDMS) polymer. Rapid Ag diffusion and nano-metallic-particle formation in a phase-separated surface layer of the PDMS creates unique sub-surface-based composites whose properties vary based on rate of deposition and average Ag thickness. Additionally, nanometallic-particle spacing can be altered with fair reproducibility and reversibility by physically manipulating the Ag-PDMS composite. The optical properties of the materials are studied by visible wavelength optical extinction spectrometry and surface-enhanced Raman scattering (SERS), including studies performed during physical manipulation. Direct current (DC) conductivity measurements were made during Ag deposition to study percolation conditions for the materials. Depth-profiling was performed by X-ray photoelectron spectrometry. Sample Raman spectral data collected with the composite as a SERS substrate are included. A practical technological characteristic of these composite materials arises from their potential to be molded into functional devices.     

电流密度对水热电化学沉积HA涂层性能的影响

在含0.15mol/L HF,2mol/L H_3PO_4的水溶液中对Ti6Al4V基体进行阳极氧化处理,然后在0.02mol/L CaCl_2,0.012mol/L K_2HPO_4·3H_2O,0.139mol/L NaCl的电解液中采用水热电化学沉积方法在预处理的Ti_6Al_4V基体表面制备羟基磷灰石(HA)涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、台阶仪和万能材料试验机等研究沉积过程中电流密度大小对HA涂层物相、微观形貌、厚度、生物活性及结合强度的影响。结果表明:采用水热电化学沉积方法在不同电流密度下均制备出了HA涂层,涂层表现为分层生长,部分晶体呈花簇状。HA的厚度随电流密度的增加先增大后减小,在1.25mA/cm~2时达到最大为26.4μm,此时涂层最为致密,与基体的结合强度最高,约为20.0MPa。模拟体液(SBF)浸泡实验能较快诱导类骨磷灰石(CHA)的生成,最大直径达到7~8μm,表明涂层具有较好的生物活性。     

Linear birefringence control and magnetization in sputter-deposited magnetic garnet films

Birefringence control is essential in the fabrication of on-chip magnetooptic Faraday isolators. We report on film thickness and stress studies of birefringence in sputter-deposited single-layer bismuth-substituted iron garnet films and double-layer iron garnet films with gadolinium gallium garnet (GGG) covers. We examine compressively and tensilely strained films and analyze the photoelastic response of the sputter-deposited garnet films. We show that the net birefringence can be ed out under planar compressive strain conditions. Bilayer GGG on iron garnet film yields a reduced birefringence. Temperature control during the sputter deposition of the GGG cover is critical and strongly influences the magnetic moment and birefringence level in the waveguide. High-temperature deposition lowers the magnetization in the underlying iron garnet film.     

Kerr effect enhancement in ferromagnetic films

The enhancement of the Kerr magneto-optic effect by overcoating a ferromagnetic film with a dielectric film is studied. It is treated as an impedance-matching problem for the light wave. Closed form solutions are obtained for the polar Kerr effect. The same analysis, with modifications, can be applied to the longitudinal Kerr effect. The effect of the dielectric thickness on the enhancement is continuously monitored with a laser beam (λ = 6328Å) during the dielectric film deposition. The amplification of the longitudinal Kerr signal with SiO films on iron film is of the order of five, and the enhancement varies periodically as a function of dielectric thickness. The experimentally observed period, 1600Å, agrees well with the calculated value. The sense ofB-Hloops, which also varies periodically as a function of the dielectric thickness, is explainable in terms of the phase factor which appears in the difference between the reflection coefficients.