In situ thin film differential thermal analysis of amorphous V2O5 thin films

In situ differential thermal analysis (DTA) experiments were performed on highly quenched amorphous V₂O₅ thin films directly evaporated onto a thin film differential thermocouple microprobe. Irreversible low temperature relaxations were thus evidenced, a result impossible to obtain with a classical DTA apparatus using microcrucibles such as Setaram or Mettler TA 2000 devices.     

An alternative sol-gel route for the preparation of thin films in CeO2-TiO2 binary system

Thin films of titania-ceria have been prepared via sol-gel processing by employing titanium and cerium chloride compounds in highly acidic conditions for the precursor sol. This sol-gel route allows obtaining titania-ceria and cerium titanate films, CeTi₂O₆, after thermal treatment in air. The films exhibit a high optical transparency which is modulated by controlling the composition and the thermal treatment. The materials have been characterized by X-ray diffraction, UV-visible spectroscopy, ellipsometric spectroscopy and atomic force microscopy. The titania-ceria films show, as a function of the composition, the formation of different phases after thermal treatment in air at 800 °C. In particular, with the composition Ce25-Ti75 we have obtained a pure cerium titanate phase, CeTi₂O₆, which can be formed only in a very strict range of compositions.     

In situ epitaxial MgB2 thin films for superconducting electronics

The newly discovered 39-K superconductor MgB2 holds great promise for superconducting electronics. Like the conventional superconductor Nb, MgB2 is a phonon-mediated superconductor, with a relatively long coherence length. These properties make the prospect of fabricating reproducible uniform Josephson junctions, the fundamental element of superconducting circuits, much more favourable for MgB2 than for high-temperature superconductors. The higher transition temperature and larger energy gap of MgB2 promise higher operating temperatures and potentially higher speeds than Nb-based integrated circuits. However, success in MgB2 Josephson junctions has been limited because of the lack of an adequate thin-film technology. Because a superconducting integrated circuit uses a multilayer of superconducting, insulating and resistive films, an in situ process in which MgB2 is formed directly on the substrate is desirable. Here we show that this can be achieved by hybrid physical-chemical vapour deposition. The epitaxially grown MgB2 films show a high transition temperature and low resistivity, comparable to the best bulk samples, and their surfaces are smooth. This advance removes a major barrier for superconducting electronics using MgB2.     

Computational analysis of martensitic thin films using subdivision surfaces

This paper studies numerically the deformation of thin films made of materials undergoing martensitic phase transformations by using subdivision surfaces. These thin films have received interest as potential microactuators, and specifically a tent‐like configuration has recently been proposed. In order to model martensitic materials we use a multi‐well strain energy combined with an interfacial energy penalizing strain gradients. The study of such configurations requires adequate resolution of inhomogeneous in‐plane stretch, out‐of‐plane deformation and transition regions across which the deformation gradient changes sharply. This paper demonstrates that subdivision surfaces provide an attractive tool in the numerical study of such configurations, and also provides insights into the tent‐like deformations. Copyright © 2007 John Wiley & Sons, Ltd.     

Precision metrology for studying thin films and surfaces

Evaluation techniques that are appropriate for characterizing the surface topography of optical thin films and surfaces are briefly described. These include microscopes ranging from low power optical microscopes to scanning probe microscopes that can measure topography of individual atoms or groups of atoms, optical non-contact and mechanical contact profilers, some of which can give topographic maps of surface areas, and total integrated scattering and angle-resolved scattering that yield statistical properties of surfaces. Theories are needed to relate scattering to surface topography; these are valid only for certain types of topographies. Examples are given showing how various surface evaluation techniques can be applied to selected surfaces.     

in situ Preparation of superconducting HgBa2CuO4 thin films

Superconducting thin films of HgBa₂CuO₄ have been grown in situ by using a sputtering method for the first time. (100) SrTiO₃ was used as substrates and heated between 500 ° C to 600 ° C during the film deposition. By setting the deposition conditions properly, c axis oriented HgBa₂CuO₄ films were grown perpendicularly to the substrate surface. It was found that Hg composition in the deposited films had close relation to the sputtering gas, namely, the oxygen partial pressure, Hg could remain in the film when the partial pressure of oxygen was lower than in the case of the other oxide superconductors such as Bi cuprates. The optimum oxygen partial pressure for the crystallized thin film ranged from 0.1 Pa to 0.01 Pa with total gas pressure of 0.6 Pa. The superconducting transition was observed at around 75K.     

Experimental system for GaN thin films growth and in situ characterisation by electron spectroscopic methods

A double chamber vacuum system was constructed for the electron spectroscopy study of GaN layer growth. The samples are prepared by vacuum deposition from Knudsen-type Ga source in the afterglow atmosphere of active nitrogen produced by high-pressure RF-plasma source. The growth chamber is connected to the analysis chamber equipped with electron spectroscopy (XPS, AES) analysis, permitting to study the chemical composition of layers as a function of growing conditions. It is shown that the new RF-source is suitable for preparation of pure stoichiometric GaN layers.     

Kinetic process of phase separation in Co-SiO2 thin films and preparation of mesoporous SiO2 thin films with mesopore channels aligned perpendicularly to substrate surfaces

A physical co-sputter deposition process under a relevant working gas pressure condition was used to produce a multi-component thin film with a longitudinally self-organized microstructure. In this paper, Co-Si-O thin films were prepared by radio frequency (RF) magnetron sputtering, and their growth structures were studied by means of SEM, TEM, XRD and XPS. The microstructural changes in the Co-Si-O thin film and their dependence on Ar working gas pressure were investigated; the formation of Co-Si-O thin films, having a regular array of needle-like Co columns aligned perpendicularly to the substrate surfaces, was observed with appropriate Ar working gas pressure, and the diameter of the columns increased with increasing Ar pressure. Mesoporous silica thin films having perpendicular mesopore channels were obtained by chemical etching of the columnar Co parts in the Co-Si-O thin films. Through experimental observations, we propose that the phase separation and resultant microstructures in the thin films are determined by the surface mobility of the two components (Co and silica) on the film surface. A simple model, incorporating a diffusion process in the simultaneous deposition of two components, is presented. The model demonstrates the general trends of a kinetically self-organized microstructure in a two-component thin film.     

In situ annealing of hydroxyapatite thin films

Hydroxyapatite is a bioactive ceramic that mimics the mineral composition of natural bone. Unfortunately, problems with adhesion, poor mechanical integrity, and incomplete bone ingrowth limit the use of many conventional hydroxyapatite surfaces. In this work, we have developed a novel technique to produce crystalline hydroxyapatite thin films involving pulsed laser deposition and postdeposition annealing. Hydroxyapatite films were deposited on Ti–6Al–4V alloy and Si (100) using pulsed laser deposition, and annealed within a high temperature X-ray diffraction system. The transformation from amorphous to crystalline hydroxyapatite was observed at 340 °C. Mechanical and adhesive properties were examined using nanoindentation and scratch adhesion testing, respectively. Nanohardness and Young's modulus values of 3.48 and 91.24 GPa were realized in unannealed hydroxyapatite films. Unannealed and 350 °C annealed hydroxyapatite films exhibited excellent adhesion to Ti–6Al–4V alloy substrates. We anticipate that the adhesion and biological properties of crystalline hydroxyapatite thin films may be enhanced by further consideration of deposition and annealing parameters.     

Microwave annealing for preparation of crystalline hydroxyapatite thin films

A sol was spun on single crystal silicon substrates at a spin-rate of 3000–5000 rpm followed by a low temperature cure to form a stable sol–gel/silicon structure. Good quality crystalline HA films of thickness ∼300–400 nm were obtained by annealing the sol–gel/Si structure in a conventional cavity applicator microwave system with a magnetron power of 1300 W, frequency of 2.45 GHz, and at a low processing temperature of 425 °C for annealing times ranging from 2–60 min. X-ray Diffraction and FTIR analysis confirmed that the crystalline quality of the thin films were comparable or better than those heat-treated under the same processing conditions (temperature and time) in a Rapid Thermal Annealing (RTA) system. The RBS data suggests a composition corresponding to stoichiometric hydroxyapatite Ca₁₀(PO₄)₆(OH)₂, the major inorganic component of bone. The results showed that the HA film thickness decreases with increasing sol spin-rate. The HA films showed good biocompatibility because little monocyte adhesion occurred and hence no inflammatory response was activated in vitro. The potential of microwave annealing for rapid and low temperature processing of good crystalline quality HA thin films derived from sol–gel is demonstrated.     

Electromigration in thin gold films on molybdenum surfaces

Electric current was passed through thin gold films deposited onto molybdenum surfaces. The edge of the gold film closer to the cathode was seen to move towards the anode, leaving a free molybdenum surface. Large hillocks and crystallites were seen to accumulate on the gold edge pointing toward the anode. The velocity of the film edge was assumed to represent the average drift velocity for electromigration.The velocity of the gold edge was found to be constant at any given temperature and current density. At any constant temperature, the velocity was proportional to the current density. Finally, the velocity depended exponentially on the temperature.Current densities of 10⁵–10⁶ Acm^-2 were used at temperatures of 260°–500°C. The “activation energy” for the drift velocity was found to be 0.6 eV in most samples, while some samples showed an energy of about 0.9eV. The drift velocities per unit current density ranged between 10^-13 and 10^-15 cm³ A^-1 s^-1 and the gold motion was always in the direction of electron flow.     

CoSnS2薄膜的制备及性能研究

采用两种方法制备了CoSnS2薄膜。在两步电沉积法中，先沉积SnS薄膜，再在其上制备CoS沉积薄膜，最后进行退火处理形成厚度约为1250nm的CoSnS2薄膜。在三元共沉积法中，加入EDTA(乙二胺四乙酸二钠)配合剂来调整Sn、Co、S的沉积电势以实现这三种元素的共沉积，从而一步形成厚约620nm的CoSnS2薄膜。探讨了薄膜的制备机理和制备条件对薄膜结构特性和光学特性的影响。得到的薄膜为多晶γ-Co6S2(立方晶系)和SnS(斜方晶系)结构，其直接光学带隙和间接光学带隙分别在1．05～1．25eV和0．11～0．71eV之间可调。     

Antimony-incorporated TiO2 thin films: preparation and optical and electrical characteristics

Antimony-incorporated TiO₂ thin films were prepared using the spray-pyrolysis technique. The optical characteristics (percentage transmittance, refractive index, extinction coefficient) and the film thickness were investigated. The resistivity of the prepared samples was measured, and the effect of Sb concentration and film thickness on the measured parameters was discussed. The effect of Sb on the band-gap was also studied.     

In situ preparation of calcium carbonate films

The in situ preparation of calcium carbonate films in an ultra high vacuum (UHV) is inhibited by the decomposition of CO₂ molecules at the surface and the absence of CO₂ bulk diffusion. Therefore, it is not possible to prepare such films simply by CO₂ exposure to a calcium layer.We investigated different approaches for the preparation of CaCO₃ films in an UHV. Among these, only the simultaneous evaporation of Ca atoms in a mixed O₂ and CO₂ atmosphere is able to produce well defined stoichiometric calcium carbonate films. Metastable Induced Electron Spectroscopy, Ultraviolet Photoelectron Spectroscopy and X-ray Photoelectron Spectroscopy are employed to verify quality and purity of the films.     

In situ preparation of Calcium hydroxide films

The in situ preparation of Calcium hydroxide films in an ultra high vacuum (UHV) is constrained by the decomposition of species at the surface and the absence of OH bulk diffusion. Therefore, it is not possible to prepare such films simply by water exposure to a Calcium layer.We present four different approaches for the preparation of Ca(OH)₂ films in an UHV. Two of these methods are found to be ineffective for the preparation, the other two are shown to produce Calcium hydroxide films. Both of the two effective procedures make use of H₂ gas exposure. Metastable Induced Electron Spectroscopy, Ultraviolet Photoelectron Spectroscopy, and X-ray Photoelectron Spectroscopy are employed to verify quality and purity of the films.     

纳米晶TiO2薄膜的制备、表征及其光催化性能的研究

采用sol-gel法制备TiO2薄膜。用XRD、UV－vis、AFM对其结构、光谱吸收及表面形貌进行了表征。以具有典型偶氮染料结构的甲基橙水溶液为目标反应物，对膜的光催化性能进行了研究。结果表明，在普通玻璃衬底上得到了比较好的锐钛矿型TiO2薄膜，其紫外吸收谱带拓宽，该膜对低浓度甲基橙有较好的光催化降解功能。     

氮化锆薄膜色度特性与工艺参数研究

制备了ZrN薄膜，通过采用二次正交旋转组合试验设计方案，建立了薄膜颜色和氮气浓度、靶功率与镀膜时间的数学模型，给出了各参数对薄膜颜色的影响趋势。经模型寻优，求出了在不同目标色度坐标下的最优参数组合方案。     

A chemical method for the preparation of TlS thin films

A method has been developed for chemically depositing thin films of TlS onto glass substrates using a thallous nitrate solution, ammonia and thiourea as the reacting agents. The material was characterized through X-ray powder diffraction, optical and photoelectric studies. The films were found to be p type with an optical energy gap of about 1.02 eV.