C. R. Ottermann

Density of thin TiO2 films

Abstract Thin oxide films have a broad range of applications in optical devices. Titania (TiO2) is a frequently used oxide material for optical coatings because of its high refractive index (≈ 2.4) and low absorption. The development of devices and optimization of production parameters require proper knowledge of the film properties, such as refractive index, composition, contaminations and density. In thin-film analysis, RBS is usually employed for the determination of the film stoichiometry and contaminations. We have used a combination of RBS analysis and optical measurements to deduce absolute values for the density of thin films. Results for thin TiO2 films are presented demonstrating the usefulness of this approach. A strong correlation of density and refractive index is found. The density values are compared with data gained by X-ray reflection spectrometry. The differences of the density values obtained by both techniques are discussed, focusing on the uncertainties of the 4He stopping power values.

Hydrogen dynamics in electrochromic multilayer systems investigated by the 15N technique

Abstract The resonant reaction 1H(15N, αγ)12C was used to determine the depth distribution of hydrogen in two electrochromic multilayer systems. The systems can be bleached and colored by applying an external voltage. To test models explaining this effect by a change of H content (cH) in electrochromic layers, H profiles of the systems were measured as a function of the applied voltage. For NiOx, cH was found to vary as predicted, whereas for WO3, cH changes were smaller than expected. Additionally, H uptake into the ITO electrode was observed.

Stress of Tio2 Thin Films Produced by Different Deposition Techniques

Stress in thin films has been measured very precisely ( 2 films of approximately 100 nm thickness were prepared by reactive evaporation (RE), reactive ion plating (IP), plasma impulse chemical vapor deposition (PICVD) and spin coating (SC). Large variations in stress are found for different coating techniques and deposition conditions. This can be correlated to differences in optical properties, film density and crystalline structure. Relaxation effects and the influence of thermal treatment are also studied. The crystallization of amorphous TiO 2 during heat treatment is accompanied by significant changes in film stress. The crystal size and morphology of TiO 2 films after heat treatment strongly depend on the deposition technique and process conditions.

Analysis of tungsten oxide films using MeV ion beams

Abstract Tungsten oxide films produced by reactive evaporation were analyzed using the 15N technique for H profiling, RBS with 4He ions and ERD with 40Ar ions. The film stoichiometry was determined as WO3.0H0.3+aH2O, where the second term describes the uptake of water molecules during storage after film production. It was found that the stoichiometry of the films is not influenced by ion irradiation over a large range of ion doses and that the coloration of the films induced by ion irradiation is not connected with changes of the H content.

Young`s modulus and density of thin TiO{sub 2} films produced by different methods

The Young`s modulus and density are analyzed for 280 and 500 nm thick TiO{sub 2} layers deposited by reactive evaporation (RE) and ion plating (IP) by means of surface acoustic wave spectroscopy (SAWS) and grazing incidence X-ray reflection spectroscopy (GIXR). The layers are amorphous or polycrystalline, and have densities between 2.9 g/cm{sup 3} and 3.8 g/cm{sup 3}, depending on the deposition conditions. The measured Young`s moduli vary between 65 GPa for RE films and 147 GPa for IP layers. They are independent of film thickness, but correlate with the density. A change of the Young`s modulus due to the phase transition from amorphous to anatase is described, which occurs at temperatures above 210 C.

Stress and Density of Thin TiO 2 Films Produced by Different Methods

Stress, density and refractive behavior are analyzed for TiO 2 layers deposited by reactive evaporation (RE), ion plating (IP), plasma impulse chemical vapour deposition (PICVD) and spin coating (SP) from bending of the substrate and by means of Rutherford Backscattering Spectroscopy (RBS), respectively. Densities between 2.7 gem -3 and 3.8 gem -3 are obtained depending on coating techniques and coating conditions. Refractive index depends linear on density. A correlation between film stress and density is observed which is independent from coating process, production parameters and crystal structure of the as-deposited films. Stress is tensile at low densities and compressive for films with densities of the order of the crystal phase of anatase (3.84 gem -3 ). The phase transition from amorphous to anatase due to annealing induces an increase in stress. Film density determines the transition temperature, and the magnitude of stress increase.

Nonlinear acoustic response in thin oxide layers on fused silica

Nonlinear mechanical properties of layered systems of Ta{sub 2}O{sub 5} and TiO{sub 2} films deposited on fused silica by reactive evaporation (RE), reactive ion plating (IP) and spin coating (SC) are investigated by means of an ultrasonic technique. The coatings with thickness of 100 nm possess differences in density and crystal structure, due to the different deposition conditions. The nonlinear acoustic response of the film/substrate systems depends on film material. Differences are observed in respect to film density as obtained by the alternate deposition methods. The origin of the differences in nonlinear acoustic response of the samples is discussed. The results are correlated to adhesion properties of the films determined by a scratch-test method.