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Substoichiometric TiO2 films have been prepared by reactive magnetron sputtering. Employing an oxygen feedback loop has enabled a precise control of the sub-stoichiometry in the growing TiO2-x film as well as a high level of sample reproducibility. TiO2-x was deposited on unheated substrates and subsequently annealed at 300 °C. These films have been characterized by a variety of techniques to unravel the interplay between stoichiometry and optical as well as electronic properties. Capping the films by a Si3N4 layer was sufficient to prepare films with resistivities as low as 8 mΩcm showing a high mobility of up to 15 cm2/Vs. At the same time, a high transparency above 80% could be realized for these samples. The results verify that metal-like conductivity and high transparency can be realized simultaneously in undoped TiO2-x. Upon variation of the film stoichiometry a metal-insulator transition has been observed in temperature dependent electrical measurements performed down to 2 K.

The growth of crystallographical pores (crysto pores) in n-type InP and GaAs has been investigated in detail in this work. The dependence on several experimental parameters, like the substrate doping concentration ND, the etching current density j, nucleation, and etching time lead to a large amount of data. It could be shown that the data can be consistently understood in the framework of a simple model for crysto pore growth developed earlier by the authors. The stochastic nature of the model allowed for its implementation into 3-dimensional Monte-Carlo simulations, which were already able to reproduce the major features of crysto pores, as well as many detailed results. In this framework, this work serves as expansion of the parameter space which is subjected to the simulations, since the aforementioned parameters serve as free input parameters for the simulations. First results indicate that the main model parameters, the branching probabilities at pore tips and walls (ktips and kwall) are higher for InP as compared to GaAs. This effect has been interpreted as caused by a stronger passivation of GaAs surfaces by HCl in comparison to InP.