Laser Induced Reactions in and at Thin Semiconductor Films Progress Report

Abstract

Focussed laser light can be used to induce chemical or electrochemical reactions in the μm scale. The attainable high power densities allow to achieve fast reaction rates. At metals and insulators thermal heating dominates. On semiconductors short pulses or low energy densities cause mainly electronic processes under isothermal conditions. These will be emphasized in this paper for thin semiconductor films in electrolyte solutions. The induced reactions measured under potentiostatic or potentiodynamic conditions include electron (ETR) and ion transfer (ITR) as well.—Examples are discussed for n‐type semiconducting passive films on some base metals with thicknesses in the range from nm to μm. The ETR depend mainly on the potential showing the tendency to saturation while the ITR depend on the field strength. Doping by ion implantation reduces ETR and ITR as well. Amorphous films show a smaller tendency to inner reactions like breakdown. Bubble formation can be detected in a microscopic scale. Substrate effects are due to epitaxy on various grains, changes of the structure and crystallinity (suboxide and TiN) and electronic processes at the substrate surface (Al/Al2O3).