Influence of electrical machining of the surface of a semiconductor sensitive layer of a gas sensor on its electrical properties

Abstract

Features of the modification of the composition and structure of the surface layer of silicon using electrical discharge machining (EDM) for the formation of a sensitive layer (SL) of a gas sensor are studied. Electrical properties of silicon-passed EDM with energy of 0.4 J by a nickel electrode with subsequent annealing in nitrogen at 1000°C for 1 h are investigated by the methods of atomic-force microscopy, deep level transient spectroscopy, and voltage-capacitance characteristics. It is shown that EDM of silicon by a nickel electrode leads to developed surface relief varying irregularity height more than eightfold and surface roughness more than elevenfold. This is accompanied by an increase in the density of surface states by an order of magnitude to 1013 cm−2 eV−1. In addition, acceptor deep levels (DL) with ionization energies of 0.24, 0.34, 0.40, and 0.55 eV are found in the silicon band gap. The bend in the energy bands, which appears on the semiconductor surface and is caused by the nonuniform distribution of DLs formed by EDM as well as by a high density of surface states, and developed surface microrelief, will substantially affect the sorption processes on the SL surface of gas sensors, their sensitivity, and selectivity.