The lateral resolution of photocurrent techniques such as light-addressable potentiometric sensors (LAPS) or scanning photo-induced impedance microscopy (SPIM) is limited by the properties of the semiconductor material used. We investigated metal-insulator-semiconductor (MIS) structures based on amorphous silicon (a-Si) prepared as a thin layer on transparent glass substrates. It was shown that a sub-micrometer resolution can be achieved for this material, which is much better than the results for single crystalline Si. Some limitations caused by light scattering in the structure were observed.

The silicon based semiconductor structure Si/SiO2/Si3N4/LaF3/Pt can be used as a potentiometric oxygen sensor working at room temperature. A thermal re-activation can be applied to overcome the earlier disadvantage of an increase in response time with continuous use. Using the Pt gate electrode as a resistive heater, very short electrical high-power pulses can be applied. A heating time as short as 300 ns was sufficient for the re-activation of the sensor. This way, only the sensitive thin layer system LaF3/Pt was heated, and the whole sensor was at room temperature immediately after heating. Impedance spectroscopy, X-ray photoelectron spectroscopy (XPS) and quadruple mass spectrometric (QMS)–thermogravimetry (TG) were used to investigate the mechanism of deterioration in dynamic sensor behaviour and re-activation. The formation of hydrated carbonate and the desorption of CO2 and H2O have been shown to be the causes.