Application of the transverse acoustoelectric effect to studying silicon surface charging upon water adsorption

Water adsorption on a silicon surface in a layered Si–LiNbO$_3$ structure with an air gap is studied using the transverse acoustoelectric effect on surface acoustic waves. A generalized analysis of measurements of the transverse acoustoelectric effect makes it possible to determine the initial band bending of the Si surface, its changes during gas cycles, hence, the sign and charging kinetics of Si upon H$_2$O adsorption. Depending on the properties of the semiconductor surface defects, both the donor and acceptor nature of the interaction of H$_2$O with Si are observed. For samples with a thermal oxide, the donor-type interaction occurs; for samples with a natural oxide, both interaction types take place. Based on the used physical model of oxide charging upon exposure to an adsorbate, a comprehensive methodical approach is proposed, which allows the targeted development of acoustoelectronic structures for sensor applications.