Study of the Chemical and Morphological Characteristics of Al2O3 and HfO2 Surfaces after Immersion in Time-Dependent pH Solutions

Abstract

The chemical and morphological characteristics of ALD Al2O3 and HfO2 layers after the immersion in no-buffer pH solutions have been obtained. These films are usually used as sensing layers in chemical sensors applications, and the morphology and chemical characteristics are of great importance to the chemicall sensitivity which they can provide. Hence, morphological changes has been recorded by atomic force microscopy (AFM), while the chemical characteristics has been obtained by Fourirer Transform Infrared Spectroscopy (FTIR). Also, the electrical characteristics, which need to be of high quality in ion-sensing applications, has been determined by High-Frequency Capacitance Voltage (C-V) measurements in Metal-Insulator-Metal capacitors (MIM). The results suggest that the changes experienced by the films under immersion are highly time and ionstrenght dependent, and this might be the main cause of drift in ionsensitive solid state sensors. Moreover, the data shows that HfO2 and Al2O3 exihibit different chemical characteristics after immersion than Si3N4, nonetheless, due to their high chemical sensitivity and higher dielecric constant these materials are well suited for applications in ion-sensing devices.