Alkaline ion sensitivity of insulator-silicon structures with glass membranes prepared by the sol-gel technique

The advantages of using sol-gel glass sensing layers for insulator-silicon structures include good adhesion on Si and Si-related insulators, easy and reproducible deposition, and the possibility of patterning the films by photolithography. Electrolyte-glass membrane-insulator-semiconductor (EMIS) and electrolyte-glass membrane-metal-insulator-semiconductor (EMMIS) structures, in which sodium aluminosilicate glass layers were prepared by the sol-gel method to obtain an alkali ion sensitivity and a high selectivity with respect to the hydrogen ions, were characterised by C-V curves. Results for the EMIS structure indicated a high selectivity for the alkali ions with respect to the hydrogen ions. The selectivity was greater for Na+ than K+. Identical behaviour for EMMIS samples showed that the presence of a thin metal layer between the glass membrane and the top insulator does not affect the chemical characteristics of the structure. Calculation of the K(K,Na) coefficient also indicated a slightly higher selectivity for Na+ than for K+, against expectation. The reason for this is not clear. 5 refs.