Operation of Diamond Solution-Gated Field-Effect Transistor in the Frequency Domain

Here, the effect of frequency-domain sensing with diamond solution-gated field-effect transistors (SGFET) was investigated, where a sine wave with different frequencies (3, 30, 300, and 3 kHz) was applied at the gate. Variation of the power spectral density (PSD) amplitudes of the drain–source current was examined by using the NaCl gate electrolyte with various concentrations. With the increase of NaCl concentration, the PSD amplitudes basically increase for hydrogen-terminal diamond SGFET, however, the change of PSD amplitudes is not so obvious. When the diamond surface is partially oxidized by the UV radiation in the atmosphere, the PSD amplitudes increase first and then decrease with the concentration of NaCl aqueous solution. And the sensitivity of oxidized diamond SGFET is higher than that of hydrogen-terminated and increases with the increase of oxidation degree.