Abstract
We propose a charge transfer type ion image sensor operated using a charge accumulation technique that accumulates the output signal and integrates it temporally. This technique is expected to image hydrogen ion distributions with a high signal-to-noise (S/N) ratio. The sensor was fabricated using large-scale integration technology, so that its size was very compact, and its specialized charge transfer characteristics allowed it to amplify the signal without any external amplification. The sensor noise was independent of the sensing area size, and the noise power was determined by the noise of the source follower circuit. In 5 accumulation cycles, the S/N ratio increased by √5 times and the pH-referred noise, which indicates the pH sensor resolution, was reduced from 0.09 to 0.06 pH. The sensor effectively obtained a real-time image of the hydrogen ion distribution in a solution with a resolution of pH 0.1, which would not be possible without charge accumulation.