P-I-N amorphous silicon light-addressable potentiometric sensors for high-photovoltage chemical image

For higher photo signal of chemical image sensor, a new device structure of P-I-N amorphous silicon (a-Si) on ITO/glass is first applied in light-addressable potentiometric sensor (LAPS). Niobium oxide (NbO_x) is used as pH sensing membrane. All processes of device are lower than 300oC, which are suitable for glass substrate. Based on photovoltage versus gate bias characteristics, calculated pH sensitivity and linearity between pH 2 to 10 is 40 mV/pH and 99.4%, respectively. Compare to conventional intrinsic amorphous silicon structure, improvement on photocurrent, and spatial resolution are 50% and 15%, respectively. In the meantime, higher frequency of ac signal of laser up to 20 kHz could be used for high speed scanning by means of red laser and analog micromirror scanning system.