Thin silicon light-addressable potentiometric sensor by Deep reactive-ion etching

To have a high photocurrent and spatial resolution of 2-dimensional (2D) chemical image in light-addressable potentiometric sensor (LAPS), silicon substrate is thinned down to about 100 μm by Deep reactive-ion etching (DRIE). Compare to commercial Si substrate with thickness of 350 μm, photocurrent is increased for 4.5 times and operation frequency is increased to 20 kHz. pH sensitivity is 67.09 mV/pH for NbOx sensing membrane. A clear 2D image to recognize a pattern with width of 100 μm can be obtained. Higher signal to noise ratio is benefit for high-speed and spatial resolution of 2D chemical image.