Size-dependent UV photosensitivity of indium zinc oxide

We investigated the photosensitivity of indium zinc oxide (IZO) stripe structures that had different widths from 50 nm to 4 μm and the same thickness of 50 nm deposited by RF magnetron sputtering. The distance of two Ti/Au Ohmic electrodes along the IZO stripes was kept constant at 25 μm. In the dark and under 365/254 nm UV illumination, the photosensitivity was measured in air. A very slow decay of the photoresponse was observed-a typical signature of surface states. Above the critical size of 80 nm, the photosensitivities of the indium zinc oxides were less than 1%. By sharp contrast, as the size of the indium zinc oxide stripes decreased from 80 nm to 50 nm, the photosensitivity of the indium zinc oxides increased from 1% to 16%. A significant increase of the photosensitivity at the size below a critical value of 80 nm was observed, which could be explained by the high surface-to-volume ratio and surface charge trapping effects.