Photoconductivity of single-crystalline selenium nanotubes

The photoconductivity of single-crystalline selenium nanotubes (SCSNTs) under a range of illumination intensities of a 633 nm laser is examined using a novel two-terminal device arrangement at room temperature. It is found that SCSNTs forms Schottky barriers with W and Au contacts, and the barrier height is a function of the light intensity. In the low-illumination regime below 1.46 × 10^-4 μW μm^-2, the Au-Se-W hybrid structure exhibits sharp on/off switching behaviour, and the turn-on voltages decrease with increasing illuminating intensities. In the high-illumination regime above 7 × 10^-4 μW μm^-2, the device exhibits ohmic conductance with a photoconductivity as high as 0.59 Ω cm^-1, which is significantly higher than the reported values for carbon and GaN nanotubes. This finding suggests that a SCSNT is potentially a good photo-sensor material as well as a very effective solar cell material.