Stepped-surfaced GeSe2 nanobelts with high-gain photoconductivity†

Single crystalline stepped-surfaced GeSe2 nanobelts (NBs) were synthesized by vapor transport and deposition method with the presence of Au catalyst. The NBs were grown via VLS mechanism with catalytic Au–Ge–Se alloy droplet formed at the tip of the NBs. The dynamic reshaping of the catalyst particle leads to formation of steps along the NB. Photodetectors comprising individually isolated NBs were fabricated to study their photodetection properties. The photoresponsivity of the devices was investigated at four different excitation wavelengths of 405 nm, 532 nm, 808 nm and 1064 nm. High photoresponsivity of 1040 A W 1 and a photoconductive gain of 121 800% was achieved at a wavelength of 1064 nm, suggesting that the excitation to defect-related energy states near or below the mid band-gap energy plays a major role in the generation of photocurrent in these highly stepped NB devices.