Aluminium-doped n-type ZnS nanowires as high-performance UV and humidity sensors

Abstract

Controlling the electrical transport properties of II–VI nanostructures is vital to their practical applications. Here, we report the synthesis of n-type ZnS nanowires (NWs) by using aluminium (Al) as a dopant via a simple thermal co-evaporation method. The conductivities of the ZnS:Al NWs were greatly enhanced upon Al doping and could be further tuned in a wide range of 3 orders of magnitude by adjusting the doping level. Field-effect transistors (FETs) fabricated from individual ZnS:Al NWs revealed an electron concentration up to 1.3 × 10¹⁸ cm⁻³ in the NWs. Significantly, the doped NWs showed great potential as visible-blind UV sensors with an extremely high responsivity of 4.7 × 10⁶ A W⁻¹, giving rise to a large gain-bandwidth (GB) of ∼0.1 GHz. The high sensitivity of the ZnS:Al NWs to humidity was also investigated; the devices displayed a resistance variation of about 2 orders of magnitude in the relative humidity (RH) range of 50–90%. Our results demonstrate that the n-type ZnS:Al NWs have important applications in nanoelectronic and nano-optoelectronic devices.