Controllable synthesis of p-type Cu₂S nanowires for self-driven NIR photodetector application

Face-centered cubic Cu₂S nanowires with length of up to 50 μm and diameters in the range of 100–500 nm are synthesized on Si substrates through the chemical vapor deposition method using a mixed gas of Ar and H₂ as the carrier gas under a chamber pressure of about 700 Torr. It was found that the growth of quasi 1D nanostructure followed a typical vapor-liquid-solid (VLS) mechanism in which the element Cu was reduced by H₂ as the catalyst. The as-synthesized Cu₂S nanowires exhibited typical p-type semiconducting characteristics with a conductivity of about 600 S cm⁻¹ and a hole mobility (μ _h) of about 72 cm² V⁻¹ s⁻¹. Further study reveals that p-Cu₂S nanowires/n-Si heterojunction exhibits distinct rectifying characteristics with a turn-on voltage of ~0.6 V and a rectification ratio of ~300 at ±1 V in the dark and a pronounced photovoltaic behavior with an open circuit voltage (V _oc) of 0.09 V and a short circuit current (I _sc) of 65 nA when illuminated by the NIR light (790 nm, 0.35 mW cm⁻¹), giving rise to a responsivity (R) about 0.8 mA W⁻¹ and specific detectivity (D*) 6.7 × 10¹⁰ cm Hz^1/2 W⁻¹ at zero bias, which suggests the potential of as-synthesized Cu₂S nanowires applied in the field of self-driven NIR photodetector.