Nitrogen doped n-type CdS nanoribbons with tunable electrical and photoelectrical properties

Single-crystal nitrogen doped CdS nanoribbons (NRs) with wurtzite structure were synthesized in ammonia atmosphere via a thermal evaporation deposition route. X-ray diffraction patterns reveal a significant contraction of the lattice constants due to the incorporation of nitrogen. Temperature-varied photoluminescence spectra of CdS:N NRs exhibit spectral features near the band edge, which can be ascribed to free excition and neutral acceptor-bound excition emissions. Electrical and photoelectrical properties of the CdS:N NRs were systemically studied by constructing the field-effect transistors based on individual NRs. The conductivity of the NRs can be tuned by two orders of magnitude by controlling the N doping concentration. Moreover, by post-annealing, the device performance is remarkably improved, in particular, the mobility of the CdS:N NRs is increased by nearly three orders of magnitude from approximately 10(-1) to hundreds of cm2/Vs. I(on)I(off) ratio of the annealed device reaches over 10(4). Photoconductive properties of the CdS:N NRs were also studied. The doped NRs show high sensitivity to the light with energy larger than band-gap and the response amplitude and speed depend on the doping concentration.