Optical and electrical properties of Al–WS2 films via H2S sulfurization of Al–WOx

Abstract

We have studied the composition, structure, optical and electrical properties of the Al–WS2 (un-doped and Al-doped WS2) films deposited by radio frequency (RF) magnetron sputtering and post-sulfuration processing. Results of Raman spectra show that Al–WS2 films have two predominant peaks at ∼350cm−1 and ∼420cm−1, assigned to E2g1 and A1g of pure WS2. Meanwhile, the intensity of the Raman peak (at ∼252cm−1) corresponding to Al2S3 increases with adding the Al doping contents. As for optical properties, absorption excitonic peaks at ~1.94 and ~2.35eV are comparable to those of WS2 single crystals. The optical band gaps of the Al–WS2 films can be tuned by different Al doping contents. Hall measurements were performed to study the electrical properties. Hall mobility of un-doped WS2 films is 1.40×101cm2V−1s−1, and that of the Al–WS2 films decreases to 1.16cm2V−1s−1 with Al content increasing to 3.66%. The comparable Hall mobility of Al–WS2 films can be obtained by controlling appropriate Al doping contents. Furthermore, WS2 films undergo transitions from n-type conductivity to p-type conductivity when the films are doped with Al.