Enhanced photocurrent and photoluminescence spectra in MoS2 under ionic liquid gating

• Published in: Nano research Vol. 7; no. 7; pp. 973 - 980
• Main Authors: Li, Zhen, Chang, Shun-Wen, Chen, Chun-Chung, Cronin, Stephen B.
• Format: Journal Article
• Language: English
• Published: Heidelberg Tsinghua University Press 01.07.2014
• Subjects: Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Chemistry and Materials Science; Condensed Matter Physics; Materials Science; Nanotechnology; Research Article; 二硫化钼; 光电流; 光致发光光谱; 复合中心; 浇注; 离子液体; 表面状态; 陷阱电荷; ionic liquid; MoS; passivation; photoluminescence; photocurrent; dichalcogenide
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-014-0459-2

We report substantial improvements and modulation in the photocurrent （PC） and photoluminescence （PL） spectra of monolayer MoS2 recorded under electrostatic and ionic liquid gating conditions. The photocurrent and photo- luminescence spectra show good agreement with a dominant peak at 1.85 eV. The magnitude of the photoluminescence can be increased 300% by ionic liquid gating due to the passivation of surface states and trapped charges that act as recombination centers. The photocurrent also doubles when passivated by the ionic liquid. Interestingly, a significant shift of the PL peak position is observed under electrostatic （14 meV） and ionic liquid （30 meV） gating, as a result of passivation. The ionic liquid provides significant screening without any externally applied voltage, indicating that these surface recombination centers have net charge. The acute sensitivity of monolayer MoS2 to ionic liquid gating and passivation arises because of its high surface-to-volume ratio, which makes it especially sensitive to trapped charge and surface states. These results reveal that, in order for efficient optoelectronic devices to be made from monolayer MoS2, some passivation strategy must be employed to mitigate the issues associated with surface recombination.