title: Electrical and photo-electrical properties of MoS2nanosheets with and without an Al2O3capping layer under various environmental conditions.
abstract: The electrical and photo-electrical properties of exfoliated MoS2were investigated in the dark and in the presence of deep ultraviolet (DUV) light under various environmental conditions (vacuum, N2gas, air, and O2gas). We examined the effects of environmental gases on MoS2flakes in the dark and after DUV illumination through Raman spectroscopy and found that DUV light induced red and blue shifts of peaks (E12 gand A1 g) position in the presence of N2and O2gases, respectively. In the dark, the threshold voltage in the transfer characteristics of few-layer (FL) MoS2field-effect transistors (FETs) remained almost the same in vacuum and N2gas but shifted toward positive gate voltages in air or O2gas because of the adsorption of oxygen atoms/molecules on the MoS2surface. We analyzed light detection parameters such as responsivity, detectivity, external quantum efficiency, linear dynamic range, and relaxation time to characterize the photoresponse behavior of FL-MoS2FETs under various environmental conditions. All parameters were improved in their performances in N2gas, but deteriorated in O2gas environment. The photocurrent decayed with a large time constant in N2gas, but decayed with a small time constant in O2gas. We also investigated the characteristics of the devices after passivating by Al2O3film on the MoS2surface. The devices became almost hysteresis-free in the transfer characteristics and stable with improved mobility. Given its outstanding performance under DUV light, the passivated device may be potentially used for applications in MoS2-based integrated optoelectronic circuits, light sensing devices, and solar cells.
authors.affiliation: Department of Physics & Astronomy and Graphene Research Institute, Sejong University , Seoul 05006 , Korea.
authors.forename: Muhammad Farooq
authors.initials: MF
authors.lastname: Khan
authors.affiliation: Department of Physics & Astronomy and Graphene Research Institute, Sejong University , Seoul 05006 , Korea.
authors.forename: Ghazanfar
authors.initials: G
authors.lastname: Nazir
authors.affiliation: Department of Physics & Astronomy and Graphene Research Institute, Sejong University , Seoul 05006 , Korea.
authors.forename: Volodymyr M
authors.initials: VM
authors.lastname: Lermolenko
authors.affiliation: Department of Physics & Astronomy and Graphene Research Institute, Sejong University , Seoul 05006 , Korea.
authors.forename: Jonghwa
authors.initials: J
authors.lastname: Eom
keywords: 100 Materials; 105 Low-Dimension (1D/2D) materials; 200 Applications; 201 Electronics / Semiconductor / TCOs; 212 Surface and interfaces; 40 Optical; DUV light; MoS2; Raman spectroscopy; electrical property; magnetic and electronic device materials; photoresponse parameters; transition metal dichalcogenides