Studies On The Optical And Electrical Properties Of Monolayer MoS₂

Two-dimensional transition metal sulfide, such as molybdenum disulfide (MoS2), is a low-dimensional semiconductor material with broad-band gap. Monolayer MoS2has direct band gap (1.8ev), which is a good candidate for building field-effect transistors with low quiescent power drain and high on-off ratio.In this paper,"top-down" micro-mechanical stripping method has been adopted to manufacture monolayer or multilayer grapheme-like molybdenum disulfide nanosheets, and Raman spectrum adopted to characterize the microstructures of the target products. Using photolithography and lift-off technique, Au/MoS2nanosheet/Au devices have been fabricated based on monolayer and multilayer MoS2nanosheets. The electrical transport properties of the devices have been characterized under different conditions on Keithley2602SourceMeter with Lab VIEW program. The main results of this paper are listed as follow:1. Monolayer MoS2nanosheets have been successfully exfoliated by micro-mechanical stripping method. Photoelectric devices based on monolayer MoS2have been successfully fabricated with photolithography. 2. We have measured the monolayer MoS2photoelectric properties of the devices under illumination of laser with different wavelength. Experimental results indicate that the MoS2devices exhibit excellent photosensitivity. The devices exhibit highest photosensitivity in the blue-violet light region, and then in green light region and in red light region. The conductivity of the MoS2devices increases over four orders of magnitude under light illumination.3. We have built field-effect transistors based on monolayer MoS2and studied the influences of H2O on the electrical properties the MoS2transistors. Experimental results show that the conductivity and the on and off voltages of the transistors increase correspondingly with relative humidity increasing.