Transport and Optoelectronics properties of MoS2 thin film transistors

• Main Authors: Li-Tsung Liu, 劉立悰
• Other Authors: Yuen-Wuu Suen
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/34575185711739466706

碩士 === 國立中興大學 === 奈米科學研究所 === 102 === We investigate electrical and optoelectrical properties of a multilayer MoS2 field effect transistor (FET) devices. We use image analysis method, atomic force microscope (AFM), and Raman spectroscopy to identify the thickness and number of layers of the MoS2 flakes, and defined the electrodes by e-beam lithography. The electron mobility deduced from the electrical characteristics of the MoS2 field effect transistor (FET) with a channel length of 4.5 μm and a width of 2.95 μm is about 3.56 cm2V-1s-1 in the air and 5.57 cm2V-1s-1 in vacuum at room temperature. The temperature dependence of the electrical properties indicates that the Schottky barrier between contacts and the MoS2 film significantly affect the electrical performance. We map out the distributions of the photocurrent of the MoS2 devices by using a confocal microscope with a sample stage scanner at the bias voltage of 3 V and the back-gate voltage of 20 V in the air at room temperature. We found that the photocurrent distribution is not symmetric between the source and drain electrodes and the magnitude is dominated by the barrier of the metal-semiconductor interface. The decay of photocurrent of MoS2 TFT can be divided into three stages after the excited source is turned off. The photocurrent first decays rapidly after laser is off because off the electron-hole recombination. And then the photocurrent decreases with a relaxation time about 20 second due to the exciton relaxation and thermoelectric effect. The last part with a relaxation time about 1300 second can be attributed to the slow charge trapping at the surface defect sites of MoS2.