| dc.description.abstract | Molybdenum disulfide (MoS2) is considered to have the potential to break through the physical limits of conventional semiconductor materials due to its good optoelectronic properties, such as high carrier mobility and tunable bandgap, etc. leading people extensive research on it. This study aims to grow uniform and controllable-layer MoS2 thin films at low temperature. Two methods have been used to grow MoS2 with different results. The first method is a two-step chemical vapor deposition (CVD) process, where molybdenum (Mo) thin films are first sputtered, then sulfur powder was applied to sulfide the molybdenum films. The second method is a one-step physical vapor deposition (PVD) process, where molybdenum targets are sputtered directly with hydrogen sulfide plasma to be reacted as molybdenum disulfide. The parameters, sputtering time, power, and temperature are adjusted in both methods to determine the best processing conditions. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy have been applied to confirm the molecular structure, elemental composition, and photoluminescence efficiency of the thin films.
Raman area scanning and atomic force microscopy (AFM) have also been used to analyze the uniformity and the surface roughness of the films. The experimental results show that both methods can control the number of layers by adjusting the sputtering time. However, in terms of roughness and uniformity, the roughness of the one-step process is 0.318 nm, which is significantly lower than that the two-step process at 3.62 nm, and the mapping results also have better uniformity. Moreover, the photoluminescence efficiency of the one-step process at 190°C is similar to that the two-step process at 550°C. From the results of the study, it is confirmed that the one-step process can produce flat and uniform MoS2 thin films with good photoluminescence efficiency at lower temperatures. | en_US |