在常压条件下使用CVD法生长单层WS2, 通过改变实验条件实现控制晶粒大小或生长成薄膜的目的。采用光学显微镜、拉曼、光致发光谱等对制备的样品进行表征, 得到了结晶质量高、尺寸达120 μm的单层WS2晶粒。同时讨论了几个重要参数如温度、生长时间以及钨源用量等对生长单层WS2的影响。结果表明: 温度对CVD生长WS2影响最大, 高温有助于生长高结晶质量的WS2。调节生长时间可以控制WS2晶粒的大小, 较长时间能生长出连续的薄膜。过量的S蒸汽会抑制WS2生长, 影响结晶质量。

Single layer WS2 was synthesized by atmospheric pressure CVD method. The mono-WS2 of triangular grain was grown by the single controlled quartz tube furnaces on well cleaned sapphire substrates. The grain size could be controlled by adjusting the experimental conditions. Optical microscopy, Raman spectroscopy, and photoluminescence emission spectroscopy were utilized to characterize WS2 samples. The Optical microscopy shows the length of triangle domain up to 120 μm and the uniform of WS2. Raman spectrum of a WS2 single domain demonstrates the characteristic E12g (in-plane vibrational ) mode and A1g (out-of-plane vibrational) mode at 355.1 cm-1 and 418.1 cm-1, respectively. The frequency difference between E12g mode and A1g mode is 64 cm-1 which matches the single-layer-thick WS2 films. The PL peak of WS2 is located at 619 nm (2.0 eV) which consistents with its direct-band-gap. Furthermore, the PL intensity of monolayer WS2 is very strong, which reveals its high crystalline. The experiment results demonstrate that the large size mono-WS2 flakes with high crystalline can be synthesized controllable on sapphire. The effects of some essential growth parameters such as the temperature, the growth time and the precursor on the controlled growth of mono-layer WS2 are also discussed.