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Texture control and growth mechanism of WSe2 film prepared by rapid selenization of W film

Hongchao Li,Di Gao,Kun Li,Mengde Pang,Senlin Xie,Rutie Liu,Jianpeng Zou

The tungsten diselenide (WSe 2 ) films with different orientation present unique properties suitable for specific applications, such as WSe 2 with a C-axis⊥substrate for optoelectronics and WSe 2 with a C-axis // substrate for electrocatalysts. Orientation control of WSe 2 is essential for realizing the practical applications. In this letter, a WSe 2 film has been prepared via rapid selenization of a magnetron-sputtered tungsten (W) film. The influence of the magnetron-sputtered W film on WSe 2 film growth was studied systematically. Scanning electron microscopy, X-ray diffractometry and high-resolution transmission electron microscopy were used to evaluate the morphology, microstructure and phase composition of the W and WSe 2 films. The substrate temperature has a significant effect on the W film phase composition, but little effect on the WSe 2 film orientation. The WSe 2 orientation can be controlled by changing the W film microstructure. A dense W film that is deposited at low pressure is conducive to the formation of WSe 2 with a C-axis⊥substrate, whereas a porous W film deposited at high pressure favors the formation of WSe 2 with a C-axis // substrate. A growth model for the WSe 2 film with different texture has been proposed based on the experimental results. The direction of selenium (Se) vapor diffusion differs at the top and side surfaces. This is a key factor for the preparation of anisotropic WSe 2 films. Highly oriented WSe 2 films with a C-axis⊥substrate grow from the dense W film deposited at low pressure because Se vapor can only diffuse into the W film from the top surface where it is converted into selenide. Highly oriented WSe 2 with a C-axis // substrate can be achieved for the porous W film that is deposited at high pressure because the nanopores provide a fast transmission tunnel for Se vapor diffusion. These findings will contribute to the controlled fabrication of WSe 2 film and provide a theoretical basis for its application.