Low temperature CVD growth of WSe₂ enabled by moisture-assisted defects in the precursor powder

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been proposed for a wide variety of applications, such as neuromorphic computing, flexible field effect transistors, photonics, and solar cells, among others. However, for most of these applications to be feasible, it is necessary to integrate these materials with the current existing silicon technology. Although chemical vapor deposition (CVD) is a promising method for the growth of high-quality and large-area TMD crystals, the high temperatures necessary for the growth make this technique incompatible with the processes used in the semiconductor industry. Herein, we demonstrate the possibility of low-temperature growth of TMDs, using tungsten selenide (WSe2) as a model, by simply using moisture-assisted defective tungsten oxide (WO3) precursor powders during the growth of these materials. DFT calculations reveal the mechanism by which moisture promotes the defect formation on the precursor crystal structure and how it dictates the reduction of the temperature of the growth. The results were compared with the standard growth at high temperatures and with a precursor mixture with alkali salts to show the high quality of the WSe2 grown at temperatures as low as 550 °C. To conclude, the work improves the understanding of nucleation and growth mechanisms of WSe2 at low temperatures and provides a useful strategy for the growth of TMDs at temperatures required for the back-end-of-line (BEOL) compatibility with current silicon technology.

Two-dimensional materials for future information technology: status and prospects

“…Chen et al reported the direct synthesis of semiconducting PtSe2 layers at 450 • C [1016] and metallic PdSe2 layer at 300 • C [1017] on SOI to fabricate phototransistors, in which the top Si layer and the 2D layers as photoactive channel and the gate bias was applied to the bottom Si layer of the SOI. In addition, other 2D materials such as WSe2 [1018], SnS2 [1019], PdS2 [1020], PdSe2 [1021], and more have also achieved low-temperature growth compatible with BEOL through various methods. It is worth noting that besides the transfer and synthesis processes, other operations for integrating 2D materials with silicon also need to meet BEOL compatibility conditions.…”

Recent Advances in Layered MX2-Based Materials (M = Mo, W and X = S, Se, Te) for Emerging Optoelectronic and Photo(electro)catalytic Applications

“…Sassi et al [233] demonstrate the possibility of the low-temperature growth of WSe 2 using moisture-assisted defective WO 3 precursor powders. Through DFT calculations, the mechanism by which moisture promotes defect formation on the precursor crystal structure, leading to the reduction in the growth temperature, is elucidated.…”

Application of Two-Dimensional Materials towards CMOS-Integrated Gas Sensors

“…The typically required temperature is too high for BEOL integration, which requires temperatures in the 400 °C to 500 °C range. Some recent studies have worked to reduce the temperature, achieving minimal gains and managing to grow MoS 2 films at 560 °C for 50 min [ 169 ] or WSe 2 at 550 °C [ 170 ], albeit with slight modification to the typical CVD method.…”