Impact of synthesis temperature and precursor ratio on the crystal quality of MOCVD WSe₂ monolayers

Abstract

Structural defects in transition metal dichalcogenide (TMDC) monolayers (ML) play a significant role in determining their (opto)electronic properties, triggering numerous efforts to control defect densities during material growth or by post-growth treatments. Various types of TMDC have been successfully deposited by MOCVD (metal-organic chemical vapor deposition), which is a wafer-scale deposition technique with excellent uniformity and controllability. However, so far there are no findings on the extent to which the incorporation of defects can be controlled by growth parameters during MOCVD processes of TMDC. In this work, we investigate the effect of growth temperature and precursor ratio during MOCVD of tungsten diselenide (WSe2) on the growth of ML domains and their impact on the density of defects. The aim is to find parameter windows that enable the deposition of WSe2 ML with high crystal quality, i.e. a low density of defects. Our findings confirm that the growth temperature has a large influence on the crystal quality of TMDC, significantly stronger than found for the W to Se precursor ratio. Raising the growth temperatures in the range of 688 °C to 791 °C leads to an increase of the number of defects, dominating photoluminescence (PL) at low temperatures (5.6 K). In contrast, an increase of the molar precursor ratio (DiPSe/WCO) from 1,000 up to 100,000 leads to less defect-related PL at low temperatures.

Button shear testing for adhesion measurements of 2D materials

“…CVD hexagonal boron nitride (hBN) was also transferred from a copper growth substrate onto O 2 plasma-treated thermal SiO 2 substrates by a wet-etching process 49 , and subsets with hBN were annealed up to 1000 °C between the transfer process and button fabrication. Metal-organic chemical-vapor-deposited (MOCVD) molybdenum disulfide (MoS 2 ) 50 , 51 and MOCVD tungsten diselenide (WSe 2 ) 52 was transferred from the sapphire growth substrate onto O 2 plasma-treated thermal SiO 2 substrates. Schematic cross-sections of all samples are shown in Supplementary Fig.…”

Flexible Complementary Metal‐Oxide‐Semiconductor Inverter Based on 2D p‐type WSe2 and n‐type MoS2

“…The growth time for the multi-layer film was 6 h 25 min (SEM picture of the multilayer in Figure S1, Supporting Information). [55] Device Fabrication: The devices were fabricated using a flexible PI substrate, which is prepared by spin-coating liquid PI onto a Si substrate. The PI is then cured at 350 °C for 30 min, resulting in a thickness of approximately 7 μm.…”

“…The growth time for the multi‐layer film was 6 h 25 min (SEM picture of the multilayer in Figure S1, Supporting Information). [ 55 ]…”

Dual-Limit Growth of Large-Area Monolayer Transition Metal Dichalcogenides

“…This dilemma mainly results from the uncontrollable growth kinetics that cause a competition between the lateral growth of monolayer TMDCs and the vertical nucleation of multilayer TMDCs. Wherein, the spatial distribution of precursors, which always changes with increasing reaction time, determines the uniformity of as-grown products and thus plays essential roles in manipulating the lateral growth and vertical nucleation of CVD-grown TMDCs. − As a result, the CVD growth of large-scale monolayer TMDCs requires the precise control of precursors distribution in both space and time dimensions.…”