Large-Area WS2 Film with Big Single Domains Grown by Chemical Vapor Deposition

Abstract

High-quality WS2 film with the single domain size up to 400 μm was grown on Si/SiO2 wafer by atmospheric pressure chemical vapor deposition. The effects of some important fabrication parameters on the controlled growth of WS2 film have been investigated in detail, including the choice of precursors, tube pressure, growing temperature, holding time, the amount of sulfur powder, and gas flow rate. By optimizing the growth conditions at one atmospheric pressure, we obtained tungsten disulfide single domains with an average size over 100 μm. Raman spectra, atomic force microscopy, and transmission electron microscopy provided direct evidence that the WS2 film had an atomic layer thickness and a single-domain hexagonal structure with a high crystal quality. And the photoluminescence spectra indicated that the tungsten disulfide films showed an evident layer-number-dependent fluorescence efficiency, depending on their energy band structure. Our study provides an important experimental basis for large-area, controllable preparation of atom-thick tungsten disulfide thin film and can also expedite the development of scalable high-performance optoelectronic devices based on WS2 film.Electronic supplementary materialThe online version of this article (10.1186/s11671-017-2329-9) contains supplementary material, which is available to authorized users.

CVD controlled growth of large-scale WS2 monolayers

“…[22][23][24][25][26][27] The most utilized CVD process is the sulfurization of WO 3 powders in sulfur vapor. [27][28][29][30][31][32][33][34][35][36][37][38][39][40] However, the crystal quality was inuenced by various experimental parameters, such as metal catalyst, pressure, substrate, the time of S-precursor introduction, temperature and location of precursor and substrate, carrier gas ow, pretreatment of the precursor or not, and growth temperature. 33,[41][42][43] The growth mechanism is unclear and under discussing.…”

Vapor‐phase growth of high‐quality wafer‐scale two‐dimensional materials

“…High temperature leads to low nucleation density with larger lateral size . As in the growth of graphene, the temperature can significantly affect nucleation activation energy, thus defining two nucleation density regimes: one controlled by carbon adatom species capture at low temperature (<870°C) and another controlled by desorption at high temperature (>870°C).…”

“…The higher collision frequency usually leads to a higher reaction rate and a higher nucleation rate. Thus, the low‐pressure mode is favored to achieve low nucleation density, but the included vacuum process makes it tedious and costly …”

“…High temperature leads to low nucleation density with larger lateral size. 46,80 As in the growth of graphene, the temperature can significantly affect nucleation activation energy, thus defining two nucleation density regimes: one controlled by carbon adatom species capture at low temperature (<870 C) and another controlled by desorption at high temperature (>870 C). Increasing temperature can improve the capture probability of a supercritical nucleus, due to the increase in carbon adatom mobility (at low temperature) or desorption rate (at high temperature), thus reducing the saturation nucleation density.…”

“…Thus, the low-pressure mode is favored to achieve low nucleation density, but the included vacuum process makes it tedious and costly. 80…”