CVD growth of large-area monolayer WS2 film on sapphire through tuning substrate environment and its application for high-sensitive strain sensor

Abstract

Large-area, continuous monolayer WS2 exhibits great potential for future micro-nanodevice applications due to its special electrical properties and mechanical flexibility. In this work, the front opening quartz boat is used to increase the amount of sulfur (S) vapor under the sapphire substrate, which is critical for achieving large-area films during the chemical vapor deposition processes. COMSOL simulations reveal that the front opening quartz boat will significantly introduce gas distribute under the sapphire substrate. Moreover, the gas velocity and height of substrate away from the tube bottom will also affect the substrate temperature. By carefully optimizing the gas velocity, temperature, and height of substrate away from the tube bottom, a large-scale continues monolayered WS2 film was achieved. Field-effect transistor based on the as-grown monolayer WS2 showed a mobility of 3.76 cm2V−1 s−1 and ON/OFF ratio of 106. In addition, a flexible WS2/PEN strain sensor with a gauge factor of 306 was fabricated, showing great potential for applications in wearable biosensors, health monitoring, and human–computer interaction.

Optimized Substrate Orientations for Highly Uniform Metal Halide Perovskite Film Deposition

“…In a typical tubular chemical vapor deposition (CVD) system, the substrate’s position within the furnace and orientation relative to the carrier gas flow critically affect its surface distribution of temperature and precursor concentration, which are key parameters for film uniformity. , Here, we obtained CH 3 NH 3 PbI 3 (MAPbI 3 ) films using a two-step vapor deposition process: the deposition of a PbI 2 primary layer followed by a conversion reaction with CH 3 NH 3 I (MAI) vapor (see Figure S1 for detailed temperature and gas flow profiles). , Given the significant differences in the molecular diffusion and reaction rates of PbI 2 and MAI, , it is necessary to decouple the PbI 2 primary layer growth from the conversion step, thereby independently optimizing each process. Consequently, the effect of the substrate orientation on each step can be individually assessed.…”

Large-area single-crystal TMD growth modulated by sapphire substrates

“…134 Yang et al simulated the gas flow distribution in unopened and front-opened quartz boats. 9 The results revealed that the front opening quartz boat can greatly increase the S vapor distribution near the substrate. They realized large-scale continuous monolayer WS 2 films in front-opened quartz boat by adjusting the growth temperature, gas flow rate, and substrate height.…”

“…In addition, too fast flow rate carries away the heat from the substrate and leads to thermal loss at the growth temperature. 9 Therefore, at a low flow rate, the nucleation density is relatively low and it is easy to form a large monolayer, while at a higher flow rate, the nucleation density is high and it is easy to form many small-sized crystal domains (Fig. 12b).…”

“…They realized large-scale continuous monolayer WS 2 films in front-opened quartz boat by adjusting the growth temperature, gas flow rate, and substrate height. 9…”

“…, specific gases, pressure, humidity, and temperature) and stable under ambient conditions, thus they can be applied to prepare sensors. 9,10 However, impurities and defects in TMD materials can greatly affect these intrinsic physical and chemical properties ( e.g. , electrical conductivity and stability) of the materials.…”