Suzuki Hiroo, Hashimoto Ryoki, Misawa Masaaki, Liu Yijun, Kishibuchi Misaki, Ishimura Kentaro, Tsuruta Kenji, Miyata Yasumitsu, Hayashi Yasuhiko
Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
Faculty of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
ACS Nano. 2022 Jul 26;16(7):11360-11373. doi: 10.1021/acsnano.2c05076. Epub 2022 Jul 6.
Transition metal dichalcogenides (TMDCs), including MoS and WS, are potential candidates for next-generation semiconducting materials owing to their atomically thin structure and strong optoelectrical responses, which allow for flexible optoelectronic applications. Monolayer TMDCs have been grown utilizing chemical vapor deposition (CVD) techniques. Enhancing the domain size with high crystallinity and forming heterostructures are important topics for practical applications. In this study, the size of monolayer WS increased via the vapor-liquid-solid growth-based CVD technique utilizing the confined space of the substrate-stacked microreactor. The use of spin-coated metal salts (NaWO and NaMoO) and organosulfur vapor allowed us to precisely control the source supply and investigate the growth in a systematic manner. We obtained a relatively low activation energy for growth (1.02 eV), which is consistent with the surface diffusion-limited growth regime observed in the confined space. Through systematic photoluminescence (PL) analysis, we determined that a growth temperature of ∼820 °C is optimal for producing high-quality WS with a narrow PL peak width (∼35 meV). By controlling the source balance of W and S, we obtained large-sized fully monolayered WS (∼560 μm) and monolayer WS with bilayer spots (∼1100 μm). Combining two distinct sources of transition metals, WS/MoS lateral heterostructures were successfully created. In electrical transport measurements, the monolayer WS grown under optimal conditions has a high on-current (∼70 μA/μm), on/off ratio (∼5 × 10), and a field-effect mobility of ∼7 cm/(V s). The field-effect transistor displayed an intrinsic photoresponse with wavelength selectivity that originated from the photoexcited carriers.
过渡金属二硫属化物（TMDCs），包括MoS和WS，由于其原子级薄的结构和强烈的光电响应，是下一代半导体材料的潜在候选者，这使得它们适用于柔性光电子应用。单层TMDCs已通过化学气相沉积（CVD）技术生长。提高具有高结晶度的畴尺寸并形成异质结构是实际应用中的重要课题。在本研究中，利用衬底堆叠微反应器的受限空间，通过基于气-液-固生长的CVD技术增加了单层WS的尺寸。使用旋涂金属盐（NaWO和NaMoO）和有机硫蒸气使我们能够精确控制源供应并系统地研究生长过程。我们获得了相对较低的生长活化能（1.02 eV），这与在受限空间中观察到的表面扩散限制生长模式一致。通过系统的光致发光（PL）分析，我们确定约820°C的生长温度对于生产具有窄PL峰宽（约35 meV）的高质量WS是最佳的。通过控制W和S的源平衡，我们获得了大尺寸的完全单层WS（约560μm）和带有双层斑点的单层WS（约1100μm）。结合两种不同的过渡金属源，成功创建了WS/MoS横向异质结构。在电输运测量中，在最佳条件下生长的单层WS具有高导通电流（约70μA/μm）、开/关比（约5×10）和约7 cm²/(V·s)的场效应迁移率。场效应晶体管表现出具有波长选择性的本征光响应，该响应源自光激发载流子。
