Pulsed Carrier Gas Assisted High-Quality Synthetic 3R-Phase Sword-like MoS2: A Versatile Optoelectronic Material

Synthesizing a material with the desired polymorphic phase in a chemical vapor deposition (CVD) process requires a delicate balance among various thermodynamic variables. Here, we present a methodology to synthesize rhombohedral (3R)-phase MoS2 in a well-defined sword-like geometry having lengths up to 120 mu m, uniform width of 2-3 mu m and thickness of 3-7 nm by controlling the carrier gas flow dynamics from continuous mode to pulsed mode during the CVD growth process. Characteristic signatures such as high degree of circular dichroism (similar to 58% at 100 K), distinct evolution of low-frequency Raman peaks and increasing intensity of second harmonic signals with increasing number of layers conclusively establish the 3R-phase of the material. A high value (similar to 844 pm/V) of second-order susceptibility for few-layer-thick MoS2 swords signifies the potential of MoS2 to serve as an atomically thin nonlinear medium. A field effect mobility of 40 cm2/V-s and Ion/Ioff ratio of similar to 106further confirm the electronic-grade standard of this 3R-phase MoS2. These findings are significant for the development of emerging quantum electronic devices utilizing valley-based physics and nonlinear optical phenomena in layered materials.

Automated summary

This study presents a methodology for synthesizing rhombohedral-phase MoS2 in a sword-like geometry using chemical vapor deposition. By controlling the carrier gas flow dynamics during the growth process, the researchers were able to achieve a material with specific polymorphic phase and characteristic signatures such as high circular dichroism and distinct Raman peaks.