Development of Self-Doped Monolayered 2D MoS2 for Enhanced Photoresponsivity

Transition metal dichalcogenides (TMDs) exist in two distinct phases: the thermodynamically stable trigonal prismatic (2H) and the metastable octahedral (1T) phase. Phase engineering has emerged as a potent technique for enhancing the performance of TMDs in optoelectronics applications. Nevertheless, understanding the mechanism of phase transition in TMDs and achieving large-area synthesis of phase-controlled TMDs continue to pose significant challenges. This study presents the synthesis of large-area monolayered 2H-MoS2 and mixed-phase 1T/2H-MoS2 by controlling the growth temperature in the chemical vapor deposition (CVD) method without use of a catalyst. The field-effect transistors (FETs) devices fabricated with 1T/2H-MoS2 mixed-phase show an on/off ratio of 10(7). Photo response devices fabricated with 1T/2H-MoS2 mixed-phase show approximate to 55 times enhancement in responsivity (from 0.32 to 17.4 A W-1) and 10(2) times increase in the detectivity (from 4.1 x 10(10) to 2.48 x 10(12) cm Hz W-1) compare to 2H-MoS2. Introducing the metallic 1T phase within the 2H phase contributes additional carriers to the material, which prevents the electron-hole recombination and thereby increases the carrier density in the 1T/2H-MoS2 mixed-phase in comparison to 2H-MoS2. This work provides insights into the self-doping effects of 1T phase in 2H MoS2, enabling the tuning of 2D TMDs properties for optoelectronic applications.