Giant enhancement of photoluminescence emission in monolayer WS 2 by femtosecond laser irradiation
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Front. Phys. 16(1), 12501 (2021)
Research article Giant enhancement of photoluminescence emission in monolayer WS2 by femtosecond laser irradiation Cheng-Bing Qin1,2,† , Xi-Long Liang1,2 , Shuang-Ping Han1,2 , Guo-Feng Zhang1,2 , Rui-Yun Chen1,2 , Jian-Yong Hu1,2 , Lian-Tuan Xiao1,2,‡ , Suo-Tang Jia1,2 1
State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China 2 Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China Corresponding authors. E-mail: † [email protected], ‡ [email protected] Received August 3, 2020; accepted September 7, 2020
Monolayer transition metal dichalcogenides have emerged as promising materials for optoelectronic and nanophotonic devices. However, the low photoluminescence (PL) quantum yield (QY) hinders their various potential applications. Here we engineer and enhance the PL intensity of monolayer WS2 by femtosecond laser irradiation. More than two orders of magnitude enhancement of PL intensity as compared to the as-prepared sample is determined. Furthermore, the engineering time is shortened by three orders of magnitude as compared to the improvement of PL intensity by continuous-wave laser irradiation. Based on the evolution of PL spectra, we attribute the giant PL enhancement to the conversion from trion emission to exciton, as well as the improvement of the QY when exciton and trion are localized to the new-formed defects. We have created microstructures on the monolayer WS2 based on the enhancement of PL intensity, where the engineered structures can be stably stored for more than three years. This flexible approach with the feature of excellent long-term storage stability is promising for applications in information storage, display technology, and optoelectronic devices. Keywords monolayers, WS2 , giant enhancement, photoluminescence, femtosecond laser irradiation, micropatterning, exciton, trion, quantum yield
1 Introduction Inspired by the significant advances of graphene, the transition metal dichalcogenides (TMDs) with finite bandgaps have begun to receive increasing attention in the last decade [1–3]. Unique optical and electrical properties of these TMDs, including massive excitonic effect [4, 5], remarkable many-body interaction [6, 7], and giant spinvalley coupling [8, 9], make them promising candidates for next-generation optoelectronic devices. However, the intrinsic defects, such as vacancies and impurities for asprepared monolayers, generally result in the extremely low photoluminescence (PL) quantum yield (QY, ranging from 0.01 % to 6 % at room temperature [10]), obscuring the further development of high quantum efficiency optoelectronic devices [11]. Recently, many research efforts have been devoted to enhance the PL intensity of monolayer WS2 , which may be distinguished into four possibilities: (i) surface passivation with organic su∗ arXiv:
2009.09563. This article also can be found at http://journal.hep.com.cn/fop/EN/10.1007/s11467-0200995-z.
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