Spontaneous exciton dissociation in transition metal dichalcogenide monolayers

Author:

Handa Taketo1ORCID,Holbrook Madisen2ORCID,Olsen Nicholas1ORCID,Holtzman Luke N.3ORCID,Huber Lucas1ORCID,Wang Hai I.4ORCID,Bonn Mischa4ORCID,Barmak Katayun3ORCID,Hone James C.5ORCID,Pasupathy Abhay N.2ORCID,Zhu Xiaoyang1ORCID

Affiliation:

1. Department of Chemistry, Columbia University, New York, NY 10027, USA.

2. Department of Physics, Columbia University, New York, NY 10027, USA.

3. Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA.

4. Max Planck Institute for Polymer Research, Mainz 55128, Germany.

5. Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA.

Abstract

Since the seminal work on MoS 2 , photoexcitation in atomically thin transition metal dichalcogenides (TMDCs) has been assumed to result in excitons, with binding energies order of magnitude larger than thermal energy at room temperature. Here, we reexamine this foundational assumption and show that photoexcitation of TMDC monolayers can result in a substantial population of free charges. Performing ultrafast terahertz spectroscopy on large-area, single-crystal TMDC monolayers, we find that up to ~10% of excitons spontaneously dissociate into charge carriers with lifetimes exceeding 0.2 ns. Scanning tunneling microscopy reveals that photocarrier generation is intimately related to mid-gap defects, likely via trap-mediated Auger scattering. Only in state-of-the-art quality monolayers, with mid-gap trap densities as low as 10 9 cm −2 , does intrinsic exciton physics start to dominate the terahertz response. Our findings reveal the necessity of knowing the defect density in understanding photophysics of TMDCs.

Publisher

American Association for the Advancement of Science (AAAS)

Subject

Multidisciplinary

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3