Abstract

Understanding how atomic defects shape the nanoscale optical properties of two-dimensional (2D) semiconductors is essential for advancing quantum technologies and optoelectronics. Using scanning tunneling spectroscopy (STS) and luminescence (STML), we correlate the atomic structure and optical fingerprints of individual defects in monolayer MoS2. A bilayer of hexagonal boron nitride (hBN) effectively decouples MoS₂ from the graphene substrate, increasing its band gap and extending the defect charge state lifetime. This enables the observation of sharp STML emission lines from MoS₂ excitons and trions exhibiting nanoscale sensitivity to local potential fluctuations. We identify the optical signatures of common point defects in MoS2: sulfur vacancies (VacS-), oxygen substitutions (OS), and negatively charged carbon-hydrogen complexes (CHS-). While VacS- and OS only suppress pristine excitonic emission, CHS- generate defect-bound exciton complexes (A-X) about 200 meV below the MoS₂ exciton. Sub-nanometer-resolved STML maps reveal large spectral shifts near charged defects, concurrent with the local band bending expected for band-to-defect optical transitions. These results establish an atomically precise correlation between structure, electronic states, and optical response, enabling deterministic engineering of quantum emitters in 2D materials.

Abstract

Understanding how atomic defects shape the nanoscale optical properties of two-dimensional (2D) semiconductors is essential for advancing quantum technologies and optoelectronics. Using scanning tunneling spectroscopy (STS) and luminescence (STML), we correlate the atomic structure and optical fingerprints of individual defects in monolayer MoS2. A bilayer of hexagonal boron nitride (hBN) effectively decouples MoS₂ from the graphene substrate, increasing its band gap and extending the defect charge state lifetime. This enables the observation of sharp STML emission lines from MoS₂ excitons and trions exhibiting nanoscale sensitivity to local potential fluctuations. We identify the optical signatures of common point defects in MoS2: sulfur vacancies (VacS-), oxygen substitutions (OS), and negatively charged carbon-hydrogen complexes (CHS-). While VacS- and OS only suppress pristine excitonic emission, CHS- generate defect-bound exciton complexes (A-X) about 200 meV below the MoS₂ exciton. Sub-nanometer-resolved STML maps reveal large spectral shifts near charged defects, concurrent with the local band bending expected for band-to-defect optical transitions. These results establish an atomically precise correlation between structure, electronic states, and optical response, enabling deterministic engineering of quantum emitters in 2D materials.

Abstract

Understanding how atomic defects shape the nanoscale optical properties of two-dimensional (2D) semiconductors is essential for advancing quantum technologies and optoelectronics. Using scanning tunneling spectroscopy (STS) and luminescence (STML), we correlate the atomic structure and optical fingerprints of individual defects in monolayer MoS2. A bilayer of hexagonal boron nitride (hBN) effectively decouples MoS₂ from the graphene substrate, increasing its band gap and extending the defect charge state lifetime. This enables the observation of sharp STML emission lines from MoS₂ excitons and trions exhibiting nanoscale sensitivity to local potential fluctuations. We identify the optical signatures of common point defects in MoS2: sulfur vacancies (VacS-), oxygen substitutions (OS), and negatively charged carbon-hydrogen complexes (CHS-). While VacS- and OS only suppress pristine excitonic emission, CHS- generate defect-bound exciton complexes (A-X) about 200 meV below the MoS₂ exciton. Sub-nanometer-resolved STML maps reveal large spectral shifts near charged defects, concurrent with the local band bending expected for band-to-defect optical transitions. These results establish an atomically precise correlation between structure, electronic states, and optical response, enabling deterministic engineering of quantum emitters in 2D materials.

Abstract

Understanding how atomic defects shape the nanoscale optical properties of two-dimensional (2D) semiconductors is essential for advancing quantum technologies and optoelectronics. Using scanning tunneling spectroscopy (STS) and luminescence (STML), we correlate the atomic structure and optical fingerprints of individual defects in monolayer MoS2. A bilayer of hexagonal boron nitride (hBN) effectively decouples MoS₂ from the graphene substrate, increasing its band gap and extending the defect charge state lifetime. This enables the observation of sharp STML emission lines from MoS₂ excitons and trions exhibiting nanoscale sensitivity to local potential fluctuations. We identify the optical signatures of common point defects in MoS2: sulfur vacancies (VacS-), oxygen substitutions (OS), and negatively charged carbon-hydrogen complexes (CHS-). While VacS- and OS only suppress pristine excitonic emission, CHS- generate defect-bound exciton complexes (A-X) about 200 meV below the MoS₂ exciton. Sub-nanometer-resolved STML maps reveal large spectral shifts near charged defects, concurrent with the local band bending expected for band-to-defect optical transitions. These results establish an atomically precise correlation between structure, electronic states, and optical response, enabling deterministic engineering of quantum emitters in 2D materials.