Year: 2024
Type: article
Abstract: Atomic defects associated with vacancies in two-dimensional transition metal dichalcogenide monolayers efficiently trap charged carriers and strongly localize excitons. Defects in semiconducting monolayers are seldomly utilized for enhancing optical phenomena, although they may provide resonant intermediate states within the energy band gap for applications with multiphoton excitations, like highly efficient and thermally robust photon upconversion. In an MoS 2 monolayer encapsulated by hBN with high defect and resident electron densities, we observe an upconversion of localized exciton (X L ) emission with a huge energy gain of up to 290 meV. The upconverted X L emission is robust up to temperatures of about 120 K and exhibits a sublinear or a nearly linear laser power dependence for the energy gain of about 100 meV and above 200 meV, respectively. The upconversion mechanism is explained by a cooperative energy transfer process between the photocreated and resident electrons, in which hybridized pairs of single sulfur vacancies likely act as real intermediate states. Additionally, we find a weak upconversion of the neutral exciton photoluminescence with an energy gain of about 350 meV for quasi-resonant excitation of the X L exciton. It is attributed to a two-step, two-photon absorption.
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Awards: TRR 160: Kohärente Manipulation wechselwirkender Spinanregungen in maßgeschneiderten Halbleitern, G434337789, Probing of optical properties of multilayered van der Waals
heterostructures of transition metal chalcogenides for optoelectronics and spintronics application, QuantERA II ERA-NET Cofund in Quantum Technologies, QuantERA II ERA-NET Cofund in Quantum Technologies, G6855453483
OpenAlex ID: W4403940875