Strain-Induced Spatial and Spectral Isolation of Quantum Emitters in Mono- and Bilayer WSe₂

Abstract

Two-dimensional transition metal dichalcogenide semiconductors are intriguing hosts for quantum light sources due to their unique optoelectronic properties. Here, we report that strain gradients, either unintentionally induced or generated by substrate patterning, result in spatially and spectrally isolated quantum emitters in mono- and bilayer WSe2. By correlating localized excitons with localized strain variations, we show that the quantum emitter emission energy can be red-tuned up to a remarkable ∼170 meV. We probe the fine-structure, magneto-optics, and second-order coherence of a strained emitter. These results raise the prospect of strain-engineering quantum emitter properties and deterministically creating arrays of quantum emitters in two-dimensional semiconductors.

Single photon emission from deep-level defects in monolayerWSe2

“…1,10 It can be assumed to be a result of the competition between different kinds of radiative recombination. The 2D excitons and weakly bounded excitons are more easily to be trapped by strong localization centers newly created by hydrostatic pressure.…”

“…their energies are nearly overlapped with the L broadband seen at low pressure, as represented by DL1 and DL2 marked in exciton decay time of a few ns of a discrete line is in agreement with the typical value for the quantum emitters in 2D materials. 3,10 Instead, the reported decay time of the broad L excitons is shorter, from ten picoseconds 16 to hundreds picoseconds. 17 This means that the lifetime of discrete lines is about one or two order longer than the lifetime of the broad L band emission.…”

Phonon induced line broadening and population of the dark exciton in a deeply trapped localized emitter in monolayer WSe_2

“…Recently, localized excitons hosted in monolayered semiconductors have been identified as a new class of solid state quantum emitters [5][6][7][8][9]. Thus far, except one recent report [ 20], the emission wavelength of these emitters was mainly found in the spectral range between 730 and 770 nm (1.6-1.7 eV) and evolved from a rather dense emitter array. This makes it challenging to spectrally isolate single emitter lines, and imposes major obstacles to combine them with well-established GaAs based photonic devices and microcavity architectures due to the spectral absorbtion in GaAs.…”

Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

“…The application of a bias voltage between the top Cr/Au electrodes and the n-doped Si substrate (used as a back gate) enables electrical tuning of the resident carrier density. Experiments at T ¼ 4 K are carried out in a confocal microscope, 29,37 and magnetic fields up to jB z j ¼ 9 T can be applied perpendicular to the sample plane, i.e., parallel to the light propagation axis (Faraday geometry). 23 The detection spot diameter is 1lm, i.e., considerably smaller than the ML size of typically $10 lm  10 lm.…”

“…FWHM of 150-400 leV, similar to those found in WSe 2 MLs. [24][25][26][27][28][29] The top and the bottom panels of Fig. 1(b) show two sets of QD-like PL spectra which were taken from samples 1 and 2.…”