Fig. 3
From: Room temperature multi-phonon upconversion photoluminescence in monolayer semiconductor WS2
Photoluminescence, reflectance contrast and Raman scattering. a Examples of photoluminescence spectra of monolayer WS2 deposited on SiO2/Si substrate and on hBN/SiO2/Si substrates with different thicknesses of hBN layers, excited with incident photon energies of 2.33 eV (532 nm), and recorded in ambient at 295 K. The inset shows the T/X emission intensity ratio for different flakes, 1, 2 and 3, respectively. b Examples of photoluminescence spectra of monolayer WS2 deposited on hBN/SiO2/Si substrates with different thicknesses of hBN layers, excited with incident photon energies of 2.33 eV (532 nm), and recorded in vacuum at 7 K. c The red-shift of neutral exciton (X) emission line for increasing thickness of hBN layer. d The comparison of low temperature PL and RC spectra recorded in WS2/hBN(21 nm)/SiO2/Si. e The temperature evolution of PL spectra in WS2/hBN(21 nm)/SiO2/Si. f Helicity resolved Raman spectra excited with 532 nm laser line for WS2/SiO2/Si
