hBN-encapsulated WSe2 Monolayer Photoluminescence

A hBN-encapsulated WSe₂ monolayer was obtained by sequentially transferring a bottom hBN flake, ML WSe₂, and top hBN flake, which were mechanically exfoliated from bulk crystals, onto a quartz substrate [14 (link)]. In the PL experiments, an objective lens with a numerical aperture of 0.5 was used to collect PL signals and to focus the laser beam onto the sample with a spot size of about 1 μm. The spot size was measured by both the knife edge method and charge-coupled device (CCD) intensity. The collected emission was sent to a spectrometer (Acton Research Corporation SpectroPr-275) equipped with a thermoelectrically cooled CCD (Andor iDus 401, Abingdon, UK). The sample was kept at a temperature of 80 K inside an optical cryostat (Linkam Scientific, Tadworth, UK), in which motorized motion was used to enable spatially resolved PL mapping. Laser power was in the range 50–300 μW. In the PL excitation measurements, we used a home-built broadband Ti:sapphire laser that covers a wavelength range of 660–980 nm.