Cryogenic photoluminescence setup for rapid prototyping and active device biasing of monolayer 2D semiconductors for quantum applications

Monolayer transition metal dichalcogenides (TMDs) are promising 2D semiconductors that feature direct bandgaps useful for various quantum and optoelectronic applications. We present on our progress in establishing a cryogenic photoluminescence setup using a cryogenic probe station with bare multi-mode fibers that allows for active-device biasing of novel material platforms. Using this system, we are able to detect the photoluminescence signal from various chemical vapor deposited (CVD) and molecular beam epitaxy (MBE) grown 2D semiconductors on sapphire (0001) substrates in vacuum. We observe a temperature dependent direct bandgap red-shift of around 40nm (from 8K to 450K) for CVD grown monolayer WS2 and CVD grown monolayer WSe2 on sapphire (0001) substrates. We observe a temperature dependent direct bandgap red-shift of around 37nm (from 6K to 450K) for MBE grown monolayer MoSe2 on sapphire (0001) substrates. Interestingly, for monolayer MoS2 on sapphire (0001) substrates, we observe the emergence of a strong photoluminescence signal at cryogenic temperatures below 100K, in addition to the A exciton luminescence signal, which is attributed to bound excitons.