Enhanced Spontaneous Emission of Monolayer MoS<sub>2</sub> on Epitaxially Grown Titanium Nitride Epsilon-Near-Zero Thin Films.
basic_science · Level V
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- Record sourced from PubMed, PMID 34109795.
- Also identified by DOI 10.1021/acs.nanolett.1c00491.
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Abstract
Room-temperature photoluminescence enhancement of molybdenum disulfide (MoS<sub>2</sub>) monolayers on epitaxial titanium nitride (TiN) thin films grown by molecular-beam-epitaxy as well as magnetron-sputtered TiN films is observed by a confocal laser scanning microscope with excitation wavelengths covering the transition of TiN's macroscopic optical properties from dielectric to plasmonic. The photoluminescence enhancement increases as TiN becomes more metallic, and strong enhancement is obtained at the excitation wavelengths equal to or longer than the epsilon-near-zero (ENZ) wavelength of TiN films. A good agreement is observed between measured and calculated enhancements. The enhancement is attributed to the increased excitation field in MoS<sub>2</sub> at TiN's ENZ wavelength and interference effects for thick spacers that separate the MoS<sub>2</sub> flakes from TiN films in the metallic regime. This study enriches the fundamental understanding of emission properties on ENZ substrates that could be important for the development of advanced nanoscale lasers/light sources, optical/biosensors, and nano-optoelectronic devices.