Abstract
Abstract Photoluminescence (PL), a photo-excited spontaneous emission process, provides a wealth of optical and electronic properties of materials, which enable microscopic and spectroscopic imaging, biomedical sensing and diagnosis, and a range of photonic device applications. However, conventional far-field PL measurements have limitations in sensitivity and spatial resolution, especially to investigate single nano-materials or nano-scale dimension of them. In contrast, tip-enhanced photoluminescence (TEPL) nano-spectroscopy provides an extremely high sensitivity with <10 nm spatial resolution, which allows the desired nano-scale characterizations. With outstanding and unique optical properties, low-dimensional quantum materials have recently attracted much attention, and TEPL characterizations, i. e., probing and imaging, and even control at the nano-scale, have been extensively studied. In this review, we discuss the fundamental working mechanism of PL enhancement by plasmonic tip, and then highlight recent advances in TEPL studies for low-dimensional quantum materials. Finally, we discuss several remaining challenges of TEPL nano-spectroscopy and nano-imaging, such as implementation in non-ambient media and in situ environments, limitations in sample structure, and control of near-field polarization, with perspectives of the approach and its applications.
Highlights
With fundamental understanding as well as engineering studies for a range of organic and inorganic materials and hard and soft matter systems, we have achieved remarkable developments in modern device technologies
PL (TEPL) nano-spectroscopy and -imaging [20], has emerged for multifunctional nano-characterizations of low-dimensional quantum materials, since it provides high spatial resolution of ∼10 nm with high optical sensitivity owing to the plasmonic nano-optical antenna effect [21, 22]
Since understanding local excitonic processes was desirable at the early stage of new emerging transition metal dichalcogenides (TMDs) monolayers, similar tip-enhanced photoluminescence (TEPL) work has done by Su et al for MoS2 monolayer at about the same time [55]
Summary
With fundamental understanding as well as engineering studies for a range of organic and inorganic materials and hard and soft matter systems, we have achieved remarkable developments in modern device technologies. While we mainly used bulk material systems for device applications in the past several decades [1], they have reached the limit in their electrical and optical properties, device performance, and application range. Confocal microscopy combined with PL spectroscopy allows to investigate these optical responses in ambient condition, yet with diffraction limited spatial resolution and low sensitivity [19]. To this end, near-field PL measurement approach, i. PL (TEPL) nano-spectroscopy and -imaging [20], has emerged for multifunctional nano-characterizations of low-dimensional quantum materials, since it provides high spatial resolution of ∼10 nm with high optical sensitivity owing to the plasmonic nano-optical antenna effect [21, 22]. We discuss several remaining challenges of TEPL nano-spectroscopy and nano-imaging, such as implementation in non-ambient media and in situ environments, limitations in sample structure, and control of near-field polarization, with perspectives of the approach and its further applications
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