Improved Tip-Enhanced Photoluminescence (TEPL) Resolution Through Demodulation

Photoluminescence (PL) spectroscopy has proven a potent tool for investigating nanoscale structures and materials. Nevertheless, conventional PL techniques find themselves confined by the diffraction limit, which hinders their ability to unveil intricate details. To surmount this limitation, researchers have turned to tip-enhanced photoluminescence (TEPL) spectroscopy. By employing sharp tips that enhance both excitation and emission processes, TEPL empowers imaging and spectroscopy at resolutions exceeding the diffraction limit. In our study, we leverage a demodulation technique using an AFM tip in intermittent contact mode to meticulously segregate the PL signal from background noise. This strategic refinement substantially boosts the signal-to-noise ratio. Through the integration of a photomultiplier tube (PMT), our detection mechanism achieves heightened sensitivity and efficiency, facilitating the precise capture of even the faintest PL signals. We have validated the technique by PL imaging experiments involving fluorescent beads and monolayer MoS2. These preliminary experiments serve as prime examples of our enhanced spatial resolution and sensitivity.