Correlated PL, Raman and IR nanospectroscopy for studying single-photon emitters in hBN

• Applicant: Dr. Iris Niehues
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2021 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467576442

This proposed project aims on studying single photon emitters (SPEs) in hexagonal boron nitride (hBN) with the help of near-field techniques providing nanoscale spatial resolution.SPEs are essential for future quantum technologies, where single photons on demand are needed. For future applications, SPEs must fulfill special requirements, e.g., they should be stable at room temperature and tunable in energy. SPEs that fulfill these aspects are color centers in hexagonal boron nitride (hBN), whose characteristics are not fully understood yet. For example, it is expected that strain has a major influence on their emission properties, but the underlying mechanisms are still not understood. Novel insights might be achieved by studying the fundamental SPE properties with a spatial resolution much better than the optical diffraction limit. For that reason, I want to use infrared nanoimaging and nanospectroscopy techniques (s-SNOM and nano-FTIR, respectively) as well as tip-enhanced Raman spectroscopy (TERS) and tip-enhanced photoluminescence spectroscopy (TEPL) to study the interplay between local strain and photoluminescence (PL) of SPEs in hBN with nanoscale spatial resolution. For a most reliable correlation of the complementary information provided by these techniques, the project aims on developing a combined nano-FTIR and TERS setup, allowing, for the first time, for simultaneous measurements of nanoscale-resolved infrared, Raman and PL spectra. It is also planned to perform theses studies after manipulation of the emitters’ optical properties by creating macroscopic strain fields in their vicinity, for example via nanointendation. The findings will help for a better understanding of the influence of strain on the emitters´ origin, activation and transition energy.The proposed research will be carried out in the nanooptics group at CIC nanoGUNE (San Sebastian, Spain), which is led by Rainer Hillenbrand, who pioneered the development and application (e.g. mapping phonon polaritons in hBN) of s-SNOM and nano-FTIR. The group also demonstrated that the nano-FTIR instrumentation is well suited for TERS and TEPL measurements, which so far have been developed in parallel, but separately, to s-SNOM and nano-FTIR.My research is currently located in the field of optomechanics of semiconductors, focusing on the PL and absorption studies of strained 2D materials. Besides, I am studying the phononic properties of these materials via Raman spectroscopy and correlate them with their PL. Recently, I investigated the influence of strain on mono- and bilayers and showed that it can be used to manipulate the optical properties via exciton-phonon coupling. I also worked with SPEs in WSe2 monolayers, which I created deterministically by generating nanoscale strain profiles.I am convinced that my background in optomechanics and SPEs combined with the equipment and expertise at CIC nanoGUNE will lead to a successful implementation of the proposed project.

• DFG Programme: WBP Fellowship
• International Connection: Spain
• Host: Professor Dr. Rainer Hillenbrand