Secondary Radiation in Microdiamonds with NV Centers
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ICAL PROPERTIES OF CRYSTALS
Secondary Radiation in Microdiamonds with NV Centers V. S. Gorelika,b,*, S. A. Savinova, V. V. Sycheva, and D. Bib a Lebedev b
Physical Institute, Russian Academy of Sciences, Moscow, 119991 Russia Bauman Moscow State Technical University, Moscow, 105005 Russia *e-mail: [email protected]
Received March 29, 2020; revised April 10, 2020; accepted April 10, 2020
Abstract—The regularities in the secondary radiation (fluorescence and Raman) spectra of single diamond microcrystals have been investigated. The Raman spectrum excited by infrared laser radiation exhibits the fundamental diamond mode with a frequency of 1332 cm–1 and a two-phonon band peaking at a frequency of 2615 cm–1. The fluorescence spectra contain zero-phonon lines of NV centers with a pronounced phonon structure. DOI: 10.1134/S1063774520060164
INTRODUCTION Diamond is characterized by several unique properties: chemical stability, mechanical strength, large bandgap energy, record thermal conductivity, and high Debye temperature. The optical properties of diamond crystals, in particular, photoluminescence (PL) spectra, were analyzed in many studies [1–3]. The Raman spectra of diamonds of various types were investigated in [4–13]. A strong peak with a frequency of 1332 cm–1, corresponding to the optical phonon near the Brillouin zone center (with a quasi-momentum close to zero), was found in the Raman spectra of natural diamonds. A work second-order Raman continuum, corresponding to two-phonon scattering processes with participation of phonon pairs from the entire Brillouin zone, including its boundaries, was registered in the Raman spectrum of natural diamonds at a higher excitation intensity [8, 9]. The secondary-radiation spectra of natural diamonds with impurities contain also luminescent bands due to the deexcitation of impurity centers. Photoluminescence was practically absent in pure diamond crystals because of their large bandgap (5 eV), and the samples were colorless. Centers with nitrogen atoms incorporated into the diamond crystal lattice are most widespread and best studied among several hundreds of observed color centers [1]. The most interesting ones are NV centers, which are formed by a nitrogen atom and a vacancy located nearby along the {111} diagonal of face-centered cubic diamond lattice. The centers exist in two charge states: neutral NV0 and negatively charged NV–; the optical properties of the latter demonstrate a spin-dependent character of PL. The paramagnetism of NV– center with a possibility of optical recording
and reading of spin state became a basis for studies in the field of quantum technologies [14] (communication channels protected by quantum physics laws, quantum computers, quantum sensors). The studies of the quantum memory on 13С nuclei resulted in a new direction: optically induced hyperpolarizability, which provides a giant increase in sensitivity of the nuclear magnetic resonance and magnetic resonance tomography [15]. The formation of fluorescent labels for protection of industri
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