Efficient single photon emission from a high-purity hexagonal boron nitride crystal

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Efficient single photon emission from a high-purity hexagonal boron nitride crystal

L. J. Martínez, T. Pelini, V. Waselowski, J. R. Maze, B. Gil, G. Cassabois, and V. Jacques

Phys. Rev. B 94, 121405(R) – Published 22 September 2016

Abstract

Among a variety of layered materials used as building blocks in van der Waals heterostructures, hexagonal boron nitride (hBN) appears as an ideal platform for hosting optically active defects owing to its large band gap ( $\sim 6 eV$ ). Here we study the optical response of a high-purity hBN crystal under green laser illumination. By means of photon correlation measurements, we identify individual defects emitting a highly photostable fluorescence under ambient conditions. A detailed analysis of the photophysical properties reveals a high quantum efficiency of the radiative transition, leading to a single photon source with very high brightness ( $\sim 4 \times 10^{6} counts s^{- 1}$ ). These results illustrate how the wide range of applications offered by hBN could be further extended to photonic-based quantum information science and metrology.

Received 15 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.121405

Physics Subject Headings (PhySH)

Color centers Excitons

III-V semiconductors

Optical absorption spectroscopy Photoluminescence

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

L. J. Martínez¹, T. Pelini¹, V. Waselowski², J. R. Maze², B. Gil¹, G. Cassabois¹, and V. Jacques^1,*

¹Laboratoire Charles Coulomb, Université de Montpellier and CNRS, 34095 Montpellier, France
²Facultad de Física, Pontificia Universidad Católica de Chile, Santiago 7820436, Chile

^*vincent.jacques@umontpellier.fr

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Issue

Vol. 94, Iss. 12 — 15 September 2016

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Images

Figure 1
(a) Microscope image of a high-purity hBN crystal from HQ Graphene. (b) PL raster scan of the sample. (c) $g^{(2)} (τ)$ function recorded from the PL spot shown by the white arrow in (b) for a laser excitation power $P = 150 μ W$ and a bin width $w = 200$ ps. The solid line is data fitting using a three-level model while including the IRF of the detection setup (see main text). For this experiment we obtain $λ_{1} = 0.51 {ns}^{- 1}, λ_{2} = 0.14 μ s^{- 1}$ , and $a = 0.6$ . Inset: IRF measured using 50-ps laser pulses. The solid line is a Gaussian fit.
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Figure 2
(a)–(d) Typical PL time traces recorded from different individual defects in a high-purity hBN crystal. The switching rate between the $on$ and off states varies significantly from one emitter to another. The laser excitation power is set to $P = 10 μ W$ . Bin size: 10 ms.
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Figure 3
(a), (b) PL spectra recorded from individual defects in hBN at room temperature under green laser illumination. The solid lines are data fitting with Gaussian functions. The insets show the corresponding second-order correlation function $g^{(2)} (τ)$ . The spectrum shown in (a) [respectively, (b)] corresponds to the PL time trace shown Fig. 2 [respectively, Fig. 2]. (c) Histogram of the ZPL energy for a set of 13 single defects. Two families of defects can be observed with ZPL energies at $1.97 \pm 0.02$ eV and $2.08 \pm 0.01$ eV. (d) Bottom: Histogram of the energy detuning between phonon replica. The solid line is a guide for the eye. Top: phonon density of states (DOS) in hBN extracted from Ref. [39].
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Figure 4
(a) Three-level model including a radiative transition between the ground (1) and excited (2) levels, and a nonradiative decay through a metastable level (3). The coefficient $r_{i j}$ denotes the transition rate from level $(i)$ to level $(j)$ . (b) PL decay recorded under optical excitation with 50-ps laser pulses. The solid line is data fitting with a single exponential function. (c) Decay rate of the metastable state $r_{31}$ as a function of the laser excitation power. The solid line is data fitting with a linear function (see main text). (d) PL saturation curve of the defect. The red solid line is data fitting with a saturation function (see main text). The inset shows a PL time trace recorded for a laser excitation power $P = 400 μ W$ . We note that short blinking events start to be observed for such laser power above the saturation of the transition. All these measurements are performed on the same individual defect.
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