Investigation of Implanted NV Centers in Diamond Using Photoelectrical Readout Technique

Color centers in diamond, especially the Nitrogen-Vacancy (NV) center, are one of the leading platforms for room temperature quantum sensing and computing. This is because the unique properties of the NV center and a long coherence time of the electronic ground state spin. The spin state readout protocols typically rely on off-resonant excitation with a 532 nm laser. The red-shifted fluorescence is then collected. This approach, however, has several limitations. For example, it uses bulky confocal microscopes and has poor photon extraction efficiency from bulk diamond. The focus of this study is on the novel photoelectrical (PE) readout technique [1], which has recently been applied to single ingrown NV centers in diamond and promises to overcome these limitations [2]. We have applied this technique to study artificial single NV centers created by ion implantation. For the first time, we have observed coherent control and PE readout of the spin state, despite parasitic ionization from substitutional nitrogen surrounding. We have also compared deep ingrown NV centers with implanted NV centers using the PE readout method and studied the influence of photocurrent on the coherence times of the NV electronic ground state spin.<br/><br/>The PE readout method utilizes efficient charge collection generated from an NV center. The NV center undergoes a charge cycle in a closed loop from NV^- to NV⁰ charge states and back using the same green laser excitation, typically above 1 mW at 532 nm. This process leads to continuous creation of electrons and holes with spin-dependent rates. To collect those charges, planar Ti/Au electrodes (10 um spacing) are fabricated on the diamond surface using standard optical lithography and lift-off techniques [2]. The electrodes exhibit typical double-Schottky I/V characteristics. Detection was performed using a commercial high-gain (10¹¹ I/V) amplifier with the limited bandwidth of 200 Hz. By biasing one electrode, the detected current from the NV center is around 1 pA.<br/><br/>These results are an important step towards room temperature integrated quantum sensors and computers based on color centers in diamond. Where precise creation of NV centers is especially important.<br/><br/>[1] Bourgeois, E., Jarmola, A., Siyushev, P., Gulka, M., Hruby, J., Jelezko, F., ... & Nesladek, M. (2015). Photoelectric detection of electron spin resonance of nitrogen-vacancy centres in diamond. Nature Communications, 6(1), 8577.<br/>[2] Siyushev, P., Nesladek, M., Bourgeois, E., Gulka, M., Hruby, J., Yamamoto, T., ... & Jelezko, F. (2019). Photoelectrical imaging and coherent spin-state readout of single nitrogen-vacancy centers in diamond. Science, 363(6428), 728-731.