Laser Beam Induced Charge Collection for Defect Mapping and Spin State Readout in Diamond

The detection of laser-induced photo-currents in diamond is shown with about 100 fA resolution in the pico- to nanoampere range. A micro-electronic approach enables to work without using lock-in techniques. For that purpose, a commercially available and low-cost precision integrating amplifier is utilized on a home-built printed circuit board. This technique is applied to three different diamond samples with different defect concentrations. Two ultra-pure diamond samples with shallow implanted defects, predominantly nitrogen-vacancy (NV) centers and substitutional nitrogen (P1 centers), are investigated. The third sample is an electron-irradiated type Ib diamond with a much higher intrinsic defect concentration. For all samples, spatially resolved photo-current maps as well as laser power and bias voltage-dependent measurements are recorded. Furthermore, photo-currents are successfully recorded without an applied bias voltage. Finally, the technique is used to perform continuous wave photoelectric detection of magnetic resonances (PDMR) using NV centers. The presented approach paves the way for time-resolved photo-current measurements of individual defects and pulsed PDMR measurements without lock-in technology.