Detection of Low-Penetrating Ions in Diamond at Room Temperature

Single-ion implantation as a technique for fabricating future quantum devices requires high precision in placing individual ions in the semiconductor material. One way to achieve this precision is to use focused ion beams and verify the implantation of each ion by detecting the charge it induces in the semiconductor. This method has already been demonstrated for silicon substrates but has yet to be successfully performed for wide-bandgap materials. One of the most promising materials for future quantum devices is a diamond. Quantum centers in diamond, such as nitrogen vacancies, can serve as information carriers in quantum computers—qubits—and are stable at room temperature. This work focuses on understanding the critical parameters required for the successful detection of shallow, low-energy ions in diamonds using commercially available diamond crystals and front-end electronics. Depth profiling of the electric field in the diamond crystal was performed using ions of different species and energy. State-of-the-art front-end electronics were also used to achieve high energy resolution. Using the XGLab CUBE PRE031 preamplifier, an energy resolution of 6 keV was achieved for the detection of 400-keV protons. Detection of 140-keV copper ions, penetrating an average of 100 nm into the diamond, was also demonstrated. The optimal position of implantation sites was determined from the spatial distribution of charge collection efficiency.