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内容記述 |
Nitrogen-Vacancy (NV) centers in diamond are expected as highly sensitive magnetic sensors operable at room temperature. One major challenge in improving sensitivity is controlling the NV axis orientation. In diamond crystals, NV centers are typically randomly oriented along four crystallographic axes. Since only NV centers on a specific axis are utilized, NV centers on other axes act as fluorescence noise. Therefore, selectively forming NV centers along a single crystallographic axis is expected to enhance sensitivity. Perfectly oriented NV centers can be fabricated by nitrogen doping during chemical vapor deposition (CVD) growth, however, achieving a high NV center density remains challenging. In contrast, a high NV center density can be achieved by electron-beam irradiation followed by post-annealing, although orientation control remains difficult. In this study, we attempted to control NV center orientation by applying microwave annealing after electron-beam irradiation. Generally, microwave irradiation of material induces heating via Joule, dielectric and magnetic losses. Diamond has negligible dielectric and magnetic losses, so a boron doped diamond layer was formed as conductive layer and microwave annealing was performed via Joule loss. Because the conductive layer is thin, an electric field is applied throughout the whole diamond, resulting in a drift current flowing across the diamond. We thought that by controlling this current in the [111] direction, it would be possible to preferentially form [111]-oriented NV centers. |
