Diamond defects, previously applied in measurement of electromagnetic fields and temperature, can now be used to sense rotations.

We report on the fabrication and measurement of hydrogen-terminated diamond field-effect transistors (FETs) incorporating V₂O₅ as a surface acceptor material to induce transfer doping. Comparing a range of gate lengths down to 50 nm, we observe inversely scaling peak output current and transconductance. Devices exhibited a peak drain current of ~700 mA/mm and a peak transconductance of ~150 mS/mm, some of the highest reported thus far for a diamond metal semiconductor FET (MESFET). Reduced sheet resistance of the diamond surface after V₂O₅ deposition was verified by four probe measurement. These results show great potential for improvement of diamond FET devices through scaling of critical dimensions and adoption of robust transition metal oxides such as V₂O₅.

We measure electron- and nuclear-spin transition frequencies in the ground state of nitrogen-vacancy (N-$V$) centers in diamond for two nitrogen isotopes (${}^{14}\mathrm{N}$-$V$ and ${}^{15}\mathrm{N}$-$V$) over temperatures ranging from 77 to 400 K. Measurements are performed using Ramsey interferometry and direct optical readout of the nuclear and electron spins. We extract coupling parameters $Q$ (for ${}^{14}\mathrm{N}$-$V$), $D$, $A_{\parallel }$, $A_{\perp }$, and ${\gamma }_e/{\gamma }_n$, and their temperature dependences for both isotopes. The temperature dependences of the nuclear-spin transitions within the $m_s=0$ spin manifold near room temperature are found to be 0.52(1) ppm/K for ${}^{14}\mathrm{N}$-$V$ ($|m_I=-1⟩\leftrightarrow |m_I=+1⟩$) and $-1.1(1)$ ppm/K for ${}^{15}\mathrm{N}$-$V$ ($|m_I=-1/2⟩\leftrightarrow |m_I=+1/2⟩$). An isotopic shift in the zero-field splitting parameter $D$ between ${}^{14}\mathrm{N}$-$V$ and ${}^{15}\mathrm{N}$-$V$ is measured to be $\sim 120$ kHz. Residual transverse magnetic fields are observed to shift the nuclear-spin transition frequencies, especially for ${}^{15}\mathrm{N}$-$V$. We have precisely determined the set of parameters relevant for the development of nuclear-spin-based diamond quantum sensors with greatly reduced sensitivity to environmental factors.

Diamond is a semiconductor material with remarkable structural, thermal, and electronic properties that has garnered significant interest in the field of electronics. Although hydrogen (H) and oxygen (O) terminations are conventionally favored in transistor designs, alternative options, such as silicon (Si) and germanium (Ge), are being explored because of their resilience to harsh processing conditions during fabrication. Density-functional theory was used to examine the non-oxidized and oxidized group-IV (Si and Ge)-terminated diamond (100) surfaces. The (3 × 1) reconstructed surfaces feature an ether configuration and show relative stability compared with the bare surface. Hybrid-functional calculations of the electronic properties revealed reduced fundamental bandgaps (<1 eV) and lower negative electron affinities (NEAs) than those of H-terminated diamond surfaces, which is attributed to the introduction of unoccupied Si (Ge) states and the depletion of negative charges. Furthermore, oxidation of these surfaces enhanced the stability of the diamond surfaces but resulted in two structural configurations: ether and ketone. Oxidized ether configurations displayed insulating properties with energy gaps of ∼4.3 ± 0.3 eV, similar to H-terminated diamond (100) surfaces, whereas bridged ether configurations exhibited metallic properties. Oxidization of the metallic ketone configurations leads to the opening of relatively smaller gaps in the range of 1.1–1.7 eV. Overall, oxidation induced a shift from NEAs to positive electron affinities, except for the reverse-ordered ketone surface with an NEA of −0.94 eV, a value comparable to the H-terminated diamond (100) surfaces. In conclusion, oxidized group-IV-terminated diamond surfaces offer enhanced stability compared to H-terminated surfaces and display unique structural and electronic properties that are influenced by surface bonding.