Yanfeng Wang

In this paper, two dielectric layers of Al₂O₃ and Gd₂O₃ were prepared by an atomic layer deposition (ALD) and magnetron sputtering deposition (SD), respectively. Based on this, a metal-oxide-semiconductor field-effect transistor (MOSFET) was successfully prepared on a hydrogen-terminated single-crystal diamond (H-diamond), and its related properties were studied. The results showed that this device had typical p-type channel MOSFET output and transfer characteristics. In addition, the maximum current was 15.3 mA/mm, and the dielectric constant of Gd₂O₃ was 24.8. The effective mobility of MOSFET with Gd₂O₃/Al₂O₃ was evaluated to be 182.1 cm²/Vs. To the best of our knowledge, the bilayer dielectric of Gd₂O₃/Al₂O₃ was first used in a hydrogen-terminated diamond MOSFET and had the potential for application.

In this work, a hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with HfAlO_x/Al₂O₃ bilayer dielectrics is fabricated and characterized. The HfAlO_x/Al₂O₃ bilayer dielectrics are deposited by the atomic layer deposition (ALD) technique, which can protect the H-terminated diamond two-dimensional hole gas (2DHG) channel. The device demonstrates normally-on characteristics, whose threshold voltage (V_TH) is 8.3 V. The maximum drain source current density (I_DSmax), transconductance (G_m), capacitance (C_OX) and carrier density (ρ) are −6.3 mA/mm, 0.73 mS/mm, 0.22 μF/cm² and 1.53 × 10¹³ cm⁻², respectively.

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

In this paper, we successfully synthesized homoepitaxial diamond with high quality and atomically flat surface by microwave plasma chemical vapor deposition. The sample presents a growth rate of 3 μm/h, the lowest RMS of 0.573 nm, and the narrowest XRD FWHM of 31.32 arcsec. An effect analysis was also applied to discuss the influence of methane concentration on the diamond substrates.

In this study, nitrogen-vacancy center emissions from nanocone structures fabricated on diamond surfaces by gold film annealing and inductively coupled plasma etching techniques were characterized. First, the diamond substate deposited with gold film was annealed to form a nano-sized dot mask. Second, through inductively coupled plasma etching, nanocone-shaped structures were fabricated using optimized gold dots as masks. Finally, the as-fabricated nanocone and planar structures were investigated with photoluminescence experiments at temperatures ranging from room temperature to 80 K, with the results showing approximately two-fold higher emission values for nitrogen-vacancy centers from nanocones.

In this study, contact properties of platinum/gold (Pt/Au) on the surface of hydrogen-terminated single crystal diamond (H-SCD) were studied with several treatment conditions. The electrodes of Pt (20 nm)/Au (100 nm) were deposited on H-SCD surface by electron beam evaporation technique. Then, the specific contact resistance (ρ_c) of the as-fabricated sample was measured by the circular transmission line model, which showed good ohmic properties with the value of 5.65 × 10⁻⁴ Ω·cm². To identify the thermal stability of Pt/Au/H-SCD, the sample was annealed in hydrogen ambient from 200 to 700 °C for 20 min at each temperature. As the temperature increased, ρ_c demonstrated better thermal stability. In addition, the barrier height was evaluated to be −0.67 ± 0.12 eV by X-ray photoelectron spectroscopy (XPS) technique.

Submicron lenses and cylinders exhibiting excellent properties in photodetector and quantum applications have been fabricated on a diamond surface by an inductively-coupled plasma (ICP) etching technique. During ICP etching, a layer containing 500 nm diameter balls of SiO₂ was employed as mask. By changing the mixing ratio of O₂, Ar and CF₄ during ICP etching, several submicron structures were fabricated, such as cylinders and lenses. The simulation results demonstrated that such submicron structures on a diamond’s surface can greatly enhance the photon out-coupling efficiency of embedded nitrogen-vacancy center.