A 2.45 GHz microwave-plasma chemical-vapor deposition (MPCVD) reactor was designed and built in-house by collaborating with Guangdong TrueOne Semiconductor Technology Co., Ltd. A cylindrical cavity was designed as the deposition chamber and a circumferential coaxial-mode transformer located at the top of the cavity was adopted as the antenna. Two quartz-ring windows that were placed far away from the plasma and cooled by water-cooling cavity walls were used to affix the antenna to the cavity and act as a vacuum seal for the reactor, respectively. This design improved the sealing and protected the quartz windows. In addition, a numerical simulation was proposed to predict the electric-field and plasma-density distributions in the cavity. Based on the simulation results, a microwave-plasma reactor with TM₀₂₁ mode was built. The leak rate of this new reactor was tested to be as low as 1 × 10⁻⁸ Pa·m³·s⁻¹, and the maximal microwave power was as high as 10 kW. Then, single-crystal diamond films were grown with the morphology and crystalline quality characterized by an optical microscope, atomic force microscope (AFM), Raman spectrometer, photoluminescence (PL) spectrometer, and high-resolution X-ray diffractometer. It was shown that the newly developed MPCVD reactor can produce diamond films with high quality and purity.

In this paper, a phenomenon of generation and transport of droplets is proposed, which is based on the dielectric liquid electroconvection induced by corona discharge. We placed the dielectric fluid on a conductive/nonconductive substrate, and then it broke apart to become many small droplets that move along the conductive microchannel. The behaviors of dielectric droplets were experimentally observed on different conductive microchannels in details. Spreading speeds and sizes of dielectric droplets were analyzed at different driving voltages and conductive microchannels. This work highlights a simple approach to produce and manipulate dielectric droplets along microchannels.

The ultrafast transport processes of electrons and holes excited by femtosecond laser pulses are essential for a better understanding of carrier dynamics in semiconductors. Transient optical techniques are commonly used to investigate the carrier excitation and transport in these materials. Recently, ultrafast scanning electron microscopy has been employed to elucidate the ballistic dynamics of such hot carriers near a $p\text{−}n$ junction. We provide here a model not only to explain the previously reported superfast expansion of electron-hole clouds but also to predict plasma wave behavior at high laser fluences. In addition to a bipolar junction, we also investigate the well structure of a $p\text{−}n\text{−}p$ junction sandwiched by insulating layers. By confining hot carriers inside junctions, these carriers begin to oscillate as a result of Coulomb interactions among carriers and with the intrinsic field at the depletion zone, leading to the occurrence of terahertz-scale plasma waves for potential applications as pulsed terahertz light sources.

The study of the excited-state properties of diamond is crucial for understanding its electronic structure and surface physicochemical properties, providing theoretical support for its applications in optoelectronic devices, quantum technologies, and catalysis. This research employs Density Functional Theory (DFT) with the fixed electron occupation method to simulate the electron excitation. Using the Generalized Gradient Approximation (GGA) within DFT, we systematically investigated the excited-state characteristics of diamond by simulating the transfer of a fraction of electrons from the Highest Occupied Crystal Orbital (HOCO) to the Lowest Unoccupied Crystal Orbital (LUCO). Theoretical calculations indicate that with increasing electron excitation levels, the diamond crystal structure transitions from cubic to tetragonal, accompanied by a gradual decrease in the bandgap. Mechanical property analysis reveals that both Young’s modulus and shear modulus decrease with increasing excitation rate, while the bulk modulus remains nearly constant. These findings indicate a significant impact of electronic excitation on the mechanical stability of diamond. Phonon dispersion curves exhibit reduced degeneracy in high-frequency optical branches and a marked decrease in crystal symmetry upon excitation. This study not only advances the understanding of diamond’s excited-state properties but also offers valuable theoretical insights into its structural evolution and performance tuning under such extreme conditions.