Graphitic carbon nitride (g−CN), a promising visible-light-responsive semiconductor material, is regarded as a fascinating photocatalyst and heterogeneous catalyst for various reactions due to its non-toxicity, high thermal durability and chemical durability, and “earth-abundant” nature. However, practical applications of g−CN in photoelectrochemical (PEC) and photoelectronic devices are still in the early stages of development due to the difficulties in fabricating high-quality g−CN layers on substrates, wide band gaps, high charge-recombination rates, and low electronic conductivity. Various fabrication and modification strategies of g−CN-based films have been reported. This review summarizes the latest progress related to the growth and modification of high-quality g−CN-based films. Furthermore, (1) the classification of synthetic pathways for the preparation of g−CN films, (2) functionalization of g−CN films at an atomic level (elemental doping) and molecular level (copolymerization), (3) modification of g−CN films with a co-catalyst, and (4) composite films fabricating, will be discussed in detail. Last but not least, this review will conclude with a summary and some invigorating viewpoints on the key challenges and future developments.

Ni-based superalloys are widely used to manufacture gas turbine core components, but reports on the reliability of superalloys at cryogenic temperatures are still limited. Considering the actual application of superalloys in the field of cryogenic temperature, the tensile deformation behavior of directionally solidified superalloy DZ406 was investigated at cryogenic temperatures from −125 °C to 25 °C, and the comparative analysis of room temperature and 1000 °C was carried out. The yield strength and ultimate strength at cryogenic temperatures were close to that at room temperature, and twice that at 1000 °C. The elongation was maintained at 10–15% and exhibited a certain plasticity at cryogenic temperatures. The morphologies and chemical composition of γ′ precipitates were close at cryogenic temperatures, room temperature and 1000 °C. The microstructure difference that was caused by different temperatures was mainly reflected in the fracture mode and dislocation configuration. At cryogenic temperature, the fracture samples basically exhibited no necking phenomenon, and the cracks were basically located in the interdendritic regions and occurred in MC carbide itself; at room temperature and 1000 °C, dimples with carbides inside were distributed on the fracture surface. Slip bands and dislocations contributed to the tensile deformation at cryogenic temperatures and room temperature, while only the dislocations worked at 1000 °C.

In this work, we investigate the degradation behavior and mechanism of p-gate AlGaN/GaN high-electron mobility transistors (HEMTs) for the first time under hydrogen (H₂) atmosphere. The experimental results reveal significant decrease in drain-to-source current, negative drift in threshold voltage, increase in off-state gate leakage current, and deterioration of subthreshold swing in the p-gate AlGaN/GaN HEMT after H₂ treatment. The degradation of the electrical parameters is considered to hydrogen poisoning phenomenon. Through secondary ion mass spectrometry and variable temperature photoluminescence spectroscopy, we observe the increase in hydrogen concentration in the p-GaN layer and the formation of electrically inactive Mg–H complexes after H₂ treatment. As results, the effective hole concentration decreases and the trap density of the device increases, which are confirmed by Hall effect measurement and low-frequency noise analysis, respectively. The detrimental effect of hydrogen on p-gate AlGaN/GaN HEMTs can be attributed primarily to the compensation of Mg doping and the generation of defects.

GaN-based terahertz (THz) Schottky barrier diodes (SBDs) are critical components for achieving high-power performance in THz frequency multipliers. However, the space applications of GaN-based THz SBDs are significantly constrained due to insufficient research on the effects of space irradiation. This work investigates the effects of 450 MeV Kr swift heavy ion (SHI) irradiation on the electrical characteristics and induced defects in GaN-based THz SBDs. It was found that the high-frequency performance of GaN-based THz SBDs is highly sensitive to Kr SHI irradiation, which can be attributed to defects induced in the GaN epitaxial layer by the irradiation. Low-frequency noise analysis reveals trap states located at an energy level of approximately 0.62 eV below the conduction band. Moreover, the results from SRIM calculation and photoluminescence spectra confirmed the presence of irradiation-induced defects caused by Kr SHI irradiation.