Sialon and Alumina Modified UV-Curable Coatings with Improved Mechanical Properties and Hydrophobicity

This article describes the modification of UV-curable coatings with silicon aluminum oxynitride (Sialon) and aluminum oxide (Alu C), which improve the hydrophobicity of the coating surface and the scratch hardness. The contact angle is greater due to surface roughness being enhanced with inorganic fillers. Improved scratch resistance results from the formation of a sliding layer triggered by the diffusion of Sialon or alumina on the coating surface. One can observed an increase in the surface hydrophobicity as well as in the scratch hardness (up to 100%) when small amounts (5 wt.%) of the inorganic compounds are added. Imaging microscopies, i.e., SEM, OM, and AFM (with nanoscopic Young’s modulus determination), revealed the good distribution of both types of fillers in the studied matrix.

Combustion Synthesis of Aluminum Oxynitride in Loose Powder Beds

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

Effects of Recessed-Gate Structure on AlGaN/GaN-on-SiC MIS-HEMTs with Thin AlOxNy MIS Gate

This study investigated the effects of a thin aluminum oxynitride (AlOxNy) gate insulator on the electrical characteristics of AlGaN/GaN-on-SiC metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs). The fabricated AlGaN/GaN-on-SiC MIS-HEMTs exhibited a significant reduction in gate leakage and off-state drain currents in comparison with the conventional Schottky-gate HEMTs, thus enhancing the breakdown voltage. The effects of gate recess were also investigated while using recessed MIS-HEMT configuration. The Johnson’s figures of merit (= fT × BVgd) for the fabricated MIS-HEMTs were found to be in the range of 5.57 to 10.76 THz·V, which is the state-of-the-art values for GaN-based HEMTs without a field plate. Various characterization methods were used to investigate the quality of the MIS and the recessed MIS interface.

Применение покрытий AlN для защиты поверхности гетероструктур системы AlGaAs/GaAs от взаимодействия с атмосферным кислородом

The paper presents the results of the synthesis of thin aluminum nitride films by reactive ion-plasma sputtering and the study of their properties with the aim of using as the protective coatings for the high-power AlxGa1-xAs/GaAs semiconductor laser heterostructures. EDS studies and ellipsometry showed that at a residual pressure in the chamber of the order of ~10-5 Torr, a layer of aluminum oxynitride is formed in the films. In this case, the film-substrate heterointerface can undergo oxidation. However, AlN films with a thickness of the order of 100 nm grown in a pure nitrogen medium with a residual pressure of ~10-7 Torr apparently do not contain oxygen, and can reliably prevent its penetration into the heterointerface region. Potentially, they can serve as effective protection for oxidation sensitive heterostructures.