Electron. Mater., Volume 6, Issue 1 (March 2025) – 4 articles

Al₂O₃ ceramics are widely used in vacuum electronic devices. However, surface flashover in a vacuum during the application of high voltage significantly influences their reliability and restricts the development of vacuum electronic devices. The secondary electron emission yield (SEY) and surface resistivity of ceramics are the main factors affecting the vacuum withstand voltage of ceramic materials. In this study, the bulk density, microstructure, and surface properties—including SEY and surface resistivity—of Al₂O₃ ceramics were tested. The relationship between these properties and the vacuum withstand voltage of the ceramics was investigated. The influence of the addition ratio of Cr₂O₃ to MnO₂ and the sintering temperature was investigated. The results show Cr/Mn-doped Al₂O₃ ceramics, with appropriate amounts of Cr₂O₃ and MnO₂ and sintered at suitable temperatures, exhibit low SEY, high withstand voltage, and excellent stability in vacuum. Full article

This research is on the structural, optical, and electrical properties of SnO₂ and ZnO thin films, which are increasingly used in many electronic devices, including gas sensors, light-emitting diodes, and solar cells. For the various applications, it is essential to accurately determine the band gap energy, as it controls the optical and electrical behavior of the material. However, there is no single method for its determination; rather, different approximations depend on the crystalline quality and the doping level because these modify the energy band structure of the semiconductor. With the aim of analyzing the various approaches, SnO₂ and ZnO films were prepared by sputtering on unheated glass substrates and subsequently annealed in N₂ at various temperatures between 250 °C and 450 °C. These samples showed different crystallite sizes, absorption coefficients, and free carrier concentrations depending on the material and the annealing temperature. Analysis of the results shows that the expression developed for amorphous materials underestimates the band gap value, and the so-called unified method tends to overestimate it, while the equations for perfect or heavily doped crystals give band gap energies more consistent with the doping level, regardless of the crystalline quality of the films. Full article

Amorphous oxide semiconductor transistors with a high current density output are highly desirable for large-area electronics. In this study, wrapping amorphous indium-gallium-zinc-oxide (a-IGZO) transistors are proposed to enhance the current density output relative to a-IGZO source-gated transistors (SGTs). Device performances are analyzed using technology computer-aided design (TCAD) simulations. The TCAD simulation results reveal that, with an optimized device structure, the current density of the wrapping a-IGZO transistor can reach 7.34 μA/μm, representing an approximate two-fold enhancement compared to that of the a-IGZO SGT. Furthermore, the optimized wrapping a-IGZO transistor exhibits clear flat saturation and pinch-off behavior. The proposed wrapping a-IGZO transistors show significant potential for applications in large-area electronics. Full article

We investigated the tribological, thermal, kinetic, and surface microtextural characteristics of chemical mechanical polishing (CMP) of 300 mm p-type <100> prime silicon wafers (and their native oxide) at various pressures, sliding velocities, and starting platen temperatures. Results showed the dominant tribological mechanism for both native oxide and silicon polishing to be boundary lubrication. Using frictional data, we pinpointed the exact time that corresponded to the total removal of the native oxide and the onset of silicon polishing. This allowed us to separately characterize removal rates of each layer. For native oxide, while the rate depended on temperature, the presence of a temperature-independent shear force threshold and the low observed rates suggested that its removal by the slurry was dominantly mechanical. In contrast, for silicon polish, the absence of a distinctive shear force threshold and the fact that, for the same set of consumables, rates were more than 200 times larger for silicon than for native oxide suggested a dominantly chemical process with an average apparent activation energy of 0.34 eV. It was further confirmed that rate selectivity between native oxide and PE-TEOS based SiO₂ control wafers was around 1 to 7, which underscored the importance of being able to directly measure native oxide removal rates. In all cases, we achieved excellent post-polish surfaces with S_a and S_q values of below 1 nm. Due to thermal softening of the thermoplastic pad at elevated temperatures, which we confirmed via dynamic mechanical analysis, overall process vibrations were significantly higher when platen heating was employed. Full article