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Highlights • A unified explanation is proposed to consistently explain the two-step degradation of a-IGZO TFTs under DC PBTI stress without or with different stress V ds. • For PBTI stress without stress V ds , the initial negative V th shift is believed to be induced by donor-like defect states corresponding to H 2 O molecule and intrinsic defects. • For PBTI stress with stress V ds , the negative shift is believed to be induced by donor-like defect states corresponding to oxygen vacancies. The gate-bias-induced electron trapping mechanism is responsible for the positive V th shift. Abstract A unified explanation is proposed to consistently explain the two-step degradation of amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) under DC positive bias temperature instability (PBTI) stress without or with different drain stress voltages (V ds). For PBTI stress without stress V ds , this initial negative V th shift is believed to be induced by donor-like defect states corresponding to H 2 O molecule and intrinsic defects, while for PBTI stress with stress V ds , the negative shift is believed to be induced by donor-like defect states corresponding to oxygen vacancies. The gate-bias-induced electron trapping mechanism is responsible for positive V th shift. These transitions from negative to positive V th shift are resulted from the competition between the donor-like states creation and electron trapping. [ABSTRACT FROM AUTHOR]

• Positive charges from H 2 O molecule induced the parasitic current path, resulting in anomalous hump in subthreshold region at elevated temperature, which disappeared after N 2 annealing. • Hump still existed under PBS, while weakened hump were observed under NBS due to positive charges trapping. In this work, we investigated an anomalous hump in the bottom-gate amorphous-InGaZnO thin-film transistors. The hump in the subthreshold region appeared at elevated temperature and disappeared after N 2 atmosphere annealing. The anomalous hump phenomenon is attributed to the existence of both main current path composed by electron and parasitic current path induced by positive charges formed by adsorbed H 2 O molecules. With the increase of the testing temperature, the hump effect becomes significant since the formation of positive charges is strengthened by heat. This hump can be weakened by negative bias temperature instability stress at high temperature due to the charge-trapping mechanism. [ABSTRACT FROM AUTHOR]

MoAlB is a ternary boride of MAB phases with strong resistance to oxidation and ablation at service temperature, thanks to preferential Al diffusion to form a protective oxide scale. However, excessive Al were often necessary in sintering of MoAlB ceramics, suggesting that a liquid-phase densification might occur thus leading to complex microstructures. By quantitative SEM analysis, ~17 mol.% Al 2 O 3 phase was found common in MoAlB ceramics. The liquid-phase of Al-Mo-B-O facilitates the direct conversion from MoB to MoAlB before in situ formation of Al 2 O 3. An intermediate Mo 3 Al 8 phase competes with layered conversion, which limits the insertion rate of Al into B-B layers of MoB to form abundant Al-deficient stacking-faults. Intermetallic Mo 3 Al 8 phase precipitates further in the intergranular regions parallel to the crystallization of Al 2 O 3 , leaving the reprecipitation of remaining Al. Both layered-conversion and intergranular oxides can improve ablation behavior for MoAlB ceramics, as well as fracture toughness and compressive strength. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Dense ZrB2–20vol% SiC ceramics (ZS) were fabricated by hot pressing using self-synthesized high purity ZrB2 and commercial SiC powders as raw materials. The high temperature flexural strength of ZS and its degradation mechanisms up to 1600°C in high purity argon were investigated. According to the fracture mode, crack origin and internal friction curve of ZS ceramics, its strength degradation above 1000°C is considered to result from a combination of phenomena such as grain boundary softening, grain sliding and the formation of cavitations and cracks around the SiC grains on the tensile side of the specimens. The ZS material at 1600°C remains 84% of its strength at room temperature, which is obviously higher than the values reported in literature. The benefit is mainly derived from the high purity of the ZrB2 powders. [Copyright &y& Elsevier]

Ultrafast High-temperature Sintering (UHS) has been successfully applied to fabricate the silicon nitride (Si 3 N 4) bulks, as the first attempt of ultra-rapid consolidation of a non-oxide ceramics. At a heating rate of 875 °C/min, the bulk Si 3 N 4 ceramic with a relative density greater than 96 % and an α-β phase transformation degree above 80 % could be obtained within 300 s. The effects of ultrafast heating on the liquid phase sintering (LPS) were also comparatively studied. Results showed that, the ultrafast heating rate and high temperature under UHS might promote the LPS system evolving to a nonequilibrium state. By comparing with other pressureless sintering processes with much lower heating rates, UHS apart from reducing the processing time, and it is also an effective method to form a bimodal microstructure composed of interlocked rod-like β-Si 3 N 4 grains. [ABSTRACT FROM AUTHOR]