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Abstract Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV–visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.

Sr[sub 0.8]Bi[sub 2]Ta[sub 2]O[sub 9] (SBT) ferroelectric film constructed on Al[sub 2]O[sub 3]/Si to form metal-ferroelectricinsulator-semiconductor (MFIS) was prepared to study the degradation behavior of SBT films under forming gas annealing (FGA). Although the diffusion of hydrogen ions has been detected during FGA treatment, no significant differences in the microstructure and crystalline phase are observed for the SBT film compared to that without FGA treatment. However, the diffusion of hydrogen ions leads to the rapid decrease in the dielectric constant but shows no apparent influence on the memory window of Sr[sub 0.8]Bi[sub 2]Ta[sub 2]O[sub 9]/Al[sub 2]O[sub 3]/Si capacitors. In addition, it was found that FGA shows a positive effect on the leakage current of MFIS in contrast to that of metal/ferroelectric/metal structure. The leakage current density of MFIS dramatically decreases as much as two orders of magnitude after FGA at 500 °C compared to that without FGA treatment that was attributed to the reduced defects at the interface of Al[sub 2]O[sub 3]/Si. [ABSTRACT FROM AUTHOR]

The effect of forming gas annealing on the physical characteristics and electrical properties of SBT/Al2O3/Si are described. Due to the diffusion of hydrogen ions, a rapid decrease in the dielectric constant is observed and the FGA shows a positive effect on the leakage current of metal-ferroelectric/insulator/semiconductor in contrast to that of a metal/ferroelectric/metal structure.

AlGaN and GaN sidewalls were turned into Al x Ga 2- x O 3 and Ga 2 O 3 , respectively, by thermal oxidation to improve the optoelectrical characteristics of deep ultraviolet (DUV) light-emitting diodes (LEDs). The thermally oxidized Ga 2 O 3 is a single crystal with nanosized voids homogenously distributed inside the layer. Two oxidized Al x Ga 2- x O 3 layers were observed on the sidewall of the AlGaN layer in transmission electron microscopy images. The first oxidized Al x Ga 2- x O 3 layer is a single crystal, while the second oxidized Al x Ga 2-x O 3 layer is a single crystal with numerous nanosized voids inside. The composition of Al in the first oxidized Al x Ga 2- x O 3 layer is higher than that in the second one. The thermal oxidation at high temperature degrades the quality of the p-GaN layer and increases the forward voltage from 8.18 to 11.36 V. The thermally oxidized Al x Ga 2- x O 3 sidewall greatly enhances the light extraction efficiency of the lateral light of the DUV LEDs by combined mechanisms of holey structure, graded refractive index, high transparency, and tensile stress. Consequently, the light output power of the DUV LEDs increases from 0.69 to 0.88 mW by introducing a 420 nm thick Al x Ga 2- x O 3 sidewall oxidized at 900 °C, in which the enhancement of light output power can reach 27.5%., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)