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Effects of post annealing on the physical and electrical properties of solar-blind polycrystalline gallium oxide (Ga2O3) ultraviolet photodetectors on the sapphire substrate are investigated. The grain size of poly-Ga2O3 becomes larger with the post annealing temperature (PAT) increasing from 800 °C to 1000 °C, but it gets smaller with further raising PAT to 1100 °C. A blue shift is observed at the absorption edge of the transmittance spectra of Ga2O3 on sapphire as increasing PAT, due to the incorporation of Al from the sapphire substrate into Ga2O3 to form (AlxGa1–x)2O3. The high-resolution X-ray diffraction and transmittance spectra measurement indicate that the substitutional Al composition and bandgap of (AlxGa1–x)2O3 annealed at 1100 °C can be above 0.30 and 5.10 eV, respectively. The Rmax of the sample annealed at 1000 °C increases about 500% compared to the as-deposited device, and the sample annealed at 1000 °C has short rise time and decay time of 0.148 s and 0.067 s, respectively. This work may pave a way for the fabrication of poly-Ga2O3 ultraviolet photodetector and find a method to improve responsivity and speed of response. [ABSTRACT FROM AUTHOR]

In this study, an eddy current (EC) detector is integrated in an additive/subtractive hybrid manufacturing (ASHM) process. The detector facilitates in-process inspection and repair operations through material deposition, defect detection, and removal processes layer by layer. A feasibility test is carried out on eddy current detection of subsurface defects in additively manufactured parts by using an EC detector. The study compares the results obtained from the EC detection with those by the X-ray computed tomography and the destructive methods. Experiments and simulations are conducted to investigate the effect of excitation frequency on intensity of the eddy current signal. The effects of residual heat of an additively manufactured specimen and lift-off distance of an EC probe on impedance changes are also investigated. In addition, the effect of defect width on EC signal is analyzed. The study shows that the EC method is capable of detecting subsurface defects in the ASHM parts. It is promising to integrate the EC detection and subtractive manufacturing into additive manufacturing to produce parts with improved quality and better performances. [ABSTRACT FROM AUTHOR]