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An n-GaO x thin film is deposited on a single-crystal boron-doped diamond by RF magnetron sputtering to form the pn heterojunction. The n-GaO x thin film presents a small surface roughness and a large optical band gap of 4.85 eV. In addition, the band alignment is measured using x-ray photoelectron spectroscopy to evaluate the heterojunction properties. The GaO x /diamond heterojunction shows a type-II staggered band configuration, where the valence and conduction band offsets are 1.28 eV and 1.93 eV, respectively. These results confirm the feasibility of the use of n-GaO x as a termination structure for diamond power devices.

The novel ultralight material Mg-10.1Li-3.1Al-2.9Zn alloy (Mg-Li alloy) of which the density is about half that of pure magnesium has a wide application prospect in various industrial fields, while its weldability is rarely investigated. This study explored the fiber laser welding of 5 mm-thick Mg-Li alloy in butt-welding configuration through a L16 (43) orthogonal experiment design. The microstructures of the base metal and the joint obtained under the optimum condition were observed. The results showed that the strengthening precipitates in base metal were τ1 (Li8MgSi6), τ3 (Li2MgSi) and MgLiAl2 with a size in several microns and nano-sized AlLi, while that in fusion zone were nano-sized Li0~0.9Mg2Si and MgLiAl2. The tensile strength of the welded joint was equivalent to that of BM while the impact toughness and plasticity slightly reduced. It was found that the corrosion resistance of fusion zone with the single-phase matrix (β-Li) was about 3.2 times that of BM with the dual-phase matrix (α-Mg + β-Li). The results provided guiding significance for the popularization and application of the novel ultralight material Mg-Li alloy in industry.

With the improvement of the reliability of NC machine tools, it is becoming more and more difficult to obtain a large number of fault data. To deal with this problem, the improved Bootstrap sampling method is proposed. The failure data, which is gained by using seven a type of NC machine tools to monitor failure data for half year, is used respectively for the improved Bootstrap sampling method and the classic series research method. The results have been analyzed and calculated, and show that the Bootstrap sampling method’s relative error is obviously lower than the classic series research method’s. The improved Bootstrap sampling method is proved to be feasible in reliability modeling.

A homogenized surface potential is desirable for the observation of a pre-irradiated insulating specimen using a scanning electron microscope because the residual surface potential may affect the imaging properties of the specimen. To homogenize the residual surface potential, the specimen should be subjected to the irradiation of an electron beam with the total electron yield greater than one. The expression of the equilibrium potential is derived based on the charge balance condition in the equilibrium state and the potential value is found to increase mainly with the secondary electron (SE) yield and the most probable emission energy of SEs. Further numerical calculations of SE trajectories show that affected by different surface potentials, SEs leave or return to the specimen surface to change the net charge flux into the specimen. This thereby increases the surface potential below the equilibrium potential and decreases that above the equilibrium potential, homogenizing the surface potential.

Height variation of a tilted specimen may alter the magnification and image rotation because of re-focusing with an objective lens. Evaluating the height of the tilted specimen by means of the objective excitation, we derive approximate expressions for the alteration of the magnification and the image rotation. They are in the form of a second-order expansion of the lens-current variation. Theoretical results are validated by measurements in an ultra-high-voltage electron microscope. These expressions are especially useful for correcting images in the quantitative application to electron tomography.

We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV. The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons. The dynamic spatial distribution of charges is obtained and validated by existing experimental data. Our simulations show that excess negative charges are concentrated near the edge of the electron range. However, the formed region of high charge density may extend to the surface and bottom of a kapton sample, due to the effects of the electric field on electron scattering and charge transport, respectively. Charge trapping is then demonstrated to significantly influence the charge motion. The charge distribution can be extended to the bottom as the trap density decreases. Charge accumulation is therefore balanced by the appearance and increase of leakage current. Accordingly, our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.

We perform numerical simulations of the leakage current characteristics of an insulating thin film of SiO2 negatively charged by a low-energy nonpenetrating focused electron beam. For the formation of leakage current, electrons are demonstrated to turn from diffusion to drift after clearing the minimum potential barrier due to electron-hole separation. In the equilibrium state, the leakage current increases approximately linearly with the increasing primary beam current and energy. It also increases with the increasing film thickness and trap density, and with the decreasing electron mobility, in which the film thickness has a greater influence. Validated by some existing experiments, the simulation results provide a new perspective for the negative charging effects of insulating samples due to the low-energy focused electron beam.