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Understanding the metal/semiconductor interface is very significant for real-time optoelectronic device applications. In particular, the presence of interface states and other defects is detrimental to photodetector applications. In this study, the electrical transport properties of a pristine gallium nitride (GaN) nanorod (NR)-based Schottky diode are demonstrated at different temperatures by current–voltage characteristics in the range of 200–360 K. An enhancement in the Schottky barrier height (0.65 eV for hydrogen-passivated GaN NRs compared to 0.56 eV for pristine ones) is noticed. The effect of deep traps residing within the forbidden gap of GaN NRs is investigated using deep-level transient spectroscopy. Two deep defects are found at E C − 0.19 eV and E C − 0.31 eV in pristine GaN NRs; the E C − 0.31 eV defect peak is attributed to V Ga or nitrogen interstitials. After hydrogenation the peak at E C − 0.31 eV is suppressed and that at E C − 0.19 eV remains unchanged. The hydrogenated GaN NRs show a high photoresponse, which is nearly 2.83 times higher than that of pristine GaN NRs. The hydrogenated GaN NRs exhibit a photoresponsivity of 4.7 × 10−3 A W−1 and detectivity of 1.24 × 1010 Jones under UV illumination of λ = 382 nm. The enhanced performance is attributed to the deep defect passivation by hydrogenation along with the surface-state-free interface between the GaN NRs and metal contacts. The experimental results demonstrate the significance of hydrogen treatment use in the fabrication of GaN-based optoelectronic devices.

In this work, the first time we made InN/In2O3 core-shell heterostructure by hydrogen plasma treatment. InN nanorods (NRs) were grown by using plasma-assisted molecular beam epitaxy and hydrogen plasma treatment was performed by using the reactive ion etching system at room temperature. From X-ray photoemission spectroscopy studies, it was noticed that the bonding partner of In changes from N to O and N 1s completely disappeared in hydrogenated InN NRs. Further, high-resolution transmission electron microscopy revealed that the formation of InN/In2O3 core-shell NRs by hydrogenation plasma treatment. The resistance of pristine InN NRs was decreased in NO2 ambient. Interestingly, the resistance of the InN/In2O3 core-shell was increased while introducing NO2 gas. InN NRs surface exhibits downward band bending due to the electron accumulation, in NO2 ambient, the surface band bending was decreased due to the increase in bulk conduction channel. This reversed gas sensing behavior in InN/In2O3 core-shell NRs was attributed to the increase in depletion layer while reducing conduction channel width by absorption of NO2. The InN/In2O3 core-shell NRs exhibited a response of 22.43 % at 50 oC, which was 5.11 times higher than that of pristine InN NRs.

To determine the electron energy spectra for medical accelerator effectively, we investigate a nonlinear programming model with several nonlinear regression algorithms, including Levenberg?Marquardt, Quasi?Newton, Gradient, Conjugate Gradient, Newton, Principal-Axis and NMinimize algorithms. The local relaxation-bound method is also developed to increase the calculation accuracy. The testing results demonstrate that the above methods could reconstruct the electron energy spectra effectively. Especially, further with the local relaxation-bound method the Levenberg?Marquardt, Newton and NMinimize algorithms could precisely obtain both the electron energy spectra and the photon contamination. Further study shows that ignoring about 4% photon contamination would increase error greatly, and it also inaccurately makes the electron energy spectra 'drift' to the low energy.

A multi-objective hybrid genetic based optimization algorithm is proposed according to the multi-objective character of inverse planning. It is based on hybrid adaptive genetic algorithm, which combines the simulated annealing, uses adaptive crossover and mutation, and adopts niched tournament selection. The result of the test calculation demonstrates that excellent converge speed can be achieved using this approach. Key words- Inverse Planning Multi-objective optimization Genetic algorithm Hybrid.

The effects of various parameters including thickness and dielectric constants of substrates, shapes of nanoparticles, and polarization direction of incident light, on the extinction spectra of periodic gold nanoparticle arrays are investigated by the full-vectorial three-dimensional (3D) finite difference time domain (FDTD) method. The calculated results show that the substrate affects the extinction spectra by coupling the fields co-excited by the substrate and gold nanoparticles. Extinction spectra are influenced by the shapes of the nanoparticles, but there are no obvious changes in extinction spectra for similar shapes. The polarization direction of incident light has a great influence on the extinction spectra. The implications of these results are discussed.

We investigate the effect of a symmetric gap surface plasmon polariton (SPP) waveguide on ultrashort pulses with a central wavelength of 850 nm and a width of 20 fs using the finite-difference time-domain method. The length of the waveguide is 560 nm. Linear and nonlinear dielectrics are chosen to be the core layers whose thicknesses are set to be 20, 50, 100 and 200 nm, respectively. The results show that for the linear case, strong coupling of the SPP mode can lead to the pulse tailing phenomenon and spectrum compression due to waveguide resonance. For the nonlinear case, the output pulse is broadened and the fluctuation is more complex than the input pulse and can induce the spectrum splitting as well. The smaller the thickness of the core layer is, the more distinct the pulse distortion is, which may be due to the combined effects of dispersion, waveguide resonance and self-phase modulation.

We investigated the influence of extinction of gold nanoparticles periodic arrays by varying the substrate properties and the shapes of nanoparticles with the full vectorial three dimensional finite difference time domain method. Substrates of different thicknesses and dielectric constants and ten topologically different gold nanostructures including diamond, cycle ring, rectangle ring, pentagon ring, five-pointed star, flower shape, L, Y, T and X shapes are considered. The results show that substrate properties have a significant impact on the extinction spectrum due to coupling of the modes excited in substrates and the one excited by localized surface plasmon. The extinction spectra are changed with the different shapes of nanoparticles periodic array. However, with similar structure particles periodic arrays, the extinction spectra appear similar in the visible regime. Therefore we can find an eligible shape and substrate which can be used in integrated devises.