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In this paper, different efficiency behaviors of blue LEDs fabricated on the conventional sapphire substrate (C-LEDs) and patterned sapphire substrate (PSSLEDs) by metal organic chemical vapor deposition are investigated. Maximum external quantum efficiency (EQE) of PSSLEDs shows about 23.5 % improvement compared with that of C-LEDs. However, PSSLEDs have lower peak-efficiency-current at which the EQE reaches maximum, and suffer more serious efficiency droop. Besides, slight changes of efficiency droop for these two type LEDs in aging experiments indicate that structure defects do not play major roles for efficiency droop, and faster broadenings of the full width at half maximum of the electro-luminescence (EL) spectrum when injection current increases suggest stronger band filling effects in PSSLEDs. From the rate equation analyses, the value of coefficient C' is found to be two orders larger than Auger coefficient, and PSSLEDs have a greater coefficient C', which implies more carriers overflow from QWs in PSSLEDs. Therefore, it is suggested that, compared to Auger recombination, carrier overflow from QWs would play a more important part in the efficiency droop of blue LEDs. [ABSTRACT FROM AUTHOR]

Nanostructures with high electrical conductivity were fabricated on silicon surfaces using a laser-assisted scanning tunneling microscope (LA-STM). The nanostructures, dots and lines, were fabricated on H-passivated p-doped silicon (110) surfaces. By precisely controlling the experimental conditions such as pulse energy and tip-surface gap distance, feature sizes (dot diameters and line widths) and heights of the fabricated nanostructures could be controlled. For instance, a dot with a diameter of 30 nm and a line with a width of 30 nm were obtained. In addition, scanning tunneling microscopy investigation of the structures revealed that their band gaps were changed during the LA-STM process. As a consequence, the local conductivity (more precisely the tunneling probability) was enhanced. Numerical simulations based upon the finite-difference-time-domain algorithm provide detailed insight into the spatial distribution of the enhanced optical field underneath the STM tip and associated physical phenomena. Potential applications of the developed nanostructuring process are anticipated in various nanotechnology fields, particularly in the field of nanoelectronics. [ABSTRACT FROM AUTHOR]

A technique was developed to achieve enhanced Raman scattering of the silicon photon modes using closely packed micro- and submicron silica spherical particles. Investigation on the particle-size dependence of Raman enhancement revealed that the strongest enhancement occurs when the particle diameter is equal to the spot size of the incident laser beam. Calculations using the OPTIWAVE™ software based on the finite difference time domain algorithm under the perfectly matched layer boundary conditions were carried out. The results showed that photonic nanojets are formed in the vicinity outside the particles along the propagation direction of incident light. It was found that the nanojets are confined to a length of 100 nm with a waist of 120 nm. The presence of the strongly localized electromagnetic fields within the nanojets accounts for the enhanced Raman scattering. This technique has potential applications both in modern and traditional areas of surface science such as surface oxidation, adhesion, corrosion, and catalytic processes, and many other areas in biology, chemistry, materials science, and microelectronics. [ABSTRACT FROM AUTHOR]

Laser-assisted chemical vapor deposition was applied in fabricating three-dimensional (3D) spherical-shell photonic band gap (PBG) structures by depositing silicon shells covering silica particles, which had been self-assembled into 3D colloidal crystals. The colloidal crystals of self-assembled silica particles were formed on silicon substrates using the isothermal heating evaporation approach. A continuous wave Nd:YAG laser (1064 nm wavelength) was used to deposit silicon shells by thermally decomposing disilane gas. Periodic silicon-shell/silica-particle PBG structures were obtained. By removing the silica particles enclosed in the silicon shells using hydrofluoric acid, hollow spherical silicon-shell arrays were produced. This technique is capable of fabricating structures with complete photonic band gaps, which is predicted by simulations with the plane wave method. The techniques developed in this study have the potential to flexibly engineer the positions of the PBGs by varying both the silica particle size and the silicon-shell thickness. Ellipsometry was used to investigate the specific photonic band gaps for both structures. [ABSTRACT FROM AUTHOR]

Focuses on a study which described pulsed laser deposition of hydrogenated amorphous diamond-like carbon films from a polymer target. Experimental details; Results and discussion; Summary and conclusion.