The fabrication process and performance characteristics of the laser lift-off ͑LLO͒ GaN light-emitting diodes ͑LEDs͒ were investigated. The LLO-GaN LEDs were fabricated by lifting off the GaN LED wafer structure grown on the original sapphire substrate by a KrF excimer laser at 248 nm wavelength with the laser fluence of 0.6 J/cm 2 and transferring it onto a Cu substrate. The LLO-GaN LEDs on Cu show a nearly four-fold increase in the light output power over the regular LLO-LEDs on the sapphire substrate. High operation current up to 400 mA for the LLO-LEDs on Cu was also demonstrated. Based on the emission wavelength shift with the operating current data, the LLO-LEDs on Cu show an estimated improvement of heat dissipation capacities by nearly four times over the light-emitting devices on sapphire substrate. The LLO process should be applicable to other GaN-based LEDs in particular for those high light output power and high operation current devices.

The hydrogen adsorption of Mg-doped graphene oxide (GO) has been studied using density functional theory calculations. It has been found that hydroxyl can be reduced from the surface of GO by Mg doping no matter whether the hydroxyl exhibits an acidity or alkalinity. The remaining Mg is strongly bound to GO in the form of −(C–O) x –Mg (x = 1 or 2). H2 can be strongly adsorbed on Mg-doped GO with a binding energy of 0.38 eV/H2 because Mg and O can jointly produce a stronger electric field and polarize H2 along almost the same direction. If Mg and O separately polarize this H2 along different direction, the charge redistribution along different directions reduces the binding energy of H2 to 0.25 eV/H2. When eight H2 molecules are adsorbed on each side of Mg-doped GO, the theoretical hydrogen storage capacity can reach to 5.6 wt % at a temperature of 200 K without any pressure.

Based on a density functional theory simulation, we proposed a reduction mechanism of graphene oxide (GO) under a sodium hydroxide solution containing anions (OH(-)), cations (Na(+)) and neutral H2O molecules as main components. OH(-) anion can interact with hydroxyl in GO and transfer electrons to the graphene sheet, resulting in negatively charged GO, and these electrons obviously lower the barrier of the ring-opening reaction of epoxy. Na(+) cations can be attracted by the negatively charged GO, and this reaction is equivalent to the one between metallic Na and GO. The opened epoxy is reduced with the assistance of Na(+) cation and water molecule. In such a reduction process, NaOH can be viewed as a catalyst and more defects should be formed because of these diffused epoxies on the negatively charged graphene sheet. Our results may be helpful to understand further the nature of the reduction of GO among various reducing agents.

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We report a very high performance lOOnm gate length CMOS transistor structure operating at 1.2-1 SV. These transistors are incorporated in a 180nm logic technology generation. Various process enhancements are incorporated to significantly improve transistor current drive capability relative to the results published in [I]. Unique transistor features responsible for achieving high performance are described. NMOS and PMOS devices demonstrate drive current of 1.04 mA/pm and 0.46 mA/pm respectively at 1.5V and 3nA/pm IOFF. These are the best drive currents reported to date at fixed IOFF. They represents 10% drive current improvement for both NMOS and PMOS devices relative to the results published in Ref.[l] without any change in gate-oxide thickness. High performance is demonstrated down to 1.2V. Inverter delay of less than 10 psec is reported at 1.5V at very moderate IOFF values.