Ultralow threading dislocation density in GaN epilayer on near-strain-free GaN compliant buffer layer and its applications in hetero-epitaxial LEDs.

High threading dislocation (TD) density in GaN-based devices is a long unresolved problem because of the large lattice mismatch between GaN and the substrate, which causes a major obstacle for the further improvement of next-generation high-efficiency solid-state lighting and high-power electronics. Here, we report InGaN/GaN LEDs with ultralow TD density and improved efficiency on a sapphire substrate, on which a near strain-free GaN compliant buffer layer was grown by remote plasma atomic layer deposition. This "compliant" buffer layer is capable of relaxing strain due to the absorption of misfit dislocations in a region within ~10 nm from the interface, leading to a high-quality overlying GaN epilayer with an unusual TD density as low as 2.

Atomic-layer-deposited silver and dielectric nanostructures for plasmonic enhancement of Raman scattering from nanoscale ultrathin films.

Plasmonic silver nanostructures and a precise ZnO cover layer prepared by capacitively coupled plasma atomic layer deposition (ALD) were exploited to enhance the Raman scattering from nanoscale ultrathin films on a Si substrate. The plasmonic activity was supported by a nanostructured Ag (nano-Ag) layer, and a ZnO cover layer was introduced upon the nano-Ag layer to spectrally tailor the localized surface plasmon resonance to coincide with the laser excitation wavelength. Because of the optimized dielectric environment provided by the precise growth of ZnO cover layer using ALD, the intensity of Raman scattering from nanoscale ultrathin films was significantly enhanced by an additional order of magnitude, leading to the observation of the monoclinic and tetragonal phases in the nanoscale ZrO2 high-K gate dielectric as thin as ∼6 nm on Si substrate.

Enhancement of light emission from silicon by precisely tuning coupled localized surface plasmon resonance of a nanostructured platinum layer prepared by atomic layer deposition.

Plasmonic enhancement of photoluminescence from bulk silicon was achieved by spectrally tailoring coupled localized surface plasmon resonance (LSPR) in the Al2O3 cover/nanostructured platinum (nano-Pt)/Al2O3 spacer/silicon multilayer structures prepared by atomic layer deposition (ALD). Agreement between the simulation and experimental data indicates that the plasmonic activity originates from absorption enhancement due to coupled LSPR. Because of the optimized dielectric environment deposited by ALD around the nano-Pt layer, absorption of the multilayer structure was enhanced by the precise tuning of coupled LSPR to coincide with the excitation wavelength.

Improved characteristics of near-band-edge and deep-level emissions from ZnO nanorod arrays by atomic-layer-deposited Al2O3 and ZnO shell layers.

We report on the characteristics of near-band-edge (NBE) emission and deep-level band from ZnO/Al2O3 and ZnO/ZnO core-shell nanorod arrays (NRAs). Vertically aligned ZnO NRAs were synthesized by an aqueous chemical method, and the Al2O3 and ZnO shell layers were prepared by the highly conformal atomic layer deposition technique. Photoluminescence measurements revealed that the deep-level band was suppressed and the NBE emission was significantly enhanced after the deposition of Al2O3 and ZnO shells, which are attributed to the decrease in oxygen interstitials at the surface and the reduction in surface band bending of ZnO core, respectively.

Single-element ultrasound transducer for combined vessel localization and ablation.

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm.