Nanoporous GaN by selective area sublimation through an epitaxial nanomask: AlN versus SiN.

Nanoporous GaN layers were fabricated using selective area sublimation through a self-organized AlN nanomask in a molecular beam epitaxy reactor. The obtained pore morphology, density and size were measured using plan-view and cross-section scanning electron microscopy experiments. It was found that the porosity of the GaN layers could be adjusted from 0.

WALANT technique versus locoregional anesthesia in the surgical management of metacarpal and phalangeal fractures: Lessons from the Covid-19 crisis.

Wide Awake Local Anesthesia No Tourniquet (WALANT) is an anesthetic method which uses a local injection of anesthetic and epinephrine, avoiding use of a tourniquet. During the COVID-19 pandemic, human and logistic resources had to be reorganized, and WALANT ensured resilience in our department to maintain access to surgical care. The objective of the present study was to compare hand function recovery 3 months after surgery for unstable metacarpal or phalangeal fracture under regional anesthesia versus WALANT.

Exploration of irradiation intensity dependent external in-band quantum yield for ZnO and CuO/ZnO photocatalysts.

Decorating metal oxides with wide band-gap semiconductor nano-particles constitute an important approach for synthesizing nano-photocatalysts, where the photocatalytic activity is attributed to the band diagram related effective charge separation and external in-band quantum yield (EIQY). However, up to now, the correlation between the irradiation intensity and the functionalization of the in-band quantum yield has not yet been explained. In this work, by investigating the photocatalytic activity of ZnO and CuO/ZnO (CZO) nano-photocatalysts under various irradiative intensities, we show that the effective charge separation in the CuO/ZnO band alignment is sensitive to weak illumination, while ZnO exhibits a competitive photocatalytic activity with CZO under strong illumination.

Polarity Control within One Monolayer at ZnO/GaN Heterointerface: (0001) Plane Inversion Domain Boundary.

In semiconductor heterojunction, polarity critically governs the physical properties, with an impact on electronic or optoelectronic devices through the presence of pyroelectric and piezoelectric fields at the active heteropolar interface. In the present work, the abrupt O-polar ZnO/Ga-polar GaN heterointerface was successfully achieved by using high O/Zn ratio flux during the ZnO nucleation growth. Atomic-resolution high-angle annular dark-field and bright-field transmission electron microscopy observation revealed that this polarity inversion confines within one monolayer by forming the (0001) plane inversion domain boundary (IDB) at the ZnO/GaN heterointerface.

The microstructure, local indium composition and photoluminescence in green-emitting InGaN/GaN quantum wells.

In this work, we analyse the microstructure and local chemical composition of green-emitting In Ga N/GaN quantum well (QW) heterostructures in correlation with their emission properties. Two samples of high structural quality grown by metalorganic vapour phase epitaxy (MOVPE) with a nominal composition of x = 0.15 and 0.

The structure of InAlGaN layers grown by metal organic vapour phase epitaxy: effects of threading dislocations and inversion domains from the GaN template.

Defects in quaternary InAlGaN barriers and their effects on crystalline quality and surface morphology have been studied. In addition to growth conditions, the quality of the GaN template may play an important role in the formation of defects in the barrier. Therefore, this work is focused on effects caused by threading dislocations (TDs) and inversion domains (IDs) originating from the underlying GaN.

Effective absorption correction for energy dispersive X-ray mapping in a scanning transmission electron microscope: analysing the local indium distribution in rough samples of InGaN alloy layers.

We have applied our previous method of self-consistent k*-factors for absorption correction in energy-dispersive X-ray spectroscopy to quantify the indium content in X-ray maps of thick compound InGaN layers. The method allows us to quantify the indium concentration without measuring the sample thickness, density or beam current, and works even if there is a drastic local thickness change due to sample roughness or preferential thinning. The method is shown to select, point-by-point in a two-dimensional spectrum image or map, the k*-factor from the local Ga K/L intensity ratio that is most appropriate for the corresponding sample geometry, demonstrating it is not the sample thickness measured along the electron beam direction but the optical path length the X-rays have to travel through the sample that is relevant for the absorption correction.

Morphology and valence band offset of GaSb quantum dots grown on GaP(001) and their evolution upon capping.

This work presents a detailed study of GaSb quantum dot (QD) epitaxy on (001) GaP substrates by means of molecular beam epitaxy. Despite the large mismatch between GaP and GaSb, we show that in the nucleation-diffusion regime, the QD size distribution follows the predictions of the scaling theory. Scanning transmission electron microscopy analysis of grown QDs reveal that they are plastically relaxed by 60° pairs of misfit dislocations and the valence band offset measured by x-ray photoelectron spectroscopy on such QDs amounts to 0.

Influence of nanoscale faceting on the tunneling properties of near broken gap InAs/AlGaSb heterojunctions grown by selective area epitaxy.

We report on the selective area molecular beam epitaxy of InAs/AlGaSb heterostructures on a GaSb (001) substrate. This method is used to realize Esaki tunnel diodes with a tunneling area down to 50 nm × 50 nm. The impact of the size reduction on the peak current density of the diode is investigated, and we show how the formation of the InAs facets can deeply affect the band-to-band tunneling properties of the heterostructure.

Antimony-mediated control of misfit dislocations and strain at the highly lattice mismatched GaSb/GaAs interface.

Determining the atomic structure of misfit dislocations at highly lattice mismatched interface is essential to optimize the quality of the epitaxial layer. Here, with aberration corrected scanning transmission electron microscopy at sub-Angstrom resolution and molecular dynamics simulation, we investigated the atomic structure of misfit dislocations at GaSb/GaAs interface. New types of Lomer misfit dislocation formed on an Sb wetting monolayer were observed, in contrast to a conventional misfit dislocation whose core is located at interface.

Strain relief and growth optimization of GaSb on GaP by molecular beam epitaxy.

In this paper, the impact of growth parameters on the strain relaxation of highly lattice mismatched (11.8%) GaSb grown on GaP substrate by molecular beam epitaxy has been investigated. The surface morphology, misfit dislocation and strain relaxation of the GaSb islands are shown to be highly related to the initial surface treatment, growth rate and temperature.

Defect structure in heteroepitaxial semipolar (1122) (Ga, Al)N.

The defect structures in semipolar (1122)-GaN, AlN layers grown on m-sapphire by metal organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE) are characterized by transmission electron microscopy. The epitaxial relationships are identified as [1010](GaN) || [1120]sap and [1213](GaN) || [0001]sap. Defects are identified as mostly partial dislocations, I1-basal and prismatic stacking faults.

High Curie temperature for La(0.7)Sr(0.3)MnO(3) thin films deposited on CeO(2) /YSZ-based buffered silicon substrates.

Two kinds of epitaxial structures were grown by standard pulsed laser deposition on (001) Si, namely La(0.7)Sr(0.3)MnO(3)/Bi(4)Ti(3)O(12)/CeO(2) /YSZ/Si (BTO-based), and La(0.

Piezoelectric field around threading dislocation in GaN determined on the basis of high-resolution transmission electron microscopy image.

A new method of determining the piezoelectric field around dislocations from high-resolution transmission electron microscopy images is presented. In order to determine the electrical potential distribution near a dislocation core, we used the distortion field, obtained using the geometrical phase method and the non-linear finite element method. The electrical field distribution was determined taking into account the inhomogeneous strain distribution, finite geometry of the sample and the full couplings between elastic and electrical fields.