Near-Infrared Vapochromism in Lipid-Packaged Mixed-Valence Coordination Polymers

Reversible vapochromism in the NIR region is achieved for a mixed-valence platinum complex with lipid counterions, from which exclusion of crystallization water by organic vapor alters lipid molecular orientation that...

Liquid-dependent impedance induced by vapor condensation and percolation in nanoparticle film

A liquid-dependent impedance is observed by vapor condensation and percolation in the void space between nanoparticles. Under the Laplace pressure, vapor is effectively condensed into liquid to fill the nanoscale voids in an as-deposited nanoparticle film. Specifically, the transient impedance of the nanoparticle film in organic vapor is dependent on the vapor pressure and the conductivity of the condensed liquid. The response follows a power law that can be explained by the classical percolation theory. The condensed vapor gradually percolates into the void space among nanoparticles. A schematic is proposed to describe the vapor condensation and percolation dynamics among the nanoparticles. These findings offer insights into the behavior of vapor adsorbates in nanomaterial assemblies that contain void space.

Investigation of the Electro-Optical Characteristics of GaAs/AlGaAs Multiple Quantum Well Grown by Metal Organic Vapor Phase Epitaxy

In this study, the photoluminescence measurements of GaAs/AlGaAs multi-quantum-wells heterojunction structure grown on n+-GaAs substrates by Metal Organic Vapor Phase Epitaxy (MOVPE) method are investigated. By dropping 5145 Å wavelength laser light on the sample at room temperature and low temperatures, the transitions between the bands in the structure and the changes in these transitions under the different electric fields and temperatures are observed. In addition, by making theoretically developed self-consistent potential calculations, the subband energy levels and their corresponding wave functions of the structure under the electric field and without the electric field are calculated. The obtained numerical results were found to be in full agreement with the experimental measurements and theoretical calculations.

Droplet epitaxy of InAs/InP quantum dots via MOVPE by using an InGaAs interlayer

InAs quantum dots (QDs) are grown on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix. They are fabricated via droplet epitaxy (DE) in a Metal Organic Vapor Phase Epitaxy (MOVPE) reactor. Formation of metallic Indium droplets on the In0.53Ga0.47As lattice-matched layer and their crystallization into QDs is demonstrated for the first time in MOVPE. The presence of the In0.53Ga0.47As layer prevents the formation of an unintentional non-stoichiometric 2D layer underneath and around the QDs, via suppression of the As-P exchange. The In0.53Ga0.47As layer affects the surface diffusion leading to a modified droplet crystallization process, where unexpectedly the size of the resulting QDs is found to be inversely proportional to the Indium supply. Bright single dot emission is detected via micro-photoluminescence at low temperature, ranging from 1440 to 1600 nm, covering the technologically relevant telecom C-band. Transmission Electron Microscopy (TEM) investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.

Influence of QD array positioning in GaAs solar cell p-n junction on their photoelectric characteristics

In the work, the effect of In0.8Ga0.2As quantum dots position in the i-region of a GaAs solar cell on its spectral and photoelectric characteristics has been investigated. Three solar cell structures were obtained by metal-organic vapor-phase epitaxy, in which layers of quantum dots were placed in the middle of the i-region and also have been shifted to the base and the emitter. As a result, it has been shown that the solar cell with a quantum dot array shifted to the base demonstrates the smallest open-circuit voltage drop and, accordingly, a higher efficiency value.

Numerical Analysis of the High Pressure MOVPE Upside-Down Reactor for GaN Growth

The present paper focuses on the high-pressure metal-organic vapor phase epitaxy (MOVPE) upside-down vertical reactor (where the inlet of cold gases is below a hot susceptor). This study aims to investigate thermo-kinetic phenomena taking place during the GaN (gallium nitride) growth process using trimethylgallium and ammonia at a pressure of above 2 bar. High pressure accelerates the growth process, but it results in poor thickness and quality in the obtained layers; hence, understanding the factors influencing non-uniformity is crucial. The present investigations have been conducted with the aid of ANSYS Fluent finite volume method commercial software. The obtained results confirm the possibility of increasing the growth rate by more than six times through increasing the pressure from 0.5 bar to 2.5 bar. The analysis shows which zones vortexes form in. Special attention should be paid to the transitional flow within the growth zone as well as the viewport. Furthermore, the normal reactor design cannot be used under the considered conditions, even for the lower pressure value of 0.5 bar, due to high turbulences.