Characterization of GaN Nanorods Fabricated Using Ni Nanomasking and Reactive Ion Etching: A Top-Down Approach

Large thermal mismatch between GaN surface and sapphire results in compressive stress in Gallium Nitride (GaN) layer which degrades the device performance. Nanostructuring the GaN can reduce this stress leading to reduction in Quantum Confined Stark Effect. Aligned GaN nanorods based nanodevices have potential applications in electronics and optoelectronics. This paper describes the fabrication of GaN nanorods using Ni nanomasking and reactive ion etching. The morphology of GaN nanorods was studied by field emission scanning electron microscopy. The optical properties of GaN nanorods were studied by Cathodoluminescence (CL) spectroscopy. CL results revealed the existence of characteristic band-edge luminescence and yellow band luminescence. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3099

InGaN/GaN multiquantum well nano-LEDs for a case study

The scattering in the light emission wavelength of semiconductor nano-emitters assigned to nanoscale variations in strain, thickness, and composition is critical in current and novel nanotechnologies from highly efficient light sources to photovoltaics. Here, we present a correlated experimental and theoretical study of single nanorod light emitting diodes (nano-LEDs) based on InGaN/GaN multiquantum wells to separate the contributions of these intrinsic fluctuations. Cathodoluminescence measurements show that nano-LEDs with identical strain states probed by non-resonant micro-Raman spectroscopy can radiate light at different wavelengths. The deviations in the measured optical transitions agree very well with band profile calculations for quantum well thicknesses of 2.07–2.72 nm and In fractions of 17.5–19.5% tightly enclosing the growth values. The nanorod surface roughness controls the appearance of surface optical phonon modes with direct implications on the design of phonon assisted nano-LED devices. This work establishes a new, simple, and powerful methodology for fundamental understanding as well as quantitative analysis of the strain – light emission relationship and surface-related phenomena in the emerging field of nano-emitters.1\. Auflag

Disentangling the effects of nanoscale structural variations on the light emission wavelength of single nano-emitters: InGaN/GaN multiquantum well nano-LEDs for a case study

The scattering in the light emission wavelength of semiconductor nano-emitters assigned to nanoscale variations in strain, thickness, and composition is critical in current and novel nanotechnologies from highly efficient light sources to photovoltaics. Here, we present a correlated experimental and theoretical study of single nanorod light emitting diodes (nano-LEDs) based on InGaN/GaN multiquantum wells to separate the contributions of these intrinsic fluctuations. Cathodoluminescence measurements show that nano-LEDs with identical strain states probed by non-resonant micro-Raman spectroscopy can radiate light at different wavelengths. The deviations in the measured optical transitions agree very well with band profile calculations for quantum well thicknesses of 2.07–2.72 nm and In fractions of 17.5–19.5% tightly enclosing the growth values. The nanorod surface roughness controls the appearance of surface optical phonon modes with direct implications on the design of phonon assisted nano-LED devices. This work establishes a new, simple, and powerful methodology for fundamental understanding as well as quantitative analysis of the strain – light emission relationship and surface-related phenomena in the emerging field of nano-emitters

Phenotypic diversity influenced by a transposable element increases productivity and resistance to competitors in plant populations

An accumulating body of evidence indicates that natural plant populations harbour a large diversity of transposable elements (TEs). TEs, which are especially mobilized under genomic and/or environmental stress, provide genetic and epigenetic variation that can substantially translate into a diversity of plant phenotypes within populations. However, it remains unclear what the potential ecological effects of diversity in TEs within an otherwise genetically uniform population are in terms of phenotypic diversity's effects on coexistence and ecosystem functioning. Using Arabidopsis thaliana as a proof-of-concept model, we assembled populations from individuals differing in the number and positions of ONSEN retrotransposon and tested whether the increasing diversity created by the ONSEN retrotransposon increased the phenotypic diversity of populations and enhanced their functioning under different environmental conditions. We demonstrate that TE-generated variation creates differentiation in ecologically important traits connected to different axes of the plant ‘economics’ spectrum. In particular, we show that Arabidopsis populations with increasing diversity of individuals differing in the ONSEN retrotransposon had higher phenotypic and functional diversity in resource use-related traits. Such increased diversity enhanced population productivity and reduced the performance of interspecific competitors. Synthesis. We conclude that TE-generated phenotypic and functional diversity can have similar effects on ecosystems as are usually documented for other biological diversity effects. The results of our experiment open up new fields of investigation, highlighting the ecological relevance of unexplored sources of phenotypic variability and hopefully inspiring functional trait ecologists and evolutionary biologists to begin exploring new questions at the intersection of their fields.This study was financially supported by the Czech Science Foundation (GACR 20-13637S) and the institutional research project RVO 67985939. J.P. was funded by grant FJC2020-042954-I by MCIN/AEI/10.13039/501100011033 & ‘European Union NextGenerationEU/PRTR’ and by the Irish Research Council Laureate Awards 2017/2018 (IRCLA/2017/60) to Yvonne Buckley. E.B. was funded by the ERC Consolidator grant (BUNGEE 725701) of the European Union. F.d.B. was supported by the Plan Nacional de I+D+i (project PGC2018-099027-B-I00), M.T. was financially supported by the University Research Priority Programme (URPP) Evolution in Action and the European Commission (PITN-GA-2013-608422–IDP BRIDGES).Peer reviewe

Data for Latzel et al. Journal of Ecology [Dataset]

Biomass data for Arabidopsis thaliana populations. Each row refers to a pot in the pot experiment and shows: the population code treatment (competition, drought, their combination, or control) diversity, i.e. the number of different TE lines that a population was composed of number of individuals at time of biomass harvest total pot biomass average individual biomass (pot biomass/number of individuals) weight of competitors in the pot (0 if no competitors were present)GACR 20-13637SPeer reviewe

Photon bunching reveals single-electron cathodoluminescence excitation efficiency in InGaN quantum wells

Cathodoluminescence spectroscopy is a key analysis technique in nanophotonics research and technology, yet many aspects of its fundamental excitation mechanisms are not well understood on the single-electron and single-photon level. Here, we determine the cathodoluminescence emission statistics of InGaN quantum wells embedded in GaN under 6-30-keV electron excitation and find that the light emission rate varies strongly from electron to electron. Strong photon bunching is observed for the InGaN quantum well emission at 2.77 eV due to the generation of multiple quantum well excitations by a single primary electron. The bunching effect, measured by the g(2)(t) autocorrelation function, decreases with increasing beam current in the range 3-350 pA. Under pulsed excitation (p=2-100ns; 0.13-6 electrons per pulse), the bunching effect strongly increases. A model based on Monte Carlo simulations is developed that assumes a fraction γ of the primary electrons generates electron-hole pairs that create multiple photons in the quantum wells. At a fixed primary electron energy (10 keV) the model explains all g(2) measurements for different beam currents and pulse durations using a single value for γ=0.5. At lower energies, when electrons cause mostly near-surface excitations, γ is reduced (γ=0.01 at 6 keV), which is explained by the presence of a AlGaN barrier layer that inhibits carrier diffusion to the buried quantum wells. The combination of g(2) measurements in pulsed and continuous mode with spectral analysis provides a powerful tool to study optoelectronic properties and may find application in many other optically active systems and devices.QN/Conesa-Boj La