Polarity in GaN and ZnO: Theory, measurement, growth, and devices

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Rev. 3, 041303 (2016) and may be found at https://doi.org/10.1063/1.4963919.The polar nature of the wurtzite crystalline structure of GaN and ZnO results in the existence of a spontaneous electric polarization within these materials and their associated alloys (Ga,Al,In)N and (Zn,Mg,Cd)O. The polarity has also important consequences on the stability of the different crystallographic surfaces, and this becomes especially important when considering epitaxial growth. Furthermore, the internal polarization fields may adversely affect the properties of optoelectronic devices but is also used as a potential advantage for advanced electronic devices. In this article, polarity-related issues in GaN and ZnO are reviewed, going from theoretical considerations to electronic and optoelectronic devices, through thin film, and nanostructure growth. The necessary theoretical background is first introduced and the stability of the cation and anion polarity surfaces is discussed. For assessing the polarity, one has to make use of specific characterization methods, which are described in detail. Subsequently, the nucleation and growth mechanisms of thin films and nanostructures, including nanowires, are presented, reviewing the specific growth conditions that allow controlling the polarity of such objects. Eventually, the demonstrated and/or expected effects of polarity on the properties and performances of optoelectronic and electronic devices are reported. The present review is intended to yield an in-depth view of some of the hot topics related to polarity in GaN and ZnO, a fast growing subject over the last decade

OceanSITES Innovation Report

Innovation and improvement report on the extension of capabilities to measure emerging EOVs including metagenomics across different observational platforms with links to MicroB3 best practice

Role of supplemental foods and habitat structural complexity in persistence and coexistence of generalist predatory mites

Variation in the strength of intraguild predation (IGP) may be related to habitat structural complexity and to additional resources outside the narrow predator-prey relationship. We studied the food web interactions on grape, which involves two generalist predatory mites. We evaluated the effects of grape powdery mildew (GPM) as supplemental food, and habitat structural complexity provided by domatia. Our findings suggest that structural and nutritional diversity/complexity promote predatory mite abundance and can help to maintain the beneficial mites - plants association. The effect of these factors on coexistence between predators is influenced by the supplemental food quality and relative differences in body size of interacting species

X-ray photoelectron spectroscopy study of the chemical interaction at the Pd/SiC interface

U.S. Department of Energy [FG07-01AL67358, DE-FC07-06ID14781]In order to study the chemical interaction during interface formation between Pd and SiC, Pd layers of various thicknesses were deposited on structurally disordered SiC surfaces at 800 degrees C. The Pd/SiC interface, which plays a crucial role for many applications such as high power electronic devices and tristructural-isotropic (TRISO) nuclear fuels, was studied in situ by x-ray photoelectron spectroscopy. We find that after Pd deposition, Si-C and Si-Si bonds are broken in favor of the formation of not only Pd-Si but also Pd-C bonds. In addition, various silicon oxycarbide bonds are observed at the SiC surface and the Pd/SiC interface. These results are not only of relevance for the long-term stability of TRISO fuels but also for a variety of other applications, including Schottky-barrier-type contacts in electronic devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3500374