Influence of the "second gap" on the transparency-conductivity compromise in transparent conducting oxides: an ab initio study

Transparent conducting oxides (TCOs) are essential to many technologies. These materials are doped (\emph{n}- or \emph{p}-type) oxides with a large enough band gap (ideally $>$3~eV) to ensure transparency. However, the high carrier concentration present in TCOs lead additionally to the possibility for optical transitions from the occupied conduction bands to higher states for \emph{n}-type materials and from lower states to the unoccupied valence bands for \emph{p}-type TCOs. The "second gap" formed by these transitions might limit transparency and a large second gap has been sometimes proposed as a design criteria for high performance TCOs. Here, we study the influence of this second gap on optical absorption using \emph{ab initio} computations for several well-known \emph{n}- and \emph{p}-type TCOs. Our work demonstrates that most known \emph{n}-type TCOs do not suffer from second gap absorption in the visible even at very high carrier concentrations. On the contrary, \emph{p}-type oxides show lowering of their optical transmission for high carrier concentrations due to second gap effects. We link this dissimilarity to the different chemistries involved in \emph{n}- versus typical \emph{p}-type TCOs. Quantitatively, we show that second gap effects lead to only moderate loss of transmission (even in p-type TCOs) and suggest that a wide second gap, while beneficial, should not be considered as a needed criteria for a working TCO.Comment: 6 pages, 4 figures, APS March Meetin

Physico-chemical properties of fourteen popular cocoa bean varieties in Dongnai-highland Vietnam

Cocoa (Theobroma cacao L.) is a major, crucial economic, global crop and has been maintained several nutritional benefits. The exporting volume of Vietnamese cocoa bean is increasing in the world cocoa trade. The beans of fourteen popular cocoa varieties that are commonly cultivated in Trang Bom (Dong Nai, Vietnam) were characterized for their physico-chemical qualifications on the background of post-fermented cocoa beans and dehydration in the region of Trang Bom-Dong Nai. The physical properties were determined based on mass ratio and bean’s dimension (lengh, width and thickness) as well as chemical (proximate) composition (total crude protein, ash, moisture, and lipid). These values were analysed using AOAC methods. The largest-size beans were found for the TD8 variety (1.5 g of mass, 25.02 mm of length, 14.28 mm of width and 7.96 mm of thickness). The moisture content of the cocoa beans was in the range between 5.64 and 6.99 (% wb) and the ash content in the range between 3.67% and 2.47% (wb). Noticeably, the fat content ratio (the most important value of cocoa bean) found in 8 varieties (TD1, TD2, TD5, TD9, TD11, TD12, TD13, TD14) was over 50%, thus these varieties are worthy chemical component especially for exported cocoa bean and industrized cultivation (extending the cultivation producing area)

An Extended Occlusion Detection Approach for Video Processing

Occlusions become conspicuous as failure regions in video processing when unified over time because the contraventions of the restriction of brightness have accumulated and evolved in occluded regions. The accuracy at the boundaries of the moving objects is one of the challenging areas that required further exploration and research. This paper presents the work in process approach that can detect occlusion regions by using pixel-wise coherence, segment-wise confidence and interpolation technique. Our method can get the same result as usual methods by solving only one Partial Differential Equations (PDE) problem; it is superior to existing methods because it is faster and provides better coverage rates for occlusion regions than variation techniques when tested against a varied number of benchmark datasets. With these improved results, we can apply and extend our approach to a wider range of applications in computer vision, such as background subtraction, tracking, 3D reconstruction, video surveillance, video compression

Computationally-driven, high throughput identification of CaTe and Li3_\textrm{3}Sb as promising candidates for high mobility pp-type transparent conducting materials

High-performance $p$-type transparent conducting materials (TCMs) must exhibit a rare combination of properties including high mobility, transparency and $p$-type dopability. The development of high-mobility/conductivity $p$-type TCMs is necessary for many applications such as solar cells, or transparent electronic devices. Oxides have been traditionally considered as the most promising chemical space to dig out novel $p$-type TCMs. However, non-oxides might perform better than traditional $p$-type TCMs (oxides) in terms of mobility. We report on a high-throughput (HT) computational search for non-oxide $p$-type TCMs from a large dataset of more than 30,000 compounds which identified CaTe and Li$_\textrm{3}$Sb as very good candidates for high-mobility $p$-type TCMs. From our calculations, both compounds are expected to be $p$-type dopable: intrinsically for Li$_\textrm{3}$Sb while CaTe would require extrinsic doping. Using electron-phonon computations, we estimate hole mobilities at room-temperature to be about 20 and 70 cm$^2$/Vs for CaTe and Li$_\textrm{3}$Sb, respectively. The computed hole mobility for Li$_\textrm{3}$Sb is quite exceptional and comparable with the electron mobility in the best $n$-type TCMs.Comment: 10 pages, 5 figure

Photo-to-heat conversion of broadband metamaterial absorbers based on TiN nanoparticles under laser and solar illumination

We theoretically investigate photothermal heating of ultra-flexible metamaterials, which are obtained by randomly mixing TiN nanoparticles in polydimethylsiloxane (PDMS). Due to the plasmonic properties of TiN nanoparticles, incident light is perfectly absorbed in a broadband range (300-3000 nm) to generate heat within these metamaterials. Under irradiation of an 808 nm near-infrared laser with different intensities, our predicted temperature rises as a function of time agree well with recent experimental data. For a given laser intensity, the temperature rise varies non-monotonically with concentration of TiN nanoparticles because the enhancement of thermal conductivity and absorbed energy as adding plasmonic nanostructures leads to opposite effects on the heating process. When the model is extended to solar heating, photothermal behaviors are qualitatively similar but the temperature increase is less than 13 $K$. Our studies would provide good guidance for future experimental studies on the photo-to-heat conversion of broadband perfect absorbers.Comment: 8 pages, 7 figures, accepted for publications in Materials Today Communication

Economic, social and environmental disclosure, a theoretical framework and its application in Vietnam

This study focuses on the appraisal of firms performance and on its representation and reporting. Using interviews and inquiries in firms operating in the cement industry in Vietnam, two points are investigated. First, whether firms top executives consider that firms sustainable performance may include economic, social or environmental performance that is not integrated in financial statements. The theoretical framework is the stakeholder theory complemented with the institutional theory. Second, whether economic, social and environmental performance should be disclosed to answer the expectations of the various stakeholders. Therefore, our research contributes to corporate governance studies by focusing on reporting dedicated to all the stakeholders

Determination of Fluoroquinolone antibiotics in sludge matrix using pressurized liquid extraction technique combined with high performance liquid chromatography/fluorescence detection

Joint Research on Environmental Science and Technology for the Eart

FIRST RESULTS ON NITROGEN AMMONIA REMOVAL FROM GROUND WATER BY NITRIFICATION AT CEETIA LAB

Joint Research on Environmental Science and Technology for the Eart

BASTAF : NEW TECHNOLOGY IN DECENTRALIZED WASTEWATER MANAGEMENT FOR VIETNAMESE CONDITIONS

Joint Research on Environmental Science and Technology for the Eart