Influence of Thermal Annealing on Free Carrier Concentration in (GaN)1–x(ZnO)x Semiconductors

Huang, Huafeng; Sklute, E. C.; Lehuta, Keith A.; Kittilstved, Kevin R.; Glotch, T. D.; Liu, Mingzhao; Khalifah, Peter G.

doi:10.1021/acs.jpcc.7b06455

Cited by 12 publications

(9 citation statements)

References 42 publications

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“…In other words, the glass transition evolution does not occur at the same specic volume, which is consistent with a recent experimental observation by Huang & Roth that examined the temperature-dependent specic volume of supported polystyrene with lm thickness. 80 In addition, there is generally also a reduced difference between the liquid-and glassy-state slopes in a thinner lm as compared to its bulker counterpart, indicating a reduction in the strength of glass transition upon nanoconnement, a behavior also seen in previously published literature by Kawana & Jones and Ellison & Torkelson. 81,82 The plot of glass transition temperatures versus PSF membrane thickness is provided in Fig.…”

Section: Glass Transition Temperaturesupporting

confidence: 52%

Computational insights on the role of film thickness on the physical properties of ultrathin polysulfone membranes

et al. 2017

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Although it has been reported that physical properties of polymeric membranes inherit thickness dependent characteristics, typically when they are subjected to confinement at an ultrathin dimension (<1000Å), deviations from their bulk counterpart are still not completely understood. An empirical investigation of physical properties for an ultrathin membrane at laboratory scale is difficult, time consuming, and costly which is attributed to challenges to fabricate defect-free films with ultrathin thickness and that requires special instruments at critical conditions. In our current work, a Soft Confining Methodology for Ultrathin Films was conducted to simulate ultrathin polysulfone polymeric membranes of varying thicknesses, l, to resemble their actual size in the thickness dimension. Subsequently, physical properties of the constructed ultrathin films, e.g., density and glass transition temperature, have been elucidated from an atomistic insight. Quantitative empirical models have been proposed to capture thickness-dependent physical properties upon ultrathin confinement. In addition, free volume and cavity distribution was also quantified in order to elucidate the evolution in membrane morphology and to satisfy a previous research gap of deficiency in system dimension dependent cavity sizes. On the whole, it was found that a thinner structure exhibits higher structural density and lower glass transition temperature, as well as lower free volume and cavity sizes. The findings from the present work are anticipated to propose an alternative from a molecular simulation aspect to circumvent complexities associated with experimental preparation and testing of ultrathin polymeric membranes, while providing direct elucidation and quantification of thickness-dependent physical properties in order to enhance understanding at a molecular perspective.

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Section: Glass Transition Temperaturesupporting

confidence: 52%

Computational insights on the role of film thickness on the physical properties of ultrathin polysulfone membranes

et al. 2017

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“…Consequently, for the growth of highly Zn-rich samples, postannealing of the material seems to be a more promising approach to improve the crystal quality, as it preserves the overall composition. 34 One of the most interesting open questions concerning the GZNO material system is to identify which mechanism leads to the observed band gap reduction compared to GaN or ZnO, specifically in terms of the individual roles of each of the different atomic species. Unambiguous elucidation of the underlying origin of the band gap reduction will provide opportunities for band gap engineering while preserving the beneficial energetic position of the CB edge, which is crucial for optimizing photocatalytic efficiencies.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Control of Band Gap and Band Edge Positions in Gallium–Zinc Oxynitride Grown by Molecular Beam Epitaxy

et al. 2020

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Gallium–zinc oxynitride (GZNO) is a promising material system for solar-driven overall water splitting, as it exhibits a tunable band gap in the visible range, beneficial positions of valence and conduction band edges, and promising long-term stability. Fabrication of GZNO is traditionally accomplished via a solid state reaction pathway. This limits the growth of thin films or large single crystals and the precise control of the composition, which complicates investigations about fundamental properties of the material, including, for example, the influence of the single constituent ratios on the band gap. In this work, we present the growth of GZNO thin films on sapphire by plasma-assisted molecular beam epitaxy (MBE). The thin films exhibit a crystallite size of up to 50 nm and a wurtzite crystal structure with distinct short-range disorder. Variations of Ga/Zn and N/O flux ratios are found to influence the optical absorption edge of the alloy without major impact on the Urbach energy. Controlled change of the composition of the alloy reveals that the band gap reduction is caused by both an increased valence band energy, which is correlated with the N content, and a decrease of the conduction band energy which is induced by increasing Zn content. Based on these findings, GZNO thin films with band gaps of down to 2.0 eV were fabricated and their photoelectrical properties assessed. Using MBE, we overcome compositional restrictions typically associated with stoichiometric GaN:ZnO solid solutions and provide unprecedented access to new compounds within this materials class. In doing so, we elucidate the specific role of individual elements on band edge energetics and demonstrate new routes to band gap engineering for future photocatalytic and photoelectrochemical applications.

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“…In vitro release of CHX-dg, from the thermally inducedgelling system presented in this study, was evaluated under experimental conditions, which mimic those of periodontal pocket, in terms of temperature, pH, and ionic force. [40,41] CHX-dg release from the system: Poloxamer (bCD-Jef-MPs/CHX-dg) was compared to those of (i) Poloxamer(bCD-MPs/CHX-dg), a Jeffamine-free control system, and (ii) Poloxamer(CHX-dg), where CHX-dg was directly suspended in the sol-gel matrix. The aim was to understand the role of Jeffamine segments and bCD units in the modulation of CHX-dg release profile, respectively.…”

Section: In Vitro Chx-dg Release Testmentioning

confidence: 99%

An Injectable System for Local and Sustained Release of Antimicrobial Agents in the Periodontal Pocket

Morelli

Cappelluti

Ricotti

et al. 2017

Macromolecular Bioscience

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Periodontitis treatments usually require local administration of antimicrobial drugs with the aim to reduce the bacterial load inside the periodontal pocket. Effective pharmaceutical treatments may require sustained local drug release for several days in the site of interest. Currently available solutions are still not able to fulfill the clinical need for high-quality treatments, mainly in terms of release profiles and patients' comfort. This work aims to fill this gap through the development of an in situ gelling system, capable to achieve controlled and sustained release of antimicrobial agents for medium-to-long-term treatments. The system is composed of micrometer-sized β-cyclodextrin-based hydrogel (bCD-Jef-MPs), featured by a strong hydrophilic character, suspended in a synthetic block-co-polymer solution (Poloxamer 407), which is capable to undergo rapid thermally induced sol-gel phase transition at body temperature. The chemical structure of bCD-Jef-MPs was confirmed by cross-correlating data from Fourier transform infrared (FTIR) spectroscopy, swelling test, and degradation kinetics. The thermally induced sol-gel phase transition is demonstrated by rheometric tests. The effectiveness of the described system to achieve sustained release of antimicrobial agents is demonstrated in vitro, using chlorhexidine digluconate as a drug model. The results achieved in this work disclose the potential of the mentioned system in effectively treating periodontitis lesions.

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Influence of Thermal Annealing on Free Carrier Concentration in (GaN)_1–x(ZnO)_x Semiconductors

Cited by 12 publications

References 42 publications

Computational insights on the role of film thickness on the physical properties of ultrathin polysulfone membranes

Computational insights on the role of film thickness on the physical properties of ultrathin polysulfone membranes

Control of Band Gap and Band Edge Positions in Gallium–Zinc Oxynitride Grown by Molecular Beam Epitaxy

An Injectable System for Local and Sustained Release of Antimicrobial Agents in the Periodontal Pocket

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