1,721,005 research outputs found
Electronic structure and defect state calculations for undoped and (Nb, Ta)-doped anatase using density functional theory
No full textThermodynamics of ultra-thin oxide overgrowths on binary Al-based alloys
No full textThermodynamic analyses have been carried out to understand the growth of ultrathin oxide overgrowths on single-crystalline bare [AlMg] and [AlSi] alloys due to their dry, thermal oxidation. The parameters considered in this formalism are alloy composition at the alloy/oxide interface, growth temperature, oxide-film thickness and low index crystallographic surfaces of the substrate. Along with the bulk Gibbs free energies of the respective oxides, the role of energies at the alloy/oxide interface as well as at the oxide/ambient interface were also taken into the account. Finally, this model was then compared with the already existing thermodynamic analyses for the growth of corresponding amorphous oxides on these alloy substrates and are then validated with the available experimental data from literature. It is found that, for thegrowth of only crystalline oxides on [AlMg] alloy substrate, crystalline 2 3 [Al O ] forms for a combination of lower growth temperature, Mg alloying content at the alloy/oxide interface and oxide-fim thickness, beyond which crystalline [MgO] formation on this alloy substrate is thermodynamically stabilized. However, for the growth of a thickening oxide-film on bare [AlMg] alloy substrate, amorphous 2 3 {Al O } and crystalline [MgO] are found to be preferred thermodynamically at lower and higher oxide-film thicknesses respectively. Similarly, for the growth of only crystalline oxide overgrowths on [AlSi] alloy substrate, formation of crystalline 2 3 [Al O ] is thermodynamically preferred irrespective of Si alloying content at the alloy/oxide interface, growth temperature and oxide-film thickness. Overall, amorphous 2 {SiO } and amorphous 2 3 {Al O } are found to form at lower and higher oxide-film thicknesses respectively, followed by phase transformation of amorphous 2 3 {Al O } to crystalline 2 3 [Al O ] on further thickening of oxide-film due to dry, thermal oxidation of bare [AlSi] alloy substrate only at lower growth temperature and Si alloying content at the alloy/oxide interface. At higher growth temperature, amorphous 2 3 {Al O } was found to be formed without transforming to crystalline
2 3 [Al O ] due to increased contribution of positive strain energies. Further, at higher Si alloying content at the alloy/oxide interface, crystalline 2 3 [Al O] becomes thermodynamically preferred without forming an amorphous 2 3 {Al O } phase. Crystalline 2 [SiO ] was never found to be thermodynamically favorable for the parameters considered in this study. These thermodynamic predictions are found to be in agreement with the experimental findings
Fabrication near U V transparent conductor by bandgap engineering: effect of Mg addition on the undoped and Al-doped Zno thin films
No full textDeveloping transparent conductors that can utilize a portion of the UV range of the sunlight requires bandgap engineering by varying the process parameters as well as type and concentration of dopants in the host materials. To this end, ZnO is a desired material because of its wide direct band gap (Eg) of around 3.2 eV, low cost and less toxicity. In this work, Mg2+ and/or Al3+ -doped ZnO films are prepared by varying a range of process parameters in RF magnetron sputtering. A detailed microstructural and optoelectronic characterization of all these films are then carried out by using a combination of experimental techniques, like, GIXRD, FESEM, EDS, UV-Vis-NIR, PL spectroscopy and Hall Effect measurement system. All these films are found to have high optical transparency and showed blue shift as a result of Mg2+ and/or Al3+ doping with Eg ranging from 3.24 to 3.90 eV. Moreover, (Mg2+, Al3+)-doped ZnO films are found to demonstrates better optoelectronic properties than those of the ZnO films doped only using either Mg2+ or Al3+. Whereas Mg2+ is found to increase the optical bandgap of these films, Al3+ addition is found to increase both the carrier concentration and carrier mobility, with the best values of the electrical properties being obtained when only Al3+ is added to ZnO. This study shows a possible method to harness the near UV portion of the sunlight by doing bandgap engineering of ZnO through the addition of Mg2+ and/or Al3+ without compromising much on their overall electrical properties
Interrelation between electronic structure, microstructure and optoelectronic properties of Al-doped ZnO and Cu2-xS
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Microstructure modulated optoelectronic properties of Al-doped ZnO and CuInGaSe2 films using cost-effective, scalable deposition techniques
No full textMicrostructure influenced variation in the electronic properties of the functional materials: the case of Nb doped anatase and TbFe2
No full textSynthesis of monetite through chemical precipitation and its transformation to Hydroxyapatite
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