arXiv subjects

Miran Mozetic

Publications and source records attributed to Miran Mozetic.

3 recordsLinked to original sources

arXiv2010

Reversible carrier-type transition in gas-sensing oxides and nanostructures

Despite many important applications of a-Fe2O3 and Fe doped SnO2 in semiconductors, catalysis, sensors, clinical diagnosis and treatments, one fundamental issue that is crucial to these applications remains theoretically equivocal- the reversible carrier-type transition between n- and p-type conductivities during gas-sensing operations. Here, we give unambiguous and rigorous theoretical analysis in order to explain why and how the oxygen vacancies affect the n-type semiconductors, a-Fe2O3 and Fe doped SnO2 in which they are both electronically and chemically transformed into a p-type semiconductor. Furthermore, this reversible transition also occurs on the oxide surfaces during gas-sensing operation due to physisorbed gas molecules (without any chemical reaction). We make use of the ionization energy theory and its renormalized ionic displacement polarizability functional to reclassify, generalize and to explain the concept of carrier-type transition in solids, and during gas-sensing operation. The origin of such a transition is associated to the change in ionic polarizability and the valence states of cations in the presence of (a) oxygen vacancies and (b) physisorped gas molecules.

cond-mat.str-el↗

arXiv2010

Renormalized ionic polarizability functional applied to evaluate the molecule-oxide interactions for gas-sensing applications

Metal-oxide sensors are widely used due to their sensitivities to different types of gaseous, and these sensors are suitable for long-term applications, even in the presence of corrosive environments. However, the microscopic mechanisms with quantum effects, which are required to understand the gas-oxide interactions are not well developed despite the oxide sensors potential applications in numerous fields, namely, medicine (breath-sensors), engineering (gas-sensors) and food processing (odor-sensors). Here, we develop a rigorous theoretical strategy based on the ionization energy theory (IET) to unambiguously explain why and how a certain gas molecule intrinsically prefers a particular oxide surface. We make use of the renormalized ionic displacement polarizability functional derived from the IET to show that the gas/surface interaction strength (sensing sensitivity) between an oxide surface and an isolated gas molecule can be predicted from the polarizability of these two systems. Such predictions are extremely important for the development of health monitoring bio-sensors, as well as to select the most suitable oxide to detect a particular gas with optimum sensitivity.

cond-mat.str-el↗

arXiv2010

Non-square-well potential profile and non-blinking effect in graded CdZnSe/ZnSe nanocrystals: An ionization-energy theoretic study

Randomly blinking nanocrystals have given rise to numerous and intense theoretical and experimental investigations recently. An experimental breakthrough was finally made by fabricating the non-blinking Cd$_{1-x}$Zn$_x$Se/ZnSe graded nanocrystal [Nature 459 (2009) 686]. Here, we report (1) an unequivocal and detailed theoretical investigation to understand the properties of the potential-well and the distribution of Zn content with respect to the nanocrystal radius and (2) develop a strategy to find the relationship between the photoluminescence (PL) energy peaks and the potential-well due to Zn distribution in nanocrystals. We found that the non-square-well potential can be varied in such a way that one can indeed control the PL intensity and the energy-level difference (PL energy peaks) in any non-free-electron nanocrystals accurately. This implies that we can either suppress the blinking altogether, or alternatively, manipulate the PL energy peaks and intensities systematically to give non-random blinking. Our theoretical strategy developed here is generic and can be applied to any non-free-electron nanocrystals.

cond-mat.str-el↗