Speaker
Description
The recent advances in the development of semiconductor devices based on nano-crystal technology have led to numerous applications in high-tech electronic and optoelectronic devices including, transistors, light emitting diodes, solar cells, photodetectors, thermoelectrics, and phase change memory cells. Among the potential material for such applications are the transition metal oxides, such as MoO$_{3}$, WO$_{3}$, V$_{2}$O$_{5}$, and TiO$_{2}$, which have shown promising characteristics in inducing efficient charge transport at semiconductors. These materials have recently been applied in organic photovoltaic (OPV) and light-emitting diode (OLED) devices. The formation of polarons is a pervasive phenomenon in these types of materials, and it was found that the polaron charge carrier is another important characteristic involved in multiple (opto)electronic processes during device operation, such as charge transport and exciton recombination/dissociation. Therefore, the investigation of polaron formation in transition metal oxides is an important concept to consider for the recent developments in semiconductor electronics.
In this work, we studied the polaron formation and transport in one of the transition metal oxides with the name of $\alpha$-MoO$_3$ by employing the Perturbed Angular Correlation (PAC) technique to probe the local environments of the system; together with first principle calculations within the framework of Density Functional Theory (DFT). The formation of oxygen vacancies can potentially be the main factor to improve the electrochemical performance of $\alpha$-MoO$_3$ and also the conductivity. In order to increase the values of conductivity or drift mobilities of the charge carriers in $\alpha$-MoO$_3$, doping with $^{111m}$Cd-$^{111}$Cd probe isotope has been proposed. Also, the effect of oxygen vacancies and their interaction with metal impurities has been investigated to analyze the main factors that affect the rate of electron and hole mobilities. We can find that the induced defect-complexes of Cd impurity and oxygen vacancies, the $\alpha$-MoO$_3$ system shows not only electron polaron-type orbitals but also a mixture of hole polaron states which form around the Cd impurity site.
References:
- D. R. Pereira, C. Díaz-Guerra, M. Peres, S. Magalhães, J.G. Correia, J. G. Marques, A. G. Silva, E. Alves, and K. Lorenz. Engineering strain and conductivity of MoO$_3$ by ion implantation. Acta Mater., 169:15, 2019.
- H. Ding, H. Lin, B. Sadigh, F. Zhou, V. Ozolins, and M. Asta. Computational investigation of electron small polarons in $\alpha$-MoO$_3$. J. Phys. Chem. C, 118(29):15565, 2014.
- H. Peelaers, M. L. Chabinyc, and C. G. Van de Walle. Con-
trolling n-type doping in MoO$_3$. Chem. Mater., 29(6):2563,
2017.
