A First Principles Study on the Electronic, Optical and Hole Effective Mass Properties of Mg-Doped CuAlO 2 and AgAlO 2
- PDF / 403,755 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 43 Downloads / 124 Views
MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.550
A First Principles Study on the Electronic, Optical and Hole Effective Mass Properties of Mg-Doped CuAlO2 and AgAlO2 James Shook1, Pablo D. Borges2, Luisa Scolfaro1 1 Department of Physics, Texas State University, 78666 San Marcos, Texas, United States 2
Instituto de Ciências Exatas e Tecnologia, Universidade Federal de Viçosa, 38810-000 MG, Brazil ABSTRACT
We report first principles spin-polarized density functional theory calculations to study the electronic structure of pure and Magnesium doped (replacing Al) CuAlO2 and AgAlO2 transparent conducting oxides in the hexagonal 2H structural phase. Hole effective masses are obtained from the band structure. Additionally, the complex dielectric function is obtained. A discussion of the effects of Mg-doping on the optical properties and its effectiveness in reducing hole effective masses and increasing conductivity is also presented.
INTRODUCTION The search for commercially viable p-type transparent conducting oxides (TCOs) – semiconductors with band gaps greater than 3.0 eV – to complement the abundance of well understood and commercially available n-type TCOs for the purposes of device tuning in applications such as flat panel displays, photovoltaic cells, capacitive touch screens, and thermoelectric materials [1] is an important topic and an active area of research in solid state physics and materials science. The problem facing the identification of high conductivity p-type TCOs arises from highly localized O-2p states in the upper valence bands, which lead to larger hole effective masses and lower electrical conductivity [2]. A promising group within the p-type TCOs are the delafossite transition metal oxides, such as CuAlO2 (CAO) and AgAlO2 (AAO), due to the presence of Cu-3d, or Ag-4d states, which are thought to hybridize with O-2p states and overall
3315
Downloaded from https://www.cambridge.org/core. University of Warwick, on 28 Oct 2018 at 13:17:51, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2018.550
delocalize the valence states. It has been proposed that p-doping with a group II element replacing Al increases electrical conductivity. Recently, Liu et al. reported [3] an increase in carrier concentration upon p-doping with Mg replacing Al of ͵Ǥͷʹ ൈ ͳͲଵ cm3 in CAO to ͳǤͻ ൈ ͳͲଵ଼ cm-3 in CuAl0.94Mg0.06O2 (CAMO). However, how changes to the hole effective mass upon Mg doping affect electrical conductivity is still not well understood. CAO and AAO are known to crystalize in two stable delafossite – ߙ-2H [4] and ߙ-3R [5], [6] – phases. Although the 3R phase is slightly more stable, more thoroughly studied, and the most common polymorph grown during fabrication, traces of the 2H phase may also be present in the samples [7]. The study reported here is restricted to the 2H polymorph since it is the least studied of the two delafossite XAO (X=Cu, Ag) polymorphs. To that end, a theoretical investigation is p
Data Loading...
