Substitutional and interstitial impurity p-type doping of thermoelectric Mg2Si: a theoretical study. Issue 1 (1st January 2019)

• Record Type: Journal Article
• Authors: Hirayama, Naomi; Iida, Tsutomu; Sakamoto, Mariko; Nishio, Keishi; Hamada, Noriaki
• Is Part Of: Science and technology of advanced materials. Volume 20:Issue 1(2019)
• Page Start: 160
• Page End: 172
• Publication Date: 2019-01-01
• Subjects: Magnesium silicide -- hole doping -- thermoelectric properties -- interstitial insertion -- p-type semiconductor -- structural stability; 50 Energy Materials -- 210 Thermoelectronics / Thermal transport / insulators; Materials -- Technological innovations -- Periodicals; 620.112
• DOI: 10.1080/14686996.2019.1580537
• Languages: English
• ISSNs: 1468-6996

Abstract

ABSTRACT: The narrow-gap magnesium silicide semiconductor Mg2 Si is a promising mid-temperature (600–900 K) thermoelectric material. It intrinsically possesses n-type conductivity, and n-type dopants are generally used for improving its thermoelectric performance; however, the synthesis of p-type Mg2 Si is relatively difficult. In this work, the hole doping of Mg2 Si with various impurity atoms is investigated by performing first principles calculations. It is found that the Ag-doped systems exhibit comparable formation energies Δ E calculated for different impurity sites (Mg, Si, and interstitial 4b ones), which may explain the experimental instability of their p-type conductivity. A similar phenomenon is observed for the systems incorporating alkali metals (Li, Na, and K) since their Δ E values determined for Mg (p-type) and 4b (n-type) sites are very close. Among boron group elements (Ga and B), Ga is found to be favorable for hole doping because it exhibits relatively small Δ E values for Si (p-type) sites. Furthermore, the interstitial insertion of Cl and F atoms into the crystal lattice leads to hole doping because of their high electronegativity. Graphical abstract: