Control of Carrier Concentration by Ag Doping in N-Type Bi\({}_{2}\)Te\({}_{3}\) Based Compounds  
[PERSON]  
1 Thermoelectric Conversion Research Center, Korea Electrotechnology Research Institute, Changwon 51543, Korea; [EMAIL_ADDRESS] (J.K.L. ); [EMAIL_ADDRESS] (J.H.S. ); [EMAIL_ADDRESS] (B.R. ); [EMAIL_ADDRESS] (S.D.P). [PERSON]  
1 Thermoelectric Conversion Research Center, Korea Electrotechnology Research Institute, Changwon 51543, Korea; [EMAIL_ADDRESS] (J.K.L. ); [EMAIL_ADDRESS] (J.H.S. ); [EMAIL_ADDRESS] (B.R. ); [EMAIL_ADDRESS] (S.D.P). [PERSON]  
2 Center for Convergence Property Measurement, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea; [EMAIL_ADDRESS] 2  
[PERSON]  
1 Thermoelectric Conversion Research Center, Korea Electrotechnology Research Institute, Changwon 51543, Korea; [EMAIL_ADDRESS] (J.K.L. ); [EMAIL_ADDRESS] (J.H.S. ); [EMAIL_ADDRESS] (B.R. ); [EMAIL_ADDRESS] (S.D.P). [PERSON]  
3 Department of Electrical Engineering, KAIST, Daejeon 34141, Korea; [EMAIL_ADDRESS] 3  
[PERSON]  
4 Mineral Resources Division, Korea Institute of Geoscience and Mineral Resources, Daejeon 34132, Korea; [EMAIL_ADDRESS] 4  
[PERSON]  
1 Thermoelectric Conversion Research Center, Korea Electrotechnology Research Institute, Changwon 51543, Korea; [EMAIL_ADDRESS] (J.K.L. ); [EMAIL_ADDRESS] (J.H.S. ); [EMAIL_ADDRESS] (B.R. ); [EMAIL_ADDRESS] (S.D.P). [PERSON]  
5 Department of Materials Science and Engineering, Hanbat National University, Daejeon 31458, Korea  
5 Correspondence: [EMAIL_ADDRESS]; Tel. : +82-42-821-12475  
Ag (0.01-0.2 wt %) decreased electrical resistivity and the Seebeck coefficient, an effect which they attributed to the Ag particles, which did not substitute for Bi or Sb [16]. [PERSON] et al. reported that \(\rho\) and \(\alpha\) decreased with Ag, which substituted for Bi or Sb in p-type (Bi,Sb)\({}_{2}\)Te\({}_{3}\)[17]. The substitution of Ag for Bi or Sb was also reported by [PERSON] et al. [18]. All of these results said that the Ag acted as an acceptor in the p-type (Bi,Sb)\({}_{2}\)Te\({}_{3}\) compounds. For n-type Bi\({}_{2}\)Te\({}_{3}\), a different Ag behavior has been reported. [PERSON] et al. found that interstitial Ag was formed in n-type Bi\({}_{2}\)Te\({}_{3}\) and behaved as a donor, while Ag behaved as an acceptor in Sb\({}_{2}\)Te\({}_{3}\)[19]. [PERSON] et al. reported that interstitial Ag formed in n-type Bi\({}_{2}\)(Te,Se)\({}_{3}\) and acted as an n-type donor when Ag content was less than 0.2 wt %, and like a p-type acceptor at higher Ag content (> 0.2 wt %) [20]. However, both studies deduced the existence of interstitial Ag by investigating electrical transport properties, and there was no direct evidence to confirm that interstitial Ag formed in the Bi\({}_{2}\)Te\({}_{3}\) unit cell. They noted that electrical conductivity and electron concentration increased after the addition of Ag to n-type Bi\({}_{2}\)Te\({}_{3}\) and then they argued that the electrons were donated by the interstitial Ag. [PERSON] et al. reported that even though interstitial Ag was formed in the n-type Bi\({}_{2}\)(Te,Se)\({}_{3}\), the electron concentration was reduced when Ag content was less than 0.5 wt %., while the concentration increased with higher Ag content (>0.5 wt %) [21]. Controversy about the effect of Ag in n-type Bi\({}_{2}\)(Te,Se)\({}_{3}\) has arisen; low Ag content has been reported to reduce electron concentration [21] and to increase electron concentration [20]. Accordingly, we think that the location of Ag in the Bi\({}_{2}\)Te\({}_{3}\) unit cell, and the effect of Ag on the electrical transport properties, have not been clearly demonstrated. In this study, Ag was added to n-type Bi\({}_{2}\)(Te,Se)\({}_{3}\) and the effect of the Ag addition on the carrier concentration was investigated. With both experimental and theoretical investigations, we tried to establish whether Ag occupies a position in the Bi\({}_{2}\)Te\({}_{3}\) unit cell and acts as an acceptor or donor.