Effect of Native Defects on Transport Properties in Non-Stoichiometric CoSb3

Abstract

The effect of native defects originated by a non-stoichiometric variation of composition in CoSb3 on I-V curves and Hall effect was investigated. Hysteretic and a non-linear behavior of the I-V curves at cryogenic temperatures were observed; the non-linear behavior originated from the Poole-Frenkel effect, a field-dependent ionization mechanism that lowers Coulomb barriers and increases emission of charge carriers, and the hysteresis was attributed to the drastic decrease of specific heat which produces Joule heating at cryogenic temperatures. CoSb3 is a narrow gap semiconductor and slight variation in the synthesis process can lead to either n- or p-type conduction. The Sb-deficient CoSb3 presented an n-type conduction. Using a single parabolic model and assuming only acoustic-phonon scattering the charge transport properties were calculated at 300 K. From this model, a carrier concentration of 1.18 × 1018 cm−3 and a Hall factor of 1.18 were calculated. The low mobility of charge carriers, 19.11 cm2/V·s, and the high effective mass of the electrons, 0.66 m0, caused a high resistivity value of 2.75 × 10−3 Ω·m. The calculated Lorenz factor was 1.50 × 10−8 V2/K2, which represents a decrease of 38% over the degenerate limit value (2.44 × 10−8 V2/K2).

Charge-carrier behavior in Ba-, Sr- and Yb-filled CoSb3 : NMR and transport studies

“…8 provides a consistent picture of both the transport and NMR results and thus indicates the importance of states near the conduction band edge in filled CoSb 3 . This differs from unfilled CoSb 3 , for which native deep acceptor states are believed to dominate the behavior [13,18], although recent experimental evidence also indicates n-type behavior for the case of large Sb deficit [14].…”

“…Recently, filled CoSb 3 -based materials have been studied intensely due to their excellent thermoelectric response [9][10][11][12]. Therefore, the native electronic defects in these skutterudites have been particularly interesting because of their crucial importance for improving thermoelectric efficiency [13][14][15][16][17][18].…”

Fabrication of Co–Sb Junction Nanowires by Galvanostatic Electrodeposition

“…Therefore, there is a heterojunction in the NW since they present a segment rich in Sb, which has p-type conduction and another segment rich in Co exhibits n-type behavior. However, a transition from n-to p-type conduction occurs at a temperature above 500 K for the segment rich in Co. 18 The electrical transport properties such as Seebeck coefficient and electrical conductivity vary with the alloy stoichiometry, as reported in ref 44. Recently, an n/n bulk heterojunction was shown by assembling CoSb 3 skutterudite with different Yb-doping contents.…”

“…The electrical transport properties of skutterudite materials are modified by stoichiometry deviations. For Co–Sb, when the alloy is rich in Sb, a p-type conduction has been found whereas a transition from n- to p-type conduction occurs in Co-rich alloys at a temperature above 500 K . Few literature reports deal with the cobalt–antimony NW synthesis by electrodeposition. ,,,− The electroplating conditions are summarized in Table .…”