Dependence of the Electric Properties and the Positron Lifetimes on the Dopant Content in La‐doped SrTiO₃

Abstract

The resistivity, the dielectric constant, and the positron lifetimes in La-doped SrTiOa have been measured for La content x of 0-10 at.%. It was found that with increasing x, the variations of the resistivity and the dielectric constant and the positron lifetime parameters are nonmonotonic. The positron experiments have shown that the La-doping induces mainly formation of Sr vacancies and variation of Sr vacancy configuration; the most probable configuration is the isolated Sr vacancies (Vg,) as z < 0.5 at.%, the associated defects (La&V&) for 0.5 < x < 1 at.%, and the associated defects (2 Las,Vg,) above x = 1 at.%. The results suggest that the variation of the resistivity can be regarded as variation of electron density, and the variation of the dielectric constant results mainly from variations of the space-charge polarization and Sr-vacawy concentration and configuration.

Electronic transport in dopedSrTiO3: Conduction mechanisms and potential applications

“…%͒. 34,86,87 Of most relevance to the current discussion, this behavior has been observed for both Nb ͑Ref. 88͒ and La ͑Ref.…”

“…83 Finally, although the available data are not entirely complete, some measurements of r as a function of impurity concentration have been made. 34 6. ͑Color online͒ Temperature dependence of the lowtemperature conductivity ͑linear-linear scale͒ of ͑a͒ an n = 8.5 ϫ 10 15 cm −3 sample, and ͑b͒ an n = 2.9ϫ 10 16 cm −3 sample.…”

“…At the impurity concentrations of relevance to the current paper r is actually increased over the undoped value. 34,88 It should be noted that this is not a general phenomenon and other dopants may behave differently.…”

“…31 Of most relevance to this work, STO also displays fascinating, and potentially useful, electronic transport properties. The material is a semiconductor with a 3.2 eV band gap 1, 32 and can be doped n type [32][33][34][35][36][37][38][39][40][41][42][43][44] or p type. [45][46][47][48][49][50][51] n-type conduction has been most commonly achieved by substitution of La 3+ for Sr 2+ ͑i.e., Sr 1−x La x TiO 3 ͒, 1,33,34 Nb 5+ for Ti 4+ ͑i.e., SrTi 1−y Nb y O 3 ͒, [35][36][37] or by reduction to SrTiO 3−␦ , 32,35,[38][39][40][41][42][43][44] where, in a simple picture, each O vacancy generates two doped electrons.…”

Review on fabrication methods of SrTiO3-based two dimensional conductive interfaces

“…Besides, the UV light of 300 nm and the Cr, Nb, La ion doping can also induce insulator-metal phase transition of bare STO single crystals. [106][107][108][109][110] Fig. 12 a) Temperature dependence of the sheet resistance in air and the partial pressure of ∼5, 5× 10 −2 and 5×10 −4 Pa at the laser energy density of 500 mJ/cm 2 .…”