Detection of charge transfer processes in Cr-doped SrTiO3 single crystals

Abstract

An insulator-to-metal transition is observed in Cr-doped SrTiO3 single crystals upon extended exposure to a high electric field, namely, electroconditioning (EC). Electron paramagnetic resonance (EPR) and transport measurements under laser irradiation show anticorrelation between the Cr3+ EPR signal and the electrical current. This proves that the Cr3+ ions are responsible for the photocurrent that initiates the EC process. We observe the presence of Cr3+/Cr4+ mixed valencies in the bulk in the conducting state. The EPR characterization of the spectra in the conducting state excludes the possibility of a Cr3+-oxygen vacancy complex in the bulk as a result of the EC.

Controlled oxygen vacancies and space correlation withCr3+inSrTiO3

“…The accumulation of V o s in a confined conductive path ͑filamentary͒ has experimentally been shown 12,13 to result from a dc electroconditioning procedure. 7,9 Local reduction/oxidation processes have been proposed by some authors as an explanation for the resistance-switching mechanism, 17,19 in contradiction to other experimental evidence of trapping/detrapping processes involving the Cr dopant. 8,9 A promising concept for tailoring electronic properties on the nanometer scale arises from the possibility of creating V o s in confined regions.…”

“…7,9 Local reduction/oxidation processes have been proposed by some authors as an explanation for the resistance-switching mechanism, 17,19 in contradiction to other experimental evidence of trapping/detrapping processes involving the Cr dopant. 8,9 A promising concept for tailoring electronic properties on the nanometer scale arises from the possibility of creating V o s in confined regions. 17,18,20,21 The formation of V o is accompanied by the transfer of two electrons to the 3d͑z 2 ͒ orbitals of the two Ti atoms along the Ti-V o -Ti axis 22 and, at higher content of V o , an insulator-to-metal transition occurs.…”

“…The capability of controlling point defects, such as oxygen vacancies ͑V o s͒ or transition-metal ͑TM͒ dopants, is essential for the development of semiconducting electronic devices based on perovskite compounds. [6][7][8][9] Current-induced bistable resistance effects on metal-insulator-metal ͑MIM͒ structures based on doped perovskite oxides, such as Cr-doped SrTiO 3 , have attracted substantial interest because of their potential technological applications for nonvolatile memory devices. 10,11 Although various models have been proposed for the resistive switching in SrTiO 3 , [12][13][14] a clear understanding of the role and the nature of intrinsic defects or dopants has not yet been achieved.…”

Electron paramagnetic resonance studies of manganese centers in SrTiO3: Non-Kramers Mn3+ ions and spin-spin coupled Mn4+ dimers

“…Strontium titanate, the so called incipient ferroelectric with perovskite structure, has become in the focus of interest in attempt to combine magnetic and ferroelectric properties of the material [5][6][7][8][9][10][11]. In this work we use EPR spectroscopy for the accurate determination of different oxidation states and local environment of manganese impurities in SrTiO 3 .…”

Ultrafast photovoltaic effects in miscut Nb-doped SrTiO3 single crystals

“…10,11 Previously, the charge transfer processes in Cr-doped SrTiO 3 single crystals under laser irradiation were reported. 12 So far, the ultrafast photoresponse characteristics in doped SrTiO 3 single crystals have not been investigated. In this paper, we report the transient photovoltaic response in miscut Nb-doped SrTiO 3 single crystal.…”