TDPAC study of Fe-implanted titanium dioxide thin films

Juliana Schell,Peter Schaaf,Doru C Lupascu,Ulrich Vetter

doi:10.1063/1.4994247

Juliana Schell, Peter Schaaf + Show 2 more

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https://doi.org/10.1063/1.4994247

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Abstract

Fe-doping in TiO2 has been proven to improve several of its properties, including the photocatalytic activity. Time-differential perturbed angular correlation (TDPAC) as the applied spectroscopy method is particularly interesting because it can probe the electric and magnetic interactions on a local atomic scale. In this work the hyperfine interactions on 111Cd atoms substituting Ti atoms in TiO2 due to nearby Fe atoms also diluted within the TiO2 lattice were measured as a function of temperature. The results review two fractions with distinct quadrupole interaction parameters. One site, occupied by the 111Cd probes, presents the smaller quadrupole interaction frequency, namely υq1 = 45 MHz, and can be ascribed to sites that are more distant from the Fe substitutional site whereas the second site characterized with υq2 = 62 MHz is related to Cd probe atoms that are closer to the Fe defect. Additionally, the system has been characterized using electron dispersive spectroscopy.

Highlights

Pure or Fe-doped TiO2 can be used as photocatalyst for water purification or energy converter in solar cells, besides technology applications in the electronics industry.[1,2,3,4] Fe doping has been proven to improve the photocatalytic activity of titanium oxide and makes possible the absorption of light at a higher wavelength.[1]The TiO2 was one of the first material to being investigated as diluted magnetic semiconductor (DMS) and ferromagnetism was first reported by Matsumoto et al[5] in a study done by the addition of Co in the system
Following the earliest publication of the work of Dietl et al[7] several studies have been published investigating the candidates for DMS through measurements and first-principles calculations; one of the most frequent observations was an interaction that would be responsible for magnetism, whose range is determined by the polaron and works for low concentrations of TM associated to oxygen vacancies
In the present work we measured the signal that can be obtained from the hyperfine interactions by means of time-differential perturbed angular correlation (TDPAC) on Cd probe atoms inserted into Fe-doped TiO2

Summary

Introduction

Pure or Fe-doped TiO2 can be used as photocatalyst for water purification or energy converter in solar cells, besides technology applications in the electronics industry.[1,2,3,4] Fe doping has been proven to improve the photocatalytic activity of titanium oxide and makes possible the absorption of light at a higher wavelength.[1]The TiO2 was one of the first material to being investigated as diluted magnetic semiconductor (DMS) and ferromagnetism was first reported by Matsumoto et al[5] in a study done by the addition of Co in the system. The TDPAC technique measures the perturbation ajuliana.schell@cern.ch 2158-3226/2017/7(9)/095010/7 The coefficient Cn can be numerically calculated for a known η.8 The coefficients sn denote the amplitudes of the transition frequencies ωn and are summations of Wigner 3j-symbols products running over the allowed magnetic splitting hyperfine states.[9] If there are probe atoms exposed to j different lattice environments, and each of them creates a characteristic field gradient at fraction f of probe atom sites, the perturbation function becomes R (t) = A22 j fjGj22 (t).

Results

Conclusion