Local Structure And Magnetic,transport Properties Of Fe And Li Co-doped In2O₃ Diluted Magnetic Semiconductors

In this paper,the effect of?Fe,Li?-codoping on the structural,magnetic and transport properties of In₂O₃ based films was investigated.These films were deposited on the surface of SiO₂,Si?001?and ultra-white glass substrates using the RF-magnetron sputtering technique.The samples were systematically studied by XRD,XPS,XAFS,R-T,Hall,MR,SQUID et al.,the following results were obtained:1.The samples of(In_0.96-xLi_xFe_0.04)₂O₃ films with different Li doping concentration were prepared by RF-magnetron sputtering technique.The X-ray diffraction measurements?XRD?indicated that well incorporation of Li ions in the lattice of In₂O₃ and led to unit cell contraction,there is no Fe,Li related elementary phase or oxide second phase in the system.The results from XPS revealed that the Fe presents mixed valence state of+2 and+3 state and there are a lot of oxygen vacancies in the films.The Fe ions exhibited divalent and trivalent state and substitute In³⁺sites as confirmed by XAFS measurements and the local environment of Fe does not change with the increase of Li doping concentration.Hall effect measurements showed that the carrier concentration decreases with the increase of Li doping concentration,this can be explained by the electrons arising from the n-type oxygen vacancies may be partly compensated by holes produced by the substitution of p-type Li,resulting in a decrease in carrier concentration and an increase in resistivity.The results of R-T indicated that Transport behavior of metal-semiconductor transition in thin films and Conductive behavior of semiconductors has gradually become apparent,the Mott variable range hopping?VRH?behaviors was used to interpret the electronic conducting mechanism.The results of MR measurements indicated that the samples exhibit negative magnetic resistance,and the magnetic resistance has a tendency to change negative into positive with the Li doping concentration.Magnetic measurements showed that the doping of Li can obviously improve the ferromagnetism of the system.The orbital hybridization between Li atoms and surrounding O atoms can be used to explain the enhancement of ferromagnetism.2.The samples of(In_0.94-yFe_y Li_0.06)₂O₃ films with different Fe doping concentration were prepared by RF-magnetron sputtering technique.The XRD revealed the cubic bixbyite structure corresponding to the phase of In₂O₃ in the films.The Fe ions exhibited divalent and trivalent state and substitute In₁ sites as confirmed by XAFS measurements.The Hall and R-T measurements indicated that the carrier concentration decreasing with the increase of Li doping concentration.The combination of Mott variable range hopping?VRH?at low temperature and Hard band gap hopping behaviors at high temperature was used to interpret the electronic conducting mechanism,suggesting that the carriers are strongly localized.The results of MR measurements indicated that the transition from negative magnetic resistance to positive magnetic resistance has been realized with Fe doping concentration increases at 10K.The contribution of positive and negative magnetic resistance to the samples can be influenced by the doping concentration of Fe and the testing temperature.All samples exhibit intrinsic room temperature ferromagnetism,the M_s firstly decreased,and then increased.Oxygen vacancies and the strong lattice distortion around Fe ions are related to the production of ferromagnetism.