The Preparation And Study Of Fe-doped In₂O₃ Dilute Magnetic Semiconductor Films And Nanodot Arrays

Dilute magnetic semiconductors?DMS?have attracted great interest in spintronic devices because the charge and spin of the electrons can be simultaneously controlled,and they show a lot of excellent magnetic,magneto-electric,magneto-optical performance.Since Dietl et al.theoretically predicted the room temperature ferromagnetism in Mn doped Zn O semiconductors,a mass of research have been carried out on oxide-based dilute magnetic semiconductors.Among them,Fe-doped In₂O₃ magnetic semiconductor is very attractive mainly because of its high solubility of Fe ions in In₂O₃ host lattice,which could effectively avoid the formation of metallic Fe and Fe oxide impurities.Great efforts have been devoted to research about thin films and powders of Fe-doped In₂O₃,but the preparation and research of Fe-doped In₂O₃ nanodot arrays has not reported.We studied the Fe-doped In₂O₃ nanodot arrays because their unique tiny size and large specific surface area could influence their magnetic properties.?1?The Fe-doped In₂O₃ films with different thickness were fabricated by pulsed laser deposition.The films are indexed as In₂O₃ cubic bixbyite structure and exhibit a?222?preferred orientation.Fe ions are incorporated into the In3+ sites of the In₂O₃ host matrices,and behave as a mixture of +2 and +3 valence.The(In_0.95Fe_0.05)₂O₃ films show room temperature ferromagnetism with Cure temperature above 300 K and the magnetization are independent of film thickness,which rules out the possibility that the magnetic property is originate from the interface of the film.?2?We have fabricated the(In_0.95Fe_0.05)₂O₃ nanodot arrays with different sizes and shapes by pulsed laser deposition?PLD?and with the aid of ultrathin porous anodized aluminum?PAA?templates.X-ray diffraction patterns of the nanodot arrays indicate all samples are indexed as In₂O₃ cubic bixbyite structure and exhibit a?222?preferred orientation.There are no extra diffraction peaks of secondary phases such as metallic Fe and Fe oxides detected.The(In_0.95Fe_0.05)₂O₃ nanodot arrays present a strong ferromagnetism.The saturation magnetization?Ms?of nanodot arrays is higher than that of the films and the Ms value of the(In_0.95Fe_0.05)₂O₃ nanodot arrays increases as the nanodot size decreases.The large surface and surface area of the nanodots increase with the dots size decreases,resulting in more defect sites in the form of unsaturated bonds,which may be the major reason for their giant Ms magnetization.And this may also due to the quantum confinement effect of the(In_0.95Fe_0.05)₂O₃ nanodots.Moreover,we could adjust the bandgap of the(In_0.95Fe_0.05)₂O₃ nanodots by control their size.In summary,we studied the preparation,structure and properties of highly ordered Fe-doped In₂O₃ films and nanodot arrays.We found that,the magnetic property and the band gap of the(In_0.95Fe_0.05)₂O₃ nanodots can be controled by their size.The giant Ms of the(In_0.95Fe_0.05)₂O₃ nanodot arrays is very promising for future spin storage and logic function devices.