To realize the room-temperature ferromagnetism (RTFM) in diluted magnetic semiconductors (DMS), we
prepared a series of Cobalt-doped ZnO thin films using pulsed laser deposition (PLD) at deposition temperatures 500°C
under oxygen pressure from 2.5×10-4 Pa to 15 Pa. To elucidate the physical origin of RTFM, Co 2p spectra of
cobalt-doped ZnO thin films was measured by X-ray photoelectron spectroscopy (XPS). The magnetic properties of
films were measured by an alternating gradient magnetometer (AGM), and the electrical properties were detected by a
Hall Effect instrument using the Van der Pauw method. XPS analysis shows that the Co2+ exists and Co clusters and
elemental content change greatly in samples under various deposition oxygen pressures. Not only the valence state and
elemental content but also the electrical and magnetic properties were changed. In the case of oxygen pressure 10 Pa, an
improvement of saturation magnetic moment about one order of magnitude over other oxygen pressure experiments, and
the film exhibits ferromagnetism with a curie temperature above room temperature. It was found that the value of carrier
concentration in the Co-doped ZnO film under oxygen pressure 10Pa increases about one order of magnitude than the
values of other samples under different oxygen pressure. Combining XPS with AGM measurements, we found that the
ferromagnetic signals in cobalt-doped ZnO thin film deposited at 500 °C under oxygen pressure 10 Pa only appear with
the detectable Co2+ spectra from incompletely oxidized Co metal or Co cluster. So oxygen pressure 10 Pa can be
thought the best condition to obtain room-temperature dilute magnetic semiconductor about cobalt-doped ZnO thin
films.
The amorphous oxide semiconductors (AOSs) are promising for emerging large-area optoelectronic applications because
of capability of large-area, uniform deposition at low temperatures such as room temperature
(RT). Indium–gallium–zinc oxide (InGaZnO) thin film is a promising amorphous semiconductors material in thin film
transistors (TFT) for its excellent electrical properties. In our work, the InGaZnO thin films are fabricated on the SiO2
glass using pulsed laser deposition (PLD) in the oxygen partial pressure altered from 1 to 10 Pa at RT. The targets were
prepared by mixing Ga2O3, In2O3, and ZnO powder at a mol ratio of 1: 7: 2 before the solid-state reactions in a tube
furnace at the atmospheric pressure. The targets were irradiated by an Nd:YAG laser(355nm). Finally, we have three
films of 270nm, 230nm, 190nm thick for 1Pa, 5Pa, 10Pa oxygen partial pressure. The product thin films were
characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Hall-effect investigation. The comparative
study demonstrated the character changes of the structure and electronic transport properties, which is probably occurred
as a fact of the different oxygen partial pressure used in the PLD.
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