| Tin oxide (SnO2) is a well-known material for its applications in transparent conducting layers and gas sensors. However, pure SnO2 usually needs modifications in terms of additive incorporation to modify its conductivity, optical absorption and gas sensitivity. Recently, diluted magnetic semiconductors (DMS) obtained by doping magnetic transition elements into nonmagnetic semiconductors such as SnO2 have received increasing attention due to their potential applications in spin-based electronics, or spintronics. However, there are two key problems in oxide DMS for the development of practical devices, one is the enhancement of Curie temperature (Tc) and the other is the origin of ferromagnetism.In this thesis, SnO2 and metal doped SnO2 materials were synthesized by sol-gel and pulsed laser deposition. The properties of the materials were investigated. The results are as follow:(1) High quality SnO2 thin films were successfully fabricated on Si(111) substrates via sol-gel. The quality of the thin films was improved by using various additives. It was intensively investigated the influence of rapid thermal annealing (RTA) on the characteristics of SnO2 thin films. The film annealed at 600℃shows the relatively perfect crystallization with moderate grain size. The phenomenon of photoluminescence of the films was studied. It was found that red shift of photoluminescence in the visible band due to the quantum confinement effect and related to the point defects, such as oxygen vacancies and tin interstitials. When the temperature increases to 800℃, peak around 3400 cm-1 owning to the O-H vibrating mode of the absorbed water still exists, which indicates that SnO2 thin film prepared by sol-gel technique has strong absorbability of water from the air. Porous SnO2 thin films were successfully synthesized and the problem of thin-film prepared by sol-gel easy to crack was successfully modified by using additives.(2) It was investigated the Sn1-xFexO2-δsynthesized by sol-gel technique. It was found that the Fe content and annealing temperature have a great effect on the microstructure and magnetic properties. When x< 0.1 the obtained material is corresponding to pure tetragonal rutile SnO2. The diffraction peak become broaden with Fe doped, indicateing the decreased grain size for Fe3+ ion with the smaller ionic radius (0.069 nm) replaces the Sn4+ion with the larger ionic radius (0.083 nm). When x> 0.1 the rhombohedral phase of a-Fe2O3 can be observed. The saturation magnetization of the Sn0.9Fe0.1O2-δdecreased with the sintering temperature, decreased by 71.82% after being annealed at 500℃, and further decrease by 56.78% after being annealed at 700℃. In theory, the size and the number of the iron clusters will increase with the doping amount and will bring larger ferromagnetism. However, this experiment has a reversed trend, indicating ferromagnetism in this experiment was not induced by the iron clusters, although it can not rule out the presence of iron. The samples exhibit a conventional ferromagnetism, showing a curve consistent with a Curie-Weiss Law. The Curie temperature (Tc) is about 719 K for x= 0.1. These values are higher than the reported values for pure SnO2 and for TM-doped SnO2 materials fabricated by other techniques.(3) High quality tin-doped indium oxide (ITO) thin films were successfully fabricated on Si and glass substrates by pulsed laser deposition. In pulsed laser deposition technique, substrate temperature and gas pressure are very important for the characteristics of thin films. It was intensively investigated the influence of substrate temperatures and argon/oxygen pressure on the microstructure, morphology, transmittance, resistivity, carrier concentration and Hall mobility of ITO thin films. The film with substrate temperature of 500℃and oxygen pressure of 1.4Pa showed the optimal property, which had higher transmittance and low resistivity at the same time, with average transmittance of 84.5% and resistivity of 2.25×10-4Ωcm. When deposited under argon pressure of 2.8×10-2 Pa and substrate temperature of 500℃, the sample has the lowest resistivity of 1.88x10-4Ωcm due to the higher carrier concentration of 14.85×1020 cm-3 and Hall mobility of 22.59 cm2/Vs. It was the first time to probe the low-temperature (300-11K) electrical properties, which is important for the development of practical devices applied to military such as in extreme cold zone.(4) It was intensively investigated the preparation and characteristics of SnO2 and Fe-doped SnO2 thin films deposited by pulsed laser technique. The relationship of magnetic properties, microstructure, morphology, surface valence state and magnetic properties with gas pressure and substrate temperature were studied. It was found that the oxygen pressure has great effect on the quality of Fe doped SnO2 thin film. In our experiment, the appropriate range of oxygen pressure to get high quality Fe doped SnO2 thin films is about 15Pa with substrate temperature 500℃. The magnetic moments per unit surface area of the pure SnO2 thin film decreased from 0.50x10-4emu/cm2 to 0.38×10-4emu/cm2 with oxygen pressure increased from 10Pa to 22Pa while Fe doped SnO2 thin film decreased from 0.25×10-4emu/cm2 to 0.20×10-4emu/cm2, indicating the weak ferromagnetism was related to oxygen vacancy, however, the selected area diffraction pattern (SAED) showed that there was the other diffraction point besides SnO2, which can be attributed to Fe2O3, and the XPS further confirmed there was Fe3+. So, the possibility of Fe2O3 causing the ferromagnetism can not rule out.
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