Structure And Properties Of Manganese-doped Titanium Dioxide Thin Films Prepared By RF Magnetron Sputtering

Diluted Magnetic Semiconductors (DMSs) have been arisen to pay abroad attention and to make deep investigation by science and technology workers because it has much interest for their potential application in the devices of calculation, electron storage and spintronics. Furthermore, Diluted Magnetic Semiconductors Oxides (DMSO) such as transition metal doped TiO₂, ZnO and SnO₂, have recently become a research brightness in condensed matter physics, materials physics and magneto-electronics because it has ferromagnetic properties at room temperature (RT) and at more than RT, high refractive index and dielectric constant, transparence in visible and infrared light, unti-oxidation, self-cleaning and good physical-chemical properties. These would accelerate a development on basic theory, technology of preparation materials and optoelectronic devices.In this paper, The Ti1-xMnxO₂ (0.10≤x≤0.23) films were deposited by radio frequency magnetron co-sputtering. The crystal structure, chemical state, magnetic and optical properties were studied by X-ray diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM), X-ray photoemission spectra (XPS), vibrating sample magnetometer (VSM), laser Raman scattering, and UV-VIS spectrophotometer.The experimental results are shown as follows: (1) X-ray diffraction (XRD) measurements indicate that the samples prepared at 500oC are easy to form rutile structure, and the sizes of the crystal grains grow bigger as the Mn concentration increases. It can be indicated from the SEM pictures that the surface of the films become rougher and Mn-TiO₂ clusters appear as the Mn concentration increases. High resolution transmission electronic microscope (HRTEM) photos confirm that there isn't any other phase besides rutile TiO₂ structure when the Mn concentration is 21%, which indicates that the Mn ions have been doped into the rutile TiO₂ structure, and the Mn 4+ substitution of some site of Ti 4+. (2) The VSM measurements indicate that the Ti1-xMnxO₂ (x=0.21) film is ferromagnetic at room temperature, and the saturation magnetization, coercivity, and saturation field are 16.0emu/cm3, 167.5Oe and 3740Oe at room temperature, respectively. The mechanism of ferromagnetism of the films is contributed to the new structure formed by the substitution of the Mn 4+ for Ti 4+ in the TiO₂ crystal,and the ferromagnetic origination may be explained using the RKKY/Zener model. But when the Mn concentration gets over a level of 23%, the films appear to be a little antiferromagnetic. Also, it is indicated from the optical measurements that the doped Mn ions can effect the transmission optical absorption edges obviously.