Fabrication of semi-conductor titanium oxide films containing isolated fine iron-based metal particles and measurement of the GMR effect under illumination of UV light

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The objects of this research are to fabricate new functional titanium oxide films containing isolated fine iron particles which show the GMR (giant magnetic resistance) effect, and to confirm that such nanocomposite films provide enhancement of the GMR effect under illumination of UV light. After several improvements of the sputtering chamber used in this study, nanocomposite films composed of isolated fine iron particles in the matrix titanium oxide were fabricated by using titanium oxide plate and iron plate as a target. The crystal structure, optical transparency, electrical resistance, magnetic properties including the GMR effect under a magnetic field were examined with reference to preparation conditions such as deposition conditions and annealing conditions. Main sputtering conditions : in-put electric power ; 50〜70W, sputtering Ar gas pressure ; 3〜6 x10^<-3> Torr. The deposition of iron particles was manually controlled by measuring deposition time. During this study, however, … More several unexpected machine troubles including unstable sputtering argon gas flow during sputtering and pumping rate delayed the original plan. The main results are : (1) Composite films composed of isolated fine iron particles dispersed in the matrix titanium oxide showed amorphous state after deposition, but after 200℃ annealing in air they became crystalline state of titanium oxide. (2) Some films provided a very small GMR, ΔR/R=0.02%, at room, and the transparency of the films decreased with increasing total deposition amount of iron particles and thus such films did not show any GMR. (3) After 400℃ annealing in air, the films showing metallic brightness became transparent and yellow-like, probably because of oxidization of iron particles in the anatase-type matrix titanium. The films, however, did not show any GMR. X-ray analysis did not confirm the existence of iron oxides. (4) A relationship among transparency, resistance and magnetic property was found to be important for measuring the magnetoresistance of fabricated films ; Optically transparent films proved to be impossible to measure the magnetoresistance and provided no GMR effect. It also proved that the well-controlled fabrication is very important to get optimum nanocomposite films which are in a measurable range of the GMR. After several improvements of the present experimental failures, we will try to enhance the GMR effect under illumination of UV light through various fabrication processes including a mixture ratio of sputtering Ar and N2 gases. Less