Effect of growth temperature on the structural and transport properties of magnetite thin films prepared by pulse laser deposition on single crystal Si substrate

摘要

Magnetite (Fe_3O_4) thin films are prepared by pulsed laser deposition using an α-Fe_2O_3 target on silicon (111) substrate in the substrate temperature range of 350 ℃ to 550 ℃. X-ray diffraction (XRD) measurement shows that the film deposited at 450 ℃ is a single phase Fe_3O_4 film oriented along [111] direction. However, the film grown at 350 ℃ reveals mixed oxide phases (FeO and Fe_3O_4), while the film deposited at 550℃ is a polycrystalline Fe_3O_4. X-ray photoelectron spectroscopy study confirms the XRD findings. Raman measurements reveal identical spectra for all the films deposited at different substrate temperatures. We observe abrupt increase in the resistivity behavior of all the films around Verwey transition temperature (T_V) (125 K-120 K) though the transition is broader in the film deposited at 350 ℃ We observe that the optimized temperature for the growth of Fe_3O_4 film on Si is 450 ℃. The electrical transport behavior follows Shklovskii and Efros variable range hopping type conduction mechanism below T_V for the film deposited at 450 ℃ possibly due to the granular growth of the film.