The Investigation Of Coexistence Of Lateral Photovoltage And Magnetoresistance In Metal-Oxide-Semiconductor Structures

Since the lateral photoeffect (LPE) was first discovered by Schottky in 1930 and later expanded upon by Wallmark in 1957, it has been utilized in position-sensitive detectors (PSDs) until now. As soon as the giant magnetoresistance (GMR) was first discovered in 1988, it swiftly raised a global research upsurge due to its tremendous importance in application. The Nobel Prize in Physics for 2007 was awarded jointly to the French scientist Albert Fert and the German scientist Perter Grunberg for their contributions to the discovery of GMR. Though separated researches on each individual property of lateral photovoltage (LPV) and magnetoresistance (MR) have made much progress, the work that integrates two phenomena into one sort of structure has never been reported. In this work, we first tried this idea and successfully achieved both effects in one material like some metal-oxide-semiconductor (MOS) structures. Such researches provide valuable information for expanding functional materials such as information materials sensitive to both magnetic field and light, and developing new sensors based on magnetic field and light. The main researches are as follows:(a) The coexistence of LPV and MR in Co₃Mn₂O/SiO₂/Si MOS structure:1) We investigated the LPE in Co₃Mn₂O/SiO₂/Si MOS structure. The largest position sensitivity in this structure is 34.3 mV/mm. We presented the relation between LPV and transverse photovoltage (TPV), as well as the LPV's dependence on laser position, wavelength and power of the laser.2) We studied the magnetotransport properties of Co₃Mn₂O/SiO₂/Si MOS structure. The experiments showed that the Co₃Mn₂O film is an insulating granular film consisting of CoO, MnO, Co and Mn. The effective resistivity showed a marked transition for temperature at around 240 K. Both negative MR of -11% at 4.2 K and a large positive MR of 70% at 400 K at a magnetic field of 6 T were observed. These phenomena can be explained by the conducting channel switching effect from the upper film to the Si inversion layer.3) The preliminary modulation of LPV by an external magnetic field was studied. The relative variation of LPV at 2 T is about 93.2%, which is almost one order larger in magnitude than the corrresponding MR value (13.3%).(b) The dependence of both LPV and MR on the Co film thickness in Co/SiO₂/Si MOS structures:1) We investigated the LPE using the obverse and the reverse measurement modes respectively. The position sensitivities for both modes depend similarly on the Co film thickness. The optimal position sensitivities, 42.64 mV/mm for the obverse mode and 51.98 mV/mm for the reverse mode, were produced at a certain film thickness (28 (?)). With increasing Co film thickness from the optimal point, however, the sensitivity for the obverse mode reduces more rapidly to zero than that measured in the reverse mode. We explained these phenomena by the shorting effect of the metallic film.2) We also compared a variety of figures of merit of such MOS structures Co/SiO₂/Si used as PSDs for both modes. The measured datas showed that the correlation coefficient and the nonlinearity for both modes are all very good.3) We investigated the relation between MR and the Co film thickness for Co/SiO₂/Si MOS structures at room temperature. As the Co film thickness is the thinnest (16 (?)), the MR reaches the largest value (31.2%). With increasing the Co film thickness, the MR drops as dramatically as the effective resistivity. These phenomena can also be explained by the conducting channel switching effect from the upper metal film to the Si inversion layer.4) The relative variation of LPV at 2 T is about 46.3%, which is almost one order larger in magnitude than the corresponding MR value (4%).