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<p><p>This thesis concerns design and construction of an ultra high vacuum chamber to fabricate and characterize spintronic devices.  The long term intention is to fabricate spin valve structures with V[TCNE]₂ (hybrid organic inorganic semiconductor room temperature magnet) sandwiched between two ferromagnetic electrodes, which requires better than 10^-8mbar of vacuum. Due to an uncured leak in the chamber, the current vacuum is limited to 4*10^-7mbar. The V[TCNE]₂ thin film prepared in this vacuum, oxidized completely  by  the presence of oxygen during the film growth. Organic magnetoresistance (OMAR) devices which are simple organic diode structures were fabricated and characterized, as they are compatible with high vacuum conditions. A magnetoresistance measurement set up was arranged and the possible problems in fabrication and characterization are analyzed.</p><p> </p><p>To fabricate OMAR devices-ITO/P3HT/Al, RR-P3HT (regio regular poly (3-hexylthiophene)) an effective hole transport polymer with higher hole mobilities was used as an active layer and Al (aluminum) as a cathode. A thermal evaporation setup was added to the vacuum chamber to evaporate Al electrodes. The devices were kept in argon and vacuum environments, while characterizing in dark to suppress the exitons generated by photo illumination. The Organic magnetoconductance of about 1% is observed for the less concentration P3HT (3mg/1ml), and significantly improved to -23% for the high concentration P3HT (10mg/ml) solution. The results support that the negative magnetoconductance is due to the formation of bipolaron under the influence of an external magnetic field.</p><p> </p><p>Finally, suggestions to improve the performance of the vacuum chamber to fabricate and characterize the spintronic devices and OMAR devices are presented.</p></p>

This thesis concerns design and construction of an ultra high vacuum chamber to fabricate and characterize spintronic devices.  The long term intention is to fabricate spin valve structures with V[TCNE]2 (hybrid organic inorganic semiconductor room temperature magnet) sandwiched between two ferromagnetic electrodes, which requires better than 10-8mbar of vacuum. Due to an uncured leak in the chamber, the current vacuum is limited to 4*10-7mbar. The V[TCNE]2 thin film prepared in this vacuum, oxidized completely  by  the presence of oxygen during the film growth. Organic magnetoresistance (OMAR) devices which are simple organic diode structures were fabricated and characterized, as they are compatible with high vacuum conditions. A magnetoresistance measurement set up was arranged and the possible problems in fabrication and characterization are analyzed.   To fabricate OMAR devices-ITO/P3HT/Al, RR-P3HT (regio regular poly (3-hexylthiophene)) an effective hole transport polymer with higher hole mobilities was used as an active layer and Al (aluminum) as a cathode. A thermal evaporation setup was added to the vacuum chamber to evaporate Al electrodes. The devices were kept in argon and vacuum environments, while characterizing in dark to suppress the exitons generated by photo illumination. The Organic magnetoconductance of about 1% is observed for the less concentration P3HT (3mg/1ml), and significantly improved to -23% for the high concentration P3HT (10mg/ml) solution. The results support that the negative magnetoconductance is due to the formation of bipolaron under the influence of an external magnetic field.   Finally, suggestions to improve the performance of the vacuum chamber to fabricate and characterize the spintronic devices and OMAR devices are presented.

In the growing field of spintronics there is a strong need for development of flexible lightweight semi-conducting magnets. Molecular organic-based magnets are attractive candidates since it is possible to tune their properties by organic chemistry, making them so-called “designer magnets”. Vanadium tetracyanoethylene, V(TCNE)x, is particularly interesting since it is a semiconductor with Curie temperature above room temperature (TC~400 K). The main problem with these organic-based magnets is that they are extremely air sensitive. This thesis reports on the frontier electronic structure of the V(TCNE)x by characterization with photoelectron spectroscopy (PES) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. It also presents a new and more flexible preparation method of this class of organic-based thin film magnets. The result shows improved air stability of the V(TCNE)x prepared with this method as compared to V(TCNE)x prepared by hitherto used methods.

<p>In the growing field of spintronics there is a strong need for development of flexible lightweight semi-conducting magnets. Molecular organic-based magnets are attractive candidates since it is possible to tune their properties by organic chemistry, making them so-called “designer magnets”. Vanadium tetracyanoethylene, V(TCNE)_x, is particularly interesting since it is a semiconductor with Curie temperature above room temperature (T_C~400 K). The main problem with these organic-based magnets is that they are extremely air sensitive. This thesis reports on the frontier electronic structure of the V(TCNE)_x by characterization with photoelectron spectroscopy (PES) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy. It also presents a new and more flexible preparation method of this class of organic-based thin film magnets. The result shows improved air stability of the V(TCNE)_x prepared with this method as compared to V(TCNE)_x prepared by hitherto used methods.</p>