Magnetic and electrical characterization of "ferromagnet/insulator/silicon" diodes

This work is focused on the study of magnetic and electrical properties of ferromagnet/semiconductor heterostructures that can be used for spin injection into silicon. Three different studies are conducted whose principal results will be presented. In all these studies, a simple diode-like ferromagnet/insulator/semiconductor (FM/I/S) structure is used. The first study aimed to investigate whether a magnetic "dead" layer is obtained at the ferromagnet/oxide barrier that could lead to spin depolarization of the injected electrons. The results show the absence of such layer even after annealing at temperatures up to 723 K (450 °C). The second study focused on the mechanisms of electrical transport through the insulator barrier. Capacitance-voltage as well as current-voltage characteristics have been measured. The results underline the importance of controlling the ferromagnet deposition process in obtaining defect-free silicon-insulator interface, a prerequisite to spin conservative direct-tunnel transport process. In the third study, magnetic characterization of diodes that may be used for spin injection and collection were performed.