| This thesis is motivated by the need to better understand spin dependent hot electron transport through materials and material interfaces. Spin dependent transport and injection is important for devices that utilize the spin as well as the charge of the electron, such as giant magneto resistance spin valves used in magnetic data storage. To study spin transport, ballistic electron emission microscopy was modified to measure spin dependent hot electron transport. This new spin-polarized ballistic electron emission microscopy technique was employed on ferromagnetic-metal/semiconductor Schottky diodes, which are technologically important due to their possible use as efficient spin injectors. This allowed the spin dependent attenuation lengths to be determined on the Fe/Si(001) system. The interface band structure was found to affect the energetic dependence of the attenuation lengths and the spin dependent transport properties. Other transition-metal/Si interfaces were studied and it was found that Fe and Mn thin films on Si(001) resulted in an interface band structure with multiple conduction band minima. The addition of 19% carbon in the Fe film was found to suppress the second conduction band minimum. Thickness dependent ballistic electron emission microscopy studies on Fe/Si(001) and Fe81 C19/Si(001) Schottky diodes revealed that the addition of carbon had little effect on the electron transport properties in the metal films. As in the polarized experiments, the additional conduction band minimum at the Fe/Si(001) interface was found to dramatically affect the energetic dependence of the attenuation length measured in this system. To confirm this effect an additional study was performed on the Au/GaAs system, an interface known to have three conduction band minima, where a similar effect was observed. |
