Hot electron transport through molecular diodes

Single-molecule devices potentially offer a promising future for next-generation electronics. Understanding the mechanism of electron transport through single molecules is fundamental for developing such molecular electronics. In this thesis, we apply the method ballistic electron emission microscopy (BEEM) to study hot electron transport through a two-dimensional, self-assembled molecular layer. The molecular layer is sandwiched by a thin layer of metal and a semiconductor substrate, either silicon or gallium arsenide. Various linear organic molecules with different end functional groups were studied attached in a monolayer to the substrate via Si-C or (GaAs)-S bonds. We conclude that the presence of the organic can dramatically change the electrical properties of the metal/molecule/semiconductor diode and that the end-functional group plays a key role in controlling the barrier height and electron transmission. Those molecules bonded to the top metal contacts via metal-S bonds resulted in an insulating layer at the junction, while those bonded via weak van de Waals bonds resulted in an intermixed layer with the Au. We conclude that this molecular interface design offers a promising method for control of device function.