Studies of Light Illumination and Substrate Material Effects on Aluminum Single Electron Transistors: Towards an Understanding of Background Charge

Significant attention has been given to the so-called 'blinking dot' phenomenon, which describes the fluorescence intermittency exhibited by a wide variety of nanoscale objects such as quantum dots, and nanowires. It is believed that blinking is associated with spatial charge redistribution within the nanoscale blinking objects. The natural choice to detect these charge fluctuations is single-electron transistors (SETs). Evidently, the electrometers used for this measurement should not be affected by light illumination. We studied the effects of light illumination, from near infrared to blue, on the characteristics of Al/AlOx SETs at low temperatures (0.3 Ì¢‰âÂ' 4.2K). Based on the results of this study, we developed a fabrication processes for producing SETs on wide bandgap insulating substrates (quartz and sapphire), and the fabrication of metal shields on top of the SET devices (which demonstrates the possibility of post-processing of SETs). Among the most important outcomes of this study is the realization of the significant influence that the substrate material has on SET devices. These results led us to further study the characteristics of the charge traps and investigate the causes of background charge in SETs. In addition, we developed a fabrication method for producing metallic SETs with tunnel barriers made by atomic layer deposition. This provides tunnel barriers with higher quality and holds the promises of a reduction of individual trap effects related to disordered materials surrounding the SET's island and leads (Source/Drain).