Download files
Abstract
This thesis describes the development and demonstration of two types of devices, namely silicon microdosimeters and quantum dots in the field of classical and quantum electronics respectively. The microdosimeters, which demonstrate well-defined sensitive volumes, have significant potential for applications in regional microdosimetry. And, the highly tunable gate-defined quantum dots, which allow the observation of the single-electron regime, provide significant promise for quantum computation in coupled quantum dots.
The design, fabrication and demonstration of novel cylindrical silicon-on-insulator (SOI) single-diode microdosimeters and arrayed microdosimeters is presented. The single diode structure was modelled usingTechnology Computer Aided Design (TCAD) to optimise the design parameters. Experimental characterisation using ion-beam-induced charge collection (IBICC) technique shows that the devices achieve well-defined cylindrical sensitive volumes with excellent charge collection characteristics. Results also show that arrays of these sensitive volumes can be successfully read out in a parallel mode.
Next, a few-electron double quantum dot was fabricated using metal-oxide-semiconductor-compatible technology and low-temperature transport measurements were performed to study the energy spectrum of the device. The double dot structure is electrically tunable, enabling the interdot coupling to be adjusted over a wide range, as observed in the charge stability diagram. Resonant single-electron tunnelling through ground and excited states of the double dot was clearly observed in bias spectroscopy measurements.
Low-temperature electronic transport measurements of a silicon metal-oxide-semiconductor quantum dot, with independent gate control of electron densities in the leads and the quantum dot island is also reported. This architecture allows the dot energy levels to be probed without affecting the electron density in the leads, and vice versa. Appropriate gate biasing enables the dot occupancy to be reduced to the single-electron level, as evidenced by magnetospectroscopy measurements of the ground state of the first two charge transitions. Independent gate control of the electron reservoirs also enables discrimination between excited states of the dot and density of states modulations in the leads.