| Summary: | 博士 === 國立中央大學 === 電機工程學系 === 103 === In this thesis, fabrication and characterization of germanium (Ge) quantum-dot (QD) single-electron transistors (SETs) as well as the associated applications were investigated. Using the fidelity of spacer-layer deposition and nanopattern-dependent oxidation of SiGe we have demonstrated the precise placement of a single Ge QD between nanoelectordes through symmetrical tunneling barriers of Si3N4/SiO2 in self-organized approach. In order to effectively realize a Ge-QD SET using selectively oxidizing SiGe patterned structure, the lithographical patterning and etching profile of the nanostructure are to be optimally designed. The fabricated 11-nm Ge-QD SHT exhibits clear Coulomb oscillation and Coulomb diamond features under gate and drain modulation from T = 77 K to 150 K, providing a way to resolve the electronic structure of the QD through tunneling spectroscopy.
On the other hand, Ge-QD thermometry has demonstrated based on extraordinary temperature-dependent oscillatory differential conductance (GD) characteristics of Ge-QD SHTs in the few-hole regime. Full-voltage width-at-half-minimum, V1/2, of GD valleys appears to be fairly linear in the charge number (n) within the QD and temperature in a relationship of eV1/2 (1-0.11n)5.15kBT, providing the primary thermometric quantity. The depth of GD valley is proportional to charging energy (EC) and 1/T via GD EC/9.18kBT, providing another thermometric quantity.The experimental results reveal that our Ge-QD SHT truly paves an affirmatory path for nanothermometry to measure temperature in the local QD with detection temperature as high as 155 K with temperature accuracy of sub-millikelvin in a spatial resolution on the order of the QD size (~10 nm).
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