製造穩定的超導點接觸是實現超導量子彈道裝置的關鍵，本論文致力於開發一種利用聚焦離子束(FIB)制定超導體鋁(Al)奈米結的技術。我們對離子撞擊鋁薄膜和矽基板進行SRIM-2013/TRIM的蒙地卡羅模擬，建立模擬與實驗的關聯，使我們能夠估計實驗所需的銑削條件。通過利用鋁薄膜和矽基板銑削速率和濺射率的變化，我們能夠在鋁觸點下雕刻矽，使薄膜變薄並形成尺寸約為30奈米的三維懸橋。我們測量嵌入在SQUID結構之奈米觸點的電流與電壓特性，發現明顯的次諧波間隙特徵和超電流。在間隙狀態中觀察到的強非線性表明了耗散性質，並表明在奈米點接觸中發生了多重安德列夫反射。我們的工作可能為開發超導量子點接觸裝置開闢一條路徑，例如安德列夫量子位元，以及一種修復超導電路的方法。

Fabricating a stable superconducting point contact is key challenge to realize superconducting quantum ballistic device. This thesis is devoted to develop a technique to tailor a superconducting aluminum (Al) adjacent nano-point junctions by using focused ion beam (FIB). We perform the SRIM-2013/TRIM Monte Carlo simulation to Al thin film and Si-substrate under the impinging of ions, and subsequently correlate the estimated displacement depth to the milling rate as a function of ion dosages in experiments, thus establish an empirical rule to guide us the milling conditions. By utilizing variance of milling rate and sputter yield of Al thin film and Si-substrate, we are able engrave the Si underneath Al contacts, thinner the film and form a suspended three-dimensional nano-bridge with size about 30 nm. We measure the current vs. voltage I(V) characteristics of the nano-contacts embedded in a SQUID geometry, and find distinct subharmonic gap features and a super-current. The observed strong non-linearities in the gap regime indicates a dissipative nature and suggest the occurrence of multiple Andreev-reflection in the nano-point contacts.
Our work could potentially open a route for developing superconducting quantum point contact devices, e.g. Andreev qubits, and a way to repair superconducting circuits.

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