Character And Fabrication Of Al/Al₂O₃/Al Tunnel Junctions For Qubit Application

A quantum computation is a new computation system which exceeds its classical counterpart. The superconducting quantum computation is an important approach and a scalable scheme. Because of its solid state nature, macroscopic phase coherence and similarity to conventional semiconductor circuits one of the more promising technologies appears to be Josephson junction circuits. A typical flux qubit consists of an isolated superconductive junction and a SQUID. In a SQUID the tunnel junctions are in parallel and form a superconducting loop. So, superconductive Josephson junction is the key device of superconducting quantum computation.The double angle evaporation technique was used to fabricate the Al/Al2O3/Al tunnel junctions. This technique has the advantage of allowing for creating of small junction overlaps with sizes down to submicron level with a relatively simpler progress and without breaking vacuum. In order to create the small junction overlaps, aluminum is evaporated at an angle to the substrate.As one of the only two pioneer national institutes in superconducting qubits research, we've done lots of work on the research of Al/Al2O3/Al tunnel junctions. The total work in this thesis will be introduced in three aspects below:(1) Uniform and electrically continuous films are critical to high quality barriers. We fabricated Al thin films on Si substrate by e-gun evaporation. In the process several problems were solved and parameters were explored. We observed Jc and AFM of the Al thin films.(2) For qubit application, we researched how electronic-properties of the Al/Al2O3/Al tunnel junction, including critical current density Jc and junction specific resistance Rc, depend on the oxygen pressure and the oxidizing time during the formation of the tunneling barrier. We adjusted the exposure condition by changing either the oxygen pressure or the oxidizing time during the formation of tunnel barriers.(3) High-quality Al/Al2O3/Al tunnel junctions with a low level of dissipation were successfully fabricated.High-quality Al/Al2O3/Al tunnel junctions were successfully fabricated by the barrier layer preparation conditions of the control of specific parameters with the double angle evaporation technique. The fabricated tunnel junctions with a low level of dissipation are suitable for qubit application. It laid a good foundation for preparation the circuit of superconducting qubits.