Fig.1 Josephson junction

Fig.1 Josephson junction

A Josephson junction is made of two superconductors separated by a thin insulating barrier. In superconducting metal, electrons are bound together forming bosonic particles called Cooper pairs, which can tunnel through the barrier and generates super-current through the Josephson junction. The Josephson junction can act as a nonlinear inductor which is a function of its current.

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Applications of the Josephson junction

Fig.2 Superconducting qubits made of Josephson junctions

Fig.2 Superconducting qubits made of Josephson junctions

Superconducting Qubit

Using the nonlinearity of Josephson junction to make the energy of LC circuit to be anharmonic with unequally spacing. Thus, we can use the two lowest energy levels as a qubit.

Fig.3 SQUID [Marcon&Ostanina, PIERS Proceedings, 2012.]

Fig.3 SQUID [Marcon&Ostanina, PIERS Proceedings, 2012.]

SQUID Magnetometer

Superconducting quantum interference device or SQUID is made of two Josephson junctions placed in parallel on a closed loop. The voltage of this loop is a function of flux through the loop. We can use the properties to identify a tiny magnetic field applied to the ring by probing the change of its voltage. The resolution is about one quantum flux which is $2.07 \times 10^{-15}$ Wb.

Our work

In this work, we would like to study the $Al/Al_2O_3/Al$ Josephson junction fabrication using Electron Beam Lithography (EBL) at BL6, Synchrotron Light Research Institute (SLRI). The EBL is a techniques of drawing custom patterns on a surface with nanometre resolution by using a focused electron beam.

Fig.4 Our design of each layer of Josephson junction

Fig.4 Our design of each layer of Josephson junction

Fig.5 EBL machine at BL6

Fig.5 EBL machine at BL6

Fig.6 EBL’s chamber view

Fig.6 EBL’s chamber view