Photolithographic Development of MgB2/MgO/MgB2 Josephson Junctions

Posted July 26th, 2011 at 5:19 pm.

Abstract: Valerie Galstad

Mentor: Xuemei Cheng

A strong drive for technological advancement and increased demand for Internet speed and efficiency have made nanoelectronics a very important field of research. With the use of superconductors in nanoelectronics comes more energy efficient electronics capable of faster operational speeds and durability. A Josephson junction is the design of two superconductors with a non-conducting material sandwiched between. This particular design has allowed the development of superconducting quantum interference devices (SQUIDs), single-electron transistors, and various other quantum electronic devices. MgB2 is such an efficient superconductor due to its higher energy pi gap and high critical temperature. These qualities allow MgB2 to operate at faster speeds and at higher temperatures, decreasing necessary cooling power in a device.

I intend to use photolithography, among other processes, to fabricate MgB2/MgO/MgB2 Josephson junctions. The method in which one creates the junction begins by depositing an MgB2 layer 100 nm thick using Hybrid Physical-Chemical Vapor Deposition (HPCVD). A very thin layer (1-2 nm) of MgO is then deposited on the sample with RF magnetron sputtering. Another layer of MgB2, 75 nm thick, is then deposited on the sample before it is covered with gold to discourage degradation of the superconductor. The sample is coated in a thin photoresist layer via spinning, and is heated before the photolithographic process can take place. The sample goes through a multi-step process beginning with exposure to UV radiation on a Mask Aligner, which patterns the sample. The sample then is developed in 351 developer, heated, goes through three ion etching steps, deposited with gold again, covered in an insulating MgO layer, and washed with acetone before it is ready for measuring.

Photolithography lets us create very small, intricate, and accurate patterns. It is utilized in the creation of integrated circuits, circuit boards, and waveguides, which are present in most electronic devices and modern technology. Due to widespread interest in technological development the skill of photolithography will most certainly prove to be a useful one. It is my goal to master the task of photolithography in order to improve the efficiency of Josephson junctions and the technology that so heavily relies on them.

Filed under: 2011,Cheng, Xuemei,Galstad, Valerie by Michelle Han

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