Tawshia Chowdhury

Major: Electrical Engineering
Mentors: Teun van Schijndel, Professor Christopher Plamstrøm

Scanning Tunneling Microscopy Study of Cryogenic Aluminum Growth on Silicon

Scanning tunneling microscopy (STM) has been used to study the growth of Al(111) film on a Si(111)-7x7 surface reconstruction using molecular beam epitaxy (MBE) at room temperature and cryogenic temperature. Aluminum on silicon is among the material systems that have been used to achieve state-of-the-art qubit coherence times. Additionally, ultra thin films of Al have been shown to demonstrate enhanced superconducting transition temperatures. For this reason, research into the interfacial relations between silicon and aluminum at low temperatures and the early stages of Al growth is of interest. In particular, we aim to understand and improve the thin film quality, as surface smoothness could potentially enhance the superconducting properties and qubit coherence that is preferred in superconducting quantum devices. In this study, we observed that if the aluminum film is grown on a silicon substrate under low-temperature MBE conditions, it will form a smooth 2D thin film. Through varied growth conditions such as temperature and monolayer thicknesses, we studied the transformation of the surface morphology. Our findings show that low temperature growth followed by annealing at room temperature leads to atomically flat surfaces, which can potentially enhance the performance of superconducting qubit devices.