1/ f noise and two-level systems in MBE-grown Al thin films

TL;DR

This study compares 1/f noise and TLS densities in MBE-grown versus evaporated aluminum thin films, showing MBE films have significantly lower noise and TLS densities, which benefits electronic and quantum device performance.

Contribution

It provides the first detailed comparison of TLS energy distributions and 1/f noise in MBE-grown and evaporated Al films, highlighting the advantages of MBE growth.

Findings

MBE-grown Al films have about three times lower noise at 300 K.

TLS densities in MBE films are about ten times lower than in evaporated films.

1/f noise is generated by thermally activated TLS at grain boundaries.

Abstract

Aluminum thin films are essential to the functionalities of electronic and quantum devices, where two-level systems (TLS) can degrade device performance. MBE-grown Al films may appeal to these applications due to their low TLS densities. We studied the energy distributions of TLS densities, g(E), in 10-nm-thick MBE-grown and electron-beam evaporated Al films through 1/f noise measurements between 80 and 360 K. At 300 K, the noise magnitudes in MBE-grown films are about three times lower than in the electron-beam evaporated films, corresponding to the g(E) values about ten times lower in the former than in the latter. Compared with previously established observations, we identified that the 1/f noise was generated by thermally activated TLS at grain boundaries.