Comparing e-beam to magnetron sputtered a-Si with an eye toward eliminating Two-Level Systems

It has previously been shown that amorphous silicon (a-Si) thin films can be produced that are free of tunneling Two-Level Systems (TLS) by e-beam depositing the films at elevated substrate temperatures, and there appears to be a strong correlation between the density of these films and the number of TLS. We have prepared higher-density films using magnetron sputtering at elevated temperatures comparable to those used in the e-beam studies. Here, we compare the atomic densities measured using RBS, and the number of TLS calculated using internal friction measurements at cryogenic temperatures of magentron sputtered a-Si flms to those of the e-beam prepared films.