Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1480587 | Journal of Non-Crystalline Solids | 2015 | 6 Pages |
Abstract
In e-beam evaporated amorphous silicon (a-Si), the densities of two-level systems (TLS), n0 and P¯, determined from specific heat C and internal friction Qâ 1 measurements, respectively, have been shown to vary by over three orders of magnitude. Here we show that n0 and P¯ are proportional to each other with a constant of proportionality that is consistent with the measurement time dependence proposed by Black and Halperin and does not require the introduction of additional anomalous TLS. However, n0 and P¯ depend strongly on the atomic density of the film (nSi) which depends on both film thickness and growth temperature suggesting that the a-Si structure is heterogeneous with nanovoids or other lower density regions forming in a dense amorphous network. A review of literature data shows that this atomic density dependence is not unique to a-Si. These findings suggest that TLS are not intrinsic to an amorphous network but require a heterogeneous structure to form.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
D.R. Queen, X. Liu, J. Karel, H.C. Jacks, T.H. Metcalf, F. Hellman,