Growth Rates

The growth rate is calibrated using XRR. The Bi films are usually too thin to see in cross-sectional SEM. The ellipsometer does not have a good model for Sb (or, in fact, for most anisotropic materials).

The Bi growth rates are relatively well calibrated. The Bi1-xSbx ones need more work to iron out the composition dependence, but can roughly be approximated by the total BEP of both Sb and Bi combined with the Bi BEP / GR conversion.

I prefer to relate the thickness directly to the BEP rather than going through the intermediate flux calculation, since 1) they're very similar numbers, and 2) the substitutional alloy thing with the BiSb and the weird A7 Bi / Si(111) alignment (see Nagao 2004) means you have to confirm the composition with XPS rather than getting it from XRD.

Bi droplets form on the surface at higher growth rates (> 0.06 A/s) and substrate temperatures (>30 C). Make sure you are doing large area AFM scans and wide-angle XRD scans to check for this.

Bi growth rates at 30 C

GR (A/s) = 0.0305* BEP (x1E-8)

Bi growth rates at 10 C

Bi growth rates at 100 C