  Under the challenge of growing a single bilayer of Bi oriented in the (111)
crystallographic direction over amorphous substrates, we have studied different
thicknesses of Bi thermally evaporated onto silicon oxide in order to shed
light on the dominant atomic structures and their oxidation. We have employed
atomic force microscope, X-ray diffraction, and scanning electron microscope
approaches to demonstrate that Bi is crystalline and oriented in the (111)
direction for thicknesses over 20 nm. Surprisingly, Raman spectroscopy
indicates that the rhombohedral structure is preserved even for ultra-thin
layers of Bi, down to $\sim 5$ nm. Moreover, the signals also reveal that
bismuth films exposed to ambient conditions do not suffer major surface
oxidation.
