Epitaxial growth of bismuth on CaF₂/Si(111): from planar films to self-organized arrays of nanostructures

Bismuth nanostructures are quite attractive in the area of colorimetry and semiconductor nanoelectronics because of their multi-coloured luminescence and quantum confinement. In this work, detailed studies of the crystalline structure and surface morphology of bismuth nanostructures grown on a planar CaF 2 /Si(111) surface have been carried out. The growth was performed using molecular beam epitaxy. The different surface morphologies of Bi on CaF 2 are demonstrated. With an increase in temperature from room temperature to 200°C, Bi undergoes a morphology change from planar to island-like, with a tendency to enlargement. At temperatures of 100–125°C, two types of nanowires with different geometric parameters are observed. Bi nano-island nucleation on a grooved and ridged CaF 2 /Si(001) surface was also studied. X-ray diffraction analysis shows an ordered multiple-domain growth character in all cases. Precise analysis of nanowire and island faceting based on a combination of scanning and transmission electron microscopy and X-ray diffraction simulations has been carried out.