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 CaF2/Si(111) surface have been carried out. The growth was performed using molecular beam epitaxy. The different surface morphologies of Bi on CaF2 are demonstrated. With an increase in temperature from room temperature to 200 degrees C, Bi undergoes a morphology change from planar to island-like, with a tendency to enlargement. At temperatures of 100-125 degrees C, two types of nanowires with different geometric parameters are observed. Bi nano-island nucleation on a grooved and ridged CaF2/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.