Study of the first stage of PbSe growth on Se-terminated CaF2 surface

Heterostructures of IV-VI compounds, such as epitaxial films of PbSe grown on Si(111) via a CaF2 layer, have been the object of increasing scientific interest in the last few years because of their detection properties, A monolithic integration of the I-R detection functions is possible on an Si conventional read-out electronics. The high mismatch and the difference of the thermal expansion coefficients between Si and PbSe require the use of a buffer layer of CaF2. The CaF2/Si(111) interface has been widely studied but PbSe/CaF2 belongs to a group of interfaces which has been rarely studied. Annealing of the CaF2 surface under Se flux in the range 200-600 degrees C shows the incorporation of Se into the CaF2 surface at a temperature higher than the growth temperature. The Se incorporation increases the stability of the CaF2 surface, avoids its oxidation and creates nucleation sites for PbSe. The optimization of the subsequent buffer layer is a key problem in the growth process. On a Se-terminated CaF2 surface, the first stage of the PbSe nucleation has been studied by AES, RHEED, XPS and AFM. (C) 1998 Elsevier Science B.V.