STUDY OF THE FIRST STAGE OF PBSE GROWTH ON SE-TERMINATED CAF2 SURFACE

Heterostructures of IV-VI compounds, such as epitaxial films of PbSe g rown on Si(111) via a CaF2 layer, have been the object of increasing s cientific interest in the last few years because of their detection pr operties, A monolithic integration of the I-R detection functions is p ossible on an Si conventional read-out electronics. The high mismatch and the difference of the thermal expansion coefficients between Si an d PbSe require the use of a buffer layer of CaF2. The CaF2/Si(111) int erface has been widely studied but PbSe/CaF2 belongs to a group of int erfaces which has been rarely studied. Annealing of the CaF2 surface u nder 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 temp erature. The Se incorporation increases the stability of the CaF2 surf ace, avoids its oxidation and creates nucleation sites for PbSe. The o ptimization of the subsequent buffer layer is a key problem in the gro wth process. On a Se-terminated CaF2 surface, the first stage of the P bSe nucleation has been studied by AES, RHEED, XPS and AFM. (C) 1998 E lsevier Science B.V.