Comparison of planar to columnar transformation of PtSi layers on Si(001) and Si(111) substrates in the Si capping layer growth process

Highly oriented PtSi layers were grown on both (001) and (111) Si substrates heated to 500° C by codeposition of Pt and Si with a stoichiometric ratio (Pt/Si=1/1) in an ultrahigh vacuum (UHV). On Si(001) substrates, the PtSi layer consists of two types of grains, PtSi(110)łSi(001) with azimuthal orientation of PtSi[001]łSi , whereas it consists of three types of grains on Si(111) substrates, PtSi(010)łSi(111) with PtSi[001]łSi. When Si was subsequently grown on the PtSi layer at temperatures lower than 400° C for Si(001) and lower than 500° C for Si(111), Si/PtSi/Si double heterostructures were obtained. However, above these temperatures, each grain forming the PtSi layer transformed into a columnar shape in the process of Si growth so as to minimize the contact area between PtSi and Si, and the space between the PtSi columns was filled epitaxially by Si.