Abstract
Interfacial reactions of Y and Er thin films on both (111) and (001)Si have been studied by transmission electron microscopy, high resolution TEM as well as scanning electron microscopy. Epitaxial YSi2-x thin films were found to form on (111) and (001)Si at a deposition temperature of 500 ℃ in an ultrahigh vacuum (UHV) e-beam evaporation chamber. The orientation relationships between YSi2-x and (111)Si were determined to be [0001]YSi2-x//[111]Si and (10 0)YSi2-x//( 2)Si. On the other hand, the orientation relationships between YSi2-x and (001)Si were determined to be [0001]YSi2-x//[1 0]Si, (1 00)YSi2-x//(001)Si and [0001]YSi2-x//[ 0]Si, (1 00)YSi2-x//(001)Si. Extra diffraction spots with streaking were observed. The extra spots are attributed to the formation of an ordered vacancy superstructure. The streaking of extra spots is resulted from the formation of out-of-step structures with a range of M values. From a combination of studying planview and cross-sectional TEM samples, the 3-dimensional vacancy ordering structures were determined. After annealing at various temperatures for 1 min by rapid thermal annealing, the range of M values was found to narrow down with annealing temperature. On the other hand, the 3-dimensional vacancy ordering structures were found to change with annealing temperature.Epitaxial ErSi2-x thin films were found to form on (111) and (001)Si by UHV e-beam deposition and subsequent rapid thermal annealing. Similar behaviors of vacancy ordering structures were found to occur in ErSi2-x/(111)Si and ErSi2-x/(001)Si systems as those in YSi2-x/(111)Si and YSi2-x/(001)Si systems.Planar defects in YSi2-x and ErSi2-x thin films were analyzed to be stacking faults on {10 0} planes with 1/6< 2 3> displacement vectors. The density of stacking faults was found to decrease with the annealing temperature. Double-domain epitaxy was found to form in YSi2-x/(001)Si and ErSi2-x/(001)Si systems. The domain size was found to increase with the annealing temperature. A high density of pinholes was found in epitaxial YSi2-x thin films. The growth of pinhole free epitaxial ErSi2-x thin films on (111)Si was carried out by capping an a-Si layer with appropriate thickness prior to the subsequent annealing. The double heteroepitaxial structures were grown in a UHV e-beam deposition chamber. The major defects in the overgrown Si layer were found to be the microtwins.