Ion Channeling Study of Epitaxial Growth of α-Fe on H-Terminated Si (111) Surfaces

Abstract

ABSTRACTEpitaxial α-Fe films deposited on H-terminated Si(111) surfaces by electron beam evaporation in ultra high vacuum were studied using ion channeling/Rutherford Backscattering spectrometry (RBS). A 700 Å thick Fe film deposited on a Si(1 11) substrate at room temperature has a surface minimum yield, χmin, of 22% at 2 MeV energy of 4He+ ions along Si <111>. A rapidly increasing yield in the aligned spectrum with the depdi of the film shows the presence of defects throughout the film. The sharp lower energy edge of the Fe signal indicates the absence of an amorphous region or a suicide layer at the interface. This establishes epitaxial growth of iron film on Si(111), a result supported by x-ray diffraction and transmission electron microscopy studies. A 700 Å thick iron film deposited at 300 °C shows a surface minimum yield of 12%. Ion channeling/ backscattering spectra of 1400 Å and 3000 Å thick Fe films deposited at 300 °C on Si(111) substrates show a χmin of about 3% for both films, indicating a substantial reduction in the defect density in the thicker Fe films. Etching of Si(111) substrates in either a 10% HF solution or a NH4F solution does not change the crystalline quality of the iron films significantly.