X-RAY SCATTERING FROM CRYSTALLINE SiO₂ IN THE THERMAL OXIDE LAYERS ON VICINAL Si(111) SURFACES. T. Shimura, H. Misaki and M. Umeno, Department of Material and Life Science, Graduate School of Osaka University, 2-1 Yamadaoka, Suita 565, Japan.

Bragg reflections were observed from the crystalline SiO₂ in the thermal oxide layers on vicinal Si(111) surfaces, of which surfaces were tilted 4 degree from the <111> toward the <1 1 -2>. The oxide layers were prepared by oxidizing the Si wafers at 950C in a dry oxygen atmosphere. The thicknesses of the oxide layers were 760A, 340A and 230A.In the X-ray diffraction patterns from these samples, very weak peaks were observed on the lower angle sides of the CTR (crystal truncation rod) scatterings around the 111 Bragg points, of which position is nearly 0.42,0.42,0.51 in the reciprocal space. The intensity of the peak depends on the thickness of the oxide layer, and the peak is not observed in the etched sample. A high resolution measurement of the intensity around the peak using a synchrotron radiation source revealed that the profile had Laue-function-like oscillation fringe pattern, of which period corresponded to the inverse of the film thickness. From these results it was concluded that these peaks were Bragg peaks originated from the crystalline SiO₂, which coexisted in the amorphous SiO₂ film having an epitaxial relationship with the Si substrate.

Furthermore, another Bragg reflection from the crystalline SiO₂ was observed on the low angle side of the CTR scattering from the 1 1 -1 Bragg point, of which position was nearly 0.74 0.74 -1.22 in the reciprocal space. With these two reflections the atomic structure model of the crystalline SiO₂ could be constructed.