Applied Surface Science, Vol.190, No.1-4, 80-87, 2002
Observation of triangular terraces and triangular craters of CaF2 film on Si(111) substrate
We have investigated the growth mode and surface morphology of CaF2 film on Si(111)7 x 7 substrate by reflection high-energy electron diffraction (RHEED) using very weak electron beam and atomic force microscopy (AFM). It was found by RHEED intensity oscillation measurements and AFM observations that three-dimensional (3D) islands grow at RT; however, rather flat surface appears with two-dimensional (2D) islands around 300 degreesC. Especially, at high temperature of 700 degreesC, characteristic equilateral triangular terraces (or islands) with flat and wide shape grow with the tops directed toward [1 1 -2] of substrate Si(111). On the other hand, the desorption process of the CaF2 film due to electron stimulated desorption (ESD) was also examined. It was found that the ESD process at 300 degreesC forms characteristic equilateral triangular craters on the film surface with the tops (or corners) directed toward [-1 - 1 2] of substrate Si(111), provided that the film was grown at 700 degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.
Keywords:CaF2/Si(111);RHEED intensity oscillation;AFM;growth mode;morphology;electron-stimulated desorption