Formation of three-dimensional silicon mounds on the Si(111) 7 x 7 surfaceusing the tip of a scanning tunneling microscope

Truncated triangular silicon pyramids are fabricated one by one on the Si(1 11) 7 x 7 surface in the temperature range from 400 degreesC to 500 degrees C. Two types of three-dimensional (3D) silicon mounds are fabricated with a mirror symmetry against the [(1) over bar 11] direction. One type consists of normal stacking mounds with {311} and {221} on the side facets and a (1 11) on the top surface. The other type consists of silicon Mounds with a st acking fault at the interface between the silicon mounds and the substrate surface, which have {311} facets. {331} facets and a (111) facet. Normal st acking mounds are produced with a probability of 75%. Silicon mounds with a stacking fault are produced with a probability of 25%. The difference in t he formation energy between normal stacking mounds and silicon mounds with a stacking fault is about 0.07eV per 1 x 1 unit cell at 500 degreesC. Silic on mounds are fabricated with large tunneling currents and sample bias volt ages near 0V. During the production of silicon mounds, the scanning tunneli ng microscope (STM) tip moves away from the substrate surface by about 26 n m. The production rates of silicon mounds are 120 +/- 10s(-1) at 440 degree sC, 220 +/- 20s(-1) at 465 degreesC and 570 +/- 80s(-1) at 485 degreesC. Th e activation energy required for the production of silicon mounds is 1.3 +/ - 0.1 eV and the pre-exponential factor is 4 x 10(11 +/-1)s(-1).