Molecular adsorption, foreign atom incorporation, and the formation of superstructures on Si(001)

1 February 2007 (Thur), 3:30 pm - 4:30 pm

6F seminar room, Sengen site

Prof. Hanchul Kim

Korea Research Institute of Standards and Science

Molecular adsorption, foreign atom incorporation, and the formation of superstructures on Si(001)

The Si(001) surface constitutes the most important substrate in the current semiconductor industry, and the decreasing size of the devices demand to develop the atomic-scale controllability. A prerequisite for such an atomic level control is to understand the behavior of the foreign atoms near the surface. In this presentation, I would like to describe a comprehensive understanding on the behavior of carbon atoms, which is achieved by the ab initio pseudopotential total energy calculations and verified by high-resolution scanning tunneling microscopy experiments. The adsorption of small molecules on Si(001) seems to be an apparently easy problem, and has been believed to be fully understood in many cases. Our studies on acetylene (C2H2) and ammonia (NH3) molecules demonstrate that the adsorption structures have only been partly understood. The existence of dimers on Si(001) makes the problem more versatile, and there are multiple adsorption configurations. The adsorbed molecules may be used as a source of foreign atoms upon an appropriate thermal treatment. The dissociated foreign atoms usually modifies the substrate and sometimes produce superstructures on Si(001). In the second half, I would like to focus on the carbon-induced modification of Si(001) and the identification of the atomic structure of the carbon-induced superstructures: 2 xn and c(4 x4). Our study lessons that a careful and accurate investigation is necessary to understand the atomic processes, which is a prerequisite for developing the atomic level controllability.

Dr. Taizo Sasaki (佐々木泰造)