New Development of Ultrahigh-Vacuum Oriented-Molecular-Beam Machine and Its Application to Chemical Reactions on Silicon Surface

Abstract

The stereochemical control of surface reactions is one of the ultimate goals of surface scientists. An oriented-molecular-beam technique based on the Stark effect of a molecule in an inhomogeneous hexapole electrostatic field is a potential tool for achieving such a goal. This technique allows us to select a specific rotational quantum state and also an orientation of a reagent molecule. We have designed, built and tuned up a new UHV-compatible oriented-molecular-beam machine for the elucidation of the reaction dynamics on surfaces and for surface manufacturing application. In the dissociative adsorption of CH 3 Cl on a Si{100} surface, we found a dynamical steric effect on the initial sticking probability ( S 0 ) using the new machine. S 0 in Cl-end collision is larger than that in CH 3 -end collision at an incident energy of 120 meV. To our knowledge, this is the first measurement of the steric effect in the chemisorption of a molecule on a Si surface.