AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeA

Paper SS2-WeA5
Gas-Surface Reaction Dynamics at the Inorganic-Organic Interface

Wednesday, November 17, 2004, 3:20 pm, Room 210C

Session: Surface Collision Dynamics
Presenter: A. Dube, Cornell University
Authors: A. Dube, Cornell University
P.F. Ma, Cornell University
A.S. Killampalli, Cornell University
M. Sharma, Cornell University
J.R. Engstrom, Cornell University
Correspondent: Click to Email
Inorganic-organic interfaces play an important role in a number of technologies. Much of the work to date in the area of gas-surface reaction dynamics has involved study of the reaction of small organic molecules with transition metal surfaces. Here, we have chosen to examine the inverse problem: the reaction of coordination compounds of transition metals with model organic surfaces using supersonic molecular beam techniques. Such reactions are the first key step to barrier formation on organic surfaces, and they may result in a superior method for the formation of contacts to molecular electronics. In the work we report here we examine explicitly the reaction of Ti- and Ta- containing coordination compounds with a variety of self-assembled monolayers (SAMs) possessing different terminal endgroups (e.g.,-CH@sub 3@,-OH, -NH@sub 2@,-COOH), using both HX-R-SiCl@sub 3@/SiO@sub 2@ and HX-R-SH/Au based SAM chemistries. For example, for the reaction of Ti[N(CH@sub 3@)@sub 2@]@sub 4@ and for molecular kinetic energies E@sub i@ = 0.5-2.0 eV, we find that the reaction probability on -OH and -NH@sub 2@ terminated R-SiCl@sub 3@/SiO@sub 2@ type SAMs passes through a minimum, near E@sub i@ ~ 1 eV. Since we have shown in other work that penetration of the SAM by the coordination compound is possible, these results suggest that penetration is enhanced at sufficiently high E@sub i@. On the other hand, variation of both the substrate temperature and the angle of incidence indicates that reaction with these two terminal endgroups follows a trapping-mediated chemisorption channel. In selected cases we also make comparison to results from ab initio quantum chemistry calculations of the potential energy surface. For example, these calculations are consistent with a barrier near the vacuum level for the reaction on -OH terminated SAMs, which we observe experimentally, yet they suggest that reaction with an isolated -NH@sub2@ may be activated by as much as 15 kcal-mol@super -1@.