AVS 49th International Symposium
    Thin Films Friday Sessions
       Session TF-FrM

Paper TF-FrM4
Si@sub 1-y@C@sub y@/Si(001) Gas-source Molecular Beam Epitaxy from Si@sub 2@H@sub 6@ and CH@sub 3@SiH@sub 3@: Surface Reaction Paths and Growth Kinetics

Friday, November 8, 2002, 9:20 am, Room C-101

Session: Fundamentals of Thin Flm Growth
Presenter: Y.L. Foo, University of Illinois
Authors: Y.L. Foo, University of Illinois
K.A. Bratland, University of Illinois
B. Cho, University of Illinois
P. Desjardins, École Polytechnique de Montréal, Canada
J.E. Greene, University of Illinois
Correspondent: Click to Email
Si@sub 1-y@C@sub y@(001) alloy layers were grown by gas source molecular-beam epitaxy (GS-MBE) from Si@sub 2@H@sub 6@/CH@sub 3@SiH@sub 3@ mixtures as a function of C concentration y (0 to 2.6 at%) and deposition temperature T@sub s@ (500-600 °C). High-resolution x-ray diffraction reciprocal lattice maps show that all layers are in tension and fully coherent with their substrates. Film growth rates R decrease with both y and T@sub s@, and the rate of decrease in R as a function of y increases rapidly with T@sub s@. In-situ isotopically-tagged D@sub 2@ temperature-programmed desorption (TPD) measurements reveal that C segregates to the second-layer during steady-state Si@sub 1-y@C@sub y@(001) growth. This, in turn, results in charge-transfer from Si surface dangling bonds to second-layer C atoms, which have a higher electronegativity than Si. From the TPD results, we obtain the Coverage@sub Si*@(y,T@sub s@) of Si* surface sites with C backbonds as well as H@sub 2@ desorption energies E@sub d@ from both Si and Si* surface sites. Coverage@sub Si*@ increases with increasing y and T@sub s@ in the kinetically-limited segregation regime while E@sub d@ decreases from 2.52 eV for H@sub 2@ desorption from Si surface sites with Si backbonds to 2.22 eV from Si* surface sites. This leads to an increase in the H@sub 2@ desorption rate, and hence higher film deposition rates, with increasing y and/or T@sub s@ during Si@sub 1-y@C@sub y@(001) growth. This effect, however, is more than offset by the decrease in Si@sub 2@H@sub 6@ reactive sticking probabilities at Si* surface sites. Film growth rates R(T@sub s@,J@sub Si 2H6@,J@sub CH3SiH3@) calculated using a simple transition-state kinetic model, together with measured kinetic parameters, were found to be in good agreement with the experimental data.