STRUCTURE ANALYSIS OF CoSi2/Si1-xGex/Si(001) INTERFACES. M. Rodewald, TH Darmstadt, FB21, FG Strukturforschung, Petersenstr. 20, D64287 Darmstadt, Germany

In the last decade silicide growth and silicide/silicon interfaces have become of interest in solid state science because epitaxial metal silicides are a promising material for novel micro-electronic devices like the metal-base and the permeable base transistors.

In the present investigation monocrystalline (001) oriented films of CoSi2 have been formed on Sil-xGex/Silicon(001) heterostructures with Ge-contents up to 25at.% by molecular beam epitaxy (1). The atomic structure of the CoSi2/Sil-xGex interface has been investigated by high resolution electron microscopy (HREM) combined with image contrast simulations.

A domain-like structure is observed consisting of areas with different interface structure interconnected with steps. Two different atomic structure models for the different interface areas have been found by comparison of simulated and experimental images. In the first model evidence for a 2x1 (and 1x2) interface reconstruction was found. This interface reconstruction is different from the already known interface reconstruction of CoSi2/Si(001) interfaces (2, 3). In the second model the Co-atoms are 6fold coordinated at the interface and the tetrahedral coordination of the silicon atoms is everywhere maintained. This model is well known from CoSi2/Si(001) interfaces.

1. Schäffer, C., Rodewald, M., J. Cryst. Growth, in press

2. Loretto, D., Gibson, J. M., Yalisove, S. M., Phys. Rev. Lett. 63(3) 298-301 (1989)

3. Bulle-Lieuwma, C. W. T., De Jong, A. F., Vandenhoudt, D. E. W., Phil. Mag. A64(2) 255-280 (1991)