Misoriented Epitaxial Growth of (111)CoSi ₂ on Offset (111)Si Substrates

Abstract

Single crystal epitaxial films of CoSi₂ were grown by MBE on various (111)Si single crystal substrates, whose surfaces were purposely tilted towards the < 110>>_g, direction by small angles ϕ_g,†, 0°, ≤ϕ_g, ≤, 4° measured between the surface normal and the < 111>>_g, direction of Si. The actual offset angle, .ϕ₈,, was determined by back Laue reflection method. The average perpendicular strain of the CoSi₂ epilayer, ε^┵, and the < 111 >_f orientation of the epitaxial CoSi₂ film were determined by double crystal diffractometry. We find that the misorientation angle, a, measured between the Si < 111>_g, and CoSi₂ < 111>_f directions, increases linearly with the offset angle, ϕ_g, up to ϕ^g, = 4°. A simple geometrical model is developed which predicts that α = ε┵ × tan ϕ_g,. The model agrees quantitatively with the experimental data. The equivalent strain energy associated with the misorientation is approximated by that of a low angle tilt boundary. The misorientation angle α of the equilibrium state, determined by minimizing the total strain energy of the epitaxial film, is nonzero in general.