MISORIENTED EPITAXIAL GROWTH OF (lll)CoSi2 ON OFFSET (lll)Si SUBSTRATES

Single crystal epitaxial films of CoSi2 were grown by MBE on various (111)Si single crystal substrates, whose surfaces were purposely tilted towards the < 1IO >, direction by small angles 4>, t, 0° :54>, :5 4°, measured between the surface normal and the < 111 >. direction of Si. The actual offset angle, 4>,, was determined by back Laue reflection method. The average perpendicular strain of the CoSh epilayer, £.l, and the < 111 > 1 orientation of the epitaxial CoSi2 film were determined by double crystal diffractometry. We find that the misorientation angle, a, measured between the Si < 111 >, and CoSi2 < 111 > 1 directions, increases linearly with the offset angle, 4>., up to 4>, = 4°. A simple geometrical model is developed which predicts that a = E.l x tan t/r,. 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 a of the equilibrium state, determined by minimizing the total strain energy of the epitaxial film, is nonzero in general.