ON THE NATURE OF CROSS-HATCH PATTERNS ON COMPOSITIONALLY GRADED SI1-XGEX ALLOY LAYERS

The effect of strain relaxation on the surface morphology of compositi onally graded Si1-xGex layers grown at 550-degrees-C has been investig ated by a combination of transmission electron and atomic force micros copy. By annealing unrelaxed graded layers, we have found that shear d isplacements caused by dislocation glide roughen the surface dramatica lly. This effect is attributed to the formation of a network of disloc ation clusters which give rise to the pronounced slip-band pattern on the surface of the graded layers. It is shown that the surface plastic displacements produced by such a network during growth of the graded layer contribute significantly to the formation of the cross-hatch pat terns.