A REFLECTION ELECTRON-MICROSCOPY INVESTIGATION OF THE DIVERGENCE OF THE MEAN CORRELATED DIFFERENCE OF STEP DISPLACEMENTS ON A SI(III) VICINAL SURFACE

A Si(111) vicinal (misorientation approximate to 0.6) is studied by in situ Reflection Electron Microscopy at 1173 K. A statistical study is done of the distances between pairs of m(th) neighbours in a step tra in. The mean correlated difference of the step displacements from thei r mean positions G(m) =< (u(i) - u(i+m))(2) > is determined as a funct ion of m. Evidence is given for the roughness of the surface. A logari thmic behaviour of G(m) versus m is demonstrated unambiguously up to m = 7. Quantitative agreement is found with the theoretical predictions of Villain, Grempel and Lapujoulade. For more distant pairs of steps a different behaviour is demonstrated: G(m) increases faster than Log( m), a fact already found by another author.