TRANSMISSION ELECTRON MICROSCOPE STUDY OF INTERNAL STRESSES AT RECONSTRUCTED CLEAN AND METAL ADSORBED SURFACES

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Transmission electron microscopy (TEM) in an ultra-high vaccuum condition can reveal structures of surfaces and surface dynamic processes. One of the characteristics of the technique is in that it can characterize internal surface stresses at surfaces which are due to surface reconstruction. Most of the surface recon-structions and adosrbate structures, if it is free from the substrates are not always have the same lattice period with that of the substrate lattice underneath. This is the origin of the interna lsurface stresses. This causes bending of thin crystal films. Inversely, on the bend crystals surface structures or surface structure domians which favor such strain nominates. In the former cases, multi-domain formation does not cause bending even in cases of strong internal tress. TEM can see lattice strain caused by internal surface stress.Our observations were summarized as follows.(1) Si (111) 4x1-In structure does not have internal stress.(2) Si (001) 2x1 surface is anisotro … More pically stressed.(3) Si (111) 7x7 structure is under a delatational stress and phase boundaies between 7x7 and 1x1 structure have strong lattice strain.(4) Si (111) 5x2-Au surface has anisotropic lattice stress. Domain boundaies of the 5x2 structure have strong strain contrast in TEM images.(5) Steps on Si (111) have lattice strain parallel to the surface. This may be partly due to surface reconstruction.In the present reseach project we designed and constructed a electron microscope specimen holder by which we can apply strain on surfaces. It was found that Si specimen can be heated in-situ in the microsocpe up-to 1200ﾟC and surface strain of about 0.1% can be applied.With use of this holder, we could observe that Si (001) 2x1 domains domainate on the surface under a compressive strain and 1x2 domains dominate under a delatational strain. It was previously reported that a step up current causes major domains of 2x1 on Si (001) surface. However, it was found that current effect is weaker than the strain effect. Less