(7X1) RECONSTRUCTION OF THE (1120) SURFACES OF HOLMIUM AND ERBIUM

We report the (7 x 1) reconstruction of the clean (112BAR0) surfaces of the lanthanide elements Ho and Er. For both elements low-energy electron diffraction showed a sharp sixfold symmetric pattern of spots, indicating a collapse of the ideal open surface to a close-packed structure very similar to a (0001) surface. The absence of any diffraction spots from the underlying ideal structure implies that the reconstruction is many layers deep. Angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) data taken from the reconstructed Ho(112BAR0)-(7 x 1) surface are found to be virtually indistinguishable from those taken from a Ho(0001) sample-minor discrepancies may be due to differing surface topographies of the samples. The stability of the ARUPS spectra with temperature implies that the Ho(112BAR0)-(7 x 1) surface remains reconstructed at temperatures up to 1000 K. By contrast, the spectra from Er(112BAR0) change considerably in the temperature range 800-1000 K. It is not yet known whether this is due to a transformation of the reconstructed surface back to its ideal structure or simply a roughening of the surface.