SINGLE-CRYSTAL ALIGNMENT METHOD FOR LEED EXPERIMENTS WITH UNGRADED TILT SAMPLE-HOLDERS

Good visual alignment of single crystal Cu(100)-p(1 x 1) and c(2 x 2)- Bi surfaces was obtained, with an ungraded tilt sample-holder, by iter atively varying (i) the current in three sets of orthogonal Helmholtz coils around the LEED chamber, and (ii) the sample tilt, at low and hi gh electron energies, respectively, until the observed diffraction pat terns were symmetric at all energies. LEED I-V profiles of beams nomin ally equivalent by symmetry are shown for a total of 16 nonequivalent beams, between the two surfaces investigated. For Cu(100)-c(2 x 2)Bi, where magnetic field elimination was more accurate than for clean Cu, comparison of integral order beams with their average resulted in R-2 factors of 0.02 or better.