ORDERING OF MISSING-ROW-DEFECTS FORMING (2XN)-BI PHASES ON THE SI(100) 2X1 SURFACE STUDIED BY THE SCANNING TUNNELING MICROSCOPY

(2 x n)-Bi phases formed on the Si(100) 2 x 1 surface are studied by LEED and scanning tunneling microscopy. A series of well ordered (2 x n) superlattices, with n ranging from 5 to 12, are observed. The STM images show that the (2 x n) structures result from the formation of the periodic arrays of the missing Bi-dimer rows. The n of the (2 x n) structure is found to depend on the Bi coverage theta with a relationship of theta = 1 - 1/n. However, for the phases with n smaller than 5, the ordering of missing rows in the ''n'' direction is found to be disturbed by the competing formation of rectangular and linear type defects. The formation of successive (2 x n) phases as a function of coverage suggests the presence of strong long range repulsive elastic interactions among missing Bi-dimer rows.