A LEED study of structures produced by H2 on (100) W

摘要: Abstract The LEED structures resulting from hydrogen adsorption on (100)W are studied as functions of coverage and surface temperature for temperatures above 78 °K. Coverages determined by flash desorption. Diffraction beam intensity profiles also examined. It is found that at 300°K the maximum c(2 × 2) pattern occurs 0.16 monolayer these beams vanish a 0.35. Splitting half-order begins attains distance 1 4 lattice spacing both 300 195 At °K observed, but no splitting occurs. When which has been heated to ~2500°K allowed cool below in ultrahigh vacuum, sharp intense characteristic configuration observed even though more than .01 adsorbed gases can be detected extra decreases with increasing appears function crystal alone. Treatment oxygen reduces this structure clean surface, after heating briefly hydrogen, again surface. suggested “clean” may due structural rearrangement tungsten or an state goes into solution upon heating. Since endothermic its solubility decreasing temperature, therefore migrate cooling accumulate there. implications results regard states discussed.