Probe-hole field emission microscopy has been used to study submonolay
er and monolayer amounts of iron on various tungsten planes. The adsor
ption is found to be insensitive to the substrate deposition temperatu
res of 300, 600, and 1100 K as seen by the variation of the workfuncti
on and the pre-exponential factor with the adsorbate doses. The workfu
nction of the adsorbate covered surface reduces in case of the (110),
(100), and (112) tungsten planes, while it increases in case of the (1
11) and (116) planes, becoming coverage independent with a workfunctio
n of 4.6 eV. This has been attributed to surface alloying of iron atom
s with tungsten because of the stricture of these two planes. The resu
lts are discussed in the light of the existing experimental results on
metallic adsorbates on tungsten.