Surface States on Tungsten

There have been sevex'al recent theoreti. cal papers predicting that surface states can exist in d-band metals near the cx'ossover of s and d bands of the same symmetry. ' ' This paper reports the first direct experimental evidence of surface states on clean single-crystal faces of tungsten. Total energy di.stributions of field emitted electrons from single-crystal planes reveal surface-dependent electronic structure in good agreement with the surface state model of Forstmann, Pendry, and Heine. " The agreement is especially striking on the (100) plane where the relativistic energy-band calculations of Loucks' can be applied. The total energy distribution of field-emitted electrons from a single-crystal plane of a freeelectron metal is' j,'(e) =As "/" /(1+e "~' ),