Surface density of states on the (0001) face of titanium

Size Effect in Photofield Emission

“…Until 1984, measurements revealing the photocurrent deviations were reported for a few (about five) different field emitters, four of which were tungsten tips and one was a barium covered tantalum tip. In three cases [2,13,25] the photocurrent deviations were noticed accidentally, and it is an additional argument indicating the microcrystal at the top of field emitter to be the source of the photocurrent oscillations. They were observed during the conventional measurement of the photocurrent curve, when the emitting microcrystal was suitably thin.…”

“…It is experimentally shown that a twice thinner microcrystal of titanium reveals twice less maxima of the density of states [25]. The titanium microcrystal at the apex of the tungsten field emitter is separated by the grain boundary, which forms Fig.…”

Densities of states of low-index surfaces of tantalum by photofield emission

“…[8]. Fine structure in the TED of the true photocurrent from a Ti microcrystal was detected in this way, and interpreted as being due to a size effect resonance [9]. This paper reports measurements of the TEDs of the true photocurrent from the (1 0 0), (1 1 0), and (1 1 1) facets of a Ta field emitter as a function of the applied electric field.…”

“…So the measured photocurrent is dominated by photofield emission at very low fields and by thermal field emission at very high fields. It follows that at very high fields the slope of the measured photocurrent characteristic approaches the slope of the field emission characteristic [9]. If the field emission characteristic (representing the thermocurrent) is scaled to match the measured photocurrent characteristic at a very high field, the difference between the two curves is the true photocurrent characteristic [8].…”

“…Instead, in the present work, the thermocurrent characteristic of each facet was for the first time measured directly by illuminating the tip with a focused laser beam in such a way that no light fell on the emitting facet, and the true photocurrent characteristic was extracted by subtracting the thermocurrent characteristic from the measured photocurrent characteristic. Differentiating the true photocurrent characteristic with respect to the energy of the barrier peak at the given field yields the total energy distribution of the photocurrent [8,9].…”