Surface atoms in Sc–O/W(1 0 0) system as Schottky emitter at high temperature

The chemical bonding state of surface atoms in the Sc–O/W(1 0 0) system as a Schottky emitter was investigated at high temperature using a profile of Auger electron peaks to elucidate the mechanism of the marked reduction of the work function of the Sc–O/W(1 0 0) Schottky emitter. For this, Sc-deposited W(1 0 0), oxygen-exposed W(1 0 0) and Sc surfaces were prepared as reference surfaces. A comparison of the profiles of the Auger electron peaks from the Sc–O/W(1 0 0) surface with those from the reference surfaces has revealed that oxygen and Sc atoms on the Sc–O/W(1 0 0) surface form the Sc–O complexes at the operating temperature of the Sc–O/W(1 0 0) emitter of 1400 K. In addition, the ratio of the number of Sc atoms to that of oxygen atoms is estimated as 1:1 by the quantitative analysis of the AES peaks. The present results strongly suggest that the work function of the Sc–O/W(1 0 0) emitter is caused by the formation of Sc–O electric dipoles aligning into the p(2 × 1)–p(1 × 2) double-domain structure [Surf. Sci. 523 (2003) L37] on the Sc–O/W(1 0 0) surface at the operating temperature.