Investigation on Scadium Thin Films on Dispenser Cathodes

The emission performance and mechanism of Ba-W cathode coated with Sc film were studied. Results show that the cathode coated with Sc layer 200 nm in thickness shows better performance. After heat treatment at
$\boldsymbol{1500 \ ^{\circ}} \mathbf{C}$
in hydrogen, the cathode could provide an emission current density of
$\boldsymbol{21.07}\mathbf{A}/\mathbf{cm^{2}}$
at
$\boldsymbol{1150\ ^{\circ}}\mathbf{C}_{\mathbf{b}}$
. The surface analysis shows that Sc is partially oxidized during heat treatment, indicating that oxidation improves performance. The experiment results are consistent with the DFT calculated results, where the work function of 25% O-25% Ba adsorbed on the Sc surface is the lowest, which is 1.4877 eV, 1.8228 eV and 1.8210 eV on the Sc (002), Sc (100) and Sc (101) respectively.