Strained epitaxial interfaces of metal (Pd, Pt, Au) overlayers on nonpolar CdS (1 0 (1)over-bar 0) surfaces from first-principles

摘要

The depositions of (1 1 1) and (1 0 0) overlayers of Pd, Pt and Au on the CdS (1 0 (1) over bar 0) surface are studied within epitaxial mismatches of 6%-7%, using spin- polarized density functional theory. For both compressively strained and tensile-strained interfaces, the (1 0 0) overlayers were found to be thermodynamically more stable owing to better interfacial matching, and higher surface uncoordination resulting in higher reactivity. Pt(1 1 1) exhibits slip dislocations even for five-atomic-layer thick Pt slabs. Along with the leading metal-S interaction, the interfacial charge transfers indicate a weak metal-Cd interaction which decreases in strength in the order Pd > Pt similar to Au. For the same substrate area, the accumulation of electronic charge for Pt overlayers is similar to 1.5-2 times larger than that of Pd and Au. The n-type Schottky barriers of Au overlayers with the minimum mismatch are within 0.1 eV of the predictions of Schottky-Mott rule, indicating a relatively ideal, scantily reactive interface structure. This is in clear contrast to the Pt epitaxial overlayers which deviate by 0.6-0.8 eV.