Epitaxial Electrodeposition of Pb-Tl-O Superlattices on Single-crystal Au(100)

Superlattices in the Pb-Tl-O system with modulation wavelengths varying from 5.2 to 18.9 nm were epitaxially electrodeposited on single-crystal Au(100) by periodically pulsing the current anodically between 0.05 and 5 mA/cm 2. The films were grown at room temperature from an aqueous solution of 0.005 M TlNO 3 and 0.1 M Pb(NO 3) 2 in 5 M NaOH. Bulk films deposited at current densities of 0.05 and 5 mA/cm 2 have compositions of approximately Pb 0.46Tl 0.54O 1.7 and Pb 0.74Tl 0.26O 1.9, respectively. X-ray diffraction (XRD) results show a strong [100] out-of-plane orientation for the electrodeposited films. Seven orders of satellite peaks are seen in the XRD pattern for a superlattice with a modulation wavelength of 18.9 nm. Azimuthal scans for the (111) reflection of Au and Pb-Tl-O show that the film is rotated 45° in-plane with respect to the substrate. The in-plane rotation of 45° reduces the lattice mismatch between the Au substrate and the deposited superlattice from 31% to -7.6%. An epitaxial relationship consistent with this rotation is Pb-Tl-O(100)[011]//Au(100)[010].