Image of the Month

August 2013

Surface concentration dependent structures of iodine on Pd(110)


Atomically resolved STM images from the Pd (110)-Ic(2×2) phase together with atomic structure models. Atomic distances are 5.5 Å in (−110) and 4.8 Å in (−111). The long red arrow points along (−110).

STM image of mixed the c(2×2) and q-hex phases.

Reference: J. Chem. Phys. 137, 204703 (2012); doi: 10.1063/1.4768165

Credits: Mats Göthelid, Michael Tymczenko, Winnie Chow, Sareh Ahmadi, Shun Yu, Benjamin Bruhn, Dunja Stoltz, Henrik von Schenck, Jonas Weissenrieder, and Chenghua Sun. – Materialfysik, ICT Electrum 229, Kungliga Tekniska Högskolan (KTH) and Australia Institute for Bioengineering and Nanotechnology, The University of Queensland

Microscope: RHK VT UHV STM/AFM Model UHV3500

Control System: RHK Technology SPM1000

Abstract: We use photoelectron spectroscopy, low energy electron diffraction, scanning tunneling microscopy, and density functional theory to investigate coverage dependent iodine structures on Pd(110). At 0.5 ML (monolayer), a c(2 × 2) structure is formed with iodine occupying the four-fold hollow site. At increasing coverage, the iodine layer compresses into a quasi-hexagonal structure at 2/3 ML, with iodine occupying both hollow and long bridge positions. There is a substantial difference in electronic structure between these two iodine sites, with a higher electron density on the bridge bonded iodine. In addition, numerous positively charged iodine near vacancies are found along the domain walls. These different electronic structures will have an impact on the chemical properties of these iodine atoms within the layer.