Examination of chemisorbed overlayers on a well-defined platinum(111) surface with atomic resolution scanning tunneling microscopy in air and in solution

Shueh-Lin Yau, Purdue University

Abstract

Chemisorbed overlayers on a well-defined Pt(111) surface have been investigated by STM in air and in solution. High quality STM atomic resolutions were used to determine the halogen adlattices on a Pt(111) surface. Three halogen overlayers, ($\sqrt{7}$ $\times$ $\sqrt{7}$)$R19.1\sp\circ$, asymmetric (3 x 3), and hexagonal (3 x 3), were found even though Br and Cl also form (4 x 4) and (3$\sqrt{3}$ x 3$\sqrt{3}$)$R30\sp\circ$ structures on Pt(111). The registries of halogen were assigned by the three dimensional atomic resolutions which were obtained in air. This study demonstrates the capability of STM to provide new structural information which has been very difficult to obtain otherwise. In situ STM imaging techniques are also explored for studying the interfacial electrochemistry at a clean Pt(111) electrode surface. The atomic resolution of Pt(111)- ($\sqrt{3}$ $\times$ $\sqrt{3}$)$R30\sp\circ$ adlattice accounts for the first demonstration of in situ STM to study electrochemical processes on an atom-by-atom basis. In situ STM techniques were used to investigate the phase transition within the Br adlattices on Pt(111), the underpotential deposition processes of Cu onto an iodine pretreated Pt(111) surface, and the compressed adlayer of CO on Pt(111).

Degree

Ph.D.

Advisors

Schardt, Purdue University.

Subject Area

Analytical chemistry

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