Desorption of Water from Distinct Step Types on a Curved Silver Crystal

Abstract

Abstract:We have investigated the adsorption of H 2 O onto the A and B type steps on an Ag single crystal by temperature programmed desorption. For this study, we have used a curved crystal exposing a continuous range of surface structures ranging from [5(111) × (100)] via (111) to [5(111) × (110)]. LEED and STM studies verify that the curvature of our sample results predominantly from monoatomic steps. The sample thus provides a continuous array of step densities for both step types. Desorption probed by spatially-resolved TPD of multilayers of H 2 O shows no dependence on the exact substrate structure and thus confirms the absence of thermal gradients during temperature ramps. In the submonolayer regime, we observe a small and linear dependence of the desorption temperature on the A and B step density. We argue that such small differences are only observable by means of a single curved crystal, which thus establishes new experimental benchmarks for theoretical calculation of chemically accurate binding energies. We propose an origin of the observed behavior based on a "two state" desorption model.

It's not just the defects – a curved crystal study of H2O desorption from Ag

“…Results for the curved Ag(111) crystal have been published before, but were newly analysed from the raw data here for consistent comparison with the curved Ag(001) crystal, leading to new insights. 14…”

“…We have previously determined this dose to correspond to a surface coverage of 0.06-0.08 ML. 14 The higher background signal after the desorption peaks (in Fig. 3 and 4) is due to the long vacuum time constant of water in our apparatus.…”

“…This system has been described previously as well. 4,14 Cleaning of samples followed the same procedure that had been confirmed by LEED and STM to deliver clean and well-defined surfaces. Water (Millipore, 18.2 MO) was degassed by multiple freeze-pump-thaw cycles prior to dosing.…”

High‐throughput methods using composition and structure spread libraries

“…Nonetheless, there are some other examples in the current literature. For example, water desorption on a curved Ag crystal was recently reported . Those authors observed a significant linear dependence of the desorption temperature on the step density of the surface.…”

Step-type and step-density influences on CO adsorption probed by reflection absorption infrared spectroscopy using a curved Pt(1 1 1) surface

“…Although the range of surface structures available on such a partial section is limited, such crystals have been employed successfully in standard UHV systems. 11,12 Generally, the direction of curvature is chosen such that the curvature results from atomically straight step edges. Dome-shaped crystals offer a continuous range of surface structures, including straight and kinked step edges.…”