Evolution of surface stress during oxygen exposure of clean Si(111), Si(100), and amorphous Si surfaces

Abstract

The evolutions of the surface stress of Si(111)-7 × 7, Si(100)-2 × 1, and a-Si surfaces upon oxygen exposure at pO2 = 1 × 10−4 Pa and room temperature have been investigated in a comparative manner using a specimen-curvature based technique. To this end, a generally applicable, dedicated set of experiments has been devised and performed to deduce and correct for the surface stress change owing to oxygen reaction(s) at the (poorly-defined) back face of the specimen only. On this basis, it could be demonstrated that exposure of clean Si(111)-7 × 7, Si(100)-2 × 1 and a-Si surfaces to pure oxygen gas results in compressive surface stress changes for all three surfaces due to the incorporation of oxygen into Si backbonds. The measured surface stress change decreases with decreasing atomic packing density at the clean Si surfaces, which complies well with the less-densily packed Si surface regions containing more free volume for the accommodation of adsorbed O atoms.

Atomistic Simulations of Al(100) and Al(111) Surface Oxidation: Chemical and Topological Aspects of the Oxide Structure

“…An interesting feature in Figure b is a small intensity peak at around 1.8 Å for the O–O pair, which remains present in the oxide film grown on the Al(111) surface after 1000 ps (Figure S6 of the Supporting Information). Its intensity is more pronounced at the early stages of the oxidation process and decreases simultaneously with decreasing intensity of the main peak at 2.89 Å. The presence of the small-intensity peak is likely due to the formation of 2D oxide clusters at an early oxidation stage , that could introduce compressive stress to the surface as it was inferred from HRTEM and XPS analyses as well as from density functional theory-based calculations . The build-up of compressive surface stress at the initial oxidation stage of Al(111) prevents the formation of a laterally continuous monolayer of oxide, and this, in turn, promotes the formation of “free volume” associated with void-type defects .…”

“…29 The present work is motivated by the absence of atomiclevel understanding of crystallographic surface orientation dependence of the growing oxide film structure and by the significant difference in microstructural evolution of oxide films grown on Al(100) and Al(111) surfaces, as observed in high resolution transmission electron microscopy (HRTEM) and Xray photoelectron spectroscopy (XPS) experiments. 30 Accord-ing to Floẗotto et al, 30 the difference may be attributed to the nucleation of a (1 × 1) structure of adsorbed oxygen and to the build-up of tensile stress on Al(111), generating "free volume" during the oxide growth. The latter promotes the oxidation process through the growth of an oriented defective γ-Al 2 O 3 .…”

Energetics and heterodiffusion of Cu on Ag(110) stepped surfaces

“…This is indeed a subject of fundamental interest both from theoretical and experimental points of view. More recently, a considerable amount of papers have been published in this field, on metals, and on semi‐conductor surfaces . The mean reason of this widespread interest towards this problem is due essentially to the important physical applications that include adsorbate on crystal surfaces, solid electrolytes for batteries and fuel cells, advanced materials like super‐alloys with superior properties at elevated temperatures, and thin film growth among others.…”