Deciphering complex features in STM images of O adatoms on Ag(110)

Abstract

Recently it was demonstrated that atomic oxygen can cause the extraction of substrate atoms off metal surfaces thus generating chemically different active sites. For Ag(110) this process occurs when O 2 is dosed at 175 K leading, at low coverage, to the formation of single Ag vacancies. Vacancy creation proceeds thereby via the formation of O-AgO complexes, which involve a local reconstruction of the surface and ignite the disruption of the Ag substrate. In this paper, we report on the details of such processes and on the isolated structures formed by the O adatoms in the limit of very low coverage. We employ scanning tunnelling microscopy and density functional theory to unravel the complex structures of O/Ag(110) which are transiently present under specific reaction conditions. A variety of features such as isolated grey dots, sombreros, shallow grey and white structures oriented along [001] and [11 0], grey stripes, and lozenges were identified and assigned to O adatoms in different configurations. The zigzag chains interact strongly with the STM tip and are easily disrupted, giving rise to highly mobile, sombrero shaped, isolated O adatoms also far away from the scanned area, i.e. from the current injection spot. Around 200 K, not only Ag vacancies, which are mobile with anisotropic migration, can merge together into rather complex features, but also the mobile Ag atoms are trapped by O adatoms, thus facilitating the formation of an oxygendecorated Ag chain along [001] which ultimately induces the well-known added row reconstruction.

Characteristics of sulfur atoms adsorbed on Ag(100), Ag(110), and Ag(111) as probed with scanning tunneling microscopy: experiment and theory

“…7,[23][24][25][26] However, a recent study of O/Ag(110) uses a methodology similar to ours. 9 We also note that effects of tip-sample separation have been studied previously by DFT and experimentally for O/Pd(111). 27 Recently, we reported that isolated adsorbed S atoms on a related surface, Cu(100), are imaged as sombreros-protrusions surrounded by a dark ring-at negative sample bias (filled states images), but with increasing bias voltage the central protrusions sink and disappear, converting into an inverted cone-shaped depression at positive sample bias (empty states images).…”

Morphological characterization and electronic properties of pristine and oxygen-exposed graphene nanoribbons on Ag(110)

“…Surface orientation and image size were calibrated from atomically resolved images of the clean Ag(110) surface (see inset of Figure 1A) or of the (nx1)-O-Ag(110) added row reconstruction. 31,32 Similarly, heights were calibrated on monatomic Ag steps. STS spectra and dI/dV maps were recorded at LHe temperature to minimize thermal drift.…”

Identification of an AgS2 Complex on Ag(110)

“…No detailed structures of these clusters have been proposed and the clusters were imaged at 77 K, leading to the clusters appearing streaky or fuzzy in STM images due to the clusters being semi-mobile on the surface. In another related system, it has been demonstrated using low-temperature STM, that oxygen on Ag(110) can produce a variety of features 32,33 . Two of these features contain a linear O-Ag-O structure.…”

“…The chain can be regarded as oxygen atoms densely decorating a pre-existing row of Ag atoms. The second feature is an isolated, linear O-Ag-O unit, where the central Ag atom is embedded in (but slightly displaced from) a pre-existing row of Ag atoms 33 . It was proposed that the embedded complex can detach from its lateral surroundings and become “free,” hence aiding in the creation of surface vacancies.…”

“…It was proposed that the embedded complex can detach from its lateral surroundings and become “free,” hence aiding in the creation of surface vacancies. These “free” AgO 2 complexes may serve as the building blocks of the Ag(110)-O-(2 × 1) added row reconstruction 33 . However, they were not observed directly.…”