Zero-bias conductance anomaly of a FeO-bound Au atom triggered by CO adsorption

Abstract

Single gold-carbonyl species adsorbed on a FeO thin film on Pt͑111͒ exhibit a pronounced zero-bias conductance anomaly in scanning tunneling spectroscopy, while bare Au atoms reveal a smooth conductance behavior. The phenomenon is attributed to the Kondo effect, which seems to be triggered by AuCO attachment to the oxide surface but originates in fact from the interplay between the Fe magnetic moments and the Pt conduction electrons. This interpretation is supported by the observation of a similar conductance anomaly even for the pristine oxide film under certain circumstances. Apparently, the FeO/Pt͑111͒ system is intrinsically susceptible to a Kondo-type behavior, which needs however to be initiated by a small, e.g., adsorbate-induced modification of its magnetic structure. The role of the AuCO in triggering the effect is explored by analyzing the geometric and electronic properties of the ad-complex on the FeO thin film via tunneling spectroscopy and density-functional theory.

CO Adsorption on Thin MgO Films and Single Au Adatoms: A Scanning Tunneling Microscopy Study

“…In general, CO attachment modifies the STM appearance of metal atoms only if low-lying atomic orbitals are affected by the bond formation and the transport behavior of the junction is altered. Such an effect was revealed, for instance, for carbonyl species on FeO(111) and NiAl(110), where the CO removes the Au 6s orbital from a region around E F and triggers a reduction of the AuCO apparent height with respect to an Au atom. , For Au atoms on the MgO film, on the other hand, the Au 6s orbital is not involved in the electron transport, as the state is spatially confined and localized well below E F . Consequently, no change in the image contrast is observed after forming the Au−CO bond.…”

Metal adatoms generated by the co-play of melamine assembly and subsequent CO adsorption

“…We also note that in the previous works of Nilius et al similar bias-dependent morphological contrast of gold adatoms have been demonstrated on both NiAl(110) and FeO(111) ultrathin films. 33,34 Based on all these results, we therefore propose that the ABSs are actually the generated Au adatoms induced upon CO exposure.…”

Ordered Array of Single Adatoms with Remarkable Thermal Stability:Au/Fe3O4(001)

“…Thus, as a substrate for nanoparticle growth, Fe 3 O 4 (001) can be viewed as a thin semiconducting layer on a metallic sup- port. As such, the system bears some resemblance to the ultrathin oxide films on metals studied extensively by Freund and coworkers [10,12,18,19], where charging of adatoms via tunneling has been demonstrated.…”

“…However, no suitable model system exists for the study of single adatom chemistry because sintering occurs well below realistic reaction temperatures [10,17]. Nevertheless, low-temperature experiments have adatom charging [9,10,12,13,[18][19][20][21], seen as important for their purported reactivity. In this paper we describe a model system in which Au adatoms are stabilized up to 400 • C in a deep adsorption well located at 2-fold coordinated "narrow" sites of the Fe…”