arXiv subjects

Igor Pis

Publications and source records attributed to Igor Pis.

5 recordsLinked to original sources

arXiv2026

Competition between clustering and dispersion of cobalt atoms on perovskite surfaces: SrTiO3(001) and KTaO3(001)

Perovskite oxides are attractive for reactions in photo/electrocatalytic schemes, and extrinsic doping is a common strategy for tuning their properties. It is widely known that extrinsic dopants impact the structure and stability of perovskite surfaces, but an atomic-scale view is missing. Here, noncontact atomic force microscopy (ncAFM) and photoelectron spectroscopy (XPS/PES) are used to combine microscopic and spectroscopic evidence of cobalt adsorption, incorporation, and clustering at surfaces of two prototypical perovskites SrTiO3 and KTaO3. A number of different sub-ML coverages and temperatures of annealing were investigated. Several common features are observed: cobalt shows a strong preference for ionic nature (+2 and +3 charge states), and remains dispersed as single atoms to a certain extent in both perovskites. Two competing mechanisms are observed upon annealing: coalescence into clusters with a mixed metallic/ionic character, and incorporation into the surface and subsurface regions. The latter is more pronounced in SrTiO3, where a cobalt-stabilized surface reconstruction is identified, whereas for KTaO3 cobalt likely incorporates in the near-surface region.

cond-mat.mtrl-sci↗

arXiv2022

Effect of the crystallographic c-axis orientation on the tribological properties of the few-layer PtSe2

Two-dimensional (2D) transition metal dichalcogenides are potential candidates for ultrathin solid-state lubricants in low-dimensional systems owing to their flatness, high in-plane mechanical strength, and low shear interlayer strength. Yet, the effects of surface topography and surface chemistry on the tribological properties of 2D layers are still unclear. In this work, we performed a comparative investigation of nanoscale tribological properties of ultra-thin highly-ordered PtSe2 layers deposited on the sapphire substrates with the in-plane and out-of-plane crystallographic orientation of the PtSe2 c-axis flakes, and epitaxial PtSe2 layers. PtSe2 c-axis orientation was found to has an impact on the nanotribological, morphological and electrical properties of PtSe2, in particular the change in the alignment of the PtSe2 flakes from vertical (VA) to horizontal (HA) led to the lowering of the coefficient of friction from 0.21 to 0.16. This observation was accompanied by an increase in the root-mean-square surface roughness from 1.0 to 1.7 nm for the HA and VA films, respectively. The epitaxial films showed lower friction caused by lowering adhesion when compared to other investigated films, whereas the friction coefficient was similar to films with HA flakes. The observed trends in nanoscale friction is attributed to a different distribution of PtSe2 structure.

cond-mat.mtrl-sci↗

arXiv2022

Boron nitride-graphene in-plane hexagonal heterostructure in oxygen environment

Aiming to improve fabrication protocols for boron nitride and graphene (h-BNG) lateral heterostructures, we studied the growth of h-BNG thin films on platinum and their behavior in an oxygen environment. We employed a surface science approach based on advanced spectroscopy and imaging techniques to investigate the evolution of surface stoichiometry and chemical intermediates at each reaction step. During oxygen exposure at increasing temperatures, we observed progressive and subsequent intercalation of oxygen, and selective etching of graphene accompanied by the oxidation of boron. Additionally, by exploiting the O2 etching selectivity towards graphene at 250{\deg}C and repeating growth cycles, we obtained in-plane h-BNG layers with controllable compositions and vertically stacked h-BN/Gr heterostructures without the use of consecutive transfer procedures. The growth using a single precursor molecule can be beneficial for the development of versatile atomically thin layers for electronic devices.

cond-mat.mtrl-sci↗

arXiv2020

Soft X-ray spectroscopies in liquids and at solid-liquid interface at BACH beamline at Elettra

The Beamline for Advanced diCHroism (BACH) of the Istituto Officina dei Materiali-Consiglio Nazionale delle Ricerche (IOM-CNR), operating at Elettra synchrotron in Trieste (Italy), works in the extreme ultra violet (EUV)-soft X-ray photon energy range with selectable light polarization, high energy resolution, brilliance and time resolution. The beamline offers a multi-technique approach for the investigation of the electronic, chemical, structural, magnetic, and dynamical properties of materials. Recently one of the three end-stations has been dedicated to experiments based on electron transfer processes at the solid/liquid interfaces and during photocatalytic or electrochemical reactions. Suitable cells to perform soft X-ray spectroscopy in the presence of liquids and reagent gases at ambient pressure were developed. Here we present two types of static cells working in transmission or in fluorescence yield, and an electrochemical flow cell which allows to carry out cyclic voltammetry in situ, electrodeposition on a working electrode (WE) and to study chemical reactions in-operando conditions. Examples of X-ray absorption spectroscopy (XAS) measurements performed in ambient conditions and during electrochemical experiments in liquid are presented.

physics.ins-det↗

arXiv2020

High carrier mobility epitaxially aligned PtSe2 films grown by one-zone selenization

Few-layer PtSe2 films are promising candidates for applications in high-speed electronics, spintronics and photodetectors. Reproducible fabrication of large-area highly crystalline films is, however, still a challenge. Here, we report the fabrication of epitaxially aligned PtSe2 films using one-zone selenization of pre-sputtered platinum layers. We have studied the influence of the growth conditions on the structural and electrical properties of the films prepared from Pt layers with different initial thickness. The best results were obtained for PtSe2 layers grown at elevated temperatures (600 {\deg}C). The films exhibit signatures for a long-range in-plane ordering resembling an epitaxial growth. Charge carrier mobility determined by Hall-effect measurements is up to 24 cm2/V.s in these films.

cond-mat.mtrl-sci↗