Surface structure and reactivity of
multi-component oxides at the atomic scale

@article{ACSMEASURE2022,

title = {Why and How Savitzky–Golay Filters Should Be Replaced},

author = {Michael Schmid and David Rath and Ulrike Diebold},

url = {https://pubs.acs.org/doi/10.1021/acsmeasuresciau.1c00054},

doi = {10.1021/acsmeasuresciau.1c00054},

year  = {2022},

date = {2022-02-17},

urldate = {2022-02-17},

journal = {ACS Measurement Science Au},

volume = {2},

number = {2},

pages = {185--196},

abstract = {Savitzky–Golay (SG) filtering, based on local least-squares fitting of the data by polynomials, is a popular method for smoothing data and calculations of derivatives of noisy data. At frequencies above the cutoff, SG filters have poor noise suppression; this unnecessarily reduces the signal-to-noise ratio, especially when calculating derivatives of the data. In addition, SG filtering near the boundaries of the data range is prone to artifacts, which are especially strong when using SG filters for calculating derivatives of the data. We show how these disadvantages can be avoided while keeping the advantageous properties of SG filters. We present two classes of finite impulse response (FIR) filters with substantially improved frequency response: (i) SG filters with fitting weights in the shape of a window function and (ii) convolution kernels based on the sinc function with a Gaussian-like window function and additional corrections for improving the frequency response in the passband (modified sinc kernel). Compared with standard SG filters, the only price to pay for the improvement is a moderate increase in the kernel size. Smoothing at the boundaries of the data can be improved with a non-FIR method, the Whittaker–Henderson smoother, or by linear extrapolation of the data, followed by convolution with a modified sinc kernel, and we show that the latter is preferable in most cases. We provide computer programs and equations for the smoothing parameters of these smoothers when used as plug-in replacements for SG filters and describe how to choose smoothing parameters to preserve peak heights in spectra.},

keywords = {P02},

pubstate = {published},

tppubtype = {article}

}

@article{Jakub2021,

title = {Rapid oxygen exchange between hematite and water vapor},

author = {Zdenek Jakub and Matthias Meier and Florian Kraushofer and Jan Balajka and Jiri Pavelec and Michael Schmid and Cesare Franchini and Ulrike Diebold and Gareth S. Parkinson},

doi = {10.1038/s41467-021-26601-4},

year  = {2021},

date = {2021-11-10},

journal = {Nature Communications},

volume = {12},

number = {6488},

issue = {1},

publisher = {Springer Science and Business Media LLC},

abstract = {Oxygen exchange at oxide/liquid and oxide/gas interfaces is important in technology and environmental studies, as it is closely linked to both catalytic activity and material degradation. The atomic-scale details are mostly unknown, however, and are often ascribed to poorly defined defects in the crystal lattice. Here we show that even thermodynamically stable, well-ordered surfaces can be surprisingly reactive. Specifically, we show that all the 3-fold coordinated lattice oxygen atoms on a defect-free single-crystalline “r-cut” (1-102) surface of hematite (α-Fe_{2}O_{3}) are exchanged with oxygen from surrounding water vapor within minutes at temperatures below 70 °C, while the atomic-scale surface structure is unperturbed by the process. A similar behavior is observed after liquid-water exposure, but the experimental data clearly show most of the exchange happens during desorption of the final monolayer, not during immersion. Density functional theory computations show that the exchange can happen during on-surface diffusion, where the cost of the lattice oxygen extraction is compensated by the stability of an HO-HOH-OH complex. Such insights into lattice oxygen stability are highly relevant for many research fields ranging from catalysis and hydrogen production to geochemistry and paleoclimatology.},

keywords = {P02, P04, P07},

pubstate = {published},

tppubtype = {article}

}

@article{Franceschi2021,

title = {Two-dimensional surface phase diagram of a multicomponent perovskite oxide: La_{0.8}Sr_{0.2}MnO_{3} (110)},

author = {Giada Franceschi and Michael Schmid and Ulrike Diebold and Michele Riva},

doi = {10.1103/physrevmaterials.5.l092401},

year  = {2021},

date = {2021-09-24},

urldate = {2021-09-24},

journal = {Physical Review Materials},

volume = {5},

number = {9},

pages = {L092401},

publisher = {American Physical Society (APS)},

abstract = {The many surface reconstructions of (110)-oriented lanthanum strontium manganite (\textbf{La_{0.8}Sr_{0.2}MnO}3}}, LSMO) were followed as a function of the oxygen chemical potential (\textit{\textbf{μ}_{O}}) and the surface cation composition. Decreasing \textit{\textbf{μ}_{O}} causes Mn to migrate across the surface, enforcing phase separation into \textit{\textbf{A}}-site-rich areas and a variety of composition-related, structurally diverse \textit{\textbf{B}}-site-rich reconstructions. The composition of these phase-separated structures was quantified with scanning tunneling microscopy, and these results were used to build a two-dimensional phase diagram of the LSMO(110) equilibrium surface structures.},

keywords = {P02},

pubstate = {published},

tppubtype = {article}

}