arXiv subjects

Edith Simmen

Publications and source records attributed to Edith Simmen.

3 recordsLinked to original sources

arXiv2026

Polarizing ultrathin ferroelectric BaTiO3 films through interfacial layer polarization

An important requirement for the integration of ferroelectric thin films into devices is deterministic control of the polarization state in films of only a few unit cells in thickness. Here, we utilize the charged atomic planes of (001)-oriented SmNiO$_3$ (SNO) buffer layers as a polarizing template to stabilize the polarization in ferroelectric BaTiO$_3$ (BTO) model system thin films. We show that an upwards (downwards) oriented polarization is achieved by selection of the [SmO]$^+$ ([NiO$_2$]$^-$) buffer termination. Most importantly, the charged atomic planes of SNO suppress the depolarizing-field-induced critical thickness in BTO, and we record the emergence of a net polarization in our BTO films from the first unit cell deposited. Our experiments, guided by density-functional-theory (DFT) calculations, further highlight the impact of charged defects on the polarizing effectiveness of the SNO buffer. Specifically, oxygen vacancies counteract the polarizing field of the negatively charged, [NiO$_2$]$^-$-terminated surface of the SNO buffer. Our findings provide important insights into the interplay of defect chemistry and polarizing interfaces to stabilize ferroelectric polarization down to the single-unit-cell limit.

cond-mat.mtrl-sci↗

arXiv2026

Journal Research Data Policies in Materials Science

Open and reproducible research in materials science relies on the availability of data, code, and common metadata standards. Journal research data policies (RDPs) remain a primary mechanism by which publication norms are defined and enforced. We survey RDPs for 171 materials science journals spanning 17 publishers, using an expanded coding framework that captures both data-and-code sharing behavior as well as refereeing standards. We find clear signs of progress in comparison to earlier research on RDPs: nearly all journals provide an RDP, and most mention data availability statements. However, enforceable requirements remain uncommon, public deposition of underlying data is rarely mandatory, and FAIR publication is typically encouraged rather than required. Expectations for research software are substantially less developed than those for data, with limited attention to versioning and persistent identifiers, dependency disclosure, reproducible execution environments, or software quality practices. Aggregating the findings on policy features into an open research data score reveals pronounced heterogeneity across journals. Neither impact factor nor access model reliably predicts policy strength. Double-coding further shows that more complex policies and stricter policies can be more challenging to interpret consistently, and we highlight challenges in consistent RDP encoding across studies. Lastly, we conclude with recommended best practice directions for the future.

cs.DL↗

arXiv2024

Interplay of metallicity, ferroelectricity and layer charges in SmNiO$_3$/BaTiO$_3$ superlattices

Using density-functional theory, we demonstrate that the formal layer charges of the metallic samarium nickelate electrode influence the spontaneous ferroelectric polarization of the barium titanate in SmNiO$_3$/BaTiO$_3$ capacitors. We find that, despite the metallic screening of SmNiO$_3$, the spontaneous polarization of BaTiO$_3$ always aligns with the layer polarization of the SmNiO$_3$ formal charges. We also find zero critical thickness for the ferroelectricity in BaTiO$_3$ in this orientation. The opposite polarization direction is highly disfavored for thin BaTiO$_3$ slabs but becomes less unstable with increasing slab thickness. We construct a simple electrostatic model that allows us both to study the behavior for thicker BaTiO$_3$ and SmNiO$_3$ slabs and to extract the influence of various material parameters on the behavior. We mimic a metal-insulator transition in the SmNiO$_3$ by varying the metallic screening length, which we find greatly influences the stability of the ferroelectric polarization. Our results show that the layer charges in the metal electrodes strongly influence the properties in ferroelectric capacitors and in fact can provide new ways to control the ferroelectric properties.

cond-mat.mtrl-sci↗