arXiv subjects

S. Wundrack

Publications and source records attributed to S. Wundrack.

3 recordsLinked to original sources

arXiv2025

Lithographically-controlled liquid metal diffusion in graphene: Fabrication and magneto-transport signatures of superconductivity

Metal intercalation in epitaxial graphene enables the emergence of proximity-induced superconductivity and modified quantum transport properties. However, systematic transport studies of intercalated graphene have been hindered by challenges in device fabrication, including processing-induced deintercalation and instability under standard lithographic techniques. Here, we introduce a lithographically controlled intercalation approach that enables the scalable fabrication of gallium-intercalated quasi-freestanding bilayer graphene (QFBLG) Hall bar devices. By integrating lithographic structuring with subsequent intercalation through dedicated intercalation channels, this method ensures precise control over metal incorporation while preserving device integrity. Magneto-transport measurements reveal superconductivity with a critical temperature Tc,onset ~ 3.5 K and the occurrence of a transverse resistance, including both symmetric and antisymmetric field components, which is attributed to the symmetric-in-field component to non-uniform currents. These results establish an advanced fabrication method for intercalated graphene devices, providing access to systematic investigations of confined 2D superconductivity and emergent electronic phases in van der Waals heterostructures.

cond-mat.mtrl-sci↗

arXiv2019

Liquid metal intercalation of epitaxial graphene: large-area gallenene layer fabrication through gallium self-propagation at ambient conditions

We demonstrate the fabrication of an ultra thin gallium film, also known as gallenene, beneath epitaxial graphene on 6H-SiC under ambient conditions triggered by liquid gallium intercalation. Gallenene has been fabricated using the liquid metal intercalation, achieving lateral intercalation and diffusion of Ga atoms at room temperature on square centimeter areas limited only by the graphene samples' size. The stepwise self-propagation of the gallenene film below the epitaxial graphene surface on the macroscopic scale was observed by optical microscopy shortly after the initial processing without further physical or chemical treatment. Directional Ga diffusion of gallenene occurs on SiC terraces since the terrace steps form an energetic barrier (Ehrlich-Schwoebel barrier),retarding the gallenene propagation. The subsequent conversion of the epitaxial graphene into quasi free-standing bilayer graphene (QFBLG) and the graphene-gallenene heterostack interactions have been analyzed by XPS and Raman measurements. The results reveal a novel approach for controlled fabrication of wafer-scale gallenene as well as for two-dimensional heterostructures and stacks based on the interaction between liquid metal and epitaxial graphene. Please note, this work was also titled as Graphene meets gallenene -- A straightforward approach to developing large-area heterostacks by gallium self-propagation https://www.researchgate.net/publication/333451130_Graphene_meets_gallenene_-_A_straightforward_approach_to_developing_large-area_heterostacks_by_gallium_self-propagation

cond-mat.mtrl-sci↗

arXiv2011

Versatile sputtering technology for Al2O3 gate insulators on graphene

We report a novel fabrication method of graphene Al2O3 gate insulators based on sputtering. Electrical performance of dual-gated mono- and bilayer exfoliated graphene devices is presented. Sputtered Al2O3 layers possess comparable quality to oxides obtained by atomic layer deposition (ALD) with respect to a high relative dielectric constant of about 8, as well as low-hysteresis performance and high breakdown voltage. We observe a moderate carrier mobility of about 1000 cm2/Vs in graphene and 350 cm2/Vs in its bilayer due to increased resonant scattering on atomic scale defects. Most likely this originated from the thin Al precursor layer evaporated prior to sputtering the Al2O3 gate oxide.

cond-mat.mes-hall↗