Mesa+ Meeting

Research Area Sessions

1Advanced materials & devices, chaired by dr.ir. Floris Zwanenburg & dr.ir. Gertjan Koster

2Fluidics & microsystems, chaired by dr.ir. Mathieu Odijk & dr. David Fernandez Rivas

3Photonics & (bio)systems, chaired by dr.ir. Annemarie Huijser & prof. dr. Pepijn Pinkse

4Soft matter & devices, chaired by dr. Saskia Lindhoud & dr. Tibor Kudernac

Advanced Materials & devices (ROOM 3)

Chairs: dr.ir. Floris Zwanenburg (NanoElectronics)/dr.ir. Gertjan Koster (Inorganic Materials Science)

INTRODUCTION

This parallel session focuses on the electronic properties of advanced nanoscale materials, varying from 2-dimensional materials such as silicene and MoS₂ to superconducting Nb islands on Au. The presenters use different techniques to study their materials, in particular low-temperature electron transport measurements, in device and STM configuration and DFT calculations.

PROGRAM

ABSTRACTS

 
Is my layer closed? Low Energy Ion Scattering as analysis tool for thin film growth

Marko Sturm (XUV Optics)

In-vacuo growth studies and thermal oxidation of ZrO2 thin films

ZrO2 thin films might be used as capping layers for protecting extreme ultraviolet (EUV) optics against oxidation and other chemical degradation processes. These coatings should be homogeneous and form a closed layer, not degrade the underneath mirror, and have a thickness in the nanometre range to keep good reflection properties of the mirror. These challenging demands were met by advanced surface science tools.

The initial growth of ZrO2 films by reactive magnetron sputtering on top of amorphous Si was monitored by in vacuo low-energy ion scattering (LEIS). With this technique, the atomic composition of the outermost atomic layer of a surface can be probed with high sensitivity. By monitoring for which deposited amount of ZrO2 the signal from the underlying Si vanishes, the ZrO2 thickness required for forming a closed layer was determined. In this way, LEIS was employed to study how deposition parameters influence the sharpness of the interface between the cap layer and Si. In-vacuo X-ray photoelectron spectroscopy (XPS) was then used to find the optimal deposition conditions and the stoichiometry of the produced layers. Depending on deposition conditions, a fully closed layer can be formed with a deposited ZrO2 thickness of only 1.7 nm. Based on the smoothness of the as deposited layers, as probed by AFM analysis, it was concluded that intermixing, rather than island formation, is limiting the sharpness of the ZrO2/Si interface. Finally, XPS was used ex-situ for probing oxygen diffusion through the capping layer after thermal oxidation in ambient. A 2 nm ZrO2 cap on top of Si showed further intermixing up to 400 °C, without increase of the oxidation of the underlying Si.

Control of interfacial octahedral rotations in oxide heterostructures

Zhaoliang Liao (Inorganic Materials Science)

Octahedral tilt plays a pivotal role in determining novel properties and functionalities in transition metal perovskite oxides. The control of octahedral rotations leads to diverse electronic ground states. Thanks to the fast developing of oxide growth technique, the precise control of structure and thickness of oxide heterostructure provides us with many additional freedoms to dig into fundamental physics and tailor properties. By playing with newly revealed and focused interfacial oxygen octahedral coupling (OOC) in perovskite oxide heterostructures, we demonstrate the capabilities to design the octahedral rotation at oxide heterostructures and thus to induce new and/or engineer existing properties in correlated heterostructures. In this presentation, I will summarize our recent results on how to control the octahedral rotation in order to manipulate magnetization in correlated oxide heterostructures at atomic scale.

Structural and electronic properties of Germanene on MoS2

Lijie Zhang (Physics of Interfaces and Nanomaterials)

To date germanene has only been synthesized on metallic substrates. A metallic substrate is usually detrimental for the two-dimensional Dirac nature of germanene because the important electronic states near the Fermi level of germanene can hybridize with the electronic states of the metallic substrate. Here we report the successful synthesis of germanene on molybdenum disulfide (MoS₂), a band gap material. Preexisting defects in the MoS₂ surface act as preferential nucleation sites for the germanene islands. The lattice constant of the germanene layer (3.8 ± 0.2 Å) is about 20% larger than the lattice constant of the MoS₂ substrate (3.16 Å). Scanning tunneling spectroscopy measurements and density functional theory calculations reveal that there are, besides the linearly dispersing bands at the K points, two parabolic bands that cross the Fermi level at the Γ point.

Pathways towards water splitting devices

Wouter Vijselaar (Molecular NanoFabrication/Mesoscale Chemical Systems)