Quantum transport in superconducting hybrids: Molecular devices and layered materials

In this thesis we investigate superconducting hybrids made from two material systems, namely, molecules and layered materials. For studies of superconducting phenomena in molecular junctions we develop two platforms which rely on the superconducting proximity effect to preserve pre-existing nano-gap formation techniques and bonding chemistries. In the second half of this thesis we investigate the thickness dependent properties of the 2H crystal phase of two layered materials; molybdenum disulfide (2H-MoS2) and tantalum disulfide (2H-TaS2).QN/van der Zant La

Investigating Laser-Induced Phase Engineering in MoS₂ Transistors

Phase engineering of MoS₂ transistors has recently been demonstrated and has led to record low contact resistances. The phase patterning of MoS₂ flakes with laser radiation has also been realized via spectroscopic methods, which invites the potential of controlling the metallic and semiconducting phases of MoS₂ transistors by simple light exposure. Nevertheless, the fabrication and demonstration of laser-patterned MoS₂ devices starting from the metallic polymorph have not been demonstrated yet. Here, we study the effects of laser radiation on 1T/1T′-MoS₂ transistors with the prospect of driving an in situ phase transition to the 2H-polymorph through light exposure. We find that although the Raman peaks of 2H-MoS₂ become more prominent and the ones from the 1T/1T′ phase fade after the laser exposure, the semiconducting properties of the laser-patterned devices are not fully restored, and the laser treatment ultimately leads to the degradation of the transport channel.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QN/Steele LabQN/van der Zant La

Thickness dependent interlayer transport in vertical MoS₂ Josephson junctions

Wereport on observations of thickness dependent Josephson coupling and multiple Andreev reflections (MAR) in vertically stacked molybdenum disulfide (MoS2)-molybdenum rhenium (MoRe) Josephson junctions. MoRe, a chemically inert superconductor, allows for oxide free fabrication of high transparency vertical MoS2 devices. Single and bilayer MoS2 junctions display relatively large critical currents (up to 2.5 μA) and the appearance of sub-gap structure given by MAR. In three and four layer thick devices we observe orders of magnitude lower critical currents (sub-nA) and reduced quasiparticle gaps due to proximitized MoS2 layers in contact with MoRe.Weanticipate that this device architecture could be easily extended to other 2D materials.Accepted Author ManuscriptQN/van der Zant LabQN/Steele La