Devices on vW Heterostructures

van der Waals (vW) materials offer a clean and uniform platform — unlike conventional 2DEG materials — and allows freedom to stack different candidates with varied properties; semiconducting, metallic or insulating. Their inherent 2D nature and substrate independence makes them an interesting candidate for quantum electronic devices. In addition, their high mechanical strength allows coupling of mechanical and electrical properties.
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Split-gate point contact on MoS2/h-BN heterostructure

Quantum Devices in MoS2/h-BN Heterostructures

van der Waals heterostructures hold the advantage of large-scale uniformity, flexibility, portability and high-temperature operation over conventional bulk semiconductor heterostructures. vW materials would be the ideal platform to realize electrostatically defined nanoscale devices and to pave the way for flexible quantum electronics.

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Pinch-off from point contact in MoS2/h-BN at 4K
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Plasma etching for layer-by-layer etching and patterning of vW materials

Layer Engineering and Phase Engineering MoS2

Etching and patterning of vW materials

A generic layer engineering technology using microwave plasma for controlled etching of vW materials to obtain large area samples of desired thickness without compromising device performance. Ability to pattern samples to desired shapes yields a scalable technique compatible with standard micro-fabrication schemes.

2H-1T MoS2 hybrid junctions

The presence of different polymorphic phases (semiconducting 2H, metallic 1T) make MoS2 a desirable platform to fabricate and study monolithic semiconducting/metallic junctions. Conventional 1T conversion processes are not scalable and also yield unstable samples. Using microwave plasma, we engineer a stable 1T phase in a scalable manner, compatible with standard device fabrication schemes. The 1T regions on the 2H sample can be achieved on desired regions.

2D Superconductivity in vW Systems

Unlike its 3D counterpart, superconductivity in 2D is interlaced with omnipresent vortices and their dynamics packed with rich physics and wide applications. Berisenskii Kosterlitz Thouless phase transition, Bose metal phase, and Ising superconductivity are seen in these systems. 

2D superconductivity in 1T-MoS2

2D superconductivity is limited to systems with sheet resistance less than the resistance quantum, RQ = h/4e2 ~6.45 kΩ . The metallic nature and high carrier concentration make 1T, the metallic phase of MoS2,  a natural choice for the study of 2D superconductivity.

Electrostatic control of quantum phases

Ionic liquid gating enables one to change the carrier concentration in a system by many orders which is not possible in conventional dielectric gating techniques. Quantum phases such as 2D superconductivity can be realised and explored in vW systems using this technique. On systems that lack centre of symmetry, interesting features such as Ising superconductivity can be observed. 

Ionic liquid gating in MoS2

Nanomechanical Resonators on 2D Systems

vW materials with excellent crystallinity, mechanical and electrical properties form a platform for coupling the electrical and mechanical degrees of freedom for novel device applications. Investigation of these systems are fascinating from a fundamental physics perspective and also has various technological applications such as quantum displacement sensors.

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