Quantum Hall effect in few-layer InSe

The discovery of graphene in 2004 with its spectacular electronic properties has opened one of the fastest rising research fields in contemporary materials science. Indeed, graphene and other two-dimensional materials offer promising application perspectives for e.g. high-speed electronics beyond silicon. Specifically, graphene, with its ultra-high mobility even at room temperatures has been proposed to replace silicon but the absence of an energy gap makes it rather unsuitable for switching applications.

Researchers from Manchester and Nottingham (United Kingdom) have now fabricated and measured devices made from ultra-thin layers of InSe encapsulated in hexagonal boron nitride with room temperature mobilities of more than 1000 cm2 V−1 s−1. Since InSe is a semiconductor with a large energy gap these devices open new venues for super-fast switching of transistors in next-generation electronics.

On a more fundamental point of view, experiments performed in collaboration with EMFL scientists at HFML-RU/FOM have revealed a fully developed quantum Hall effect at B = 30 T with spin-resolved Landau levels. They have shown that electrons in InSe behave like classical massive particles (rather than massless Dirac fermions known in graphene). Using temperature dependent Shubnikov-de Haas experiments the effective cyclotron mass of electrons in 6-layer InSe was determined as m*= (0.14 ± 0.01) me and their Landé g-factor to g* » 2.

These first results obtained on the quantum Hall effect in InSe indicate that this material system might be another fascinating playground for studying the fundamental properties of low-dimensional electron system in view of promising applications in future high-mobility nanoelectronics of ultra-thin devices.

Back gate voltage

Resistivity rxx (green, left axis) and Hall conductivity (red, right) of a 6-layer InSe field-effect transistor with a top gate and a back gate in a magnetic field B = 30 T. The numbers mark the integer filling factors of the corresponding quantum Hall states, with even numbers corresponding to Landau-level splitting and odd numbers to Zeeman spin splitting.

The inset shows a micrograph of the device with the top gate and contacts in yellow and the encapsulated InSe in brown.

Related publication:

High electron mobility, quantum Hall effect and anomalous optical response in atomically thin InSe; D.A. Bandurin et al.; Nature Nanotechnology 12, 223 (2017).
DOI: http://dx.doi.org/10.1038/nnano.2016.242

Contact: uli.zeitler@ru.nl