Ultrathin semiconductors electrically connected to superconductors

For the primary time, College of Basel researchers have outfitted an ultrathin semiconductor with superconducting contacts. These extraordinarily skinny supplies with novel digital and optical properties may pave the way in which for beforehand unimagined functions. Mixed with superconductors, they’re anticipated to offer rise to new quantum phenomena and discover use in quantum know-how.

Whether or not in smartphones, televisions or constructing know-how, semiconductors play a central position in electronics and due to this fact in our on a regular basis lives. In distinction to metals, it’s attainable to regulate their electrical conductivity by making use of a voltage and therefore to change the present move on and off.

With a view to future functions in electronics and quantum know-how, researchers are specializing in the event of latest elements that include a single layer (monolayer) of a semiconducting materials. Some naturally occurring supplies with semiconducting properties function monolayers of this type, stacked to type a three-dimensional crystal. Within the laboratory, researchers can separate these layers — which are not any thicker than a single molecule — and use them to construct digital elements.

New properties and phenomena

These ultrathin semiconductors promise to ship distinctive traits which might be in any other case very tough to manage, reminiscent of the usage of electrical fields to affect the magnetic moments of the electrons. As well as, advanced quantum mechanical phenomena happen in these semiconducting monolayers that will have functions in quantum know-how.

Scientists worldwide are investigating how these skinny semiconductors could be stacked to type new artificial supplies, referred to as van der Waals heterostructures. Nonetheless, till now, they haven’t succeeded in combining such a monolayer with superconducting contacts with the intention to dig deeper into the properties and peculiarities of the brand new supplies.


Superconducting contacts

A crew of physicists, led by Dr. Andreas Baumgartner within the analysis group of Professor Christian Sch├Ânenberger on the Swiss Nanoscience Institute and the Division of Physics of the College of Basel, has now fitted a monolayer of the semiconductor molybdenum disulfide with superconducting contacts for the primary time.

The explanation why this mix of semiconductor and superconductor is so attention-grabbing is that the consultants count on elements of this type to exhibit new properties and bodily phenomena. “In a superconductor, the electrons organize themselves into pairs, like companions in a dance — with strange penalties, such because the move of {the electrical} present with out a resistance,” explains Baumgartner, the undertaking supervisor of the examine. “Within the semiconductor molybdenum disulfide, alternatively, the electrons carry out a very totally different dance, an odd solo routine that additionally incorporates their magnetic moments. Now we wish to discover out which new and unique dances the electrons agree upon if we mix these supplies.”

Appropriate to be used as a platform

{The electrical} measurements on the low temperatures required for superconductivity — simply above absolute zero (-273.15┬░C) — present clearly the consequences attributable to the superconductor; for instance, at sure energies, single electrons are now not allowed. Furthermore, the researchers discovered indications of a powerful coupling between the semiconductor layer and the superconductor.


“Sturdy coupling is a key component within the new and thrilling bodily phenomena that we count on to see in such van der Waals heterostructures, however have been by no means capable of exhibit,” says Mehdi Ramezani, lead writer of the examine.

“And, after all, we all the time hope for brand new functions in electronics and quantum know-how,” says Baumgartner. “In precept, the vertical contacts we have developed for the semiconductor layers could be utilized to numerous semiconductors. Our measurements present that these hybrid monolayer semiconductor elements are certainly attainable -perhaps even with different, extra unique contact supplies that will pave the way in which for additional insights,” he provides.

Elaborate fabrication course of

The fabrication of the brand new element in a kind of sandwich made of various supplies requires numerous totally different steps. In every step, it is very important keep away from contaminations, as they significantly impair the transport {of electrical} expenses.

To guard the semiconductor, the researchers pack a monolayer of molybdenum disulfide between two skinny layers of boron nitride, by which they’ve beforehand etched the contacts vertically utilizing electron-beam lithography and ion etching. They then deposit a skinny layer of molybdenum rhenium as a contact materials — a cloth that retains its superconducting properties even within the presence of sturdy magnetic fields.

Working underneath a protecting nitrogen environment in a glove field, the researchers stack the boron nitride layer onto the molybdenum disulfide layer and mix the underside with an extra layer of boron nitride in addition to a layer of graphene for electrical management. The researchers then place this elaborate van der Waals heterostructure on prime of a silicon/silicon-dioxide wafer.