researchers at the university of manchester have published a report that details two decades of study into graphene and other two-dimensional materials. the team of scientists have created a new semiconductor, indium selenide (inse), that is only a few atoms thick with a higher electrical conductivity than silicon, which is the standard material in electronic devices.
university of manchester researchers have created indium selenide. (national graphene institute)
similar to graphene, which was discovered at the university of manchester’s national graphene institute, inse crystals are also ultra-thin, but it also contains an energy gap, which graphene does not. this allows “transistors to be easily switched on and off,” according to a report from the university, and that could lead to an increase in the speed of “next-generation” electronic devices.
one of the researchers, sir andre geim, who won the nobel prize for his research into graphene, labeled the new material “the golden middle” between silicon and graphene.
the researchers also managed to overcome the new material’s susceptibility to oxygen and moisture by creating atomically-thin films of inse in an argon atmosphere. there is hope that inse sheets can be produced in similar ways to graphene to make it more commercially viable.
the abstract from the report that was published in nature nanotechnology read:
“a decade of intense research on two-dimensional (2d) atomic crystals has revealed that their properties can differ greatly from those of the parent compound. these differences are governed by changes in the band structure due to quantum confinement and are most profound if the underlying lattice symmetry changes. here we report a high-quality 2d electron gas in few-layer inse encapsulated in hexagonal boron nitride under an inert atmosphere.
“carrier mobilities are found to exceed 103 cm2 v−1 s−1 and 104 cm2 v−1 s−1 at room and liquid-helium temperatures, respectively, allowing the observation of the fully developed quantum hall effect. the conduction electrons occupy a single 2d subband and have a small effective mass. photoluminescence spectroscopy reveals that the bandgap increases by more than 0.5?ev with decreasing the thickness from bulk to bilayer inse.
“the band-edge optical response vanishes in monolayer inse, which is attributed to the monolayer's mirror-plane symmetry. encapsulated 2d inse expands the family of graphene-like semiconductors and, in terms of quality, is competitive with atomically thin dichalcogenides and black phosphorus.”
this was not the only discovery that was published this month by university of manchester researchers. the day after inse was announced, the university also highlighted the work of scientists who used graphene and other 2-d material to create optoelectronic circuits that are “vital for telecommunications networks.”
the researchers combined graphene, boron nitride, and nanoscale gold grating to build a hybrid modulator for controlling the signals passed through optoelectronic devices. according to the school, “the proposed device can effectively process information using light much the same way as computers process information using electrons.”
the abstract of the report published in nature communications stated:
“two-dimensional atomic heterostructures combined with metallic nanostructures allow one to realize strong light–matter interactions. metallic nanostructures possess plasmonic resonances that can be modulated by graphene gating. in particular, spectrally narrow plasmon resonances potentially allow for very high graphene-enabled modulation depth.
“however, the modulation depths achieved with this approach have so far been low and the modulation wavelength range limited. here we demonstrate a device in which a graphene/hexagonal boron nitride heterostructure is suspended over a gold nanostripe array. a gate voltage across these devices alters the location of the two-dimensional crystals, creating strong optical modulation of its reflection spectra at multiple wavelengths: in ultraviolet fabry–perot resonances, in visible and near-infrared diffraction-coupled plasmonic resonances and in the mid-infrared range of hexagonal boron nitride’s upper reststrahlen band.
“devices can be extremely subwavelength in thickness and exhibit compact and truly broadband modulation of optical signals using heterostructures of two-dimensional materials.”
thanks to these discoveries by the university of manchester, another step has been taken in the quest to make smaller, faster electronic devices.
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