A research team coordinated by Stefano Lupi of the Department of Physics of Sapienza and by Alessandro Molle of the Institute for microelectronics and microsystems of the National Research Council (Cnr-Imm) in Agrate Brianza, together with groups from the University of Rome Tor Vergata, University of Roma Tre and in collaboration with STMircoelectronics, has obtained for the first time a two-dimensional configuration of silicon, which presents an optical response never observed before. The new structure allows, in fact, the absorption of light in an area of the optical spectrum that was considered prohibited for silicon up to now and promises great innovations in technology. The results of the study are published in the journal Nano Letters.

"Silicon is the basic material for electronics and photovoltaics. This new configuration is similar to that of graphene (hence the name silicene), a particularly versatile material in many sectors, such as energy, information technology or biomedicine, "explains Molle. "The great innovation of the study is represented by the support of sapphire, a crystallized aluminum oxide, which has an insulating behavior. On this support we deposited, by ultra-high vacuum evaporation, silicon atoms which are organized into one or more two-dimensional layers, with a structure similar to graphene, where the charge carriers behave as if they were photons ".

This silicon behavior was a surprise for the research group. "This is an unexpected response, in meaning of that the optical absorption of silicon that we have found in our study does not correspond to that conventionally known in the three-dimensional form", states Molle."Having a two-dimensional silicon, which then deviates from conventional silicon, has a totally unexplored potential and its use will no longer have the energy limits linked to the three-dimensional configuration", adds Lupi.

The newborn two-dimensional silicon seems to have according to researchers all the papers in order to revolutionize different technological fields. "We are also considering the use of the methodology in projects related to the creation of plasmonics and photonics devices thanks to the successful integration with other two-dimensional materials such as graphene, which we tested in the Teralab laboratory of the Physics Department of Sapienza", concludes Lupi.

References:

“Optical Conductivity of Two-Dimensional Silicon: Evidence of Dirac Electrodynamics”, C. Grazianetti, S. De Rosa, C. Martella, P. Targa, D. Codegoni, P. Gori, O. Pulci, A. Molle*, and S. Lupi*, Nano Letters 2018 18, 7124 . DOI: 10.1021/acs.nanolett.8b03169

Further Information:

Stefano Lupi
Department of Physics, Sapienza University of Rome
stefano.lupi@roma1.infn.it