The NESSIAS effect at Si nanostructures
Si nanowells embedded in SiO2- and Si3N4 show an electronic structure shift with respect to the vacuum level. This NESSIAS effect gives origin to intrinsic Si type II homojunctions which should remain fully functional down to extremely low temperatures, useful for peripheral electronics in qbit manipulation.
Advanced Physics Research, 2, 2200065 (2023), 10.1002/apxr.202200065
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Silicon nanowells with a thickness of less thann about 3.3 nm embedded in silicon dioxide (SiO2) versus silicon nitride (Si3N4) show an electronic structure shift with respect to the vacuum energy level Evac as measured by UPS and XAS-TFY. NWells embedded in SiO2 (Si3N4) get shifted to higher (lower) binding energies, that is, away from (towards to) Evac. This effect, named NESSIAS, (Nanoscale Electronic Structure Shift induced by Anions at Surfaces) is caused by quantum chemical properties of the anions forming the dielectric which surrounds the low nanoscale Si and it has been established in theory and experiment by a collaborative work lead by Dr. Dirk König of the Australian National University. The exact origin and quantitative description of of the NESSIAS effect has been established with a detailed quantum chemical explanation complemented with its semi-quantitative description which serves to predict NESSIAS in low nanoscale intrinsic Si for a variety of anions in embedding/coating dielectrics. To this end silicon nanowells have been fabricated and characterized at the Aachen University and experimental evidence which leads to the NESSIAS effect have been obtained with complimentary XAS and UPS measurements at Elettra at the bemlines BACH and BadElph, respectively. |
The NESSIAS effect induces a p/n junction on semiconductor nanostructures by enabling an electron flooding of the nanostructure when coated with SiO2, or a virtually complete electron drainage from the nanostructure when coated with Si3N4, introducing a high density of holes into the nanovolume by the latter process. This re-arrangement of charge carrier densities has far-reaching consequences for semiconductor devices in very large scale integration, ultra-low power and cryo-electronics. Spatial fluctuations of dopant densities, out-diffusion and self-purification impose a size limit onto very large scale integrationdevices as evident from physical gate lengths hovering around 20 nm since ca. 2014. With thermal dopant ionization not required, junctions induced by the NESSIAS effect should remain fully functional down to extremely low temperatures as useful for peripheral electronics in qbit manipulation
Origin and quantitative description of the NESSIAS effect at Si nanostructures |
