Electronic Structure Shift of Deep Nanoscale Silicon by SiO2_2- vs. Si3_3N4_4-Embedding as Alternative to Impurity Doping

Conventional impurity doping of deep nanoscale silicon (dns-Si) used in ultra large scale integration (ULSI) faces serious challenges below the 14 nm technology node. We report on a new fundamental effect in theory and experiment, namely the electronic structure of dns-Si experiencing energy offsets of ca. 1 eV as a function of SiO$_2$- vs. Si$_3$N$_4$-embedding with a few monolayers (MLs). An interface charge transfer (ICT) from dns-Si specific to the anion type of the dielectric is at the core of this effect and arguably nested in quantum-chemical properties of oxygen (O) and nitrogen (N) vs. Si. We investigate the size up to which this energy offset defines the electronic structure of dns-Si by density functional theory (DFT), considering interface orientation, embedding layer thickness, and approximants featuring two Si nanocrystals (NCs); one embedded in SiO$_2$ and the other in Si$_3$N$_4$. Working with synchrotron ultraviolet photoelectron spectroscopy (UPS), we use SiO$_2$- vs. Si$_3$N$_4$-embedded Si nanowells (NWells) to obtain their energy of the top valence band states. These results confirm our theoretical findings and gauge an analytic model for projecting maximum dns-Si sizes for NCs, nanowires (NWires) and NWells where the energy offset reaches full scale, yielding to a clear preference for electrons or holes as majority carriers in dns-Si. Our findings can replace impurity doping for n/p-type dns-Si as used in ultra-low power electronics and ULSI, eliminating dopant-related issues such as inelastic carrier scattering, thermal ionization, clustering, out-diffusion and defect generation. As far as majority carrier preference is concerned, the elimination of those issues effectively shifts the lower size limit of Si-based ULSI devices to the crystalization limit of Si of ca. 1.5 nm and enables them to work also under cryogenic conditions.Comment: 14 pages, 17 Figures with a total 44 graph

Anestro pós-parto em ovelhas de diferentes raças. Efeitos do regime de amamentação

Este trabalho teve como principal objectivo estudar o efeito de dois regimes diferentes de amamentação – permanente ou apenas durante a noite – sobre o anestro fisiológico pós-parto, em ovelhas da raça autóctone portuguesa Churra da Terra Quente (CTQ) e da raça exótica Ile de France (IF), paridas no período de Inverno - Primavera. Para o efeito, utilizou-se um total de 46 ovelhas da raça CTQ e 32 da raça IF. Considerámos que as ovelhas tinham ovulado após o parto, quando os níveis plasmáticos de progesterona se elevaram, pela primeira vez, acima dos 0,5 ng/ml (PSCPP). De acordo com os resultados alcançados, o regime de amamentação aplicado não afectou significativamente o anestro pós-parto das ovelhas CTQ e IF

Electronic Structure Shift of Deeply Nanoscale Silicon by SiO2 versus Si3N4 Embedding as an Alternative to Impurity Doping

Conventional impurity doping of deeply nanoscale silicon (dns-Si) used in ultra-large-scale integration (ULSI) faces serious challenges below the 14-nm technology node. We report on a fundamental effect in theory and experiment, namely the electronic structure of dns-Si experiencing energy offsets of approximately 1 eV as a function of SiO2 versus Si3N4 embedding with a few monolayers (MLs). An interface charge transfer (ICT) from dns-Si specific to the anion type of the dielectric is at the core of this effect and is arguably nested in the quantum-chemical properties of oxygen (O) and nitrogen (N) versus Si. We investigate the size up to which this energy offset defines the electronic structure of dns-Si by density-functional theory (DFT), considering the interface orientation, the embedding-layer thickness, and approximants featuring two Si nanocrystals (NCs), one embedded in SiO2 and the other in Si3N4. Working with synchrotron ultraviolet- (UV) photoelectron spectroscopy (UPS), we use SiO2- versus Si3N4-embedded Si nanowells (NWells) to obtain their energy of the top valence-band states. These results confirm our theoretical findings and gauge an analytic model for projecting maximum dns-Si sizes for NCs, nanowires (NWires), and NWells where the energy offset reaches full scale, yielding a clear preference for electrons or holes as majority carriers in dns-Si. Our findings can replace impurity doping for n- or p-type dns-Si as used in ultra-low-power electronics and ULSI, eliminating dopant-related issues such as inelastic carrier scattering, thermal ionization, clustering, out-diffusion, and defect generation. As far as majority-carrier preference is concerned, the elimination of those issues effectively shifts the lower size limit of Si-based ULSI devices to the crystallization limit of Si of approximately 1.5 nm and also enables them to work under cryogenic conditions

Origin and Quantitative Description of the NESSIAS Effect at Si Nanostructures

Abstract The electronic structure of SiO2‐ versus Si3N4‐coated low nanoscale intrinsic silicon (Si) shifts away from versus toward the vacuum level Evac, originating from the Nanoscale Electronic Structure Shift Induced by Anions at Surfaces (NESSIAS). Using the quantum chemical properties of the elements involved to explain NESSIAS, an analytic parameter Λ is derived to predict the highest occupied energy level of Si nanocrystals (NCs) as verified by various hybrid‐density functional calculations and NC sizes. First experimental data of Si nanowells (NWells) embedded in SiO2 versus Si3N4 were measured by X‐ray absorption spectroscopy in total fluorescence yield mode (XAS‐TFY), complemented by ultraviolet photoelectron spectroscopy (UPS), characterizing their conduction band and valence band edge energies EC and EV, respectively. Scanning the valence band sub‐structure over NWell thickness yields an accurate estimate of EV shifted purely by spatial confinement, and thus the actual EV shift due to NESSIAS. Offsets of ΔEC = 0.56 eV and ΔEV = 0.89 eV were obtained for 1.9 nm thick NWells in SiO2 versus Si3N4, demonstrating an intrinsic Si type II homojunction. This p/n junction generated by NESSIAS eliminates any deteriorating impact of impurity dopants, offering undoped ultrasmall Si electronic devices with much reduced physical gate lengths and CMOS‐compatible materials