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König D, Smith SC. Analytic description of nanowires II: morphing of regular cross sections for zincblende- and diamond-structures to match arbitrary shapes. ACTA CRYSTALLOGRAPHICA SECTION B, STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS 2022; 78:643-664. [PMID: 35975831 PMCID: PMC9370210 DOI: 10.1107/s2052520622004942] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Setting out from our recent publication [König & Smith (2021). Acta Cryst. B77, 861], we extend our analytic description of the regular cross sections of zincblende- and diamond-structure nanowires (NWires) by introducing cross section morphing to arbitrary convex shapes featuring linear interfaces as encountered in experiment. To this end, we provide add-on terms to the existing number series with their respective running indices for zinc-blende- (zb-) and diamond-structure NWire cross sections. Such add-on terms to all variables yield the required flexibility for cross section morphing, with main variables presented by the number of NWire atoms NWire(dWire[i]), bonds between NWire atoms Nbnd(dWire[i]) and interface bonds NIF(dWire[i]). Other basic geometric variables, such as the specific length of interface facets, as well as widths, heights and total area of the cross section, are given as well. The cross sections refer to the six high-symmetry zb NWires with low-index faceting frequently occurring in the bottom-up and top-down approaches of NWire processing. The fundamental insights into NWire structures revealed here offer a universal gauge and thus enable major advancements in data interpretation and the understanding of all zb- and diamond-structure-based NWires with arbitrary convex cross sections. We corroborate this statement with an exact description of irregular Si NWire cross sections and irregular InGaAs/GaAs core-shell NWire cross sections, where a radially changing unit-cell parameter can be included.
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Affiliation(s)
- Dirk König
- Integrated Materials Design Lab (IMDL), Research School of Physics and Engineering, The Australian National University, ACT 2601, Australia
- Institute of Semiconductor Electronics (IHT), RWTH Aachen University, 52074 Aachen, Germany
- Integrated Materials Design Centre (IMDC), University of New South Wales, NSW 2052, Australia
| | - Sean C. Smith
- Integrated Materials Design Lab (IMDL), Research School of Physics and Engineering, The Australian National University, ACT 2601, Australia
- Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University, ACT 2601, Australia
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König D, Frentzen M, Wilck N, Berghoff B, Píš I, Nappini S, Bondino F, Müller M, Gonzalez S, Di Santo G, Petaccia L, Mayer J, Smith S, Knoch J. Turning Low-Nanoscale Intrinsic Silicon Highly Electron-Conductive by SiO 2 Coating. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20479-20488. [PMID: 33878265 DOI: 10.1021/acsami.0c22360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Impurity doping in silicon (Si) ultra-large-scale integration is one of the key challenges which prevent further device miniaturization. Using ultraviolet photoelectron spectroscopy and X-ray absorption spectroscopy in the total fluorescence yield mode, we show that the lowest unoccupied and highest occupied electronic states of ≤3 nm thick SiO2-coated Si nanowells shift by up to 0.2 eV below the conduction band and ca. 0.7 eV below the valence band edge of bulk silicon, respectively. This nanoscale electronic structure shift induced by anions at surfaces (NESSIAS) provides the means for low-nanoscale intrinsic Si (i-Si) to be flooded by electrons from an external (bigger, metallic) reservoir, thereby getting highly electron- (n-) conductive. While our findings deviate from the behavior commonly believed to govern the properties of silicon nanowells, they are further confirmed by the fundamental energy gap as per nanowell thickness when compared against published experimental data. Supporting our findings further with hybrid density functional theory calculations, we show that other group IV semiconductors (diamond, Ge) do respond to the NESSIAS effect in accord with Si. We predict adequate nanowire cross-sections (X-sections) from experimental nanowell data with a recently established crystallographic analysis, paving the way to undoped ultrasmall silicon electronic devices with significantly reduced gate lengths, using complementary metal-oxide-semiconductor-compatible materials.
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Affiliation(s)
- Dirk König
- Integrated Materials Design Laboratory (IMDL), The Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Smart Materials and Surface Group, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Michael Frentzen
- Institute of Semiconductor Electronics (IHT), RWTH Aachen University, Aachen 52074, Germany
| | - Noël Wilck
- Institute of Semiconductor Electronics (IHT), RWTH Aachen University, Aachen 52074, Germany
| | - Birger Berghoff
- Institute of Semiconductor Electronics (IHT), RWTH Aachen University, Aachen 52074, Germany
| | - Igor Píš
- Laboratorio TASC, IOM-CNR, Area Science Park S.S. 14 km 163.5, Trieste 34149, Italy
| | - Silvia Nappini
- Laboratorio TASC, IOM-CNR, Area Science Park S.S. 14 km 163.5, Trieste 34149, Italy
| | - Federica Bondino
- Laboratorio TASC, IOM-CNR, Area Science Park S.S. 14 km 163.5, Trieste 34149, Italy
| | - Merlin Müller
- Central Facility for Electron Microscopy, RWTH Aachen University, Aachen 52074, Germany
- Ametek GmbH, BU Gatan, Ingolstädter Straße 12, Munich 80807, Germany
| | - Sara Gonzalez
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, Trieste 34149, Italy
| | - Giovanni Di Santo
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, Trieste 34149, Italy
| | - Luca Petaccia
- Elettra Sincrotrone Trieste, Strada Statale 14 km 163.5, Trieste 34149, Italy
| | - Joachim Mayer
- Central Facility for Electron Microscopy, RWTH Aachen University, Aachen 52074, Germany
| | - Sean Smith
- Integrated Materials Design Laboratory (IMDL), The Australian National University, Canberra, Australian Capital Territory 2601, Australia
- Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Joachim Knoch
- Institute of Semiconductor Electronics (IHT), RWTH Aachen University, Aachen 52074, Germany
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König D, Tilley RD, Smith SC. Design guidelines for transition metals as interstitial emitters in silicon nanocrystals to tune photoluminescence properties: zinc as biocompatible example. NANOSCALE 2020; 12:19340-19349. [PMID: 32940305 DOI: 10.1039/d0nr05156j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Silicon nanocrystals (Si NCs) are attractive candidates for biomarkers in medical imaging. Building on recent work [McVey et al., J. Chem. Phys. Lett., 2015, 6/9, 1573; McVey et al., Nanoscale, 2018, 15600], we focus on interstitial (i-) doping of Si NCs by transition metals (TMs), and investigate the optoelectronic structure with Zn as example. Carrying out extensive ground and excited state calculations using density functional theory (DFT), we provide insight into the interdependencies of parameters which define photoluminescence (PL) properties as per TM element, their position, and their density within Si NCs of realistic size. For i-Zn in Si NCs, we predict a very high radiation efficiency with a wavelength located well above the range of auto-luminescence originating from human tissue and blood. We derive general guidelines for i-TM doping of Si NCs to arrive at a desired emission wavelength with maximum radiation efficiency. Moving on from this general description, we reveal the concept of using the plasmonic resonance of i-TM dopants in the microwave (μW) spectrum to trigger selective thermal apoptosis of tagged cells in vivo after cell marking, paving the way towards a theragnostics tool with minimum side effects.
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Affiliation(s)
- Dirk König
- Integrated Materials Design Lab (IMDL), The Australian National University, ACT 2601, Australia. and School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Richard D Tilley
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Sean C Smith
- Integrated Materials Design Lab (IMDL), The Australian National University, ACT 2601, Australia. and Department of Applied Mathematics, Research School of Physics and Engineering, The Australian National University, ACT 2601, Australia
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König D, Smith SC. Analytical description of nanowires. I. Regular cross sections for zincblende and diamond structures. ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE CRYSTAL ENGINEERING AND MATERIALS 2019; 75:788-802. [DOI: 10.1107/s2052520619009351] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 06/29/2019] [Indexed: 11/11/2022]
Abstract
Semiconductor nanowires (NWires) experience stress and charge transfer from their environment and impurity atoms. In response, the environment of a NWire experiences a NWire stress response which may lead to propagated strain and a change in the shape and size of the NWire cross section. Here, geometric number series are deduced for zincblende- (zb-) and diamond-structured NWires of diameter d
Wire to obtain the numbers of NWire atoms N
Wire(d
Wire[i]), bonds between NWire atoms N
bnd(d
Wire[i]) and interface bonds N
IF(d
Wire[i]) for six high-symmetry zb NWires with the low-index faceting that occurs frequently in both bottom-up and top-down approaches of NWire processing. Along with these primary parameters, the specific lengths of interface facets, the cross-sectional widths and heights and the cross-sectional areas are presented. The fundamental insights into NWire structures revealed here offer a universal gauge and thus could enable major advancements in data interpretation and understanding of all zb- and diamond-structure-based NWires. This statement is underpinned with results from the literature on cross-section images from III–V core–shell NWire growth and on Si NWires undergoing self-limiting oxidation and etching. The massive breakdown of impurity doping due to self-purification is shown to occur for both Si NWires and Si nanocrystals (NCs) for a ratio of N
bnd/N
Wire = N
bnd/N
NC = 1.94 ± 0.01 using published experimental data.
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