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Fukata N, Jevasuwan W. Formation and characterization of Group IV semiconductor nanowires. NANOTECHNOLOGY 2024; 35:122001. [PMID: 38096568 DOI: 10.1088/1361-6528/ad15b8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 12/13/2023] [Indexed: 01/05/2024]
Abstract
To enable the application to next-generation devices of semiconductor nanowires (NWs), it is important to control their formation and tune their functionality by doping and the use of heterojunctions. In this paper, we introduce formation and the characterization methods of nanowires, focusing on our research results. We describe a top-down method of controlling the size and alignment of nanowires that shows advantages over bottom-up growth methods. The latter technique causes damage to the nanowire surfaces, requiring defect removal after the NW formation process. We show various methods of evaluating the bonding state and electrical activity of impurities in NWs. If an impurity is doped in a NW, mobility decreases due to the scattering that it causes. As a strategy for solving this problem, we describe research into core-shell nanowires, in which Si and Ge heterojunctions are formed in the diameter direction inside the NW. This structure can separate the impurity-doped region from the carrier transport region, promising as a channel for the new ultimate high-mobility transistor.
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Affiliation(s)
- Naoki Fukata
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
- Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan
| | - Wipakorn Jevasuwan
- Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
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2
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Liao X, Xiao J, Ni Y, Li C, Chen X. Self-Assembly of Islands on Spherical Substrates by Surface Instability. ACS NANO 2017; 11:2611-2617. [PMID: 28273417 DOI: 10.1021/acsnano.6b07108] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Through strain-induced morphological instability, protruding patterns of roughly commensurate nanostructures are self-assembled on the surface of spherical core/shell systems. A three-dimensional (3D) phase field model is established for a closed substrate. We investigate both numerically and analytically the kinetics of the morphological evolution, from grooves to separated islands, which are sensitive to substrate curvature, misfit strain, and modulus ratio between the core and shell. The faster growth rate of surface undulation is associated with the core/shell system of a harder substrate, larger radius, or misfit strain. On the basis of a Ag core/SiO2 shell system, the self-assemblies of SiO2 nanoislands were explored experimentally. The numerical and experimental studies herein could guide the fabrication of ordered quantum structures via surface instability on closed and curved substrates.
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Affiliation(s)
| | | | - Yong Ni
- CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China , Hefei 230026, China
| | - Chaorong Li
- Center for Optoelectronics Materials and Devices, Department of Physics, Zhejiang Sci-Tech University , Hangzhou 310018, China
| | - Xi Chen
- School of Chemical Engineering, Northwest University , Xi'an 710069, China
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3
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Kwon S, Wingert MC, Zheng J, Xiang J, Chen R. Thermal transport in Si and Ge nanostructures in the 'confinement' regime. NANOSCALE 2016; 8:13155-13167. [PMID: 27344991 DOI: 10.1039/c6nr03634a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Reducing semiconductor materials to sizes comparable to the characteristic lengths of phonons, such as the mean-free-path (MFP) and wavelength, has unveiled new physical phenomena and engineering capabilities for thermal energy management and conversion systems. These developments have been enabled by the increasing sophistication of chemical synthesis, microfabrication, and atomistic simulation techniques to understand the underlying mechanisms of phonon transport. Modifying thermal properties by scaling physical size is particularly effective for materials which have large phonon MFPs, such as crystalline Si and Ge. Through nanostructuring, materials that are traditionally good thermal conductors can become good candidates for applications requiring thermal insulation such as thermoelectrics. Precise understanding of nanoscale thermal transport in Si and Ge, the leading materials of the modern semiconductor industry, is increasingly important due to more stringent thermal conditions imposed by ever-increasing complexity and miniaturization of devices. Therefore this Minireview focuses on the recent theoretical and experimental developments related to reduced length effects on thermal transport of Si and Ge with varying size from hundreds to sub-10 nm ranges. Three thermal transport regimes - bulk-like, Casimir, and confinement - are emphasized to describe different governing mechanisms at corresponding length scales.
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Affiliation(s)
- Soonshin Kwon
- Department of Mechanical Engineering, University of California, San Diego, La Jolla, California 92093, USA.
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Day RW, Mankin MN, Lieber CM. Plateau-Rayleigh Crystal Growth of Nanowire Heterostructures: Strain-Modified Surface Chemistry and Morphological Control in One, Two, and Three Dimensions. NANO LETTERS 2016; 16:2830-2836. [PMID: 26929996 DOI: 10.1021/acs.nanolett.6b00629] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
One-dimensional (1D) structures offer unique opportunities for materials synthesis since crystal phases and morphologies that are difficult or impossible to achieve in macroscopic crystals can be synthesized as 1D nanowires (NWs). Recently, we demonstrated one such phenomenon unique to growth on a 1D substrate, termed Plateau-Rayleigh (P-R) crystal growth, where periodic shells develop along a NW core to form diameter-modulated NW homostructures with tunable morphologies. Here we report a novel extension of the P-R crystal growth concept with the synthesis of heterostructures in which Ge (Si) is deposited on Si (Ge) 1D cores to generate complex NW morphologies in 1, 2, or 3D. Depositing Ge on 50 nm Si cores with a constant GeH4 pressure yields a single set of periodic shells, while sequential variation of GeH4 pressure can yield multimodulated 1D NWs with two distinct sets of shell periodicities. P-R crystal growth on 30 nm cores also produces 2D loop structures, where Ge (Si) shells lie primarily on the outside (inside) of a highly curved Si (Ge) core. Systematic investigation of shell morphology as a function of growth time indicates that Ge shells grow in length along positive curvature Si cores faster than along straight Si cores by an order of magnitude. Short Ge deposition times reveal that shells develop on opposite sides of 50 and 100 nm Si cores to form straight 1D morphologies but that shells develop on the same side of 20 nm cores to produce 2D loop and 3D spring structures. These results suggest that strain mediates the formation of 2 and 3D morphologies by altering the NW's surface chemistry and that surface diffusion of heteroatoms on flexible freestanding 1D substrates can facilitate this strain-mediated mechanism.
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Affiliation(s)
- Robert W Day
- Department of Chemistry and Chemical Biology and ‡Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Max N Mankin
- Department of Chemistry and Chemical Biology and ‡Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
| | - Charles M Lieber
- Department of Chemistry and Chemical Biology and ‡Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
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Nguyen BM, Swartzentruber B, Ro YG, Dayeh SA. Facet-Selective Nucleation and Conformal Epitaxy of Ge Shells on Si Nanowires. NANO LETTERS 2015; 15:7258-7264. [PMID: 26447652 DOI: 10.1021/acs.nanolett.5b02313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Knowledge of nanoscale heteroepitaxy is continually evolving as advances in material synthesis reveal new mechanisms that have not been theoretically predicted and are different than what is known about planar structures. In addition to a wide range of potential applications, core/shell nanowire structures offer a useful template to investigate heteroepitaxy at the atomistic scale. We show that the growth of a Ge shell on a Si core can be tuned from the theoretically predicted island growth mode to a conformal, crystalline, and smooth shell by careful adjustment of growth parameters in a narrow growth window that has not been explored before. In the latter growth mode, Ge adatoms preferentially nucleate islands on the {113} facets of the Si core, which outgrow over the {220} facets. Islands on the low-energy {111} facets appear to have a nucleation delay compared to the {113} islands; however, they eventually coalesce to form a crystalline conformal shell. Synthesis of epitaxial and conformal Si/Ge/Si core/multishell structures enables us to fabricate unique cylindrical ring nanowire field-effect transistors, which we demonstrate to have steeper on/off characteristics than conventional core/shell nanowire transistors.
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Affiliation(s)
- Binh-Minh Nguyen
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
- Department of Electrical and Computer Engineering, University of California San Diego , La Jolla, California 92093, United States
| | - Brian Swartzentruber
- Center for Integrated Nanotechnologies, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States
| | - Yun Goo Ro
- Department of Electrical and Computer Engineering, University of California San Diego , La Jolla, California 92093, United States
| | - Shadi A Dayeh
- Center for Integrated Nanotechnologies, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States
- Department of Electrical and Computer Engineering, University of California San Diego , La Jolla, California 92093, United States
- Materials Science Program, University of California San Diego , La Jolla, California 92093, United States
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Ke SY, Yang J, Qiu F, Wang ZQ, Wang C, Yang Y. Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering. NANOTECHNOLOGY 2015; 26:445602. [PMID: 26457572 DOI: 10.1088/0957-4484/26/44/445602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.
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Affiliation(s)
- S Y Ke
- Institute of Optoelectronic Information Materials, Yunnan University, Kunming 650091, People's Republic of China. Department of Physics, Semiconductor Photonics Research Center, Xiamen University, Xiamen 361005, People's Republic of China
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7
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Neupane MR, Rahman R, Lake RK. Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals. Phys Chem Chem Phys 2015; 17:2484-93. [DOI: 10.1039/c4cp03711a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An atomistic study of Ge-core–Si-shell nanocrystals gives a detailed picture of how strain and confinement effect the electronic and optical properties.
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Affiliation(s)
- Mahesh R. Neupane
- Department of Electrical and Computer Engineering
- University of California
- Riverside
- USA
| | - Rajib Rahman
- Network for Computational Nanotechnology (NCN)
- Purdue University
- West Lafayette
- USA
| | - Roger K. Lake
- Department of Electrical and Computer Engineering
- University of California
- Riverside
- USA
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8
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Kwon S, Chen ZCY, Noh H, Lee JH, Liu H, Cha JN, Xiang J. Selective functionalization and loading of biomolecules in crystalline silicon nanotube field-effect-transistors. NANOSCALE 2014; 6:7847-7852. [PMID: 24926535 DOI: 10.1039/c4nr01508h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Crystalline silicon nanotubes (Si NTs) provide distinctive advantages as electrical and biochemical analysis scaffolds through their unique morphology and electrical tunability compared to solid nanowires or amorphous/non-conductive nanotubes. Such potential is investigated in this report. Gate-dependent four-probe current-voltage analysis reveals electrical properties such as resistivity to differ by nearly 3 orders of magnitude between crystalline and amorphous Si NTs. Analysis of transistor transfer characteristics yields a field effect mobility of 40.0 cm(2) V(-1) s(-1) in crystalline Si NTs. The hollow morphology also allows selective inner/outer surface functionalization and loading capability either as a carrier for molecular targets or as a nanofluidic channel for biomolecular assays. We present for the first time a demonstration of internalization of fluorescent dyes (rhodamine) and biomolecules (BSA) in Si NTs as long as 22 μm in length.
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Affiliation(s)
- Soonshin Kwon
- Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093, USA.
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Kempa TJ, Kim SK, Day RW, Park HG, Nocera DG, Lieber CM. Facet-selective growth on nanowires yields multi-component nanostructures and photonic devices. J Am Chem Soc 2013; 135:18354-7. [PMID: 24279423 DOI: 10.1021/ja411050r] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enhanced synthetic control of the morphology, crystal structure, and composition of nanostructures can drive advances in nanoscale devices. Axial and radial semiconductor nanowires are examples of nanostructures with one and two structural degrees of freedom, respectively, and their synthetically tuned and modulated properties have led to advances in nanotransistor, nanophotonic, and thermoelectric devices. Similarly, developing methods that allow for synthetic control of greater than two degrees of freedom could enable new opportunities for functional nanostructures. Here we demonstrate the first regioselective nanowire shell synthesis in studies of Ge and Si growth on faceted Si nanowire surfaces. The selectively deposited Ge is crystalline, and its facet position can be synthetically controlled in situ. We use this synthesis to prepare electrically addressable nanocavities into which solution soluble species such as Au nanoparticles can be incorporated. The method furnishes multicomponent nanostructures with unique photonic properties and presents a more sophisticated nanodevice platform for future applications in catalysis and photodetection.
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Affiliation(s)
- Thomas J Kempa
- Department of Chemistry and Chemical Biology and ‡School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States
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