A new characterization approach to study the mechanical behavior of silicon nanowires

Pakzad, Sina Zare; Esfahani, Mohammad Nasr; Taşdemir, Zuhal; Wollschlaeger, Nicole; Li, XueFei; Li, Taotao; Yılmaz, Mustafa Tahsin; Leblebici, Yusuf; Alaca, B. Erdem

doi:10.1557/s43580-021-00117-x

Cited by 15 publications

(50 citation statements)

References 24 publications

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“…This study uses a recently developed monolithic method to fabricate Si NWs suspended between two microscale pillars. , The fabrication process starts with a p-type, ⟨100⟩ Si wafer of 100 mm diameter, 525 μm thickness, and a resistivity range of 0.1–100 Ω cm. In this process, 33 nanoscale features are patterned using electron beam (e-beam) lithography in a 200 nm-thick hydrogen silsesquioxane (HSQ) resist (Figure a).…”

Section: Methodsmentioning

confidence: 99%

Effect of Native Oxide on Stress in Silicon Nanowires: Implications for Nanoelectromechanical Systems

Esfahani

Pakzad

et al. 2022

ACS Appl. Nano Mater.

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Understanding the origins of intrinsic stress in Si nanowires (NWs) is crucial for their successful utilization as transducer building blocks in next-generation, miniaturized sensors based on nanoelectromechanical systems (NEMS). With their small size leading to ultrahigh-resonance frequencies and extreme surface-to-volume ratios, silicon NWs raise new opportunities regarding sensitivity, precision, and speed in both physical and biochemical sensing. With silicon optoelectromechanical properties strongly dependent on the level of NW intrinsic stress, various studies have been devoted to the measurement of such stresses generated, for example, as a result of harsh fabrication processes. However, due to enormous NW surface area, even the native oxide that is conventionally considered as a benign surface condition can cause significant stresses. To address this issue, a combination of nanomechanical characterization and atomistic simulation approaches is developed. Relying only on low-temperature processes, the fabrication approach yields monolithic NWs with optimum boundary conditions, where NWs and support architecture are etched within the same silicon crystal. Resulting NWs are characterized by transmission electron microscopy and micro-Raman spectroscopy. The interpretation of results is carried out through molecular dynamics simulations with ReaxFF potential facilitating the incorporation of humidity and temperature, thereby providing a close replica of the actual oxidation environmentin contrast to previous dry oxidation or self-limiting thermal oxidation studies. As a result, consensus on significant intrinsic tensile stresses on the order of 100 MPa to 1 GPa was achieved as a function of NW critical dimension and aspect ratio. The understanding developed herein regarding the role of native oxide played in the generation of NW intrinsic stresses is important for the design and development of silicon-based NEMS.

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Section: Methodsmentioning

confidence: 99%

Effect of Native Oxide on Stress in Silicon Nanowires: Implications for Nanoelectromechanical Systems

Esfahani

Pakzad

et al. 2022

ACS Appl. Nano Mater.

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“…1,13,18,23 Bending tests are rather straightforward, where Si NW is loaded preferentially in situ with an external force-sensing probe. 21 Similarly, Si NWs can be integrated with testing devices in the form of micro- electromechanical systems (MEMS), 24 where they are exposed to bending loads. The resulting load−displacement data have then to be interpreted through appropriate models.…”

Section: ■ Introductionmentioning

confidence: 99%

“…55,56 The surface condition and crystalline orientation of NW side surfaces can also be crucial for the precision of the nanomechanical model fitted to the experimental data. 21,29,32 The initial core-surface model by Gurtin and Murdoch 40 is an idealized model as it ignores the surface layer thickness and thus describes the surface as a stretchable but not a bendable structure. 50,57−59 This approach is further improved by a series of core−shell models, 54,58,59 where the NW cross section is considered as a composite structure composed of a bulk core and a surface layer of finite thickness, each with its distinct set of elastic constants.…”

Section: ■ Introductionmentioning

confidence: 99%

“…21,22,25,34,80 A series of transmission electron microscopy (TEM) images obtained through focused-ion beam (FIB) milling reveal the cross-sectional features of the Si NW. 21,22,25,34,80 The in situ three-point bending test is performed within the vacuum chamber of dual-beam FIB/SEM equipment at ambient temperature. A micromanipulator equipped with a piezoresistive cantilever-based Kleindiek force sensor is used to measure the applied load, F, while the bending deflection, w, is quantified through image analysis of micrographs.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Further details related to the calibration of the laser power, Raman analysis, and the determination of related constants can be found elsewhere. 21…”

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Nanomechanical Modeling of the Bending Response of Silicon Nanowires

Zare Pakzad,

Nasr Esfahani,

Tasdemir

et al. 2023

ACS Appl. Nano Mater.

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Understanding the mechanical behavior of silicon nanowires is essential for the implementation of advanced nanoscale devices. Although bending tests are predominantly used for this purpose, their findings should be properly interpreted through modeling. Various modeling approaches tend to ignore parts of the effective parameter set involved in the rather complex bending response. This oversimplification is the main reason behind the spread of the modulus of elasticity and strength data in the literature. Addressing this challenge, a surface-based nanomechanical model is introduced in this study. The proposed model considers two important factors that have so far remained neglected despite their significance: (i) intrinsic stresses composed of the initial residual stress and surface-induced residual stress and (ii) anisotropic implementation of surface stress and elasticity. The modeling study is consolidated with molecular dynamics-based study of the native oxide surface through reactive force fields and a series of nanoscale characterization work through in situ three-point bending test and Raman spectroscopy. The treatment of the test data through a series of models with increasing complexity demonstrates a spread of 85 GPa for the modulus of elasticity and points to the origins of ambiguity regarding silicon nanowire properties, which are some of the most commonly employed nanoscale building blocks. A similar conclusion is reached for strength with variations of up to 3 GPa estimated by the aforementioned nanomechanical models. Precise consideration of the nanowire surface state is thus critical to comprehending the mechanical behavior of silicon nanowires accurately. Overall, this study highlights the need for a multiscale theoretical framework to fully understand the size-dependent mechanical behavior of silicon nanowires, with fortifying effects on the design and reliability assessment of future nanoelectromechanical systems.

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Developments and Future Perspectives in Nanowires Mechanics

Xiang,

Wang,

Zhou

et al. 2024

Acta Mech. Solida Sin.

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With the advancement of micro- and nano-scale devices and systems, there has been growing interest in understanding material mechanics at small scales. Nanowires, as fundamental one-dimensional building blocks, offer significant advantages for constructing micro/nano-electro-mechanical systems (MEMS/NEMS) and serve as an ideal platform for studying their size-dependent mechanical properties. This paper reviews the development and current state of nanowire mechanical testing over the past decade. The first part introduces the related issues of nanowire mechanical testing. The second section explores several key topics and the latest research progress regarding the mechanical properties of nanowires, including ultralarge elastic strain, large plastic strain, ‘smaller is stronger’, cold welding, and ductile-to-brittle transition. Finally, the paper envisions future development directions, identifying possible research hotspots and application prospects.

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A new characterization approach to study the mechanical behavior of silicon nanowires

Cited by 15 publications

References 24 publications

Effect of Native Oxide on Stress in Silicon Nanowires: Implications for Nanoelectromechanical Systems

Effect of Native Oxide on Stress in Silicon Nanowires: Implications for Nanoelectromechanical Systems

Nanomechanical Modeling of the Bending Response of Silicon Nanowires

Developments and Future Perspectives in Nanowires Mechanics

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