Effective geometric size and bond-loss effect in nanoelasticity of GaN nanowires

Wang, R.J.; Wang, C.Y.; Feng, Y. T.

doi:10.1016/j.ijmecsci.2017.06.026

Cited by 8 publications

(11 citation statements)

References 39 publications

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“…Counterintuitively, our results show that at small sizes, despite the largest adhesion, the substrate-induced distortions are the smallest. This is due to the enhanced island stiffness 16,20,21,50,51 , which makes the cost of elastic distortion prohibitive compared to what would be gained by MgO-Ag interaction energy (SI.2.3).…”

Section: Discussionmentioning

confidence: 99%

“…The archetypal mechanical properties of nanowires, on which a great attention was focused for applications to microelectromechanical systems (MEMS), question this approximation. In wires less than a few tens of nanometers in diameter, the larger surface to volume ratio results in strongly size-dependent elastic parameters [16][17][18][19][20][21] . The key question is whether such dependence can be evidenced in supported nano-objects and whether it plays a role in heteroepitaxy.…”

Section: Introductionmentioning

confidence: 99%

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Understanding nanoscale effects in oxide/metal heteroepitaxy

Cabailh

Goniakowski

Noguera

et al. 2019

Phys. Rev. Materials

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The growth mode of strained epitaxial films relies on the interaction strength, the lattice matching and the mechanical response of the system. The present work focuses on the basic physics of supported nano-islands by examining the characteristics of MgO/Ag(100) taken as a case study. The combination of experiments and simulations highlights the existence of a small size regime in which, despite the largest adhesion and the smallest mismatch, the islands are the least distorted by the substrate. We assign this unexpected behavior to the enhanced island stiffness which makes the cost of elastic distortion prohibitive compared to the associated gain of MgO-Ag interaction energy. The analysis provides a general framework to predict and/or understand nanoscale effects on interfacial pseudomorphism. These are likely to hold whatever the nature of the deposit and substrate under consideration. It may have far reaching consequences on many properties of supported nano-objects.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Understanding nanoscale effects in oxide/metal heteroepitaxy

Cabailh

Goniakowski

Noguera

et al. 2019

Phys. Rev. Materials

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“…The size-dependent elasticity is also observed in c-axis GaN NWs [18], which is again controlled by the surface effects. However, the obtained surface modulus (S ) [47] is lower than the corresponding bulk value due to the bond-loss at the surface. This low surface modulus results in a strong softening effect on the overall Young's modulus where Y decrease with the decreasing size.…”

Section: Orientation Effect On Size Dependent Young's Modulusmentioning

confidence: 82%

Mechanical responses ofa-axis GaN nanowires under axial loads

Wang

Feng

et al. 2018

Nanotechnology

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Gallium nitride (GaN) nanowires (NWs) hold technological significance as functional components in emergent nano-piezotronics. However, the examination of their mechanical responses, especially the mechanistic understanding of behavior beyond elasticity (at failure) remains limited due to the constraints of in situ experimentation. We therefore performed simulations of the molecular dynamics (MD) of the mechanical behavior of [Formula: see text]-oriented GaN NWs subjected to tension or compression loading until failure. The mechanical properties and critical deformation processes are characterized in relation to NW sizes and loading conditions. Detailed examinations revealed that the failure mechanisms are size-dependent and controlled by the dislocation mobility on shuffle-set pyramidal planes. The size dependence of the elastic behavior is also examined in terms of the surface structure determined modification of Young's modulus. In addition, a comparison with c-axis NWs is made to show how size-effect trends vary with the growth orientation of NWs.

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“…One mechanism for introducing a thickness dependence of the elastic properties of ultrathin films arises from the high proportion of atoms at the free surface of the material, which have a reduced number of nearest neighbors compared to atoms in the bulk volume. The low-coordinated surface can either soften the film since surface atoms have fewer constraints on their movement [5], or it can stiffen the film as redistributed electrons induce charging or bond contraction [6,7]. These mechanisms have been studied theoretically using continuum and atomistic approaches [5,[7][8][9][10][11], and were * travis.frazer@colorado.edu measured experimentally in materials such as nitrides [12], 51 semiconductors [10,13], polymers [14], and metals [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Full characterization of ultrathin 5-nm low- k dielectric bilayers: Influence of dopants and surfaces on the mechanical properties

Frazer

Knobloch

Hernández-Charpak

et al. 2020

Phys. Rev. Materials

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Ultrathin films and multilayers, with controlled thickness down to single atomic layers, are critical for advanced technologies ranging from nanoelectronics to spintronics to quantum devices. However, for thicknesses less than 10 nm, surfaces and dopants contribute significantly to the film properties, which can differ dramatically from that of bulk materials. For amorphous films being developed as low dielectric constant interfaces for nanoelectronics, the presence of surfaces or dopants can soften films and degrade their mechanical performance. Here we use coherent short-wavelength light to fully and nondestructively characterize the mechanical properties of individual films as thin as 5 nm within a bilayer. In general, we find that the mechanical properties depend both on the amount of doping and the presence of surfaces. In very thin (5-nm) silicon carbide bilayers with low hydrogen doping, surface effects induce a substantial softening-by almost an order of magnitude-compared with the same doping in thicker (46-nm) bilayers. These findings are important for informed design of ultrathin films for a host of nano-and quantum technologies, and for improving the switching speed and efficiency of next-generation electronics.can characterize films with thicknesses on the order of a 80 fraction of a micron, when combined with advanced modeling 81 [23,24]. Surface Brillouin light scattering, which uses the 82 interaction of light and acoustic phonons, has extracted the 83 full elastic tensor of films of thicknesses down to 25 nm [25]. 84 However, it has difficulty characterizing thinner films without 85 assuming one of the elastic constants. In past work, we used 86 coherent extreme ultraviolet (EUV) beams to characterize the 87 full elastic tensor of isotropic ultrathin films down to 11 nm 88 in thickness [21]. This allowed us to simultaneously extract 89 the Young modulus and Poisson's ratio of low-k amorphous 90 SiC:H films with varying degrees of stiffness and hydrogena-91 tion, in a single measurement. 92 In this work, we show how dopants and surfaces inter-93 play to determine the elastic properties of low-k (k < 4.2) 94 dielectric films that are being developed for next-generation 95 nanoelectronics. We use coherent short-wavelength light to 96 fully and nondestructively characterize the mechanical prop-97 erties of SiOC:H films and SiC:H bilayers with individual 98 layers as thin as 5 nm. This allows us to distinguish between 99 dopant-induced and surface-induced softening. For example, 100 in very thin (5-nm) silicon carbide films with low hydrogen 101 doping, surface effects induce a substantial softening-by al-102 most an order of magnitude-compared with the same doping 103 in thicker (46-nm) films. These findings are important for 104 informed design of ultrathin films for a host of nano-and 105 quantum technologies, and for improving the switching speed 106 and efficiency of next-generation electronics. 107 II. METHODS 108 To distinguish between surface-induced softening and 109 dopant-induced softening,...

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Effective geometric size and bond-loss effect in nanoelasticity of GaN nanowires

Cited by 8 publications

References 39 publications

Understanding nanoscale effects in oxide/metal heteroepitaxy

Understanding nanoscale effects in oxide/metal heteroepitaxy

Mechanical responses ofa-axis GaN nanowires under axial loads

Full characterization of ultrathin 5-nm low- k dielectric bilayers: Influence of dopants and surfaces on the mechanical properties

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