Flexible Germanium Nanowires: Ideal Strength, Room Temperature Plasticity, and Bendable Semiconductor Fabric

Smith, Damon A.; Holmberg, Vincent C.; Korgel, Brian A.

doi:10.1021/nn1003088

Cited by 103 publications

(107 citation statements)

References 30 publications

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“…However, these strains have recently been proven to be well within the realizable limit in nanowires. 8,9 Therefore, we predict that the phonon-limited mobility of Ge can be enormously enhanced by applying positive stress in the h111i direction, as shown in Fig. 1.…”

Section: Resultsmentioning

confidence: 90%

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Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures

Murphy-Armando

Fahy

2011

Journal of Applied Physics

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First-principles electronic structure methods are used to predict the rate of n-type carrier scattering due to phonons in highly-strained Ge. We show that strains achievable in nanoscale structures, where Ge becomes a direct bandgap semiconductor, cause the phonon-limited mobility to be enhanced by hundreds of times that of unstrained Ge, and over a thousand times that of Si. This makes highly tensile strained Ge a most promising material for the construction of channels in CMOS devices, as well as for Si-based photonic applications. Biaxial (001) strain achieves mobility enhancements of 100 to 1000 with strains over 2%. Low temperature mobility can be increased by even larger factors. Second order terms in the deformation potential of the Γ valley are found to be important in this mobility enhancement. Although they are modified by shifts in the conduction band valleys, which are caused by carrier quantum confinement, these mobility enhancements persist in strained nanostructures down to sizes of 20 nm.

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Section: Resultsmentioning

confidence: 90%

“…The first type of strain has recently been achieved on thin films of Ge grown on In x Ga 1Àx As substrates, 7 where direct gap photoluminesence has been observed. Strains of the second type have been experimentally surpassed in nanowires, 8,9 where strains up to 17% have been achieved.…”

Section: Introductionmentioning

confidence: 99%

Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures

Murphy-Armando

Fahy

2011

Journal of Applied Physics

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“…Following this report, large plasticity and the c-a transition have also been observed in other semiconductor NWs. Smith et al 75 observed that Ge NWs become amorphous at the point of maximum strain of 17%. Asthana et al 76 observed the c-a transition in the highly compressed region of the [0001] ZnO NWs after a number of loading and unloading cycles.…”

Section: Direct Atomic Mechanisms Of the Size Effect On The Unusual Pmentioning

confidence: 99%

“…These results provide a direct explanation for the ultra-large straining ability and the c-a transition mechanism for those semiconductor and ceramic nanostructures. 25,26,36,[75][76][77] …”

Section: Direct Atomic Mechanisms Of the Size Effect On The Unusual Pmentioning

confidence: 99%

In situ experimental mechanics of nanomaterials at the atomic scale

2013

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Sub-micron and nanostructured materials exhibit high strength, ultra-large elasticity and unusual plastic deformation behaviors. These properties are important for their applications as building blocks for the fabrication of nano-and micro-devices as well as for their use as components for composite materials, high-strength structural and novel functional materials. These nano-related deformation and mechanical behaviors, which are derived from possible size and dimensional effects and the low density of defects, are considerably different from their conventional bulk counterparts. The atomic-scale understanding of the microstructural evolution process of nanomaterials when they are subjected to external stress is crucial for understanding these 'unusual' phenomena and is important for designing new materials, novel structures and applications. This review presents the recent developments in the methods, techniques, instrumentation and scientific progress for atomic-scale in situ deformation dynamics on nanomaterials, including nanowires, nanotubes, nanocrystals, nanofilms and polycrystalline nanomaterials. The unusual dislocation initiation, partial-full dislocation transition, crystalline-amorphous transitions and fracture phenomena related to the experimental mechanics of the nanomaterials are reviewed. Current limitations and future aspects using in situ high-resolution transmission electron microscopy of nanomaterials are also discussed. A new research field of in situ experimental mechanics at the atomic scale is thus expected. Keywords: atomic scale; dislocation; experimental mechanics; in situ; nanomaterial; twin INTRODUCTION Recent studies on nanostructured materials, including nanowires (NWs), 1,2 nanotubes (NTs), 1,3 nanocrystals (NC), 4 micro/nanopillars (NPs) 5-7 and nanocrystalline, 8,9 have revealed a variety of 'unusual deformation' phenomena compared with their bulk counterparts, such as high strength, nano-piezoelectric effects and unusual plastic deformation behaviors. Nanostructured materials can apparently sustain a larger dynamic range of elastic and plastic strains than conventional materials. The results from these studies indicate that the fundamental dislocation processes that initiate and sustain plastic flow and fracture in nanoscale materials are considerably different than in their conventional bulk counterparts. These 'unusual' phenomena not only allow these materials to possess excellent mechanical properties but also enable the tuning of their band structures and related novel electronic, magnetic, optical, photonic and catalytic properties. Revealing the atomic-scale deformation mechanisms of nanomaterials (NM) and controlling their elastic and plastic properties are useful for realizing the desired mechanical, physical and chemical properties through the application of stress or strain.Although extensive studies have been conducted to investigate the mechanical properties of NM, 10 the majority of the atomic

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“…The figure shows a snapshot of darkening after just 15 s at low magnification, corresponding to a lower dose than previous figures. Although the theoretical tensile strength of Ge is predicted to be 14-20 GPa [30,31] while undergoing an elastic deformation, experimental measurements range from 15 to 18 GPa [32,33] for Ge nanowires to just 40-95 MPa for bulk Ge [34]. This study indicates that tensile-strained Ge is Although the theoretical tensile strength of Ge is predicted to be 14-20 GPa [30,31] while undergoing an elastic deformation, experimental measurements range from 15 to 18 GPa [32,33] for Ge nanowires to just 40-95 MPa for bulk Ge [34].…”

Section: Discussionmentioning

confidence: 99%

Extended Defect Propagation in Highly Tensile-Strained Ge Waveguides

O'Brien

Stephenson

et al. 2017

Crystals

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Tensile-strained Ge is a possible laser material for Si integrated circuits, but reports of lasers using tensile Ge show high threshold current densities and short lifetimes. To study the origins of these shortcomings, Ge ridge waveguides with tensile strain in three dimensions were fabricated using compressive silicon nitride (SiN x ) films with up to 2 GPa stress as stress liners. A Raman peak shift of up to 11 cm −1 was observed, corresponding to 3.6% hydrostatic tensile strain for waveguides with a triangular cross-section. Real time degradation in tensile-strained Ge was observed and studied under transmission electron microscopy (TEM). A network of defects, resembling dark line defects, was observed to form and propagate with a speed and density strongly correlated with the local strain extracted from both modeled and measured strain profiles. This degradation suggests highly tensile-strained Ge lasers are likely to have significantly shorter lifetime than similar GaAs or InGaAs quantum well lasers.

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Flexible Germanium Nanowires: Ideal Strength, Room Temperature Plasticity, and Bendable Semiconductor Fabric

Cited by 103 publications

References 30 publications

Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures

Giant enhancement of n-type carrier mobility in highly strained germanium nanostructures

In situ experimental mechanics of nanomaterials at the atomic scale

Extended Defect Propagation in Highly Tensile-Strained Ge Waveguides

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