Atomic structures and mechanical properties of single-crystal GaN nanotubes

Xu, B.; Lu, A. J.; Pan, Bicai; Yu, Qihao

doi:10.1103/physrevb.71.125434

Cited by 49 publications

(33 citation statements)

References 14 publications

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“…The widening of the bulk band gap is observed, although surface states within the band gap also have been seen [6]. There exists also a theoretical study on GaN single-crystal nanotubes (SCNT) devoted to the atomistic simulation of elastic properties [7]. The study predicts stiffening of SCNTs with increasing surface to volume ratio.…”

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confidence: 97%

Ab initio calculation of wurtzite‐type GaN nanowires

Guļāns

Tāle

2007

Phys. Status Solidi (c)

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PACS 61. 61.50.Ah, 62.20.Dc, 71.15.Mb Ab initio calculations of wurtzite-type GaN nanowires have been performed using density functional theory. Different shapes of nanowires of with similar diameters of around 2 nm have been considered to determine the stability of the structures. The quantitative similarities in the local properties obtained and dangling bond energies of nanowires and bulk surfaces have lead to a simple model model for a calculation of effective Young's modulus of nanowires of arbitrary diameters and shapes. The size dependence of the Young's modulus reveals a softening of GaN nanowires with the decrease of the diameter.

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confidence: 97%

Ab initio calculation of wurtzite‐type GaN nanowires

Guļāns

Tāle

2007

Phys. Status Solidi (c)

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“…Recently, molecular dynamics ͑MD͒ simulations are carried out to analyze the atomistic structures of singlecrystal GaN nanotubes and the buckling behavior of GaN nanowires. 10 Yet, the effect of surface-stresses on the structural transformation in GaN nanorods is still poorly understood and merit careful inspection. Here, MD simulations are carried out to investigate the surface transformation and defect formation in GaN nanorods.…”

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confidence: 99%

Surface transformation and inversion domain boundaries in gallium nitride nanorods

Xiao

Wang

et al. 2009

Applied Physics Letters

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Phase transformation and subdomain structure in ͓0001͔-oriented gallium nitride ͑GaN͒ nanorods of different sizes are studied using molecular dynamics simulations. The analysis concerns the structure of GaN nanorods at 300 K without external loading. Calculations show that a transformation from wurtzite to a tetragonal structure occurs along ͕0110͖ lateral surfaces, leading to the formation of a six-sided columnar inversion domain boundary ͑IDB͒ in the ͓0001͔ direction of the nanorods. This structural configuration is similar to the IDB structure observed experimentally in GaN epitaxial layers. The transformation is significantly dependent on the size of the nanorods. © 2009 American Institute of Physics. ͓doi:10.1063/1.3268467͔With a wide band gap, gallium nitride ͑GaN͒ promises superior performances for blue light-emitting diodes, 1 highpower sources, and optical data storage devices.2 Recent advances in the synthesis of one-dimensional nanostructures have brought forth possibilities for GaN to be used in more applications.3 Structural transformations and defects are subjects of active experimental and theoretical research for GaN, 4 because they lead to significant changes in physical and chemical properties and, therefore, affect applications. These transformations and defects can be caused by external or internal factors. For epitaxially grown GaN layers, because of the lack of a lattice and thermally matching substrate, they always contain large numbers of defects.5 Highresolution x-ray diffraction studies of GaN layers have indicated that both carrier mobility and the intensity of photoluminescence are strongly related to defects.6 It was also observed that a phase transformation from wurtzite ͑WZ͒ to rock-salt structure can be induced by high pressure in GaN. 7 However for GaN nanostructures, surface stresses due to high surface-to-volume ratios are another factor that may lead to structural transitions. Experimental observations and atomistic simulations show that structural reorientation can occur in metal ͑copper, silver, and gold͒ nanowires due to high surface-stresses. 8,9 This reorientation causes some of the face-centered-cubic metal nanowires to exhibit a shape memory and pseudoelasticity which are not possessed by corresponding bulk materials. 9 The microscopic details of structural transformations in nanostructures are, however, difficult to investigate through direct experimental observations. Atomistic simulations can play an important role in this regard. Recently, molecular dynamics ͑MD͒ simulations are carried out to analyze the atomistic structures of singlecrystal GaN nanotubes and the buckling behavior of GaN nanowires.10 Yet, the effect of surface-stresses on the structural transformation in GaN nanorods is still poorly understood and merit careful inspection. Here, MD simulations are carried out to investigate the surface transformation and defect formation in GaN nanorods. The analyses concern the equilibrium structure of GaN nanorods with lateral dimensions between 22.6-67.4 Å ...

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“…6͒ or GaN nanotubes. 7 This effect is caused by an increased hardness of the nanocolumn surface due to the decrease in the bond length near the surface. 8 It is known that peculiarities in the mosaic structure of nitride layers determine their electrical properties.…”

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confidence: 99%

Internal strains and crystal structure of the layers in AlGaN/GaN heterostructures grown on a sapphire substrate

Kladko

Kolomys

Slobodian

et al. 2009

Journal of Applied Physics

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In this paper, we investigate the structural properties of AlGaN/GaN heterostructures grown by metal organic chemical vapor deposition on sapphire substrates with different thicknesses using high-resolution x-ray diffraction and Raman scattering methods. We discuss the microscopic nature of spatial-inhomogeneous deformations and dislocation density in the structures. Microdeformations within mosaic blocks and the sizes of regions of coherent diffraction are determined. We reveal a gradient depth distribution of deformations in the mosaic structure of nitride layers, as well as at the interface regions of the sapphire substrate on the microscale level using confocal micro-Raman spectroscopy. We determine that an increase in substrate thickness leads to a reduction in dislocation density in the layers and an increase in the elastic deformations. The features of the block structure of nitrides layers are shown to have a significant influence on their elastic properties.

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Atomic structures and mechanical properties of single-crystal GaN nanotubes

Cited by 49 publications

References 14 publications

Ab initio calculation of wurtzite‐type GaN nanowires

Ab initio calculation of wurtzite‐type GaN nanowires

Surface transformation and inversion domain boundaries in gallium nitride nanorods

Internal strains and crystal structure of the layers in AlGaN/GaN heterostructures grown on a sapphire substrate

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