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12 Nov 2012

Volume 101, Issue 20, Articles (20xxxx)

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Appl. Phys. Lett. 101, 203102 (2012); http://dx.doi.org/10.1063/1.4747717 (4 pages)

Hyukjin Jung and Ki-Hun Jeong
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Nanoindentation study on insight of plasticity related to dislocation density and crystal orientation in GaN

Masaki Fujikane (藤金 正樹), Toshiya Yokogawa (横川 俊哉), Shijo Nagao (長尾 至成), and Roman Nowak

Appl. Phys. Lett. 101, 201901 (2012); http://dx.doi.org/10.1063/1.4767372 (4 pages)

Online Publication Date: 12 November 2012

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Yield shear stress dependence on dislocation density and crystal orientation was studied in GaN by nanoindentation examination. The yield shear stress decreased with increasing dislocation density, and it decreased with decreasing nanoindentation strain-rate. It reached and coincided at 11.5 GPa for both quasi-static deformed c-plane and m-plane GaN. Taking into account theoretical Peierls–Nabarro stress and yield stress for each slip system, these phenomena were concluded to be an evidence of heterogeneous mechanism associated plastic deformation in GaN crystal. Transmission electron microscopy and molecular dynamics simulation also supported the mechanism with obtained r-plane dislocation line.
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81.40.Lm Deformation, plasticity, and creep
62.20.fq Plasticity and superplasticity
81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
62.20.fg Shape-memory effect; yield stress; superelasticity

Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations

Shuanglin Hu (胡双林), S.-Y. Li (李姝艺), R. Ahuja, C. G. Granqvist, K. Hermansson, G. A. Niklasson, and R. H. Scheicher

Appl. Phys. Lett. 101, 201902 (2012); http://dx.doi.org/10.1063/1.4766167 (4 pages) | Cited 2 times

Online Publication Date: 13 November 2012

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Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < ħω < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.
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78.66.Nk Insulators
81.15.Cd Deposition by sputtering
68.55.aj Insulators
78.20.N- Thermo-optic effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.40.Ha Other nonmetallic inorganics

Interplay between non-bridging oxygen, triclusters, and fivefold Al coordination in low silica content calcium aluminosilicate melts

N. Jakse, M. Bouhadja, J. Kozaily, J. W. E. Drewitt, L. Hennet, D. R. Neuville, H. E. Fischer, V. Cristiglio, and A. Pasturel

Appl. Phys. Lett. 101, 201903 (2012); http://dx.doi.org/10.1063/1.4766920 (5 pages) | Cited 2 times

Online Publication Date: 13 November 2012

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In the present work the structural properties of low silica content calcium aluminosilicate melts with concentration ratio CaO/Al2O3 = 1 are investigated in the liquid and undercooled states by neutron diffraction experiments and ab initio molecular dynamics simulations. The results show the presence of AlO5 units and triclusters as well as non-bridging oxygen in the fully charge balanced compositions. Moreover, our findings allow us to identify a possible interplay between these structural units. Finally, we discuss the influence of these defective structural units on the properties of tetrahedral network and more particularly their implication on the evolution of the viscosity and the fragility.
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61.20.Ja Computer simulation of liquid structure
61.25.-f Studies of specific liquid structures
66.20.Ej Studies of viscosity and rheological properties of specific liquids
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