Neutron-Zwischenreflex-Scattering from Point Defects in Crystals

1986 ◽  
Vol 69 ◽  
Author(s):  
H. Dosch ◽  
J. Peisl
Keyword(s):  
Point Defects ◽  
Displacement Field ◽  
Defect Structure ◽  
Host Lattice ◽  
Local Defect ◽  
Defect Model ◽  
Defect Site ◽  
X Ray Scattering ◽  
Tetrahedral Sites ◽  
Diffuse Neutron

AbstractDiffuse neutron or x-ray scattering close to the Bragg peaks (Huang scattering) and far away from Bragg peaks (Zwischenreflex-scattering) supplies detailed information on point defects and small agglomerates in crystals [1]. The defect structure, i.e. the lattice location, the displacements of the near neighbours and the strength and symmetry of the long ranged displacement field can be determined. In order to demonstrate the power of this technique, we report on recent experimental results. Interstitially dissolved N and O in Nb are located on octahedral sites and create rather large displacements in their vicinity. Their long ranged displacement field shows the symmetry of the defect site. The light interstitials H and D in Nb are located on tetrahedral sites and their long ranged displacement field shows the symmetry of the host lattice. A rather complicated defect model is necessary in order to explain the local defect structure.

X-Ray Scattering from the Displacement Field of Point Defects

1972 ◽  
Vol 29 (4) ◽  
pp. 224-226 ◽  
Author(s):  
H. Lohstöter ◽  
H. Spalt ◽  
H. Peisl
Keyword(s):  
Point Defects ◽  
Displacement Field ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Hg1-xCdxTe: Defect Structure Overview

1990 ◽  
Vol 216 ◽  
Author(s):  
M.A. Berding ◽  
A. Sher ◽  
A.-B. Chen
Keyword(s):  
Point Defects ◽  
Defect Structure ◽  
Defect Formation ◽  
Activation Energies ◽  
Mass Action ◽  
Native Defect ◽  
Native Point Defects ◽  
Vacancy Migration ◽  
Formation Energies ◽  
Diffusion Activation

ABSTRACTNative point defects play an important role in HgCdTe. Here we discuss some of the relevant mass action equations, and use recently calculated defect formation energies to discuss relative defect concentrations. In agreement with experiment, the Hg vacancy is found to be the dominant native defect to accommodate excess tellurium. Preliminary estimates find the Hg antisite and the Hg interstitial to be of comparable densities. Our calculated defect formation energies are also consistent with measured diffusion activation energies, assuming the interstitial and vacancy migration energies are small.

scholarly journals First-Principles Assessment of the Structure and Stability of 15 Intrinsic Point Defects in Zinc-Blende Indium Arsenide

Crystals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 48 ◽  
Author(s):  
Qing Peng ◽  
Nanjun Chen ◽  
Danhong Huang ◽  
Eric Heller ◽  
David Cardimona ◽  
...  
Keyword(s):  
Fermi Level ◽  
Charge State ◽  
Indium Arsenide ◽  
Point Defects ◽  
First Principles ◽  
Formation Energy ◽  
Fast Diffusion ◽  
Intrinsic Point Defects ◽  
Zinc Blende ◽  
Tetrahedral Sites

Point defects are inevitable, at least due to thermodynamics, and essential for engineering semiconductors. Herein, we investigate the formation and electronic structures of fifteen different kinds of intrinsic point defects of zinc blende indium arsenide (zb-InAs ) using first-principles calculations. For As-rich environment, substitutional point defects are the primary intrinsic point defects in zb-InAs until the n-type doping region with Fermi level above 0.32 eV is reached, where the dominant intrinsic point defects are changed to In vacancies. For In-rich environment, In tetrahedral interstitial has the lowest formation energy till n-type doped region with Fermi level 0.24 eV where substitutional point defects In A s take over. The dumbbell interstitials prefer < 110 > configurations. For tetrahedral interstitials, In atoms prefer 4-As tetrahedral site for both As-rich and In-rich environments until the Fermi level goes above 0.26 eV in n-type doped region, where In atoms acquire the same formation energy at both tetrahedral sites and the same charge state. This implies a fast diffusion along the t − T − t path among the tetrahedral sites for In atoms. The In vacancies V I n decrease quickly and monotonically with increasing Fermi level and has a q = − 3 e charge state at the same time. The most popular vacancy-type defect is V I n in an As-rich environment, but switches to V A s in an In-rich environment at light p-doped region when Fermi level below 0.2 eV. This study sheds light on the relative stabilities of these intrinsic point defects, their concentrations and possible diffusions, which is expected useful in defect-engineering zb-InAs based semiconductors, as well as the material design for radiation-tolerant electronics.

Ionic conductivity, phase composition, and local defect structure of ZrO2-Gd2O3system solid solution crystals

2019 ◽  
Vol 23 (9) ◽  
pp. 2619-2626 ◽  
Author(s):  
Ekaterina A. Agarkova ◽  
Mikhail A. Borik ◽  
Tatiana V. Volkova ◽  
Alexey V. Kulebyakin ◽  
Irina E. Kuritsyna ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phase Composition ◽  
Ionic Conductivity ◽  
Defect Structure ◽  
Local Defect

Ultraviolet-Crosslinkable and Injectable Chitosan/Hydroxyapatite Hybrid Hydrogel for Critical Size Calvarial Defect Repair In Vivo

2015 ◽  
Vol 6 (4) ◽  
Author(s):  
Baoqiang Li ◽  
Lei Wang ◽  
Yu Hao ◽  
Daqing Wei ◽  
Ying Li ◽  
...  
Keyword(s):  
Bone Regeneration ◽  
Critical Size ◽  
Rabbit Model ◽  
Single Step ◽  
Calvarial Defect ◽  
Defect Model ◽  
Calvarial Bone ◽  
Hybrid Hydrogel ◽  
Defect Site

To promote bone regeneration in vivo using critical-size calvarial defect model, hybrid hydrogel was prepared by mixing chitosan with hydroxyapatite (HA) and ultraviolet (UV) irradiation in situ. The hydrosoluble, UV-crosslinkable and injectable N-methacryloyl chitosan (N-MAC) was synthesized via single-step N-acylation reaction. The chemical structure was confirmed by 1H-NMR and FTIR spectroscopy. N-MAC hydrogel presented a microporous structure with pore sizes ranging from 10 to 60 μm. Approximately 80% cell viability of N-MAC hydrogel against encapsulated 3T3 cell indicated that N-MAC is an emerging candidate for mimicking native extracellular matrix (ECM). N-MAC hydrogel hybridized with HA was used to accelerate regeneration of calvarial bone using rabbit model. The effects of hybrid hydrogels to promote bone regeneration were evaluated using critical size calvarial bone defect model. The healing effects of injectable hydrogels with/without HA for bone regeneration were investigated by analyzing X-ray image after 4 or 6 weeks. The results showed that the regenerated new bone for N-MAC 100 was significantly greater than N-MAC without HA and untreated controls. The higher HA content in N-MAC/HA hybrid hydrogel benefited the acceleration of bone regeneration. About 50% closure of defect site after 6 weeks postimplantation demonstrated potent osteoinductivity of N-MAC 100 UV-crosslinkable and injectable N-MAC/HA hybrid hydrogel would allow serving as a promising biomaterial for bone regeneration using the critical-size calvarial defect.

Effect of defect structure on gas sensitivity of LaCrO3

1996 ◽  
Vol 11 (12) ◽  
pp. 3077-3082 ◽  
Author(s):  
Rong-Fong Huang ◽  
Wei-Yean Howng
Keyword(s):  
Point Defects ◽  
Defect Structure ◽  
Isopropyl Alcohol ◽  
Sensitivity Enhancement ◽  
High Resistivity ◽  
Stoichiometric Ratio ◽  
Gas Sensitivity ◽  
Conduction Behavior ◽  
Positively Charged ◽  
Trapping Sites

The isopropyl alcohol gas sensitivity of LaCrO3 at 250 °C is found to depend on the amount of TiO2 content and cation stoichiometric ratio of the sample. The gas sensitivity enhancement is related to the defect structure and electrical conduction behavior of p-type, donor-doped semiconductive oxides. The high resistivity coupled with the increasing point defects by the donor dopants are responsible for the high gas sensitivity of TiO2 doped LaCrO3. It is believed that the positively charged ionic-type defects created by dopants act as trapping sites to adsorb oxygen.

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