Heteroepitaxial Layer Morphology and Misfit Defect Formation

1995 ◽  
Vol 399 ◽  
Author(s):  
A.G. Cullis
Keyword(s):  
Free Energy ◽  
Misfit Dislocation ◽  
Defect Formation ◽  
Elastic Stress ◽  
Stress Relief ◽  
Misfit Strain ◽  
Theoretical Modelling ◽  
Initial Growth ◽  
Dislocation Source ◽  
Heteroepitaxial Layers

ABSTRACTThe manner in which misfit strain can influence the morphology of heteroepitaxial layers is reviewed. Following a brief consideration of theoretical modelling, examples of experimental observations for two important materials systems, SiGe/Si and InGaAs/GaAs, are given. It is demonstrated that the formation of undulations of specific types is driven by partial elastic stress-relief and a lowering of the system free energy. Under these conditions, islands of deposit can be formed during initial growth and ripples can be produced upon continuous layers. Furthermore, the presence of surface morphological distortions and the accompanying strain fluctuations also can have a significant impact upon misfit dislocation introduction. Relationships between these fluctuations and dislocation source behaviour are described.

Growth of Niobium Films at High Temperatures on Sapphire

1996 ◽  
Vol 440 ◽  
Author(s):  
T. Wagner
Keyword(s):  
High Temperatures ◽  
Basal Plane ◽  
Misfit Strain ◽  
High Energy ◽  
Total Density ◽  
Initial Growth ◽  
Island Size ◽  
Transmission Electron ◽  
Orientation Density

AbstractThe growth and microstructural evolution of Nb thin films on the basal plane of α-Al2O3 were studied at different growth temperatures. The influence of island orientation, density, and misfit strain energy on the growth behavior of Nb films on (0001)α-Al2O3 at high temperatures has been investigated. The films were grown by MBE at 900°C and 1100°C. At these temperatures the Nb grows in the Volmer-Weber growth mode on the basal plane. In-situ reflection high energy electron diffraction (RHEED), Auger electron spectroscopy (AES) and transmission electron microscopy (TEM) investigations revealed that in the initial growth stage, Nb nuclei with different epitaxial orientations were formed. This leads to different orientations of thicker Nb films at different growth temperatures. At a growth temperature of 900°C the Nb{111} planes are parallel to the sapphire basal plane whereas at 1100°C Nb grows with the {110) planes parallel to the basal plane of sapphire. The formation of two different epitaxial orientations of thick Nb films can only be explained by considering both the change in the total density of Nb islands with temperature and the influence of island size on their total energy.

Entropy of Nanostructures

2017 ◽  
pp. 600-614
Author(s):  
Ottorino Ori ◽  
Franco Cataldo ◽  
Mihai V. Putz
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Defect Formation ◽  
Vacancy Concentration ◽  
Structural Evolution ◽  
Point Of View ◽  
Structural Defects ◽  
Formation Mechanisms ◽  
Topological Invariants

Recent advances in graphene studies deal with the influence of structural defects on graphene chemical, electrical, magnetic and mechanical properties. Here the complex mechanisms leading to the formation of clusters of vacancies in 2D honeycomb HD lattices are described by a pure topological point of view, aiming to correlate the variation of specific topological invariants, sensible to vacancy concentration, to the structural evolution of the defective networks driven by the topo-thermodynamical Gibbs free energy. Interesting predictions on defect formation mechanisms add details on the topological mechanisms featured by the graphenic structures with defects. Future roles of bondonic particles in defective HD materials are also envisaged.

Native Point Defect Densities and Dark Line Defects in ZnSe

1995 ◽  
Vol 408 ◽  
Author(s):  
M. A. Berding ◽  
A. Sher ◽  
M. Van Schilfgaarde
Keyword(s):  
Free Energy ◽  
Point Defect ◽  
Defect Formation ◽  
Local Density ◽  
Full Potential ◽  
Nonradiative Recombination ◽  
Dark Line ◽  
Frenkel Defect ◽  
Native Point Defect ◽  
Defect Densities

AbstractNative point defect densities (including vacancies, antisites and interstitials) in ZnSe are calculated using a quasichemical formalism, including both vibrational and electronic contributions to the defect free energy. The electronic contribution to the defect formation free energy is calculated using the self-consistent first-principles full-potential linearized muffin-tin orbital (FP-LMTO) method and the local-density approximation (LDA). Gradient corrections are included so that absolute reference to zinc atoms in the vapor phase can be made. We find that the Frenkel defect formation energy is ∼0.3 eV lower at a stacking fault than in the bulk lattice. Nonradiative-recombination-induced Frenkel defect generation at stacking faults is proposed as a mechanism responsible for the limited device lifetimes.

Characterization of the Defect Evolution in Thick Heavily Al-Doped 4H-SiC Epilayers

2014 ◽  
Vol 778-780 ◽  
pp. 151-154 ◽  
Author(s):  
Shi Yang Ji ◽  
Kazutoshi Kojima ◽  
Yuuki Ishida ◽  
Hirotaka Yamaguchi ◽  
Shingo Saito ◽  
...  
Keyword(s):  
Misfit Dislocation ◽  
Doping Level ◽  
Growth Stage ◽  
Initial Growth ◽  
Al Doping ◽  
X Ray ◽  
Defect Evolution ◽  
Koh Etching

The defect evolution on 90 μm-thick heavily Al-doped 4H-SiC epilayers with Al doping level higher than 1020 cm-3 was studied by tracing back to initial growth stage to monitor major dislocations and their propagations in each growth stage. Results from X-ray topography and KOH etching demonstrate that all existing dislocations on the surface of 90 μm-thick epilayer can be identified as the defects originating from substrate. In other words, there seems no new dislocation generated after a long-term growth. Nevertheless, a high density of misfit dislocation was found appearing near the substrate/epilayer interface for epilayer with Al doping level of 3.5×1020 cm-3, while misfit dislocation cannot be seen on epilayer with Al doping level of 1.5×1020 cm-3.

Misfit dislocation formation at heterointerfaces in (Al,In)GaN heteroepitaxial layers grown on semipolar free-standing GaN substrates

2011 ◽  
Vol 109 (3) ◽  
pp. 033505 ◽  
Author(s):  
F. Wu ◽  
A. Tyagi ◽  
E. C. Young ◽  
A. E. Romanov ◽  
K. Fujito ◽  
...  
Keyword(s):  
Misfit Dislocation ◽  
Free Standing ◽  
Heteroepitaxial Layers ◽  
Dislocation Formation

Direct Observations of Relaxation of Si/SiGe/Si on Insulator

2010 ◽  
Vol 1262 ◽  
Author(s):  
Tongda Ma ◽  
Hailing Tu
Keyword(s):  
Misfit Dislocation ◽  
Room Temperature ◽  
Sige Layer ◽  
Misfit Strain ◽  
Misfit Dislocations ◽  
Cross Sectional ◽  
Direct Observations ◽  
Transmission Electron ◽  
Dislocation Behavior ◽  
Film Specimen

AbstractMicrostructural evolution is directly observed when the cross-sectional film specimen of Si/SiGe/Si on insulator (Si/SiGe/SOI) is heated from room temperature (R.T., 291 K) up to 1113 K in high voltage transmission electron microscope (HVEM). The misfit dislocation at the lower interface of the SiGe layer begins to extend downwards even at 913 K. The lower interface takes the lead in roughening against the upper interface of the SiGe layer. The roughened interface is ascribed to elastic relaxation. As misfit strain is partially transferred to SOI top Si layer and misfit dislocation is prolonged at the lower interface, the roughened interface turns smooth again. Thereafter, the misfit dislocations are introduced into the upper roughened interface of the SiGe layer to release the increased misfit strain. It is suggested that the microscopic relaxation of the SiGe layer is related to dislocation behavior and strain transfer.

scholarly journals Enhanced Lattice Defect Formation Associated with Hydrogen and Hydrogen Embrittlement under Elastic Stress of a Tempered Martensitic Steel

2012 ◽  
Vol 98 (5) ◽  
pp. 197-206 ◽  
Author(s):  
Tomoki Doshida ◽  
Hiroshi Suzuki ◽  
Kenichi Takai ◽  
Nagayasu Oshima ◽  
Tetsuya Hirade
Keyword(s):  
Hydrogen Embrittlement ◽  
Defect Formation ◽  
Elastic Stress ◽  
Martensitic Steel ◽  
Lattice Defect
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