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Chung-ho Woo - One of the best experts on this subject based on the ideXlab platform.
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Critical Thickness for dislocation generation during ferroelectric transition in thin film on a compliant substrate
Applied Physics Letters, 2006Co-Authors: Yue Zheng, Biao Wang, Chung-ho WooAbstract:The formation energy of misfit dislocations in a ferroelectric thin film grown on compliant substrate is calculated based on the Landau-Devonshire formalism and Timosheko’s method for thermal stresses. The Critical Thickness is shown to change significantly according to the polarization in the film, leading to serious concerns, particularly for thick substrates, in the device design stage.
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curie temperature and Critical Thickness of ferroelectric thin films
Journal of Applied Physics, 2005Co-Authors: Biao Wang, Chung-ho WooAbstract:The dynamic Ginzburg–Landau theory is applied to establish the Critical conditions that control the transition between the paraelectric and ferroelectric states. Analytic expressions of the para-ferroelectric transition temperatures in a thin film under various electromechanical surface conditions are derived via a linear stability analysis of the evolutionary trajectory of the system for both first- and second-order transitions. Explicit expressions are then derived for the Critical Thickness, below which the thin film is paraelectric for all temperatures. For first-order transitions, the difference between the superheating and supercooling transition temperatures is found to be insensitive to the film Thickness and surface boundary conditions. From these expressions, the relative importance on ferroelectricity in thin films due to applied mechanical constraints on the transformation strain and the depolarizing effect of surface charges is discussed and compared with experimental data.
D J Dunstan - One of the best experts on this subject based on the ideXlab platform.
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equilibrium Critical Thickness of epitaxial strained layers in the 111 orientations
Journal of Applied Physics, 1997Co-Authors: H G Colson, D J DunstanAbstract:Critical Thickness of epitaxial strained layers is dependent on growth orientation both through crystallographic geometric factors and through elastic anisotropy. In a standard treatment of Critical Thickness, these two effects reduce Critical Thickness in all non-{001}-growth orientations except the {111}. Close to (111), where the (111) slip system is inactive, Critical Thickness is slightly increased, to 1.23 times the {001} value for GaAs and 1.37 times for silicon. The analysis also shows that Critical Thickness is decreased for any off-cut away from (001)- or (111)-growth orientations, and the off-cut directions for the smallest decreases are 〈100〉 and 〈211〉, respectively.
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numerical calculation of equilibrium Critical Thickness in strained layer epitaxy
Semiconductor Science and Technology, 1994Co-Authors: J R Downes, D J Dunstan, D A FauxAbstract:We calculate by numerical integration the energy of a strained layer in an infinite isotropic continuous elastic medium with and without a misfit dislocation dipole of pure edge character. The equilibrium Critical Thickness is the Thickness at which these energies are the same. Solving for a range of values of misfit strain, we compare the results with some versions of the existing approximate models, and we are thereby able to indicate the best analytic expressions to use to predict equilibrium Critical Thickness.
J K Angarska - One of the best experts on this subject based on the ideXlab platform.
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Critical Thickness of thin liquid films comparison of theory and experiment
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005Co-Authors: Emil D Manev, J K AngarskaAbstract:Abstract Values for the Critical Thickness of rupture (or ‘black spot formation’) of aqueous and non-aqueous (aniline and nitrobenzene) foam films were computed by the Vrij (1966) and Radoev–Scheludko–Manev (1983) theories. The ‘Critical Thickness versus film radius’ dependences were derived, using different formulae for the rate of film thinning. The theoretical values were compared to the available – from the literature, as well as the investigations conducted here – experimental data for the Critical Thickness determined in the thinnest domains of the investigated microscopic horizontal foam films. It has been established that in all cases the agreement between theory and experiment is largely enhanced when the formula of Manev et al. (1997) is employed to describe the rate of film thinning, instead of the classical Stefan–Reynolds equation.
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detection of the hydrophobic surface force in foam films by measurements of the Critical Thickness of the film rupture
Langmuir, 2004Co-Authors: J K Angarska, B S Dimitrova, Krassimir D Danov, Peter A Kralchevsky, And K P Ananthapadmanabhan, Alex LipsAbstract:At sufficiently high electrolyte concentrations (at suppressed electrostatic repulsion), the free foam films thin gradually, until reaching a certain Critical Thickness, and then they break. The value of this Critical Thickness is sensitive to the magnitude of the attractive surface forces acting in the film. We experimentally investigated the rupture of the films formed from aqueous solutions of sodium dodecyl sulfate (SDS) in the presence of 0.3 M NaCl added. The theoretical fits of the data indicate that the van der Waals interaction, alone, is insufficient to explain the measured Critical Thickness, especially for the lower SDS concentrations. If the difference is attributed to the hydrophobic attraction, then a very good agreement between the theory and experiment is achieved. From the best fit, we determine that the decay length of the hydrophobic force is about 15.8 nm, which coincides with the value obtained by other authors for hydrophobized mica surfaces. The strength of the hydrophobic interact...
Akihiro Wakahara - One of the best experts on this subject based on the ideXlab platform.
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growth of low defect density gap layers on si substrates within the Critical Thickness by optimized shutter sequence and post growth annealing
Journal of Crystal Growth, 2010Co-Authors: Keisuke Yamane, T Kawai, Y Furukawa, Hiroshi Okada, Akihiro WakaharaAbstract:Abstract We have developed a growth procedure for realizing a low defect density GaP layer on an Si substrate. The growth procedure consists of two parts. One is the post-growth annealing for the annihilation of stacking faults (SFs). We have investigated an annihilation mechanism with molecular beam epitaxy grown GaP layers. 1-monolayer-thick SFs typically generate from the GaP/Si interface in a non-annealed GaP layer. In a 700 °C annealed GaP layer, generation points of these SFs tend to shift toward the GaP surface. In a 730 °C annealed GaP layer, SFs density is effectively decreased. These results suggest that SFs are annihilated through the climb motion of two partial dislocations during the post-growth annealing. Another one is the optimized shutter sequence for migration enhanced epitaxy. We have revealed that it is effective for the suppression of both three-dimensional growth and melt-back etching to increase in a stepwise manner the number of supplied Ga atoms per cycle. As a result, the generation of threading dislocations and pits is remarkably suppressed. A root mean square surface roughness of 0.13 nm is obtained within the Critical Thickness. We have estimated etch pit density (EPD) to be ∼7×10 5 cm −2 with a GaPN/GaP/Si structure. To the best of our knowledge, this value is same as that of commercially available GaP substrates and is the lowest one in the EPD of GaP/Si heteroepitaxy.
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lattice relaxation process and crystallographic tilt in gap layers grown on misoriented si 001 substrates by metalorganic vapor phase epitaxy
Journal of Applied Physics, 2010Co-Authors: Yasufumi Takagi, Yuzo Furukawa, Akihiro WakaharaAbstract:A lattice relaxation process and a crystallographic tilt in GaP layers grown on misoriented Si(001) substrates by metalorganic vapor phase epitaxy were investigated. Strained pseudomorphic GaP layers without defects on Si were successfully achieved by the optimization of growth conditions. Below Critical Thickness, the strained GaP layers were tilted in the misoriented direction of the Si substrates and triclinically distorted. Above Critical Thickness, the residual strain in the GaP layers was progressively relaxed with increased Thickness of the GaP layers by forming 60° misfit dislocations propagating to the two orthogonal ⟨110⟩ directions at the heterointerface. X-ray diffuse scattering around the symmetrical GaP(004) diffraction was observed after introducing misfit dislocations. Diffuse scattering became dominant with an increase in the density of the misfit dislocations and resulted in a broadening of the full width at half maximum of the x-ray rocking curves. The GaP layers that were relaxed with ...
Biao Wang - One of the best experts on this subject based on the ideXlab platform.
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Critical Thickness for dislocation generation during ferroelectric transition in thin film on a compliant substrate
Applied Physics Letters, 2006Co-Authors: Yue Zheng, Biao Wang, Chung-ho WooAbstract:The formation energy of misfit dislocations in a ferroelectric thin film grown on compliant substrate is calculated based on the Landau-Devonshire formalism and Timosheko’s method for thermal stresses. The Critical Thickness is shown to change significantly according to the polarization in the film, leading to serious concerns, particularly for thick substrates, in the device design stage.
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curie temperature and Critical Thickness of ferroelectric thin films
Journal of Applied Physics, 2005Co-Authors: Biao Wang, Chung-ho WooAbstract:The dynamic Ginzburg–Landau theory is applied to establish the Critical conditions that control the transition between the paraelectric and ferroelectric states. Analytic expressions of the para-ferroelectric transition temperatures in a thin film under various electromechanical surface conditions are derived via a linear stability analysis of the evolutionary trajectory of the system for both first- and second-order transitions. Explicit expressions are then derived for the Critical Thickness, below which the thin film is paraelectric for all temperatures. For first-order transitions, the difference between the superheating and supercooling transition temperatures is found to be insensitive to the film Thickness and surface boundary conditions. From these expressions, the relative importance on ferroelectricity in thin films due to applied mechanical constraints on the transformation strain and the depolarizing effect of surface charges is discussed and compared with experimental data.