scholarly journals Solid-phase crystallization under continuous heating: Kinetic and microstructure scaling laws

2008 ◽  
Vol 23 (2) ◽  
pp. 418-426 ◽  
Author(s):  
J. Farjas ◽  
P. Roura
Keyword(s):  
Grain Size ◽  
Kinetic Parameters ◽  
Scaling Laws ◽  
Solid Phase ◽  
Scaling Law ◽  
Continuous Heating ◽  
Dimensionless Time ◽  
Solid Phase Crystallization ◽  
Average Grain Size ◽  
Length Scaling

The kinetics and microstructure of solid-phase crystallization under continuous heating conditions and random distribution of nuclei are analyzed. An Arrhenius temperature dependence is assumed for both nucleation and growth rates. Under these circumstances, the system has a scaling law such that the behavior of the scaled system is independent of the heating rate. Hence, the kinetics and microstructure obtained at different heating rates differ only in time and length scaling factors. Concerning the kinetics, it is shown that the extended volume evolves with time according to αex = [exp(κCt′)]m+1, where t′ is the dimensionless time. This scaled solution not only represents a significant simplification of the system description, it also provides new tools for its analysis. For instance, it has been possible to find an analytical dependence of the final average grain size on kinetic parameters. Concerning the microstructure, the existence of a length scaling factor has allowed the grain-size distribution to be numerically calculated as a function of the kinetic parameters.

Solid-Phase Crystallization of a-Si:H by RTA

2010 ◽  
Vol 44-47 ◽  
pp. 4151-4153 ◽  
Author(s):  
Rui Min Jin ◽  
Ding Zhen Li ◽  
Lan Li Chen ◽  
Xiang Ju Han ◽  
Jing Xiao Lu
Keyword(s):  
Thin Film ◽  
Grain Size ◽  
Amorphous Silicon ◽  
Glass Substrate ◽  
Solid Phase ◽  
X Ray Diffraction ◽  
Solid Phase Crystallization ◽  
X Ray ◽  
Average Grain Size ◽  
Electronic Microscope

Amorphous silicon films prepared by PECVD on glass substrate has been crystallized by rapid thermal annealing (RTA) at the same temperature for different time. From X-ray diffraction (XRD) and scanning electronic microscope (SEM), it is found that the grain size is biggest crystallized at 720°C for 8 min, an average grain size of 28nm or so is obtained. The thin film is smoothly and perfect structure.

Solid-phase crystallization of ultra-thin amorphous Ge layers on insulators

2021 ◽  
Author(s):  
Ryo Oishi ◽  
Koji ASAKA ◽  
Bolotov Leonid ◽  
Noriyuki Uchida ◽  
Masashi Kurosawa ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Barrier Height ◽  
Carrier Mobility ◽  
Solid Phase ◽  
Hole Mobility ◽  
Solid Phase Crystallization ◽  
Simple Method ◽  
20 Nm ◽  
Grain Boundary Barrier

Abstract A simple method to form ultra-thin (< 20 nm) semiconductor layers with a higher mobility on a 3D-structured insulating surface is required for next-generation nanoelectronics. We have investigated the solid-phase crystallization of amorphous Ge layers with thicknesses of 10−80 nm on insulators of SiO2 and Si3N4. We found that decreasing the Ge thickness reduces the grain size and increases the grain boundary barrier height, causing the carrier mobility degradation. We examined two methods, known effective to enhance the grain size in the thicker Ge (>100 nm). As a result, a relatively high Hall hole mobility (59 cm2/Vs) has been achieved with a 20-nm-thick polycrystalline Ge layer on Si3N4, which is the highest value among the previously reported works.

Transport Properties of B-, P-Doped and Undoped 50 kHz PECVD Microcrystalline Silicon

1989 ◽  
Vol 164 ◽  
Author(s):  
M.A. Hachicha ◽  
Etienne Bustarret
Keyword(s):  
Grain Size ◽  
Hall Mobility ◽  
Solid Phase ◽  
Grazing Angle ◽  
Dc Conductivity ◽  
X Ray Diffraction ◽  
Crystalline Fraction ◽  
Average Grain Size ◽  
20 Nm ◽  
Solid Phase Density

AbstractUndoped 500 nm-thick silicon layers with a crystalline fraction around 95% and an average grain size of 20 nm have been deposited at 350°C by 50 kHz triode PECVD in a H2/SiH4 mixture, in the presence of a magnetic field. Their room temperature (rt) dc conductivity μrt is 0.03 Δ−1cm−1 for a Hall mobility of 0.8 cm 2V−1s−1.The study by SIMS, infrared absorption, grazing angle x-ray diffraction and Raman scattering spectroscopies of the doped samples shows how the crystalline fraction and the grain size drop as the B2H6/SiH4 and PH3/SiH4 volumic ratios increase from 10 ppm to 1%.The rt dc conductivity reaches 2 Δ−1 cm−1 (Hall mobility: 15 cm2V−ls−1) for a solid phase density of 1019 cm−3 boron atoms, and 30 Δ−1cm−1 (Hall mobility: 55 cm2V−ls−1) at the maximum P incorporation of 8 × 1020cm−3.

Grain size, Grain Uniformity, and (111) Texture Enhancement by Solid-phase Crystallization of F- and C-implanted SiGe Films

2000 ◽  
Vol 15 (7) ◽  
pp. 1630-1634 ◽  
Author(s):  
A. Rodríguez ◽  
J. Olivares ◽  
C. González ◽  
J. Sangrador ◽  
T. Rodríguez ◽  
...  
Keyword(s):  
Grain Size ◽  
Vapor Deposition ◽  
Solid Phase ◽  
Chemical Vapor ◽  
Solid Phase Crystallization ◽  
Grain Sizes ◽  
Pressure Chemical ◽  
Film Microstructure ◽  
Si Films ◽  
Size Dispersion

The crystallization kinetics and film microstructure of poly-SiGe layers obtained by solid-phase crystallization of unimplanted and C- and F-implanted 100-nm-thick amorphous SiGe films deposited by low-pressure chemical vapor deposition on thermally oxidized Si wafers were studied. After crystallization, the F- and C-implanted SiGe films showed larger grain sizes, both in-plane and perpendicular to the surface of the sample, than the unimplanted SiGe films. Also, the (111) texture was strongly enhanced when compared to the unimplanted SiGe or Si films. The crystallized F-implanted SiGe samples showed the dendrite-shaped grains characteristic of solid-phase crystallized pure Si. The structure of the unimplanted SiGe and C-implanted SiGe samples consisted of a mixture of grains with well-defined contour and a small number of quasi-dendritic grains. These samples also showed a very low grain-size dispersion.

Elimination of an isolated pore: Effect of grain size

1995 ◽  
Vol 10 (4) ◽  
pp. 1000-1015 ◽  
Author(s):  
Wan Y. Shih ◽  
Wei-Heng Shih ◽  
Ilhan A. Aksay
Keyword(s):  
Grain Size ◽  
Monte Carlo ◽  
Sample Size ◽  
Scaling Laws ◽  
Pore Diameter ◽  
Scaling Law ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Scaling Analysis ◽  
Scaling Relationships

The effect of grain size on the elimination of an isolated pore was investigated both by the Monte Carlo simulations and by a scaling analysis. The Monte Carlo statistical mechanics model for sintering was constructed by mapping microstructures onto domains of vectors of different orientations as grains and domains of vacancies as pores. The most distinctive feature of the simulations is that we allow the vacancies to move. By incorporating the outer surfaces of the sample in the simulations, sintering takes place via vacancy diffusion from the pores to the outer sample surfaces. The simulations were performed in two dimensions. The results showed that the model is capable of displaying various sintering phenomena such as evaporation and condensation, rounding of a sharp corner, pore coalescence, thermal etching, neck formation, grain growth, and growth of large pores. For the elimination of an isolated pore, the most salient result is that the scaling law of the pore elimination time tp with respect to the pore diameter dp changes as pore size changes from larger than the grains to smaller than the grains. For example, in sample-size-fixed simulations, tp ∼ d3p for dp < G and tp ∼ d2p for dp > G with the crossover pore diameter dc increasing linearly with G where G is the average grain diameter. For sample-size-scaled simulations, tp ∼ d4p for dp < G and tp ∼ d3p for dp > G. That tp has different scaling laws in different grain-size regimes is a result of grain boundaries serving as diffusion channels in a fine-grain microstructure such as those considered in the simulations. A scaling analysis is provided to explain the scaling relationships among tp, dp, and G obtained in the simulations. The scaling analysis also shows that these scaling relationships are independent of the dimensionality. Thus, the results of the two-dimensional simulations should also apply in three dimensions.

scholarly journals Intraspecific scaling laws of vascular trees

2011 ◽  
Vol 9 (66) ◽  
pp. 190-200 ◽  
Author(s):  
Yunlong Huo ◽  
Ghassan S. Kassab
Keyword(s):  
Scaling Laws ◽  
Scaling Law ◽  
Minimum Energy ◽  
Circumflex Artery ◽  
Theoretical Derivation ◽  
Left Circumflex Artery ◽  
Least Squares Fit ◽  
Flow Length ◽  
Vascular Trees ◽  
Length Scaling

A fundamental physics-based derivation of intraspecific scaling laws of vascular trees has not been previously realized. Here, we provide such a theoretical derivation for the volume–diameter and flow–length scaling laws of intraspecific vascular trees. In conjunction with the minimum energy hypothesis, this formulation also results in diameter–length, flow–diameter and flow–volume scaling laws. The intraspecific scaling predicts the volume–diameter power relation with a theoretical exponent of 3, which is validated by the experimental measurements for the three major coronary arterial trees in swine (where a least-squares fit of these measurements has exponents of 2.96, 3 and 2.98 for the left anterior descending artery, left circumflex artery and right coronary artery trees, respectively). This scaling law as well as others agrees very well with the measured morphometric data of vascular trees in various other organs and species. This study is fundamental to the understanding of morphological and haemodynamic features in a biological vascular tree and has implications for vascular disease.

scholarly journals Kinetics of Austenite Grain Growth during a Continuous Heating of a Niobium Microalloyed Steel

2004 ◽  
Vol 467-470 ◽  
pp. 929-934 ◽  
Author(s):  
David San Martín ◽  
Francisca García Caballero ◽  
Carlos Capdevila ◽  
C. Carcía de Andrés
Keyword(s):  
Grain Size ◽  
Grain Boundaries ◽  
Heating Rate ◽  
Grain Growth ◽  
Continuous Heating ◽  
Second Phase ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Average Grain Size ◽  
The Matrix

Grain growth is a thermally activated process in which the average grain size increases as temperature and time increases. The driving force for grain growth results from the decrease in the free energy associated with the reduction in total grain boundary energy. There are several known factors that influence the migration of grain boundaries such as second phase particles precipitated in the matrix and the solute elements segregated at grain boundaries. The austenite grain boundaries are revealed using the thermal etching method. Carbon extraction replicas were prepared to determine the composition and size of precipitates present in the matrix. In this work, the evolution of the average prior austenite grain size (PAGS) of a low carbon steel microalloyed with niobium is studied as a function of temperature and heating rate. Austenite grains show a two-stage growth. It has been found that as heating rate increases, the grain coarsening temperature (TGC) increases and the grain size at that temperature decreases. TGC temperature lies around 40-60°C below the temperature for complete dissolution of carbonitrides (TDISS).

Solid Phase Crystallization of LPCVD Amorphous Si Films by Nucleation Interface Control

1996 ◽  
Vol 448 ◽  
Author(s):  
Eui-Hoon Hwang ◽  
Jae-Sang Ro
Keyword(s):  
Grain Size ◽  
Incubation Time ◽  
Solid Phase ◽  
Composite Films ◽  
Deposition Condition ◽  
Solid Phase Crystallization ◽  
Interface Control ◽  
Amorphous Si ◽  
Si Films ◽  
Deposition Conditions

AbstractA novel method for the fabrication of poly-Si films with a large grain size is reported using solid phase crystallization (SPC) of LPCVD amorphous Si films by nucleation interface control. The reference films used in this study were 1000 Ǻ -thick a-Si films deposited at 500°C at a total pressure of 0.35 Torr using Si2H6/He. Since the deposition condition changes the incubation time, i.e. nucleation rate, and since nucleation occurs dominantly at a-Si/SiO2 interface, we devised the following deposition techniques for the first time in order to obtain the larger gain size. A very thin a-Si layer (~ 50 Ǻ) with the deposition conditions having long incubation time is grown first and then the reference films (~ 950 Ǻ) are grown successively. Various composite films with different combinations were tested. The crystallization kinetics of composite films was observed to be determined by the deposition conditions of a thin a-Si layer at the a-Si/SiO2 interface. Nucleation interface was also observed to be modified by interrupted gas supply resulting in the enhancement of the grain size.

Grain Size Control by Means of Solid Phase Crystallization of Amorphous Silicon

2007 ◽  
Vol 989 ◽  
Author(s):  
Jordi Farjas ◽  
Pere Roura ◽  
Pere Roca i Cabarrocas
Keyword(s):  
Grain Size ◽  
Amorphous Silicon ◽  
Solid Phase ◽  
Size Control ◽  
Substantial Improvement ◽  
Solid Phase Crystallization ◽  
Grain Size Control ◽  
Standard Values ◽  
Standard Set ◽  
Si Films

AbstractThe grain size of thermally crystallized a-Si films is controlled by the nucleation, rN, and growth, rG, rates according to the standard Avrami's theory. Despite this evidence, most papers devoted to improve the crystallized grain size analyze their results with a qualitative reference to this theory. In this paper, we will show that one can identify the standard set of rN and rG values for a-Si and that experiments show that deviations from this standard values always result in a smaller grain size. It is also shown that one cannot expect any substantial improvement with non-conventional heat treatments. Finally, it is argued that a larger grain size is expected from a-Si films containing, in their as-grown state, a controlled density of embedded nanocrystals.

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