Direct measurement of free‐energy barrier to nucleation of crystallites in amorphous silicon thin films

1994 ◽  
Vol 76 (9) ◽  
pp. 5149-5153 ◽  
Author(s):  
Frank G. Shi
Keyword(s):  
Thin Films ◽  
Free Energy ◽  
Amorphous Silicon ◽  
Direct Measurement ◽  
Energy Barrier ◽  
Free Energy Barrier ◽  
Silicon Thin Films

Free-Energy Barrier to Crystallite Nucleation in Solid-Phase Crystallized Poly-Silicon Thin Films

1997 ◽  
Vol 472 ◽  
Author(s):  
Hideya Kumomi ◽  
Frank G. Shi
Keyword(s):  
Thin Films ◽  
Free Energy ◽  
Energy Barrier ◽  
Solid Phase ◽  
Free Energy Barrier ◽  
Solid Phase Crystallization ◽  
Silicon Thin Films ◽  
Nucleation Barrier ◽  
Amorphous Si ◽  
Amor Phization

ABSTRACTWe introduce a non-Arrhenius method for measuring free-energy barrier to nucleation, W*, directly from size distribution of crystallites. W* is determined independent of any model for the nucleation barrier and independent of energy barrier to growth. The method is applicable to three-dimensionally growing crystallites, planar crystallites in thin films, and both compact and fractal crystallites. We apply the method to dendritic crystallites obtained by solid-phase crystallization of amorphous Si thin films into which Si+ ions are implanted at various conditions prior to the isothermal annealing. The ion implantation suppresses the nucleation of the crystallites and enhances the crystallite size of the resulting polycrystalline films. The directly measured W* increases as the accelerating energy or the dose of the Si+ ions increases. This result suggests that the observed suppression of the nucleation could not be accounted for simply by the amor-phization of the preexisting crystallites by the ion bombardment.

Microstructure Evolution of Amorphous Si1-xGex Thin Films

1997 ◽  
Vol 472 ◽  
Author(s):  
H. Y. Tong ◽  
Q. Jiang ◽  
D. Hsu ◽  
T. J. King ◽  
F. G. Shi
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Free Energy ◽  
Energy Barrier ◽  
Composition Dependence ◽  
Composition Range ◽  
Thin Film Transistor ◽  
Free Energy Barrier ◽  
Amorphous Si ◽  
Good Agreement

ABSTRACTThe composition dependence of the nucleation free energy barrier W* in amorphous Si1-xGex thin films is investigated. Within the composition range of x = 0.25 ∼ 0.52, the nucleation free energy barrier exhibits a maximum, which is in a good agreement with our theoretical analysis. The results are significant for processing polycrystalline SiGe thin films with desirable microstructures for thin film transistor applications. In addition, the incubation time of crystallization of amorphous Si1-xGex (x=0.5) thin films is investigated as a function of temperature.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

scholarly journals Influence of deposition parameters on the optical absorption of amorphous silicon thin films

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Lukas Terkowski ◽  
Iain W. Martin ◽  
Daniel Axmann ◽  
Malte Behrendsen ◽  
Felix Pein ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Absorption ◽  
Amorphous Silicon ◽  
Silicon Thin Films ◽  
Deposition Parameters

Irradiation Effect on Al-Dispersed Amorphous Silicon Thin Films by Femtosecond Laser

2020 ◽  
Vol 984 ◽  
pp. 91-96
Author(s):  
Cheng Liu ◽  
Yu Hao Song ◽  
Dong Yang Li ◽  
Wei Li
Keyword(s):  
Thin Films ◽  
Amorphous Silicon ◽  
Laser Raman Spectroscopy ◽  
Irradiation Effect ◽  
Amorphous Thin Films ◽  
Laser Raman ◽  
Silicon Thin Films ◽  
Al Nanoparticles ◽  
Spot Area ◽  
Fs Laser

The structural and optical properties of amorphous silicon (a-Si) and Al-dispersed amorphous silicon (a-Si:Al) thin films irradiated by femtosecond (fs) laser at various energy densities are investigated comparatively in this article. It is found that there is an uneven crystallization in both amorphous thin films by means of optical microscopy and laser Raman spectroscopy respectively. The crystallization in each pulse spot area is gradually weakened from the center to the edge along with the energy dispersion of laser irradiation. The laser induced crystallization in a-Si thin films begins early and develops more extensively compared to that in a-Si:Al thin films, and Al nanoparticles inhibit somehow the crystallization of a-Si in a-Si:Al thin films.

Crystallization of Amorphous Silicon Thin Films by Microwave Heating

2014 ◽  
Vol 1666 ◽  
Author(s):  
Tomohiko Nakamura ◽  
Shinya Yoshidomi ◽  
Masahiko Hasumi ◽  
Toshiyuki Sameshima ◽  
Tomohisa Mizuno
Keyword(s):  
Thin Films ◽  
Heat Treatment ◽  
Amorphous Silicon ◽  
Microwave Heating ◽  
Volume Ratio ◽  
Heated Sample ◽  
Silicon Thin Films ◽  
Scattering Spectra ◽  
Raman Scattering Spectra ◽  
Si Films

ABSTRACTWe report crystallization of amorphous silicon (a-Si) thin films and improvement of thin film transistors (TFTs) characteristics using 2.45 GHz microwave heating assisted with carbon powders. Undoped 50-nm-thick a-Si films were formed on quartz substrates and heated by microwave irradiation for 2, 3, and 4 min. Raman scattering spectra revealed that the crystalline volume ratio increased to 0.42 for the 4-min heated sample. The dark and photo electrical conductivities measured by Air mass 1.5 at 100 mW/cm2 were 2.6x10-6 and 5.2x10-6 S/cm in the case of 4-min microwave heating followed by 1.3x106-Pa-H2O vapor heat treatment at 260°C for 3 h. N channel polycrystalline silicon TFTs characteristics were improved by the combination of microwave heating with high-pressure H2O vapor heat treatment. The threshold voltage decreased from 5.3 to 4.2 V and the effective carrier mobility increased from 18 to 25 cm2/Vs.

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