scholarly journals Manipulating the anisotropic phase separation in strained VO2 epitaxial films by nanoscale ion-implantation

2021 ◽  
Vol 119 (12) ◽  
pp. 121101
Author(s):  
Changlong Hu ◽  
Liang Li ◽  
Xiaolei Wen ◽  
Yuliang Chen ◽  
Bowen Li ◽  
...  
Keyword(s):  
Phase Separation ◽  
Ion Implantation ◽  
Epitaxial Films ◽  
Anisotropic Phase

Inverse Ostwald Ripening and Self-Organization of Nanoclusters due to Ion Irradiation

2000 ◽  
Vol 647 ◽  
Author(s):  
K.-H. Heinig ◽  
B. Schmidt ◽  
M. Strobel ◽  
H. Bernas
Keyword(s):  
Phase Separation ◽  
Ion Implantation ◽  
Ostwald Ripening ◽  
Ion Irradiation ◽  
Experimental Studies ◽  
Self Organization ◽  
Mathematical Treatment ◽  
Thermodynamical Equilibrium ◽  
Unusual Behavior ◽  
Thermally Activated

AbstractUnder ion irradiation collisional mixing competes with phase separation if the irradiated solid consists of immiscible components. If a component is a chemical compound, there is another competition between the collisional forced chemical dissociation of the compound and its thermally activated re-formation. Especially at interfaces between immiscible components, irradiation processes far from thermodynamical equilibrium may lead to new phenomena. If the formation of nanoclusters (NCs) occurs during ion implantation, the phase separation caused by ion implantation induced supersaturation can be superimposed by phenomena caused by collisional mixing. In this contribution it will be studied how collisional mixing during high-fluence ion implantation affects NC synthesis and how ion irradiation through a layer of NCs modifies their size and size distribution. Inverse Ostwald ripening of NCs will be predicted theoretically and by kinetic lattice Monte-Carlo simulations. The mathematical treatment of the competition between irradiation-induced detachment of atoms from clusters and their thermally activated diffusion leads to a Gibbs-Thomson relation with modified parameters. The predictions have been confirmed by experimental studies of the evolution of Au NCs in SiO2 irradiated by MeV ions. The unusual behavior results from an effective negative capillary length, which will be shown to be the reason for inverse Ostwald ripening. Another new phenomenon to be addressed is self-organization of NCs in a d-layer parallel to the Si/SiO2 interface. Such d-layers were found when the damage level at the interface was of the order of 1-3 dpa. It will be discussed that the origin of the d-layer of NCs can be assigned to two different mechanisms: (i) The negative interface energy due to collisional mixing gives rise to the formation of tiny clusters of substrate material in front of the interface, which promotes heteronucleation of the implanted impurities. (ii) Collisional mixing in the SiO2produces diffusing oxygen, which may be consumed by the Si/SiO2 interface. A thin layer parallel to the interface becomes denuded of diffusing oxygen, which results in a strong pile up of Si excess. This Si excess promotes heteronucleation too. Independent of the dominating mechanism of self-organization of a d-layer of NCs, its location in SiO2 close to the SiO2/Si interface makes it interesting for non-volatile memory application.

Precipitation of highly luminescent phases from PECVD Si suboxides

2004 ◽  
Vol 832 ◽  
Author(s):  
M. Perálvarez ◽  
M. López ◽  
B. Garrido ◽  
J.R. Morante ◽  
J. Barreto ◽  
...  
Keyword(s):  
Refractive Index ◽  
Phase Separation ◽  
Ion Implantation ◽  
Composition Profile ◽  
Matrix Composition ◽  
Light Sources ◽  
The Matrix ◽  
Detailed Composition ◽  
Preparation Route

ABSTRACTSi nanoclusters (Si-nc) embedded in SiO2 present outstanding luminescent emission in the visible and are the material of choice for the realization of efficient light sources integrated with Si technology. PECVD is an attractive preparation route but there is still the need to understand how Si excess and matrix composition affect the precipitation of Si-nc and their photoluminescence (PL) efficiency. The SiOx PECVD layers studied here have a Si excess up to 50% and a thickness between 50 and 100 nm. The phase separation, precipitation and growth of the Si-nc have been achieved by annealing at 1250 °C. For reference, the same study has been performed in Si-nc/SiO2 materials synthesized by ion implantation and annealing. Refractive index and thickness measured by ellipsometry show a densification of the layers after the H release during annealing. A detailed composition profile has been determined by XPS and FTIR analyses and shows almost complete phase separation except for the interfaces, where a depletion of Si-nc is found. EFTEM demonstrates that isolated Si-nc are formed for Si excess up to 25% while for higher Si excess a continuous Si phase is observed. The PL efficiency in PECVD samples is maximized for a Si excess of 17% which is the same Si excess than that for the most emitting implanted samples. No dependence of PL efficiency has been found on the presence of Nitrogen in the matrix (up to the 10%).

Phase equilibria in solutions of rod-like particles

1956 ◽  
Vol 234 (1196) ◽  
pp. 73-89 ◽  
Keyword(s):  
Free Energy ◽  
Phase Separation ◽  
Partition Function ◽  
Colloidal Particles ◽  
Double Layers ◽  
Positive Energy ◽  
Isotropic Phase ◽  
Electric Double Layers ◽  
Rigid Rod ◽  
Anisotropic Phase

A partition function for a system of rigid rod-like particles with partial orientation about an axis is derived through the use of a modified lattice model. In the limit of perfect orientation the partition function reduces to the ideal mixing law ; for complete disorientation it corresponds to the polymer mixing law for rigid chains. A general expression is given for the free energy of mixing as a function of the mole numbers, the axis ratio of the solute particles, and a disorientation parameter. This function passes through a minimum followed by a maximum with increase in the disorientation parameter, provided the latter exceeds a critical value which is 2e for the pure solute and which increases with dilution. Assigning this parameter the value which minimizes the free energy, the chemical potentials display discontinuities a t the concentration a t which the minimum first appears. Separation into an isotropic phase and a some what more concentrated anisotropic phase arises because of the discontinuity, in confirmation of the theories of Onsager and Isihara, which treat only the second virial coefficient. Phase separation thus arises as a consequence of particle asymmetry, unassisted by an energy term . Whereas for a large-particle asymmetry both phases in equilibrium are predicted to be fairly dilute when mixing is athermal, a comparatively small positive energy of interaction causes the concentration in the anisotropic phase to increase sharply, while the concentration in the isotropic phase becomes vanishingly small. The theory offers a statistical mechanical basis for interpreting precipitation of rod-like colloidal particles with the formation of fibrillar structures such as are prominent in the fibrous proteins. The asymmetry of tobacco mosaic virus particles (with or without inclusion of their electric double layers) is insufficient alone to explain the well-known phase separation which occurs from their dilute solutions at very low ionic strengths. Higher-order interaction between electric double layers appears to be a major factor in bringing about dilute phase separation for these and other asymmetric colloidal particles bearing large charges, as was pointed out previously by Oster.

scholarly journals Anisotropic Phase Separation through the Metal-Insulator Transition in Amorphous Alloys

1994 ◽  
Vol 73 (8) ◽  
pp. 1118-1121 ◽  
Author(s):  
Michael J. Regan ◽  
Marybeth Rice ◽  
Marcela B. Fernandez van Raap ◽  
Arthur Bienenstock
Keyword(s):  
Phase Separation ◽  
Amorphous Alloys ◽  
Insulator Transition ◽  
Metal Insulator Transition ◽  
Metal Insulator ◽  
Anisotropic Phase

Crystallization, Diffusion and Phase Separation in Sapphire Amorphised by Indium Ion Implantation

1988 ◽  
Vol 100 ◽  
Author(s):  
D. X. Cao ◽  
D. K. Sood ◽  
A. P. Pogany
Keyword(s):  
Phase Separation ◽  
Ion Implantation ◽  
Isothermal Annealing ◽  
Amorphous Layer ◽  
Dose Dependence ◽  
Rapid Diffusion ◽  
Amorphous Surface ◽  
Indium Ion

ABSTRACTIndium implantation into a-axis sapphire to peak concentrations of 8–45 mol % In produces amorphous surface layers.Migration of In during isothermal annealing at 600°C shows a strong ion dose dependence. For a dose of 6×1016In/cm2, two distinct types of In migration are seen - a) rapid diffusion of In within amorphous Al2O3 and b) diffusion of In into crystalline Al2O3 underlying the amorphous layer. For doses lower than 3×1016In/cm2 , no such migration of In is seen under identical anneal conditions. However, In undergoes phase separation into crystalline In2O3 particles embedded in amorphous Al2O3 at all doses.

Surface effects on photopolymerization induced anisotropic phase separation in liquid crystal and polymer composites

2007 ◽  
Vol 90 (19) ◽  
pp. 193510 ◽  
Author(s):  
Min Young Jin ◽  
Tae-Hee Lee ◽  
Jong-Wook Jung ◽  
Jae-Hoon Kim
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Polymer Composites ◽  
Surface Effects ◽  
Anisotropic Phase

Structural Study of BF$_{2}$ Ion Implantation and Post Annealing of BaSi$_{2}$ Epitaxial Films

2011 ◽  
Vol 50 ◽  
pp. 121202 ◽  
Author(s):  
Kosuke O. Hara ◽  
Noritaka Usami ◽  
Yusuke Hoshi ◽  
Yasuhiro Shiraki ◽  
Mitsushi Suzuno ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Structural Study ◽  
Epitaxial Films ◽  
Post Annealing

Pixel-isolated liquid-crystal mode by using a patterned anisotropic phase separation for flexible LCDs

2007 ◽  
Vol 15 (2) ◽  
pp. 119 ◽  
Author(s):  
Se-Jin Jang ◽  
Jong-Wook Jung ◽  
Hak-Rin Kim ◽  
Min Young Jin ◽  
You-Jin Lee ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Phase Separation ◽  
Anisotropic Phase
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