Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films

1991 ◽  
Vol 230 ◽  
Author(s):  
J. B. Rubin ◽  
R. B. Schwarz
Keyword(s):  
Thin Films ◽  
Cooling Rate ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Amorphous Structure ◽  
Nucleation Theory ◽  
Glass Forming ◽  
Constant Heating

AbstractWe determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.

Metastable Phase Formation in the Y-TI System by Ion Mixing

1991 ◽  
Vol 235 ◽  
Author(s):  
S. L. Lai ◽  
Z. J. Zhang ◽  
J. R. Ding ◽  
B. X. Liu
Keyword(s):  
Metastable Phase ◽  
Heat Of Formation ◽  
Crystalline Lattice ◽  
Vacuum Furnace ◽  
Multilayered Films ◽  
Glass Forming ◽  
Transmission Electron ◽  
Metastable Phase Formation ◽  
First Time

ABSTRACTAmorphization behavior was studied for the Y-Ti system, which has rather positive heat of formation being around + 22 kJ/mol, by room temperature 360 keV xenon ion mixing of YxTi100−xmultilayered films to various doses, ranging from 7×1014 to 1×1016 xe/cm2 Single and uniform amorphous phase was obtained in a narrow composition region, i.e. x=65 to 75, after ion mixing to the relevant doses. Moreover, a metastable fee crystalline Y-Ti phase was observed, for the first time, in this system. The crystalline lattice constant of the metastable phase was determined to be 4.012 Å. The re-crystallization temperature of the formed amorphous alloy was found out to be 600°C by in situ transmission electron microscope annealing as well as by vacuum furnace experiments. Possible interpretation is also discussed by comparing the experimental results with those proposed models for predicting glass forming ability.

In Situ Observation of Diffusion Behavior and Microstructural Evolution on Interfaces in Al/Cu Bimetal

2017 ◽  
Vol 898 ◽  
pp. 1020-1025
Author(s):  
Fei Cao ◽  
Fen Fen Yang ◽  
Xue Jian Wang ◽  
Hui Jun Kang ◽  
Ya Nan Fu ◽  
...  
Keyword(s):  
Transition Zone ◽  
Microstructural Evolution ◽  
Equilibrium Phase ◽  
Liquidus Line ◽  
Eutectic Growth ◽  
Equilibrium Phase Diagram ◽  
Eutectic Structure ◽  
Diffusion Behavior ◽  
Cu Alloy

Synchrotron X-ray radiography was used to in situ study the diffusion behavior and microstructural evolution of Al/Cu bimetal. The interface diffusion, dendritic/eutectic growth and the formation of intermetallic compounds around the Al/Cu bimetal interface were analyzed. During the isothermal diffusion process, a liquefied transition zone at the interface with a concentration gradient was formed when the Cu concentration exceeded eutectic composition of Al-Cu alloy. During the solidification of transition zone, the growth sequence of α-Al dendrites and eutectic structure were mainly dominated by the variation of Cu concentration and thermal field according to the temperature of the liquidus line of the equilibrium phase diagram. Finally, the transition zone around the interface were identified to be I (α-Al), II (Al+Al2Cu), III (Al2Cu) and IV (Al2Cu, AlCu and Al4Cu9), respectively.

Electron Microscopy of Ion Deposited Thin Films of the Oxides of Titanium

1985 ◽  
Vol 62 ◽  
Author(s):  
A. B. Harker ◽  
D. G. Howitt ◽  
P. J. Hood ◽  
P. Kobrin
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Ion Beam ◽  
Phase 1 ◽  
Equilibrium Phase ◽  
Free Standing ◽  
Fine Mesh ◽  
Voltage Electron ◽  
Post Deposition

ABSTRACTThe reactive ion beam deposition of ceramic films onto unheated substrates can produce amorphous films with essentially molecular mixing. The annealing and hot isotatic pressing (hipping) of these films to produce crystalline phases have reproducable effects which are sensitive to the temperature and the density of the film. Experiments with titanium oxides indicate that it is principally the equilibrium phases that are formed and that hipping can be used to encourage the same transformations at lower temperatures.Thin films of titanium oxide close to the stoichiometry of TiO2 were deposited onto unheated substrates of sodium chloride. Some of the films were removed from the substrate by floating them off in water and the remainder were either annealed or hipped to induce crystallization. The anneals were performed either in air or argon and the hipping was done under an argon pressure of about twenty thousand pounds per square inch. Several of the free standing films were annealed in the same atmospheres on nickel grids. All the specimens were prepared for transmission electron microscopy by the same floating technique and were examined in a Philips 400 T.E.M. at 125 keV. The as deposited films were amorphous and showed no visible texture other than that derived from a small amount of porosity. The films were sufficiently conductive that they could be examined directly in the T.E.M. without carbon coating provided they were supported on a grid of fairly fine mesh. One specimen was also examined in the Kratos 1.5 MeV high voltage electron microscope at the National Center for Electron Microscopy. The specimen was annealed in vacuum using an in-situ hot stage to directly observe the behavior of the film.The post deposition annealing and hipping of these films reproducibly induced the crystallization of anatase below 800°C. This is the equilibrium phase [1] and the extent to which the films transformed and the morphology of the growing crystallites were determined principally by the film thickness. There was little difference between the responses of free standing films and films left on the salt substrate. They tended to transform at about the same temperature, which was reproduced in the in-situ hot stage experiment and the microsructures which formed were very similar. The dependence upon thickness was also reflected in all the microstructures of the different post deposition treatments and it was possible to complete the transformations that were very sluggish in some of the films by hipping them at the same temperatures.

scholarly journals Spectroscopic and Thermal Analyses of Ortho-Benzylphenol Crystalline Polymorphism

2018 ◽  
Vol 63 (2) ◽  
pp. 95 ◽  
Author(s):  
J. Baran ◽  
N. A. Davydova ◽  
M. Drozd ◽  
E. A. Ponezha ◽  
V. Ya. Reznichenko
Keyword(s):  
Structural Changes ◽  
Metastable Phase ◽  
Thermal Analyses ◽  
Aromatic Rings ◽  
Methylene Bridge ◽  
Glass Forming ◽  
The Difference ◽  
Crystalline Polymorphism ◽  
First Time

In situ, we present the experimental spectroscopic proof of the existence of polymorphism in ortho-benzylphenol. Infrared spectroscopy was used for the first time to investigate the structural changes during the crystallization of a metastable phase, which is transformed, in the course of time, into a stable one. The results show that, in the stable and metastable phases, different conformers of ortho-benzylphenol molecule predominate, which differ in the orientation of the aromatic rings relative to the connecting methylene bridge. Namely, it is shown that the transformation of the metastable phase into a stable one is accompanied by the rotation of the OH-substituted aromatic ring relative to the connecting methylene bridge from 59.9∘ to 180.0∘ in the molecule of ortho-benzylphenol. The DSC experiment has shown that the process of nucleation of a metastable phase preferentially develops below ∼1.1 Tg (243 K), the crystallization occurs at ∼272 K, and the melting happens at 290.2 K. The difference in the temperature regions of nucleation and crystallization explains a good glass-forming status of ortho-benzylphenol.

Effect of Microstructure on Phase Formation in Reaction of The Nb/Al Multilayer Thin Films

1991 ◽  
Vol 230 ◽  
Author(s):  
Katayun Barmak ◽  
Kevin R. Coffey ◽  
David A. Rudman ◽  
Simon Foner
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Phase Diagram ◽  
Grain Boundary ◽  
Phase Formation ◽  
Boundary Diffusion ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Thin Layers ◽  
Multilayer Thin Films

AbstractWe investigated the phase formation sequence in the reaction of multilayer thin films of Nb/Al with overall compositions of 25 and 33 at.% AI. We report novel phenomena which distinguish thin-film reactions unequivocally from those in bulk systems. For sufficiently thin layers composition and stability of product phases are found to deviate significantly from that predicted from the equilibrium phase diagram. We demonstrate that in the Nb/Al system the length scales below which such deviations occur is about 150 nm. We believe that these phenomena occur due to the importance of grain boundary diffusion and hence microstructure in these thin films.

The Phase Formation Sequence In Titanium-Silicon Thin Films

1985 ◽  
Vol 54 ◽  
Author(s):  
Robert Beyers ◽  
Robert Sinclair
Keyword(s):  
Thin Films ◽  
Phase Formation ◽  
Integrated Circuit ◽  
Intermediate Phase ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Impurity Content ◽  
High Resistivity ◽  
Si Films ◽  
Titanium Silicon

ABSTRACTThe reliable use of TiSi2 in integrated circuit metallizations will depend in part on an intimate knowledge of the effects of processing variables — such as annealing time, temperature, and ambient — on the phase formation sequence. For this reason, transmission electron microscopy has been used to investigate the formation of TiSi2 thin films on silicon substrates [1]. For films formed either by reacting titanium with a silicon substrate or by sintering a codeposited (Ti + 2 Si) mixture, we find that a high resistivity (∼60 μΩcm), metastable phase — TiSi2(C49 or ZrSi2 structure) — forms prior to the desired low resistivity (∼15 μΩcm), equilibrium phase — TiSi2(C54 structure). In titanium-silicon diffusion couples, a thin layer of TiSi is also present on top of the metastable TiSi2- For processing temperatures above 550°C, the available data suggest that the metastable TiSi2 forms first and acts as a template for subsequent nucleation of the TiSi phase. In codeposited (Ti + 2 Si) films, TiSi2(C49 structure) is the only intermediate phase. The temperature at which the C49 structure transforms to the C54 structure increases significantly as the film impurity content increases. Differences in earlier reports of TiSi2 formation [2–5] appear to be resolved if x-ray diffraction peaks attributed to Ti5Si3 and TiSi were actually from the metastable TiSi2

In-Situ Investigation of Cu-In-Se Reactions by Thin Film Calorimetry

1997 ◽  
Vol 485 ◽  
Author(s):  
D. Wolf ◽  
G. Müller
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Equilibrium Phase ◽  
Reaction Times ◽  
Practical Interest ◽  
Ex Situ ◽  
In Situ Observation ◽  
Flux Agent ◽  
In Situ Investigation

AbstractStudies of the reaction path during annealing of Cu-In-Se thin films for solar cell absorbers have been limited up to now to ex-situ analyses of the phase composition by X-Ray Diffraction (XRD) after processing by a specific temperature-time program. As an indirect method, the application of ex-situ XRD is not sufficient for the determination of reaction temperatures and reaction times for setting up a general model of CIS-formation.We show in this paper that the use of a calorimetric method (Thin Film Calorimetry, TFC) offers the advantage of a direct (in-situ) observation of thin film reactions. Special care is taken to use film thicknesses of practical interest for industrial application (1.5 – 3 μm). In a first step we show results of binary reactions in the Cu-In, In-Se and Cu-Se systems. Their knowledge is necessary for understanding the processes involved in the ternary CIS-layers. It turned out that thin Cu-In and Cu-Se films react already at room temperature and behave as predicted by the bulk equilibrium phase diagrams during heating. In-Se thin films show prominent exothermic reactions starting with the melting of In. The first phase to be formed is generally In2Se which is then converted to more Se-rich compounds. In ternary Cu-In-Se films (Cu/In = 1.00) we observe transitions of the Cu-Se-system which can be attributed to the decomposition of CuSe2 and CuSe. Consequences for the model of improved CIS-growth by a Cu-Se flux agent are discussed.

scholarly journals Non-Equilibrium Processing of Ni-Si Alloys at High Undercooling and High Cooling Rates

2014 ◽  
Vol 790-791 ◽  
pp. 22-27 ◽  
Author(s):  
Andrew M. Mullis ◽  
Lei Gang Cao ◽  
Robert F. Cochrane
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Eutectic Structure ◽  
Eutectic Solidification ◽  
Drop Tube ◽  
High Undercooling ◽  
Cooling Rates ◽  
Β Phase ◽  
High Cooling Rates

Melt encasement (fluxing) and drop-tube techniques have been used to solidify a Ni-25 at.% Si alloy under conditions of high undercooling and high cooling rates respectively. During undercooling experiments a eutectic structure was observed, comprising alternating lamellae of single phase γ (Ni31Si12) and Ni-rich lamellae containing of a fine (200-400 nm) dispersion of β1-Ni3Si and α-Ni. This is contrary to the equilibrium phase diagram from which direct solidification to β-Ni3Si would be expected for undercoolings in excess of 53 K. Conversely, during drop-tube experiments a fine (50 nm) lamellar structure comprising alternating lamellae of the metastable phase Ni25Si9 and β1-Ni3Si is observed. This is also thought to be the result of primary eutectic solidification. Both observations would be consistent with the formation of the high temperature form of the β-phase (β2/β3) being suppressed from the melt.

An in Situ Hrem Study of Crystal Nucleation in Amorphous Silicon thin Films

1990 ◽  
Vol 202 ◽  
Author(s):  
A. S. Kirtikar ◽  
J. Morgiel ◽  
R. Sinclair ◽  
I-W. Wu ◽  
A. Chiang
Keyword(s):  
Thin Films ◽  
Solid Phase ◽  
High Resolution Electron Microscopy ◽  
Nucleation Theory ◽  
Crystal Nucleation ◽  
Classical Nucleation Theory ◽  
Interface Reactions ◽  
Silicon Thin Films ◽  
Resolution Electron

ABSTRACTIn Situ high resolution electron microscopy has proved to be a valuable tool in investigations involving interface reactions in a number of thin film systems. We have applied this technique to dynamically record nucleation and growth sequences during the amorphous (a-) to crystalline (c-) phase transformation in silicon thin films. Interpretation of the recordings has yielded a wealth of information on the mechanisms and to some extent the kinetics of solid phase crystallization. In our recordings, we have been able to capture the critical nucleus at the a-Si-SiO2 interface. Incorporating this into classical nucleation theory enables us to make an estimate of the a-Si-c-Si interfacial energy.

THE METASTABLE PHASE DIAGRAM OF THE BLUME–EMERY–GRIFFITHS MODEL IN ADDITION TO THE EQUILIBRIUM PHASE DIAGRAM USING THE PAIR APPROXIMATION

2005 ◽  
Vol 19 (10) ◽  
pp. 1741-1755 ◽  
Author(s):  
AHMET ERDİNÇ ◽  
MUSTAFA KESKİN
Keyword(s):  
Phase Diagram ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Order Parameters ◽  
Second Order ◽  
Pair Approximation ◽  
Variation Method ◽  
Metastable Phase Diagram ◽  
Phase Boundaries

As a continuation of our previously published work, the metastable phase diagram of the Blume–Emery–Griffiths model with the arbitrary bilinear (J), biquadratic (K) and crystal field interaction (D) is presented in addition to the equilibrium phase diagram in (T/K, J/K) and (T/K, D/K) plane by using the pair approximation of the cluster variation method on a body centered cubic lattice. We also calculate the phase transitions for the unstable branches of order parameters. The calculated first- and second-order phase boundaries of the unstable branches of the order parameters are superimposed on the equilibrium phase diagram and metastable phase diagram. It is found that the metastable phase diagram and the first- and second-order phase boundaries for unstable branches of order parameters always exist at low temperatures, which are consistent with the experimental and theoretical works.

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