Role of grain boundaries in the epitaxial realignment of undoped and As-doped polycrystalline silicon films

1993 ◽  
Vol 8 (10) ◽  
pp. 2608-2612 ◽  
Author(s):  
C. Spinella ◽  
F. Benyaïch ◽  
A. Cacciato ◽  
E. Rimini ◽  
G. Fallico ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Structure ◽  
Native Oxide ◽  
Thermally Induced ◽  
Si Substrates ◽  
As Doping ◽  
Fine Grain ◽  
Si Films ◽  
Polycrystalline Silicon Films ◽  
Reduced Density

The early stages of the thermally induced epitaxial realignment of undoped and As-doped polycrystalline Si films deposited onto crystalline Si substrates were monitored by transmission electron microscopy. Under the effect of the heat treatment, the native oxide film at the poly-Si/c-Si interface begins to agglomerate into spherical beads. The grain boundary terminations at the interface are the preferred sites for the triggering of the realignment transformation which starts by the formation of epitaxial protuberances at these sites. This feature, in conjunction with the microstructure of the films during the first instants of the heat treatment, explains the occurrence of two different realignment modes. In undoped films the epitaxial protuberances, due to the fine grain structure, are closely distributed and grow together forming a rough interface moving toward the film's surface. For As-doped films, the larger grain size leaves a reduced density of realignment sites. Due to As doping some of these sites grow fast and form epitaxial columns that further grow laterally at the expense of the surrounding polycrystalline grains.

Improvement of Strength and Ductility by Combining Static Recrystallization and Unique Heat Treatment in Co-20Cr-15W-10Ni Alloy for Stent Application

2021 ◽  
Vol 1016 ◽  
pp. 1503-1509
Author(s):  
Kosuke Ueki ◽  
Soh Yanagihara ◽  
Kyosuke Ueda ◽  
Masaaki Nakai ◽  
Takayoshi Nakano ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Grain Size ◽  
Static Recrystallization ◽  
High Strength ◽  
Small Variation ◽  
Grain Structure ◽  
Fine Grain ◽  
High Temperature Short Time ◽  
Average Grain Size ◽  
Strength And Ductility

The Co-20Cr-15W-10Ni (CCWN, mass%) alloy has excellent corrosion resistance and strength-ductility balance and is applied in almost all balloon-expandable stent platforms. To further reduce the invasiveness of stent placement, it is necessary to reduce the diameter of the stent. That is, both high strength and high ductility should be achieved while maintaining a low yield stress. In our previous studies, it was discovered that low-temperature heat-treatment (LTHT) at 873 K improves the elongation of the CCWN alloy. In this study, we focused on the grain refinement by swaging and static recrystallization to improve the strength of the alloy. The as-swaged alloy was recrystallized at 1373–1473 K for 100–300 s, followed by LTHT. A fine grain structure with an average grain size of 3–17 μm was obtained by static recrystallization. The η-phase (M12X-M6X type precipitates, M: metallic elements, X: C and/or N) formed during the recrystallization at 1373–1448 K. The alloys recrystallized at 1448 and 1473 K had a homogeneous structure with a small variation in the grain size. On the other hand, the alloys recrystallized at 1373 and 1423 K had an inhomogeneous structure in which fine and coarse grains were mixed. Both the strength and ductility of the CCWN alloy were improved by combining high-temperature short-time recrystallization and LTHT.

Crystallization of Tin-Implanted Amorphous Silicon Thin Films

1992 ◽  
Vol 279 ◽  
Author(s):  
Fuyu Lin ◽  
Miltiadis K. Hatalis
Keyword(s):  
Amorphous Silicon ◽  
Crystallization Process ◽  
Silicon Films ◽  
Grain Structure ◽  
Crystallization Time ◽  
Silicon Thin Films ◽  
Fine Grain ◽  
Annealing Conditions ◽  
Transmission Electron ◽  
Si Films

ABSTRACTThe crystallization of Sn-implanted amorphous silicon was studied as a function of tin implant dose and annealing conditions by transmission electron microscopy. The films were implanted at an energy of 110 keV with a dose in the range of 5 × 1014 to 5×1016 cm−2 and were annealed at a temperature in the range of 450°C to 550°C. An enhanced rate of crystallization in amorphous Si-Sn films compared to the non-implanted amorphous silicon films during thermal annealing was observed. The crystallization process of Si films implanted with tin at a dose of 2.5×1016 cm−2 or less is very similar to unimplanted silicon films except higher nucleation rates and shorter crystallization time were observed with increasing tin dose. Films implanted with tin at a dose of 2.5×1016 cm−2 or more display extremely rapid crystallization (3 hours at 450°C) and very fine grain structure (10 nm); no substantial grain growth has been observed during lurther annealing, but some single crystal-like areas were formed. In-situ annealing of silicon implanted to 5×1016 cm−2 showed that the crystallization process is enhanced by the formation of the liquid tin phase.

The Effect of Heat Treatment on Creep Resistance of Castings from the Modified Superalloy MAR-247

2013 ◽  
Vol 212 ◽  
pp. 229-236
Author(s):  
Marek Cieśla ◽  
Franciszek Binczyk ◽  
Marcin Mańka
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Creep Resistance ◽  
Nickel Superalloy ◽  
Grain Structure ◽  
Morphological Properties ◽  
High Temperature Creep ◽  
Temperature Creep ◽  
Fine Grain ◽  
Heat Treated

mpact of heat treatment on durability has been evaluated in this study in conditions of high-temperature creep of castings made from nickel superalloy MAR-247 post production rejects. Castings made in the processes of modification and filtration when pouring into moulds were subject to solubilization (1185°C/2 h) with subsequent ageing (870°C/20 h). It has been found on the basis of performed tests that in conditions of high-temperature creep at temperature 980°C with stress σ = 150 MPa the resistance of specimens of coarse-grain structure was significantly higher when compared to fine-grain material. The conditions of initiation and propagation of cracks in these specimens were analysed with consideration of morphological properties of material macro-, micro-and substructure. Moreover, it has been proven that creep resistance of heat treated MAR-247 superalloy significantly improves when compared to its condition after the process of modification only. Macrostructural changes in the MAR-247 superalloy that determine the increase of superalloy creep resistance after solubilization and ageing, as observed in the tests, were also examined.

Evolution of Microstructure and Mechanical Properties of the Thixo-Diecast 319s Alloy during Heat Treatment

2013 ◽  
Vol 765 ◽  
pp. 511-515 ◽  
Author(s):  
Da Quan Li ◽  
Xiao Kang Liang ◽  
Fu Bao Yang ◽  
You Feng He ◽  
Fan Zhang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Cast Alloy ◽  
Grain Structure ◽  
Precipitate Size ◽  
Fine Grain ◽  
Microstructure And Mechanical Properties ◽  
Optimum Heat ◽  
Evolution Of Microstructure

The evolution of microstructure and mechanical properties during solution and ageing heat treatment process was studied in terms of a thixo-diecast impeller of 319s aluminium alloy. The cast alloy exhibited a microstructure consisting of primary uniformly distributed in α-Al globules and the eutectics. A series of heat treatment studies were performed to determine optimum heat treatment parameters, in order to achieve fine grain structure, fine silicon particles and optimal precipitate size and distribution. Optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to study the evolution of microstructure and mechanical properties. The results demonstrate that, the full T6 heat treatments are successfully applied to thixo-diecast 319s impellers. A two-step solution heat treatment is employed to prevent porosity due to overheating. The tensile properties of thixo-diecast 319s impellers were substantially enhanced after T6 heat treatment. The plate-shaped θ′ precipitates and lath-shaped Q′ precipitates are the most effective for precipitation strengthening.

Epitaxial Realignment of In-Situ Doped Polycrystalline Silicon for Advanced BiCMOS Technologies

1999 ◽  
Vol 587 ◽  
Author(s):  
K. Chang ◽  
S.G. Thomas ◽  
T-C. Lee ◽  
R.B. Gregory ◽  
D. O'meara ◽  
...  
Keyword(s):  
Polycrystalline Silicon ◽  
Chemical Vapor ◽  
Layer Growth ◽  
Native Oxide ◽  
Post Deposition Annealing ◽  
Si Substrates ◽  
Si Films ◽  
Post Deposition

AbstractIndustrial feasibility of an in-situ-doped (ISD) polycrystalline Si process using chemical vapor deposition for advanced BiCMOS technologies is presented. ISD As-doped amorphous and polycrystalline Si layers have been deposited on Si substrates at 610°C and 660°C, respectively, with the deposition rate varying from 120 to 128Å /minute. Samples are compared on the basis of having been subjected to a substrate preclean prior to deposition using an HF solution and an in-situ H2 bake. TEM micrographs reveal the presence of a thin (10-15 Å) native oxide at the deposited layer/substrate interface for samples not precleaned. This is confirmed for both the amorphous and polycrystalline Si depositions. However, for the 610°C-deposited samples given the substrate preclean, a polycrystalline structure with partial epitaxial layer growth is observed. Twins and stacking faults are found at the poly Si/single crystal Si interface, causing interfacial roughness. Post-deposition annealing of the Si films typically generates grain growth, but RBS-channeling characterization of the annealed Si provides evidence of some recrystallization, the extent of which is affected by the original growth condition. Analysis shows that the amorphous deposition at 610°C results in a mixture of epitaxial and polycrystalline Si. Epitaxial realignment of the polycrystalline Si film by post deposition annealing can result in significantly improved device performance.

The Growth and Characterisation of Ir Silicide Films on (111)Si

1990 ◽  
Vol 202 ◽  
Author(s):  
M.A. Lawn ◽  
R.G. Elliman ◽  
M.C. Ridgway ◽  
R. Leckey ◽  
J.D. Riley
Keyword(s):  
Electron Microscope ◽  
Epitaxial Growth ◽  
Transmission Electron Microscope ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Grain Structure ◽  
Si Substrates ◽  
Fine Grain ◽  
Transmission Electron

ABSTRACTA study of the growth of thin Ir silicide films on (111)Si substrates has been undertaken. Thin (2.0nm) ir films deposited onto Si substrates under ultra-high vacuum conditions have been observed to display remarkable film continuity and fine grain structure (lnm). In situ annealing at 1000°C resulted in the formation of large regions (>10µm) of epitaxial IrSi3 islands (∼1µm) with identical epitaxial orientations. By means of annealing an as-deposited (2.0nm) Ir film stepwise to 1000°C within a transmission electron microscope the evolution of Ir silicide phases and morphologies were observed. The epitaxial growth of the semiconducting IrSi1.75 phase is reported along with the formation of Ir silicide islands at temperatures between 700°C and 800°C.

Scanning Kelvin Probe Studies of Cosmetic (Filiform) Corrosion on AA6016

2006 ◽  
Vol 519-521 ◽  
pp. 679-686 ◽  
Author(s):  
H.N. McMurray ◽  
A.J. Coleman ◽  
G. Williams ◽  
Andreas Afseth ◽  
Geoff M. Scamans
Keyword(s):  
Heat Treatment ◽  
Surface Layer ◽  
Polyvinyl Butyral ◽  
Open Circuit ◽  
Grain Structure ◽  
Metal Loss ◽  
Kelvin Probe ◽  
Fine Grain ◽  
Scanning Kelvin Probe ◽  
Filiform Corrosion

Scanning Kelvin Probe (SKP) potentiometry is used to systematically investigate the effect of surface abrasion and subsequent heat-treatment on the open-circuit potential in humid air of the AA6016 surface. SKP is also used to follow the kinetics of filiform corrosion and to determine characteristic potentials associated with the electrolyte-filled filiform head and dry filiform tail. It is shown that simply abrading with 180 grit SiC produces a surface potential up to 0.5V lower than the bulk. When the abraded sample is overcoated with a 30 micron layer of PVB (polyvinyl butyral) and exposed to HCl a fast, superficial filiform corrosion (FFC) is observed in which metal loss is limited to the thickness of the surface layer. Filiform head OCP values are similar to that of the surface layer, whereas filiform tail OCP values are similar to the bulk. A mechanism is proposed in which the ultra-fine grain structure of the surface layer produces an anodic activation and the potential difference between the surface layer and the bulk provides and increased thermodynamic driving force for corrosion. For post-abrasion heat treatment temperatures up to 350°C the fast filiform process is followed by a slower, deeper form of FFC.

Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates

1975 ◽  
Vol 33 ◽  
pp. 96-97
Author(s):  
R. W. Ditchfield ◽  
A. G. Cullis
Keyword(s):  
Epitaxial Growth ◽  
Electron Energy ◽  
Silicon Substrates ◽  
Secondary Phases ◽  
Si Substrates ◽  
Transmission Electron ◽  
Layer Structures ◽  
Si Films ◽  
Electron Energy Loss ◽  
Growth Centres

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.

Microstructure Development in a High Current Density NbTi Superconducting Composite

1985 ◽  
Vol 43 ◽  
pp. 186-189
Author(s):  
P. J. Lee ◽  
D. C. Larbalestier
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Cold Drawing ◽  
Heat Treatments ◽  
Grain Structure ◽  
Fine Grain ◽  
Boundary Film ◽  
Quantitative Basis ◽  
Cold Worked ◽  
Very High

Several features of the metallurgy of superconducting composites of Nb-Ti in a Cu matrix are of interest. The cold drawing strains are generally of order 8-10, producing a very fine grain structure of diameter 30-50 nm. Heat treatments of as little as 3 hours at 300 C (∼ 0.27 TM) produce a thin (1-3 nm) Ti-rich grain boundary film, the precipitate later growing out at triple points to 50-100 nm dia. Further plastic deformation of these larger a-Ti precipitates by strains of 3-4 produces an elongated ribbon morphology (of order 3 x 50 nm in transverse section) and it is the thickness and separation of these precipitates which are believed to control the superconducting properties. The present paper describes initial attempts to put our understanding of the metallurgy of these heavily cold-worked composites on a quantitative basis. The composite studied was fabricated in our own laboratory, using six intermediate heat treatments. This process enabled very high critical current density (Jc) values to be obtained. Samples were cut from the composite at many processing stages and a report of the structure of a number of these samples is made here.

Sign in / Sign up

Export Citation Format

Share Document