Active Thermal Interaction of Source and Crystal Surfaces in PVT SiC Crystal Growth

2006 ◽  
Vol 527-529 ◽  
pp. 87-90 ◽  
Author(s):  
Krzysztof Grasza ◽  
Emil Tymicki ◽  
Jaroslaw Kisielewski
Keyword(s):  
Silicon Carbide ◽  
Crystal Growth ◽  
Crystallization Front ◽  
Source Material ◽  
Thermal Interaction ◽  
Crystal Surfaces

Silicon carbide crystals were grown from the vapor. Improvement of the quality of the central part of the crystal was achieved by optimization of the geometry of the source material. Active thermal interaction of the source material and the crystallization front made possible an effective programming of the shape and morphology of the crystal. Termination of micropipes on microfacets formed on the crystallization front during growth was observed.

Crystallization of Isotactic Poly(propylene) in Solution as Followed by Slow Calorimetry

1995 ◽  
Vol 60 (11) ◽  
pp. 1905-1924 ◽  
Author(s):  
Hong Phuong-Nguyen ◽  
Geneviève Delmas
Keyword(s):  
Molecular Weight ◽  
Crystal Growth ◽  
High Temperature ◽  
Heat Of Fusion ◽  
Complete Dissolution ◽  
Polymer Molecular Weight ◽  
Solvent Quality ◽  
Temperature Ramp ◽  
Poly Propylene

Dissolution, crystallization and second dissolution traces of isotactic poly(propylene) have been obtained in a slow temperature ramp (3 K h-1) with the C80 Setaram calorimeter. Traces of phase-change, in presence of solvent, are comparable to traces without solvent. The change of enthalpy on heating or cooling, ∆Htotal, over the 40-170 °C temperature range, is the sum of two contributions, ∆HDSC and ∆Hnetwork. The change ∆HDSC is the usual heat obtained in a fast temperature ramp and ∆Hnetwork is associated with a physical network whose disordering is slow and subject to superheating due to strain. When dissolution is complete, ∆Htotal is equal to ∆H0, the heat of fusion of perfect crystals. The values of ∆Htota for nascent and recrystallized samples are compared. Dissolution is the tool to evaluate the quality of the crystals. The repartition of ∆Htotal, into the two endotherms, reflects the quality of crystals. The crystals grown more rapidly have a higher fraction of network crystals which are stable at high T in the solvents. A complete dissolution, i.e. a high temperature (170 °C or more) is necessary to obtain good crystals. The effect of concentration, polymer molecular weight and solvent quality on crystal growth is analyzed.

scholarly journals Using the Eighteenth-Century English Phonology Database (ECEP) as a teaching resource

2020 ◽  
Vol 24 (3) ◽  
pp. 591-606
Author(s):  
CHRISTINE WALLIS
Keyword(s):  
Eighteenth Century ◽  
Language Change ◽  
Historical Linguistics ◽  
Language Attitudes ◽  
Source Material ◽  
Historical Sociolinguistics ◽  
Teaching Resource ◽  
The University ◽  
Late Modern

This article reports on the use of the Eighteenth-Century English Phonology Database (ECEP) as a teaching resource in historical sociolinguistics and historical linguistics courses at the University of Sheffield. Pronouncing dictionaries are an invaluable resource for students learning about processes of standardisation and language attitudes during the Late Modern English period (1700–1900), however they are not easy to use in their original format. Each author uses their own notation system to indicate their recommended pronunciation, while the terminology used to describe the quality of the vowels and consonants differs from that used today, and provides an additional obstacle to the student wishing to interrogate such sources. ECEP thus provides a valuable intermediary between the students and the source material, as it includes IPA equivalents for the recommended pronunciations, as well as any metalinguistic commentary offered by the authors about a particular pronunciation. This article demonstrates a teaching approach that not only uses ECEP as a tool in its own right, but also explores how it can be usefully combined with other materials covering language change in the Late Modern English period to enable students to undertake their own investigations in research-led courses.

Total Energy Differences Between Silicon Carbide Polytypes and their Implications for Crystal Growth

1997 ◽  
Vol 492 ◽  
Author(s):  
Sukit Llmpijumnong ◽  
Walter R. L. Lambrecht
Keyword(s):  
Silicon Carbide ◽  
Crystal Growth ◽  
Epitaxial Growth ◽  
Size Effects ◽  
Nearest Neighbor ◽  
Orbital Method ◽  
Full Potential ◽  
Neighbor Interaction ◽  
Island Size ◽  
Annni Model

ABSTRACTThe energy differences between various SiC polytypes are calculated using the full-potential linear muffin-tin orbital method and analyzed in terms of the anisotropie next nearest neighbor interaction (ANNNI) model. The fact that J1 + 2J2 < 0 with J1 > 0 implies that twin boundaries in otherwise cubic material are favorable unless twins occur as nearest neighbor layers. Contrary to some other recent calculations we find J1 > |J2|. We discuss the consequences of this for stabilization of cubic SiC in epitaxial growth, including considerations of the island size effects.

Particle Engineering: Fundamentals of Particle Formation and Crystal Growth

MRS Bulletin ◽  
2006 ◽  
Vol 31 (11) ◽  
pp. 881-886 ◽  
Author(s):  
Alfred Y. Lee ◽  
Allan S. Myerson
Keyword(s):  
Crystal Growth ◽  
Dosage Form ◽  
Decisive Role ◽  
Product Performance ◽  
Particle Engineering ◽  
Particle Properties ◽  
Packing Arrangement ◽  
Form Development

AbstractThe engineering of particles with customized properties optimized for dosage form manufacture (tablet, capsule, ointment, etc.) has long been a goal of the pharmaceutical industry. Particles can be designed through modification in the size, morphology, and packing arrangement of the solids. The most common approach in achieving this is through crystallization. In this bottom-up process, the two main steps, nucleation and crystal growth, both play a decisive role in shaping the quality of the final crystalline product. In this review, the role of nucleation and crystal growth in controlling particle properties is discussed, and examples are provided that demonstrate the variation in solid-state properties as a function of size, habit (morphology), and internal structure of the particles. In addition, the role of particle properties in product performance and dosage form development of pharmaceuticals is also discussed.

The Effect of Modified Crucible Design and Seed Attachment on SiC Crystal Grown by PVT

2013 ◽  
Vol 740-742 ◽  
pp. 77-80
Author(s):  
Jung Young Jung ◽  
Sang Il Lee ◽  
Mi Seon Park ◽  
Doe Hyung Lee ◽  
Hee Tae Lee ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Temperature Gradient ◽  
Single Crystals ◽  
Crystal Quality ◽  
Full Width ◽  
Half Maximum ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Better Than

The present research was focused to investigate the effect of internal crucible design that influenced the 4H-SiC crystal growth onto a 6H-SiC seed by PVT method. The crucible design was modified to produce a uniform radial temperature gradient in the growth cell. The seed attachment was also modified with a use of polycrystalline SiC plate. The crystal quality of 4H-SiC single crystals grown in modified crucible and grown with modified seed attachment was revealed to be better than that of crystal grown in conventional crucible. The full width at half maximum (FWHM) values of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 285 arcsec, 134 arcsec and 128 arcsec, respectively. The micropipe density (MPD) of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 101ea/cm^2, 81ea/cm^2 and 42ea/cm^2, respectively.

Gate Stack Engineering for High Temperature Silicon Carbide CMOS ICs

2015 ◽  
Vol 2015 (HiTEN) ◽  
pp. 000033-000036 ◽  
Author(s):  
M.H. Weng ◽  
A.D. Murphy ◽  
D.T. Clark ◽  
D.A. Smith ◽  
R.F. Thompson ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Systematic Evaluation ◽  
Process Conditions ◽  
Operating Characteristics ◽  
Gate Stack ◽  
Metal Insulator ◽  
Semiconductor Interfaces

The potential to thermally grow SiO2 on silicon carbide has resulted in it becoming the technology of choice to realise high temperature CMOS circuits. The challenge to achieve a high quality gate stack relies on engineering the metal-insulator-semiconductor interfaces to enable reliable high temperature functionality. Here we describe the effect of different process conditions for the formation of the dielectric layer on the characteristics of the resulting devices. The operating characteristics at elevated temperatures depend critically on the quality of the gate stack. Therefore a systematic evaluation of the intrinsic properties of the gate stack and data from reliability tests are needed.

scholarly journals Macrodefects in Cubic Silicon Carbide Crystals

2010 ◽  
Vol 645-648 ◽  
pp. 375-378 ◽  
Author(s):  
Valdas Jokubavicius ◽  
Justinas Palisaitis ◽  
Remigijus Vasiliauskas ◽  
Rositza Yakimova ◽  
Mikael Syväjärvi
Keyword(s):  
Growth Rate ◽  
Silicon Carbide ◽  
Crystal Growth ◽  
High Temperature ◽  
Temperature Gradient ◽  
Early Stage ◽  
Growth Conditions ◽  
Temperature Ramp ◽  
Cubic Silicon Carbide ◽  
Sublimation Growth

Different sublimation growth conditions of 3C-SiC approaching a bulk process have been investigated with the focus on appearance of macrodefects. The growth rate of 3C-SiC crystals grown on 6H-SiC varied from 380 to 460 μm/h with the thickness of the crystals from 190 to 230 μm, respectively. The formation of macrodefects with void character was revealed at the early stage of 3C-SiC crystal growth. The highest concentration of macrodefects appears in the vicinity of the domain in samples grown under high temperature gradient and fastest temperature ramp up. The formation of macrodefects was related to carbon deficiency which appear due to high Si/C ratio which is used to enable formation of the 3C-SiC polytype.

Effect of Marangoni Convection on InSb Single Crystal Growth by Horizontal Bridgman Method

2001 ◽  
Vol 692 ◽  
Author(s):  
K. Kodera ◽  
A. Kinoshita ◽  
K. Arafune ◽  
Y. Nakae ◽  
A. Hirata
Keyword(s):  
Crystal Growth ◽  
Binary System ◽  
Temperature Gradient ◽  
Single Crystal ◽  
Grown Crystal ◽  
Marangoni Convection ◽  
Single Crystal Growth ◽  
Control Technique ◽  
Growth System

AbstractIt is necessary to clarify the effect of Marangoni convection on single crystal growth from a melt in order to improve the quality of the grown crystal. Particularly, the deviation of crystalmelt (C-M) interface from a planar shape is a major problem because it may deteriorate the quality of the grown crystal. In this paper, we investigated the effect of thermal and solutal Marangoni convection on C-M interface shape in an In-Sb binary system by the horizontal Bridgman (HB) method. The C-M interface concavity strongly depends on the cooling rate and the temperature gradient under uniform concentration distribution conditions in the melt. A large concavity was observed at low cooling rates and high temperature gradient conditions. The concavity was found to be caused by thermal Marangoni convection, by taking Péclet number into account. Then, we varied the composition of the In-Sb binary system to induce solutal Marangoni convection intentionally. The C-M interface was kept planar in case solutal Marangoni convection occurred in the direction opposite to the thermal one. Therefore, we believe that the utilization of solutal Marangoni convection will be a new control technique to make the C-M interface planar for the HB system. From these results, it was clarified that Marangoni convection plays a significant role in the HB crystal growth system.

Sign in / Sign up

Export Citation Format

Share Document