Growth of AlN Single Crystals

1998 ◽  
Vol 512 ◽  
Author(s):  
Glen A. Slack
Keyword(s):  
Growth Rate ◽  
Aluminum Nitride ◽  
Single Crystal ◽  
Single Crystals ◽  
Dissociation Energy ◽  
Growth Rates ◽  
Growth Process ◽  
Limiting Factor ◽  
Crucible Material ◽  
Dissociation Pressure

ABSTRACTAluminum nitride is a wurtzite structure III–V compound, although epitaxial layers of zincblende structure AIN have been made. AlN melts congruently at 2750°C with dissociation pressure of 9 atmospheres. Boules of AIN have been successfully grown by a sublimation-recondensation technique at 2300°C employing tungsten crucibles. Growth rates of 0.3 mm per hour were attained at 1 bar pressure of N2, and crystals up to 22 mm long have been grown. An analysis of the growth process shows that the 9.75eV dissociation energy of N2is the limiting factor in the growth rate. The growth rate is predicted to depend on the N2pressure, but no experiments in this area have yet been concluded. The most satisfactory crucible material found so far for growing AIN is single crystal tungsten.

Measurement of growth rates for single crystals and pressed tablets of CuSO4.5 H2O on a rotating disc

1989 ◽  
Vol 54 (11) ◽  
pp. 2951-2961 ◽  
Author(s):  
Miloslav Karel ◽  
Jaroslav Nývlt
Keyword(s):  
Growth Rate ◽  
Single Crystal ◽  
Single Crystals ◽  
Growth Rates ◽  
Diffusion Coefficients ◽  
Preferred Orientation ◽  
Rotating Disc ◽  
Dissolution Rates ◽  
Rates Of Growth ◽  
Good Agreement

Measured growth and dissolution rates of single crystals and tablets were used to calculate the overall linear rates of growth and dissolution of CuSO4.5 H2O crystals. The growth rate for the tablet is by 20% higher than that calculated for the single crystal. It has been concluded that this difference is due to a preferred orientation of crystal faces on the tablet surface. Calculated diffusion coefficients and thicknesses of the diffusion and hydrodynamic layers in the vicinity of the growing or dissolving crystal are in good agreement with published values.

scholarly journals Effect of Composition on the Growth of Single Crystals of (1−x)(Na1/2Bi1/2)TiO3-xSrTiO3 by Solid State Crystal Growth

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2357 ◽  
Author(s):  
Le ◽  
Fisher ◽  
Moon
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Solid State ◽  
Single Crystal ◽  
Single Crystals ◽  
Grain Growth ◽  
Ceramic Powder ◽  
Single Crystal Growth ◽  
Crystal Growth Rate ◽  
Mixed Control

The (1−x)(Na1/2Bi1/2)TiO3-xSrTiO3 (NBT-100xST) system is a possible lead-free candidate for actuator applications because of its excellent strain vs. electric field behaviour. Use of single crystals instead of polycrystalline ceramics may lead to further improvement in piezoelectric properties but work on single crystal growth in this system is limited. In particular, the effect of composition on single crystal growth has yet to be studied. In this work, single crystals of (NBT-100xST) with x = 0.00, 0.05, 0.10 and 0.20 were grown using the method of Solid State Crystal Growth. [001]-oriented SrTiO3 single crystal seeds were embedded in (NBT-100xST) ceramic powder, which was then pressed to form pellets and sintered at 1200 °C for 5 min–50 h. Single crystal growth rate, matrix grain growth rate and sample microstructure were examined using scanning and transmission electron microscopy. The results indicate that the highest single crystal growth rate was obtained at x = 0.20. The mixed control theory of grain growth is used to explain the single crystal and matrix grain growth behaviour.

Increased Growth Rate in a SiC CVD Reactor Using HCl as a Growth Additive

2005 ◽  
Vol 483-485 ◽  
pp. 73-76 ◽  
Author(s):  
Rachael L. Myers-Ward ◽  
Olof Kordina ◽  
Z. Shishkin ◽  
Shailaja P. Rao ◽  
R. Everly ◽  
...  
Keyword(s):  
Growth Rate ◽  
Epitaxial Growth ◽  
Gas Phase ◽  
Hydrogen Chloride ◽  
Growth Rates ◽  
Growth Process ◽  
Cluster Formation ◽  
Film Morphology ◽  
Hydrogen Carrier ◽  
Low Crystalline

Hydrogen chloride (HCl) was added to a standard SiC epitaxial growth process as an additive gas. A low-pressure, hot-wall CVD reactor, using silane and propane precursors and a hydrogen carrier gas, was used for these experiments. It is proposed that the addition of HCl suppresses Si cluster formation in the gas phase, and possibly also preferentially etches material of low crystalline quality. The exact mechanism of the growth using an HCl additive is still under investigation, however, higher growth rates could be obtained and the surfaces were improved when HCl was added to the flow. The film morphology was studied using SEM and AFM and the quality with LTPL analysis, which are reported.

On the Age and Growth Rate of Giant Cacti: Radiocarbon Dating of the Spines of Cardon (Pachycereus Pringlei)

Radiocarbon ◽  
2016 ◽  
Vol 58 (3) ◽  
pp. 479-490 ◽  
Author(s):  
Mariana Delgado-Fernández ◽  
Pedro P Garcillán ◽  
Exequiel Ezcurra
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Annual Growth ◽  
Age And Growth ◽  
Limiting Factor ◽  
Annual Growth Rate ◽  
Columnar Cacti ◽  
Rate Versus ◽  
The Mean ◽  
Pachycereus Pringlei

AbstractAge estimation has been a limiting factor in the study of giant columnar cacti. In order to test the feasibility of using radiocarbon methods to estimate the age of the giant cardon cacti (Pachycereus pringlei), we selected six sites spanning the latitudinal and precipitation range of the species in the Baja California peninsula. In each site, we selected four individuals of different heights and sampled a spine from the lowest areole in the stem. The age of the spine was estimated using 14C dating, and the mean annual growth rate of the plant was calculated dividing the height of the lead shoot by the plant’s age. Mean annual growth rate was 0.098 m/yr, with values varying between 0.03 and 0.23 m/yr. Within the range of plants sampled, mean annual growth rates were significantly correlated with the height of the plant (r2=0.82, P<0.0001), and no other site-specific variable such as precipitation or latitude was a significant predictor of mean annual growth rates. A model integrating mean growth rate versus height showed that relatively small differences in growth rates between plants accumulate during the plants’ lifetime, so that plants of similar size may have very different ages. We conclude that 14C dating provides a robust method to explore the growth and demography of columnar cacti.

scholarly journals A Cytochrome cbb3(Cytochrome c) Terminal Oxidase in Azospirillum brasilense Sp7 Supports Microaerobic Growth

1998 ◽  
Vol 180 (21) ◽  
pp. 5689-5696 ◽  
Author(s):  
Kathleen Marchal ◽  
Jun Sun ◽  
Veerle Keijers ◽  
Huub Haaker ◽  
Jos Vanderleyden
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Respiration Rate ◽  
Growth Rates ◽  
Azospirillum Brasilense ◽  
Specific Growth ◽  
Limiting Factor ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Microaerobic Conditions

ABSTRACT Spectral analysis indicated the presence of a cytochromecbb 3 oxidase under microaerobic conditions inAzospirillum brasilense Sp7 cells. The corresponding genes (cytNOQP) were isolated by using PCR. These genes are organized in an operon, preceded by a putative anaerobox. The phenotype of an A. brasilense cytN mutant was analyzed. Under aerobic conditions, the specific growth rate during exponential phase (μe) of the A. brasilense cytNmutant was comparable to the wild-type specific growth rate (μe of approximately 0.2 h−1). In microaerobic NH4 +-supplemented conditions, the low respiration of the A. brasilense cytN mutant affected its specific growth rate (μe of approximately 0.02 h−1) compared to the wild-type specific growth rate (μe of approximately 0.2 h−1). Under nitrogen-fixing conditions, both the growth rates and respiration of the wild type were significantly diminished in comparison to those under NH4 +-supplemented conditions. Differences in growth rates and respiration between the wild type and theA. brasilense cytN mutant were less pronounced under these nitrogen-fixing conditions (μe of approximately 0.03 h−1 for the wild type and 0.02 h−1 for the A. brasilense cytN mutant). The nitrogen-fixing capacity of the A. brasilense cytN mutant was still approximately 80% of that determined for the wild-type strain. This leads to the conclusion that the A. brasilensecytochrome cbb 3 oxidase is required under microaerobic conditions, when a high respiration rate is needed, but that under nitrogen-fixing conditions the respiration rate does not seem to be a growth-limiting factor.

The Role of Chlorine during High Growth Rate Epitaxy

2015 ◽  
Vol 821-823 ◽  
pp. 141-144 ◽  
Author(s):  
Robin Karhu ◽  
Ian Booker ◽  
Jawad ul Hassan ◽  
Ivan Ivanov ◽  
Erik Janzén
Keyword(s):  
Growth Rate ◽  
Charge Carrier ◽  
Growth Rates ◽  
Growth Process ◽  
Doping Concentration ◽  
Carrier Lifetime ◽  
High Growth ◽  
High Growth Rate ◽  
Charge Carrier Lifetime

The influence of chlorine has been investigated for high growth rates of 4H-SiC epilayers on 4o off-cut substrates. Samples were grown at a growth rate of approximately 50 and 100 μm/h and various Cl/Si ratios. The growth rate, net doping concentration and charge carrier lifetime have been studied as a function of Cl/Si ratio. This study shows some indications that a high Cl concentration in the growth cell leads to less availability of Si during the growth process.

scholarly journals Thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics

Cerâmica ◽  
2004 ◽  
Vol 50 (315) ◽  
pp. 247-253 ◽  
Author(s):  
A. Franco Júnior ◽  
D. J Shanafield
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Nitride ◽  
Single Crystal ◽  
Single Crystals ◽  
Conduction Mechanism ◽  
Sintering Process ◽  
Polycrystalline Aluminum ◽  
Polycrystalline Ceramics ◽  
Thermal Conductivities

In general, polycrystalline ceramics exhibit lower thermal conductivities than their associated single crystals. For instance, at 300K, the theoretical thermal conductivity of single crystal aluminum nitride (AlN) is 319 W/m-K, whereas, the values measured for polycrystalline AlN ceramics range from 17 W/m-K to 285 W/m-K. This variation is not unusual for polycrystalline ceramics. The variability is strongly dependent upon the purity of the starting materials and the details of sintering process. The process is important since it influences the microstructure and thus influences the conduction mechanism. In this paper we present the causes of this variation and how it can be controlled.

GROWTH RATES OF SINGLE CRYSTALS OF ETHYLENE DIAMINE TARTRATE

1955 ◽  
Vol 33 (6) ◽  
pp. 1155-1161 ◽  
Author(s):  
A. H. Booth ◽  
H. E. Buckley
Keyword(s):  
Growth Rate ◽  
Crystal Growth ◽  
Single Crystals ◽  
Growth Rates ◽  
Rapid Growth ◽  
Polar Axis ◽  
Ethylene Diamine ◽  
Short Intervals ◽  
Steady Growth ◽  
Controlled Conditions

Single crystals of ethylene diamine tartrate were grown under controlled conditions and the growth rate of the faces measured directly in the solution at short intervals by means of a travelling microscope. For the [Formula: see text] pair of faces, the fastest growing form, steady growth at constant supersaturation was interrupted by occasional short periods of more rapid growth. Rejecting these erratic "spurts", reasonably reproducible values could be obtained, and the dependence upon supersaturation plotted. The equivalent faces at the opposite end of the polar axis of the crystal grew, at low supersaturation, with erratic starts and stops, so that reproducible growth-rate values could not be obtained. The results are discussed in relation to existing crystal growth theories.

The observation of defects on (100) CdTe surfaces by chemical etching

1992 ◽  
Vol 50 (2) ◽  
pp. 1424-1425
Author(s):  
M.E. Lee
Keyword(s):  
Single Crystal ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Chemical Etching ◽  
Crystalline Perfection ◽  
Crystalline Defects ◽  
High Incidence ◽  
Crystallographic Defects ◽  
Cdznte Substrates ◽  
Device Technology

The crystalline perfection of bulk CdTe substrates plays an important role in their use in infrared device technology. The application of chemical etchants to determine crystal polarity or the density and distribution of crystallographic defects in (100) CdTe is not well understood. The lack of data on (100) CdTe surfaces is a result of the apparent difficulty in growing (100) CdTe single crystal substrates which is caused by a high incidence of twinning. Many etchants have been reported to predict polarity on one or both (111) CdTe planes but are considered to be unsuitable as defect etchants. An etchant reported recently has been considered to be a true defect etchant for CdTe, MCT and CdZnTe substrates. This etchant has been reported to reveal crystalline defects such as dislocations, grain boundaries and inclusions in (110) and (111) CdTe. In this study the effect of this new etchant on (100) CdTe surfaces is investigated.The single crystals used in this study were (100) CdTe as-cut slices (1mm thickness) from Bridgman-grown ingots.

Mounting an individual submicrometer sized single crystal

1996 ◽  
Vol 211 (6) ◽  
Author(s):  
R. B. Neder ◽  
M. Burghammer ◽  
Th. Grasl ◽  
H. Schulz
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Single Crystal ◽  
Single Crystals ◽  
High Vacuum ◽  
Nanometer Resolution ◽  
Micro Manipulator ◽  
Scanning Electron

AbstractWe developed a new micro manipulator for mounting individual sub-micrometer sized single crystals within a scanning electron microscope. The translations are realized via a commercially available piezomicroscope, adapted for high vacuum usage and realize nanometer resolution. With this novel instrument it is routinely possible to mount individual single crystals with sizes down to 0.1

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