Favourable growth conditions for the preparation of bulk AlN single crystals by PVT

CrystEngComm ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1762-1768 ◽  
Author(s):  
C. Hartmann ◽  
L. Matiwe ◽  
J. Wollweber ◽  
I. Gamov ◽  
K. Irmscher ◽  
...  
Keyword(s):  
Growth Rate ◽  
Single Crystals ◽  
Growth Conditions ◽  
Structural Perfection ◽  
High Structural Perfection ◽  
Deep Uv

A high seed temperature (2251 °C) reveals the highest deep UV transparency (α265nm = 27 cm−1), a high structural perfection (EPD = 9 × 103 cm−2) and a suitable growth rate (R = 200 μm h−1).

Trends in the kinetic and magnetic properties of Pb0.8Sn0.2Te single crystals of high structural perfection

1999 ◽  
Vol 41 (10) ◽  
pp. 1604-1607 ◽  
Author(s):  
M. V. Radchenko ◽  
G. V. Lashkarev ◽  
E. I. Slyn’ko ◽  
A. P. Malysheva
Keyword(s):  
Magnetic Properties ◽  
Single Crystals ◽  
Structural Perfection ◽  
High Structural Perfection

scholarly journals Dynamical X-ray diffraction imaging of voids in dislocation-free high-purity germanium single crystals

2020 ◽  
Vol 53 (4) ◽  
pp. 880-884 ◽  
Author(s):  
Kevin-P. Gradwohl ◽  
Andreas N. Danilewsky ◽  
Melissa Roder ◽  
Martin Schmidbauer ◽  
József Janicskó-Csáthy ◽  
...  
Keyword(s):  
Single Crystals ◽  
High Purity ◽  
Direct Evidence ◽  
X Ray Diffraction ◽  
Structural Perfection ◽  
X Ray ◽  
High Purity Germanium ◽  
High Structural Perfection ◽  
Diffraction Imaging ◽  
General Method

White-beam X-ray topography has been performed to provide direct evidence of micro-voids in dislocation-free high-purity germanium single crystals. The voids are visible because of a dynamical diffraction contrast. It is shown that voids occur only in dislocation-free parts of the crystal and do not show up in regions with homogeneous and moderate dislocation density. It is further suggested that the voids originate from clustering of vacancies during the growth process. A general method is proposed to verify the presence of voids for any crystalline material of high structural perfection.

UV Absorption of KDP Single Crystals as a function of Growth Conditions

1993 ◽  
Vol 329 ◽  
Author(s):  
M. I. Kolybayeva ◽  
I. M. Pritula ◽  
V. I. Salo
Keyword(s):  
Growth Rate ◽  
Absorption Coefficient ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Crystallization Temperature ◽  
Growth Parameters ◽  
Uv Spectroscopy ◽  
Growth Conditions ◽  
Uv Absorption ◽  
Spectroscopy Method

AbstractUV-spectroscopy method is used to study the influence ofdifferent varying growth parameters (growth rate, crystallization temperature, pH of the solution, complexating additions) on the absorption spectra of KH2PO4 crystals. It is found that the minimal value of the absorption coefficient (k ˜ 0.01–0.02cm−1)may be achieved under the following growth conditions: 1) crystallization temperature ˜ 55°C, 2) growth rate ˜ 1mm/24hrs, 3)pH = 4.

The Growth of Stilbene Single Crystals with High Structural Perfection

1990 ◽  
Vol 186 (1) ◽  
pp. 159-166 ◽  
Author(s):  
Sergei Budakovsky ◽  
Nikolai Galunov ◽  
Igor Krainov
Keyword(s):  
Single Crystals ◽  
Structural Perfection ◽  
High Structural Perfection

Preparation of deep UV transparent AlN substrates with high structural perfection for optoelectronic devices

CrystEngComm ◽  
2016 ◽  
Vol 18 (19) ◽  
pp. 3488-3497 ◽  
Author(s):  
C. Hartmann ◽  
J. Wollweber ◽  
S. Sintonen ◽  
A. Dittmar ◽  
L. Kirste ◽  
...  
Keyword(s):  
Optoelectronic Devices ◽  
Structural Perfection ◽  
High Structural Perfection ◽  
Deep Uv

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.

Preparation and characterization of epitaxial iron oxide films

1998 ◽  
Vol 13 (7) ◽  
pp. 2003-2014 ◽  
Author(s):  
Y. Gao ◽  
Y. J. Kim ◽  
S. A. Chambers
Keyword(s):  
Growth Rate ◽  
Iron Oxide ◽  
Oxygen Plasma ◽  
Film Surface ◽  
Surface Region ◽  
Growth Conditions ◽  
Epitaxial Films ◽  
Pure Phase ◽  
Iron Oxide Films

Well-ordered, pure-phase epitaxial films of FeO, Fe3O4, and γ–Fe2O3 were prepared on MgO(001) by oxygen-plasma-assisted MBE. The stoichiometries of these thin films were controlled by varying the growth rate and oxygen partial pressure. Selective growth of γ–Fe2O3 and α–Fe2O3 was achieved by controlling the growth conditions in conjunction with the choice of appropriate substrates. Growth of the iron oxide epitaxial films on MgO at ≥350 °C is accompanied by significant Mg outdiffusion. The FeO(001) film surface exhibits a (2 × 2) reconstruction, which is accompanied by a significant amount of Fe3+ in the surface region. Fe3O4 (001) has been found to reconstruct to a structure. γ–Fe23 (001) film surface is unreconstructed.

Emission characteristics of GaInN/GaN multiple quantum shell nanowire-based LEDs with different p-GaN growth conditions

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Sae Katsuro ◽  
Weifang Lu ◽  
Kazuma Ito ◽  
Nanami Nakayama ◽  
Naoki Sone ◽  
...  
Keyword(s):  
Growth Rate ◽  
Shell Growth ◽  
Light Output ◽  
High Growth ◽  
Growth Conditions ◽  
High Growth Rate ◽  
Current Injection ◽  
Emission Characteristics ◽  
Multiple Quantum ◽  
Plane Region

Abstract Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.

scholarly journals <sup>210</sup>Pb-<sup>226</sup>Ra chronology reveals rapid growth rate of <i>Madrepora oculata</I> and <i>Lophelia pertusa</i> on world's largest cold-water coral reef

2011 ◽  
Vol 8 (6) ◽  
pp. 12247-12283
Author(s):  
P. Sabatier ◽  
J.-L. Reyss ◽  
J. M. Hall-Spencer ◽  
C. Colin ◽  
N. Frank ◽  
...  
Keyword(s):  
Growth Rate ◽  
Coral Reef ◽  
Linear Growth ◽  
Cold Water ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Age And Growth ◽  
Linear Growth Rate ◽  
Lophelia Pertusa ◽  
Water Coral

Abstract. Here we show the use of the 210Pb-226Ra excess method to determine the growth rate of corals from one of the world's largest known cold-water coral reef, the Røst Reef off Norway. Two large branching framework-forming cold-water coral specimens, one Lophelia pertusa and one Madrepora oculata were collected alive at 350 m water depth from the Røst Reef at ~67° N and ~9° E. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and the corals trace element compositions were studied using ICP-QMS. Due to the different chemical behaviors of Pb and Ra in the marine environment, 210Pb and 226Ra were not incorporated the same way into the aragonite skeleton of those two cold-water corals. Thus to assess of the growth rates of both specimens we have here taken in consideration the exponential decrease of initially incorporated 210Pb as well as the ingrowth of 210Pb from the decay of 226Ra. Moreover a~post-depositional 210Pb incorporation is found in relation to the Mn-Fe coatings that could not be entirely removed from the oldest parts of the skeletons. The 226Ra activities in both corals were fairly constant, then assuming constant uptake of 210Pb through time the 210Pb-226Ra chronology can be applied to calculate linear growth rate. The 45.5 cm long branch of M. oculata reveals an age of 31 yr and a~linear growth rate of 14.4 ± 1.1 mm yr−1, i.e. 2.6 polyps per year. However, a correction regarding a remaining post-depositional Mn-Fe oxide coating is needed for the base of the specimen. The corrected age tend to confirm the radiocarbon derived basal age of 40 yr (using 14C bomb peak) with a mean growth rate of 2 polyps yr−1. This rate is similar to the one obtained in Aquaria experiments under optimal growth conditions. For the 80 cm-long specimen of L. pertusa a remaining contamination of metal-oxides is observed for the middle and basal part of the coral skeleton, inhibiting similar accurate age and growth rate estimates. However, the youngest branch was free of Mn enrichment and this 15 cm section reveals a growth rate of 8 mm yr−1 (~1 polyp every two to three years). However, the 210Pb growth rate estimate is within the lowermost ranges of previous growth rate estimates and may thus reflect that the coral was not developing at optimal growth conditions. Overall, 210Pb-226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals, however, removal of post-depositional Mn-Fe oxide deposits is a prerequisite. If successful, large branching M. oculata and L. pertusa coral skeletons provide unique oceanographic archive for studies of intermediate water environmentals with an up to annual time resolution and spanning over many decades.

In Situ Monitoring of the Smear-Out of the Ge Profile in GAS Source SiGe MBE Using Rheed Intensity Oscillations

1992 ◽  
Vol 263 ◽  
Author(s):  
K. Werner ◽  
S. Butzke ◽  
J.W. Maes ◽  
O.F.Z. Schannen ◽  
J. Trommel ◽  
...  
Keyword(s):  
Growth Rate ◽  
Molecular Beam ◽  
Surface Segregation ◽  
Catalytic Effect ◽  
Growth Conditions ◽  
In Situ Monitoring ◽  
Marked Contrast ◽  
Si Substrates ◽  
Gas Source

ABSTRACTWe have studied the deposition of GexSi1−x layers on (100) Si substrates by gas source molecular beam epitaxy (GSMBE) using disilane and germane.The investigation of RHEED intensity oscillations during growth reveals the well known rate enhancement obtained when adding a small amount of germane to the disilane flux. However, when exposing a previously deposited Ge layer to a pure disilane flux the growth rate during the first few monolayers remains at an enhanced value but returns to its homoepitaxial value after about 10 to 15 monolayers. This behaviour was observed under a variety of growth conditions. It is in marked contrast to the experience obtained in conventional Si/Ge MBE and suggests a catalytic effect of the particular surface present during GSMBE growth. We propose that this effect is caused by the surface segregation of Ge species and leads to a smear-out of the Ge profile in the layer.

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