摘要:

AbstractThe conditions for growing Cr‐, Mn‐, Fe‐, Co‐, Ni‐, and Cr + Al‐doped BSO crystals from a stoichiometric melt by the Czochralski method have been the subject of research. A decrease of the absorption coefficient along the growth axis was observed in undoped crystals of 50 mm diameter and 150 mm long, which is indicative of melt stoichiometry change in the course of the growth run. The transmission and reflection spectra of different crystals were measured and the absorption coefficients was determined in the range 0.38–0.70 μm. When Fe dopant concentration exceeds a limit value, the absorption spectrum is blue‐shifted relative to the undoped case and the absorption coefficient decreases. Co, Cr, Mn, and Cr + Al dopants produce a red shift and increase the absorption coefficient. Combined Cr + Al doping shift the absorption spectrum to the blue region as compared to Cr‐only doping with the sam

ISSN:0232-1300    

DOI:10.1002/crat.2170290502

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170290503

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractWe report on aerosol particles generated by bubblers in metalorganic vapour phase epitaxy (MOVPE). A triethylgallium bubbler was investigated in a MOVPE set‐up regarding the generation of aerosol. Our measurements show that aerosol particles are produced, and the production depends on the carrier gas flow bubbling through. The distribution of the particle diameters was measured and was found to range from 10 to 600 nm, with the maximum at about 200 nm. While the number of particles is not negligible the precursor is almost only transported as gas molecules. However, particles could possibly reach the substrate and create defects on the surfac

ISSN:0232-1300    

DOI:10.1002/crat.2170290504

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mass transport process of the three‐thermal‐zone solute transport method is analyzed theoretically in this paper. The growth rate of a crystal is depending on the temperature gradient and the size of the curcible. Comparing with the normal temperature gradient solute transport method, this technique can be used to grow crystals in better qual

ISSN:0232-1300    

DOI:10.1002/crat.2170290505

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170290506

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractIt is thought that the building units of crystal structures always tend to the highest possible symmetrical arrangements. These arrangements have not to correspond in every case to the energetical most favourable structure. Structures that show this distinct misfit tend to twinning. The examination of pentaerythrite and 1,2,4,5‐tetrabromobenzene, two substances usually existing as twins, leads to the finding of structures–by lattice‐energy calculations–with a better energy balance, but are not known yet as autonomous phases. Both cases showed arrangements with lower symmetry explaining the transition between the twin individuals. Following this theory the development of crystal twins is based on a structural instability caused by the conflict between the more favourable energetical arrangement and the highest available s

ISSN:0232-1300    

DOI:10.1002/crat.2170290507

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170290508

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractSuperthin niobium films of 3 to 35 Å thickness prepared by radio‐frequency sputtering have been studied by modern X‐ray methods, such as reflectometry, fluorescence analysis and grazing beam structure analysis. It has been shown that the films were polycrystalline and consisted of several layers of niobium oxides and solid solution NbO. Two simple models were used to describe erly stages of film growth. In the stage of island growth the complete oxidation of Nb to Nb2O5is inevitable. Beginning from effective thickness ∼ 5 Å the deposited film becomes continuous, and further, layer‐by‐layer growt

ISSN:0232-1300    

DOI:10.1002/crat.2170290509

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

摘要:

AbstractSome observations of growth hillocks and growth layers on the as‐grown surfaces of potassium hydrogen tartrate (KHT) crystals obtained at 30 °C from aqueuos solutions of different supersaturations are reported and discussed. It is found that macrospirals, isolated growth hillocks, and growth layers are typical features observed on these crystals. Bunching of rectilinear growth layers originating from growth hillocks produced parallel macrosteps on the {010} faces. In certain cases, interaction of thick rounded layers of unequal height, emitted from neighbouring strong sources, gave rise to residual steps (pseudo‐interlaced steps). Isolated growth hillocks produced by microbes were also obse

ISSN:0232-1300    

DOI:10.1002/crat.2170290510

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY

ISSN:0232-1300    

DOI:10.1002/crat.2170290511

出版商:WILEY‐VCH Verlag    

年代:1994

数据来源: WILEY