Growth Striae Research Articles

Defect structure of ZnGeP2 crystals grown in the furnaces with tube diameters of 70 and 130 mm

The crystal structures of two ZnGeP2 crystals grown by the Vertical Bridgman method in different furnaces were compared. The furnace tube diameter was 70 mm for the first crystal and 130 mm – for the second one. The diameter of both crystals was 30 mm. The radial temperature profiles of the furnaces show different curvatures in the growth zone. For the first crystal the profile was slightly concave, whereas, for the second one, it was flat. The structure was analyzed by X-ray diffractometry and topography methods. In the first crystal, the dislocation density changed from 102 cm−2 in the initial growth region of the sample to 104 cm−2 at the last-to-freeze end. Low-angle grain boundaries were observed. The second crystal contained only single dislocations. Both crystals showed growth striae. After thermal annealing (both crystals were treated under identical conditions), the second crystal showed a much better optical transparency than the first one.

Scallop shells as geochemical archives of phytoplankton‐related ecological processes in a temperate coastal ecosystem

AbstractPhytoplankton dynamics in coastal ecosystems is increasingly altered by land‐based human activities. Yet, this global vision conceals major disparities, among sites and through time. As conventional monitoring time series are quite sparse and relatively short, biological records of environmental variability appear as relevant tools to gain insights into phytoplankton dynamics over larger temporal and spatial scales. Here, we present results of an interdisciplinary project dealing with chemical information archived in shells of Pecten maximus (Bivalvia; Pectinidae), known to form daily growth striae on its shell surface. Several individuals were collected in the Bay of Brest (France) in 2011 and 2012, and analyzed for the molybdenum and lithium concentrations in their soft tissues and the element‐to‐calcium ratios (Mo : Ca and Li : Ca) in their calcitic striae. All shells revealed high synchrony and reproducibility in their Mo : Ca and Li : Ca profiles, characterized with a major peak at the end of May and in mid‐June 2011, respectively. Detailed analysis of physical, chemical, and biological variables measured in seawater during an extensive 9‐month environmental survey enabled a meticulous description of phytoplankton dynamics in 2011 and its impact on shell geochemistry. Main findings strongly suggest that (1) the timing of Mo : Ca peaks reflects the occurrence of silicon limitation and diatom aggregation periods, (2) the height of these peaks relates to the amplitude of the first spring diatom bloom, and (3) Li : Ca serves as a proxy for the temporal dynamics of diatom biovolume and of biogenic silica recycling at the sediment–water interface.

Structural defects in ZnGeP2single crystals revealed by X-ray topography

The results of X-ray transmission topography and diffraction analysis of a ZnGeP2single crystal grown by the vertical Bridgman method in the [001] direction are presented and discussed. The FWHM of rocking curves over a large area of a (100) longitudinal slice is about 12′′, which is indicative of the high quality of the examined sample. Glow discharge mass spectrometry does not show significant content of foreign chemical elements. X-ray topography reveals growth striations and dislocations. The predominant defects are single dislocations and their pile-ups. Near to the growth-axis region, curved dislocation bundles passing through the entire crystal are observed, on which precipitates are formed. In the initial part of the crystal, dislocations are located chaotically, while towards the middle of the sample they are aligned along the growth striae. In the final part of the crystal, the dislocation density increases.

Age and growth of Neptunea arthritica estimated from growth marks in the operculum

The age and growth of the whelk, Neptunea arthritica, was estimated based on growth striae on the operculum. Individual whelks were sexed and divided into normal and abnormal groups, based on the presence of imposex and parasite infection. The monthly marginal growth was used to determine the annual growth mark formation on the operculum. The whelk's sex (male and female), condition (normal and abnormal) and size (mature and immature) were evaluated as factors that can affect the marginal growth. Only in normal females did size affect the marginal growth, suggesting that parasite infection and imposex were not a biasing factor in the age estimation. Significant differences between low and high monthly marginal growth in normal males were found. Between operculum length and shell length and total body weight a positive relationship was found, while the same trend was observed in all female groups as well as abnormal males, but differences were not significant. The same relationship was observed between the number of stria with shell length and total body weight in all groups. The results suggest that opercula striae could be used to age N. arthritica. The Gompertz equation was the best curve that fitted the data for growth in normal groups, based on Akaike's information criteria, and it was used for all groups. The age at first sexual maturity was estimated for normal males and females to be 4.6 and 6.1 years, respectively.

Variation in life-history traits of the corallivorous gastropod Coralliophila abbreviata on three coral hosts

Coralliophila abbreviata (Lamarck) is a corallivorous gastropod that lives and feeds on several species of scleractinian coral in the Western Atlantic and Caribbean. Previous studies of C. abbreviata have revealed that snails on branching acroporid corals are larger and consume more tissue than those on massive and plating corals. To ascertain whether snail life-history and fitness are differentially affected by the coral host, an analysis of the age structure and female reproductive output of snail populations on three coral host taxa (Acropora palmata, Diploria spp., and Montastraea spp.) was conducted at four shallow (2–7 m depth) reef sites off Key Largo, Florida in June through August, 2004. Snails were, on average, almost twice as large on A. palmata than on Diploria spp. and Montastraea spp., averaging 30.3 mm shell length, compared to 17.2 and 17.6 mm, respectively. Brood size increased as a power function with female shell length. Females on A. palmata were significantly larger than females on the other two hosts and, therefore, produced more offspring per female. The number of growth striae on the inner surface of the operculum was used to estimate snail age. Estimates of growth rate were obtained by fitting the Gompertz growth function to size-at-age plots and mortality was estimated using growth parameters and size-frequency data. The data suggest that C. abbreviata inhabiting A. palmata are larger than on alternative hosts due to a combination of a faster growth rate and longer life-span. The species is believed to be a protandrous hermaphrodite. The timing of sex change varied among hosts; snails on A. palmata changed sex later at larger sizes relative to those on the other two hosts. Based on these results, it seems probable that C. abbreviata has developed reaction norms for life-history traits, allowing snails to adjust and maximize fitness in the different environments associated with various coral hosts.

TWO NEW HIRTUDISCUS SPECIES FROM COLOMBIA (GASTROPODA: SCOLODONTIDAE)

Two new Hirtudiscus species are described from Colombia. Hirtudiscus triserialis n. sp. from the Departamento Cundinamarca is characterized by a large shell with three rows of up to 1 mm long hairs at the periphery and a distinctly sunken spire. Hirtudiscus antiochiensis n. sp. from the Departamento Antiochia is characterized by a moderately large shell with moderately dense growth striae and hairs up to 0.5 mm long.

Shell of the Great Scallop Pecten maximus as a high‐frequency archive of paleoenvironmental changes

We investigate the environmental and biological controls on oxygen isotope ratios in the shells of modern Pecten maximus bivalves collected alive in the Bay of Brest (France). Seasonal δ18O profiles, obtained by drilling the daily calcite ridges deposited at the surface of the left valve, were compared with in situ measurements of temperature and salinity. We show that P. maximus δ18O values accurately track seasonal variations in bottom water temperature. Shell growth rate has no significant effect on shell δ18O values. Our study demonstrates that daily variations in water temperature can be reconstructed within about 0.5°C. Temperatures estimated with the paleotemperature equation established in this study were compared with temperatures derived from previously published equations. The comparison indicates that the most commonly used paleotemperature equation for biogenic calcite (Epstein et al., 1953) provides inaccurate temperature estimates, but the Kim and O'Neil (1997) equation, established from abiogenic calcite precipitation, provides results very similar to ours and should therefore be used for scallop individuals coming from populations where proper empirical calibration cannot be done. Pecten maximus bivalves precipitate calcite in isotopic equilibrium with seawater, produce large daily growth striae, are stenohaline, and are well preserved in archeological and geological deposits, making them an excellent high‐frequency archive of paleoenvironmental change.

Age determination of Buccinum isaotakii (Gastropoda: Buccinidae) from the growth striae on operculum and growth under laboratory conditions

Buccinum isaotakii is one of the economically important whelk fishery resources in Funka Bay, Hokkaido, Japan. Although B. isaotakii has been commercially harvested for the past four decades, only very few studies were reported. In the present study, the age of the whelk, B. isaotakii, was determined based on the growth striae on the operculum. The annual formation of the stria within the operculum was confirmed by calculating the marginal growth rate. There was a significant difference ( P<0.001) between low and high monthly marginal growth of the operculum showing that a stria was possibly formed in a year. The relationship between shell length and body weight and the growth of different size classes of whelks under laboratory conditions were also examined. Both female ( W=0.000415 L 2.5292) and male ( W=0.000247 L 2.6512) whelks showed growth in shell length superior to body weight increase, showing a negative allometric growth. The parameters for von Bertalanffy growth function; length-at-age were L t =150.52{1−e −0.117( t−2.18) } for female and L t =129.99{1−e −0.132( t−2.25) } for male. For weight-at-age parameters; W t =101.03{1−e −0.117( t−2.18) } 2.5292 for female and W t =71.12{1−e −0.132( t−2.25) } 2.6512 for male. Whelks in size classes 50, 60, 70s ( P<0.001) and 80s ( P<0.01) increased significantly in shell length. All size classes except size class 100s had significant increase ( P<0.01 for 90s and P<0.001 for 50, 60, 70 and 80s) in body weight over the 12-month experimental period. The present study confirmed the use of opercular striae as age indicator in B. isaotakii and showed that the relationship between length and weight is allometric (negative) in both sexes. Smaller (immature) whelks achieved higher growth rates than bigger (mature) whelks in the tank.

Estimation of age in the sex-changing, coral-inhabiting snail Coralliophila violacea from the growth striae on opercula and a mark-recapture experiment

Change of sex in the coral-inhabiting snail Coralliophila violacea (Lamarck) may occur in a wide range of sizes in the field. One proposed explanation for this is that the snails change their sex at a certain age and that individuals have different growth rates caused by microhabitat differences. In this study, we attempt to establish a method to determine the age of this snail and age at sex change. The growth striae on the operculum were studied and compared to the age estimated by the Gompertz growth function based on growth data obtained from mark–recapture experiments in southern Taiwan. There is a significant correlation between the number of striae on the operculum and the age estimated from the Gompertz growth function, and the relationship is 1:1. These results suggest that the number of striae on the operculum can be used as an age index, with each stria representing 1 year of age. The age of sex change of this snail, according to our estimates by both stria number and aperture-length inferences, occurs between 4 and 6 years old. Growth rates of the snails are negatively correlated to size. Furthermore, individuals undergoing sex-change grow faster than males and females.

ZnGeP 2 growth: melt non-stoichiometry and defect substructure

A real defect structure is studied for ZnGeP 2 crystals grown by the vertical Bridgman technique from the melt. Optical microscopy reveals growth striations and precipitation of second phases emerging because of deviation from stoichiometry. The revealed growth striae have a complex structure caused by temperature oscillations in the growth setup. The other type of defect, precipitates, is observed as a colony of trails orienting in the longitudinal direction. The colony of trails occurs with a concave interface and as a rule, is located in the central part of the lateral section of crystal. The most probable composition of the precipitates is a mixture of ZnGeP 2, Zn 3P 2, and Ge. The colony of the precipitate trails results in significant optical losses over the whole transparency range of ZnGeP 2.

Vertical gradient freeze growth of large diameter, low defect density indium phosphide

The demand for larger diameter, low dislocation density InP substrates has traditionally been filled by highly doped LEC-grown material. We describe the use of the vertical gradient freeze (VGF) technique to produce uniformly high quality wafers from 〈111〉 seeded, 750 g, 50 mm diameter single crystals. Typical dislocation levels are in the low 10 2 cm -2 range, independent of doping level. The dislocations are shown to be uniformly distributed across a wafer and from seed to tail. This adaptation of the VGF technique features seeded growth in pyrolytic boron nitride crucibles under low axial and radial thermal gradients as well as independent stoichiometry control. The reduction of thermally generated strain eliminates the need for impurity hardening of InP to achieve low defect levels. Comparisons with typical LEC results will be made in terms of growth striae, defect distribution and incidence of slip, as well as stoichiometry control. The design of the crystal growth equipment, the growth sequence and aspects of the process control will be discussed. Impurity incorporation will be discussed in terms of spark source mass spectrometry and low temperature compensation ratio estimates. Comparisons of room temperature mobilities are made with other high purity InP material.

Research on crystal growth and defects in cubic zirconia

Abstract The crystal growth and defects in cubic zirconia grown by the skull melting method have been investigated. The distribution coefficients of stabilizers Y 2 O 3 and CaO in the crystal were greater than 1 and less than 1 respectively. By preparing materials with 10–12 mol% Y 2 O 3 as stabilizer, it is easy to get nearly colourless transparent large cubic zirconia single crystals. The substances which influence the uniformity of the cubic zirconia crystal are not only the inclusions, but also growth striae and mosaics. The results of the observation and analysis on the inclusions by scanning electron microscopy, show that Si, Ca, Mg, Y, etc. occur mainly at the ends and in the centre of the crystal.

Rotational Striations and Diffusion in Barium Sodium Niobate Crystals

AbstractThe possibility of inducing rotational growth striae with a small period in barium sodium niobate crystals (BSN) is examined. Crystals grown had a period stability up to 1 percent and were suitable material for anisotropic light diffraction by ferroelectric domains. However intense striae were produced only for periods λ &gt; 5 m̈m. With the help of Bragg optical diffraction by growth striae the diffusion coefficient D in solid phase responsible for striae smoothing during annealing was measured. The magnitude D ≈ 10‐11 cm2 s‐1 at the melting point was obtained. Such D value leads to the vanishing of striae with λ &lt; 5 m̈m in BSN crystals during growth.

Defect‐Revealing Etches on GaAs : A Comparison of the AHA with the A/B and KOH Etches

AHA etch‐revealed features on {100} N+ wafers were compared to defects revealed by the well‐characterized A/B and molten etches on the same sample areas. It was demonstrated that the AHA etch technique reveals dislocation line segments, growth striae, and microdefects as does the A/B etch. Unlike the A/B etch the AHA etch did not result in a “memory” effect. A 1:1 correlation between molten dislocation etch pits and AHA‐revealed dislocation line segments was demonstrated.

Optical defects in barium—strontium niobate single crystals

AbstractThe distributions of edge dislocations and residual mechanical stresses in BaxSr1‐xNb2O6 (BSN) crystals are investigated and the explanation of the nature of the “growth column” is proposed. The “growth column” is a defect zone going through all of the crystal and usually repeating in its cross‐section the contour of the seed crystal. The “growth column” boundary is the closed contour with extremely high edge dislocation density. These dislocations are connected with thermal stresses due to seed‐melt contact or abrupt crystal widening. Under proper crystal seeding and widening conditions one can obtain the BSN crystals with dislocation densities less than 10 cm−2 and without the “growth column”.The method of chemico‐mechanical polishing of BSN crystals not forming a defect layer on the surface of the crystals have been developed. The high temperature diffusion annealing is shown to eliminate the growth striae in BSN crystals.

Optical anisotropy associated with growth striation of yttrium garnet, Y3 (Al, Fe)5O12

AbstractThe optical anisotropy associated with growth striae of yttrium garnet, Y3(Al, Fe)5O12, was studied in terms of optical microscopy and EPMA analysis. It turned out that the lattice mismatch due to the compositional change at the growth striae gives rise to stressbirefringence. The result can be applied to compositional characterization of garnet single crystal by determining the vibration directions of polarized rays under a microscope.

Growth striae in single crystals of gadolinium gallium garnet grown by automatic diameter control

Periodic growth striae are observed in Gd 3Ga 5O 12 single crystals grown by automatic diameter control. The spacing of these striae coincides with the period of rf power fluctuation. This fluctuation is found to be due to the stepwise variation of the programmed signal generated by a helical potentiometer. These periodic growth striae are eliminated by decreasing the amplitude of power fluctuation to less than 1%. This work should facilitate the growth of better crystals when automatic diameter control methods are employed.

Growth of optically homogeneous single crystals of Pb 5GeO 4(VO 4) 2 from the melt

The origin of growth striae in the melt grown single crystals of Pb 5GeO 4(VO 4) 2 was investigated. Under the optimized conditions in which most striae causing growth variables (such as thermal convection) were eliminated, the main cause for the formation of striae was found to be forced convection and associated temperature oscillations in the melt induced by crystal rotation. The period (ω) of the oscillation increased with the decreasing rotation rate (ω). At ω = 30 rpm a temperature oscillation of τ = 3.7 min and 3°C amplitude appeared. The striae spacing of 96 μm in the grown crystal is in close agreement with a value calculated (123 μm) on the basis of τ = 3.7 min and the growth rate of 2 mm/hr. At ω = 0, temperature oscillation and the forced convection disappeared, and homogeneous laser quality single crystals were reproducibly grown.

Helical growth defects in gadolinium gallium garnet

An X-ray topographic study of helical line defects in Czochralski grown Gd 3Ga 5O 12 is described. Both the Lang transmission configuration and the double reflection method have been employed to characterize the strain field in and around the helices. From this study it is concluded that the helix is a dislocation of the prismatic, interstitial type which surrounds a helicoidal region of smaller lattice constant. The topographs also reveal an alignment of the helix loops with the crystal growth striae.

Growth striae in single crystals of gadolinium gallium garnet

Growth striae on (111) planes were examined in core and facet-free low dislocation density boules of gadolinium gallium garnet (GGG). Lang x-ray transmission topography of (111), (21̄1̄) and (011̄) slices revealed a nearly ideal flat growth interface except for a 1–2 mm periphery. Striae were separated by 10–60 μm, of non-uniform width, and discontinous across the full boule diameter. Electron microprobe scans along [111] across the striae demonstrated fluctuations in Gd and Ga concentrations. Our observations are consistent with a proposed growth mechanism of interface attachment by layer motion.