Study on morphology of dislocation-related etch pits on pyramidal faces of KDP crystal

CrystEngComm ◽  
2021 ◽  
Author(s):  
Longyun Xu ◽  
Bo Yu ◽  
Guangwei Yu ◽  
Hui Liu ◽  
Liyuan Zhang ◽  
...  
Keyword(s):  
Dislocation Structure ◽  
Etch Pits ◽  
Kdp Crystal ◽  
Important Prerequisite ◽  
Etch Pit

The generation of etch pit with clearly morphology is an important prerequisite to study dislocation structure. The mixture of water and ethanol is used to etch pyramidal faces of rapid...

scholarly journals Nanoscale morphological evolution of monocrystalline Pt surfaces during cathodic corrosion

2020 ◽  
Vol 117 (51) ◽  
pp. 32267-32277 ◽  
Author(s):  
Nakkiran Arulmozhi ◽  
Thomas J. P. Hersbach ◽  
Marc T. M. Koper
Keyword(s):  
Growth Stage ◽  
Morphological Evolution ◽  
Local Symmetry ◽  
Alkaline Electrolyte ◽  
Etch Pits ◽  
Etch Pit ◽  
Diffusion Limited ◽  
Second Growth ◽  
Ternary Metal ◽  
Electrochemical Phenomenon

This paper studies the cathodic corrosion of a spherical single crystal of platinum in an aqueous alkaline electrolyte, to map out the detailed facet dependence of the corrosion structures forming during this still largely unexplored electrochemical phenomenon. We find that anisotropic corrosion of the platinum electrode takes place in different stages. Initially, corrosion etch pits are formed, which reflect the local symmetry of the surface: square pits on (100) facets, triangular pits on (111) facets, and rectangular pits on (110) facets. We hypothesize that these etch pits are formed through a ternary metal hydride corrosion intermediate. In contrast to anodic corrosion, the (111) facet corrodes the fastest, and the (110) facet corrodes the slowest. For cathodic corrosion on the (100) facet and on higher-index surfaces close to the (100) plane, the etch pit destabilizes in a second growth stage, by etching faster in the (111) direction, leading to arms in the etch pit, yielding a concave octagon-shaped pit. In a third growth stage, these arms develop side arms, leading to a structure that strongly resembles a self-similar diffusion-limited growth pattern, with strongly preferred growth directions.

Density and Behavior of Etch Pits on C-Face 4H-SiC Surface Produced by CIF3 Gas

2012 ◽  
Vol 717-720 ◽  
pp. 379-382 ◽  
Author(s):  
Hitoshi Habuka ◽  
Kazuchika Furukawa ◽  
Toshimitsu Kanai ◽  
Tomohisa Kato
Keyword(s):  
Substrate Temperature ◽  
Crystal Quality ◽  
Etch Pit Density ◽  
Etch Pits ◽  
Etch Pit ◽  
And Behavior

The etch pit density produced on the C-face 4H-SiC substrate using chlorine trifluoride gas at various temperatures was evaluated. Because the etch pit density formed at the substrate temperature of 713 K showed the comparable value to the current dislocation level of the Si-face 4H-SiC, the etch pit density obtained by this technique is considered to have a relationship with the crystal quality.

DISLOCATION STRUCTURE IN "AS-GROWN" HIGH-PURITY IRON SINGLE CRYSTALS

1967 ◽  
Vol 45 (2) ◽  
pp. 1041-1045 ◽  
Author(s):  
S. Kadečková ◽  
B. Šesták
Keyword(s):  
Single Crystals ◽  
Dislocation Structure ◽  
High Purity ◽  
Starting Material ◽  
Etch Pits ◽  
Dislocation Densities ◽  
Purity Iron ◽  
High Purity Iron

The dislocation structure in iron single crystals prepared by two different strain–anneal techniques from the starting material of two different purities is studied by the method of etch pits. Average dislocation densities of 2.6 × 105 to 7 × 105 cm−2 and the absence of subboundaries are observed in single crystals grown statically or dynamically from zone-refined Johnson and Matthey spectrographic iron. The presence of broad subboundaries and average dislocation densities of 8.6 × 105 to 3.3 × 106 cm−2 is characteristic for single crystals grown from the non–zone-refined J. and M. iron. Annealing of "as-grown" crystals does not greatly influence the dislocation structure. It is assumed that the impurities are mainly responsible for the observed dislocation densities.

The etching of crystal cleavages I. Mica

1957 ◽  
Vol 243 (1232) ◽  
pp. 33-40 ◽  
Keyword(s):  
Hydrofluoric Acid ◽  
The Body ◽  
Optical Study ◽  
Etch Pits ◽  
Etch Pit ◽  
Muscovite Mica ◽  
One To One ◽  
Cleavage Lines

An optical study is made of the etch pits produced by hydrofluoric acid on the cleavages of muscovite mica. Two types of etch pit are found ( a ) small widely distributed pits and ( b ) relatively large localized isolated pits. On oppositely matched cleavages there is exact one-to-one correspondence between the localization and shapes of the isolated pits. These are studied both with a light-profile microscope and interferometry. It is established that cleavage lines are displaced by the etching, and this is discussed. The mechanism of the formation of the isolated pits is discussed and they are attributed to impurities. On occasional samples winged pits are formed and the wing is shown to be an air wedge within the body of the mica.

Effects of Pretreatment on the Etch Pit Formation during the Electrochemical Etching of Aluminum

2007 ◽  
Vol 124-126 ◽  
pp. 1561-1564
Author(s):  
Jae Kwang Lee ◽  
Yun Ho Shin ◽  
Jin Wook Kang ◽  
Yong Sug Tak
Keyword(s):  
Electrochemical Etching ◽  
High Density ◽  
Aluminum Surface ◽  
Etch Pits ◽  
Phosphate Ion ◽  
Etch Pit ◽  
Pit Formation ◽  
Fluorosilicic Acid ◽  
Etching Behavior ◽  
Chemical Pretreatments

The effect of chemical pretreatments on the electrochemical etching behavior of aluminum was investigated with the topographic studies of surface and the analysis of initial potential transients. Two-step pretreatments with H3PO4 and H2SiF6 result in a high density of pre-etch pits on aluminum surface by the incorporation of phosphate ion inside the oxide film and the removal of surface layer by aggressive fluorosilicic acid solution. It generates a high density of etch pits during electrochemical etching and results in the capacitance increase of etched Al electrode by expanding the surface area, up to 61.3 μF/cm2 with the pretreatment solution of 0.5M H3PO4 at 65°C and 10 mM H2SiF6 at 45°C.

Defect-Selective Etching of Icosahedral Boron Arsenide (B12As2) Crystals in Molten Potassium Hydroxide

2011 ◽  
Vol 1307 ◽  
Author(s):  
C.E. Whiteley ◽  
A. Mayo ◽  
J.H. Edgar ◽  
M. Dudley ◽  
Y. Zhang
Keyword(s):  
Potassium Hydroxide ◽  
High Energy ◽  
Selective Etching ◽  
Etch Pits ◽  
X Ray ◽  
Etch Pit ◽  
Dislocation Densities ◽  
Boron Arsenide ◽  
Defect Densities ◽  
Molten Nickel

ABSTRACTThe present work reports on the defect-selective etching (DSE) for estimating dislocation densities in icosahedral boron arsenide (B12As2) crystals using molten potassium hydroxide (KOH). DSE takes advantage of the greater reactivity of high-energy sites surrounding a dislocation, compared to the surrounding dislocation-free regions. The etch pits per area are indicative of the defect densities in the crystals, as confirmed by x-ray topography (XRT). Etch pit densities were determined for icosahedral boron arsenide crystals produced from a molten nickel flux as a function of etch time (1-5 minutes) and temperature (400-700°C). The etch pits were predominately triangle shaped, and ranged in size from 5-25μm. The average etch pit density of the triangle and oval etch-pits was on the order of 5x107cm-2 and 3x106cm-2 (respectively), for crystals that were etched for two minutes at 550°C.

Etch pit distribution on calcite cleavage surfaces – experiments and simulation

2020 ◽  
Author(s):  
Ricarda D. Rohlfs ◽  
Elisabete Trindade Pedrosa ◽  
Inna Kurganskaya ◽  
Cornelius Fischer ◽  
Andreas Luttge
Keyword(s):  
Spatial Distribution ◽  
Kinetic Monte Carlo ◽  
Pure Water ◽  
Heterogeneous Material ◽  
Driving Mechanism ◽  
Etch Pits ◽  
Surface Evolution ◽  
Crystal Dissolution ◽  
Etch Pit ◽  
Vertical Scanning Interferometry

<p>During the dissolution at a calcite cleavage face, etch pits open around defects. Atomic steps moving outwards from these pit centres are currently considered the general driving mechanism of this dissolution process that results in heterogeneous material flux from the surface. This means that the defects that generate the etch pits are crucial for the surface evolution. Recent kinetic Monte Carlo (kMC) simulation results indicate that not only the density but also the spatial distribution of defects is critical for the influence on dissolution.</p><p>In kMC simulations used for crystal dissolution, defect positions are input and can be defined in various ways, e.g., at pre-defined coordinates or randomly drawn from a distribution. The user is free in defining the defects, although it can generally be considered reasonable to choose defect densities and distributions as close as possible to what is expected to occur in nature and technical systems.</p><p>The actual spatial distribution of screw dislocations in calcite and their influence on rate variability are still not entirely known. To make the calcite kMC simulations comparable with experimental results, we experimentally determined the etch pit distributions, analyzed them and subsequently used them as input for further kMC studies.</p><p>While the direct measurement of defects in the crystal structure is extremely difficult, the indirect approach of measuring etch pits that have formed around defect outcrops during the beginning of dissolution is more feasible. For this, cleaved calcite single crystals were etched using ultra-pure water for 3 to 4 hours to obtain a significant amount of etch pits on the surface. The topography of the crystal surfaces was analysed using Vertical Scanning Interferometry (VSI). The resulting topography maps were stitched to gain a larger area for better statistics, and the centres of visible etch pits marked. This generates two-dimensional point patterns that describe the actual defect distribution more accurately than purely randomly generated coordinates without further constraints.</p><p>Based on data analysis of the experiments, we will show the resulting point distributions and synthetic patterns with similar underlying statistics. Using these as input for modelling, we then calculate kMC simulations and geometrical models of a system close to the calcite single crystal from our experiment, and compare them also to simulations using different defect positions as input.</p>

Investigation of Basal Plane Dislocation Reduction/Elimination by Molten KOH-NaOH Eutectic Etching Method

2012 ◽  
Vol 717-720 ◽  
pp. 125-128 ◽  
Author(s):  
Hai Zheng Song ◽  
Tangali S. Sudarshan
Keyword(s):  
Epitaxial Growth ◽  
Basal Plane ◽  
Etch Pits ◽  
Etch Pit ◽  
Etching Method ◽  
Dislocation Reduction ◽  
Short Period ◽  
Basal Plane Dislocation ◽  
Non Destructive ◽  
Koh Etching

An optimized molten KOH-NaOH eutectic etching method is developed to reveal defects in highly n-doped SiC substrates and to pre-treat the substrate prior to epitaxial growth. Different from the conventional KOH etching method, by way of eutectic method, the basal plane dislocation (BPD) conversion in the subsequent epitaxial growth is independent of the etch pit size pre-generated on the substrate. Even with a short period (~3 minutes) of pretreatment which does not generate any visible etch pits or degradation of surface morphology on the substrate, an epilayer with low BPD density -2 is still achieved. This simple and non-destructive method shows high potential to be practically employed as one of the basic pretreatment steps to the substrates in SiC epitaxial growth in order to achieve very low or free BPD density.

Delineation of Defects Reducing Schottky Barrier Heights on 4H-SiC by the Electrochemical Deposition

2008 ◽  
Vol 600-603 ◽  
pp. 373-376
Author(s):  
Masashi Kato ◽  
Kazuya Ogawa ◽  
Masaya Ichimura
Keyword(s):  
Schottky Barrier ◽  
Barrier Height ◽  
Electrochemical Deposition ◽  
Schottky Barrier Height ◽  
Proper Time ◽  
Etch Pits ◽  
Barrier Heights ◽  
Etch Pit ◽  
Deposition Voltage ◽  
Deposited Films

We identified regions with low Schottky barrier height on 4H-SiC surfaces by the electrochemical deposition of ZnO. When we adopt an appropriate deposition voltage, ZnO grew preferentially at the regions with the low Schottky barrier height. Thus, we were able to identify the ZnO film only at these regions if we stopped the deposition at a proper time. We compared positions of the deposited film and etch pit after molten NaOH etching. As a result, in a bulk 4H-SiC, the films were deposited around some of micropipe positions. On the other hand, in an epitaxial 4H-SiC layer, although approximately a half of deposited films seemed to grow at the etch-pit defect positions, other deposited films were grown at positions without etch-pit defects. Therefore the Schottky barrier heights were reduced by not only defects emerging as etch pits but also other kind of origins in epitaxial 4H-SiC.

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