Number Of Etch Pits Research Articles

Methods of dislocation structure characterization in AIIIBV semiconductor single crystals

The development pace of advanced electronics raises the demand for semiconductor single crystals and strengthens the requirements to their structural perfection. Dislocation density and distribution pattern are most important parameters of semiconductor single crystals which determine their performance as integrated circuit components. Therefore studies of the mechanisms of dislocation nucleation, slip and distribution are among the most important tasks which make researchers face the choice of suitable analytical methods. This work is an overview of advanced methods of studying and evaluating dislocation density in single crystals. Brief insight has been given on the main advantages and drawbacks of the methods overviewed and experimental data have been presented. The selective etching method (optical light microscopy) has become the most widely used one and in its conventional setup is quite efficient in the identification of scrap defects and in dislocation density evaluation by number of etch pits per vision area. Since the introduction of digital light microscopy and the related transfer from image analysis to pixel intensity matrices and measurement automation, it has become possible to implement quantitative characterization for the entire cross-section of single crystal wafers and analyze structural imperfection distribution pattern. X-ray diffraction is conventionally used for determination of crystallographic orientation but it also allows evaluating dislocation density by rocking curve broadening in double-crystal setup. Secondary electron scanning electron microscopy and atomic force microscopy allow differentiating etch patterns by origin and studying their geometry in detail. Transmission electron microscopy and induced current method allow obtaining micrographs of discrete dislocations but require labor-consuming preparation of experimental specimens. X-ray topography allows measuring bulky samples and also has high resolution but is hardly suitable for industry-wide application due to the high power consumption of measurements.Digital image processing broadens the applicability range of basic dislocation structure analytical methods in materials science and increases the authenticity of experimental results.

Methods of dislocation structure characterization in A IIIB V semiconductor single crystals

The development pace of advanced electronics raises the demand for semiconductor single crystals and strengthens the requirements to their structural perfection. Dislocation density and distribution pattern are most important parameters of semiconductor single crystals which determine their performance as integrated circuit components. Therefore studies of the mechanisms of dislocation nucleation, slip and distribution are among the most important tasks which make researchers face the choice of suitable analytical methods. This work is an overview of advanced methods of studying and evaluating dislocation density in single crystals. Brief insight has been given on the main advantages and drawbacks of the methods overviewed and experimental data have been presented. The selective etching method (optical light microscopy) has become the most widely used one and in its conventional setup is quite efficient in the identification of scrap defects and in dislocation density evaluation by number of etch pits per vision area. Since the introduction of digital light microscopy and the related transfer from image analysis to pixel intensity matrices and measurement automation, it has become possible to implement quantitative characterization for the entire cross-section of single crystal wafers and analyze structural imperfection distribution pattern. X-ray diffraction is conventionally used for determination of crystallographic orientation but it also allows evaluating dislocation density by rocking curve broadening in double-crystal setup. Secondary electron scanning electron microscopy and atomic force microscopy allow differentiating etch patterns by origin and studying their geometry in detail. Transmission electron microscopy and induced current method allow obtaining micrographs of discrete dislocations but require labor-consuming preparation of experimental specimens. X-ray topography allows measuring bulky samples and also has high resolution but is hardly suitable for industry-wide application due to the high power consumption of measurements. Digital image processing broadens the applicability range of basic dislocation structure analytical methods in materials science and increases the authenticity of experimental results.

Correction method for the energy spectrum of laser-accelerated protons measured by CR-39 track detectors with stepwise energy filters

A combination of CR-39 track detectors and a stepwise energy filter is a simple method to measure the energy spectrum of laser-accelerated protons. The number of etch pits in each area of the CR-39 detector is expected to represent the energy spectrum because the different thicknesses of the filters result in different areas into which the energy reaches in CR-39. However, the higher energy regions may overlap depending on the sensitivity of CR-39. To avoid overlapping, i.e., overestimation of the number of etch pits for each energy region, a correction method for the energy spectrum from the number of etch pits was developed. Based on the calculation results of the reaching energy values and incident energy ranges for CR-39, etch pits are selected that should be counted in each area. CR-39 with stepwise energy filters provides a corrected energy spectrum of laser-accelerated protons by applying the developed method.

Analyses of single crystal diamond substrates grown in a pocket substrate holder via MPACVD

High quality single crystal diamond (SCD) substrates are required for several different important current applications. Microwave Plasma Assisted Chemical Vapor Deposition (MPACVD) is a convenient deposition method for high quality substrates. It is hence imperative to synthesize and analyze substrates grown via different CVD techniques. This paper describes the quality of single crystal diamond substrates which have been grown via one such deposition strategy, which is in a “pocket substrate holder” design. The growth process in such a holder helps in depositing substrates which have almost no polycrystalline diamond (PCD) rim growth. The exact pocket holder growth process at high pressures (240 Torr) and high microwave power densities (~ 500 W/cm3) has been discussed in a previous publication [1]. The SCD CVD substrates were analyzed with different characterization techniques. By synthesizing diamond substrates in a pocket holder, the lack of any/almost any PCD rim helped in reducing the amount of stress in the crystals. To study the electronic quality of the substrates, etching experiments were conducted to determine the etch pit density. Nomarski images confirm that the number of etch pits at the edges is higher than at the center of the etched surface thereby implying the feasibility of this simpler method of reducing the etch pit density. The pocket holder process thus not only reduces the PCD rim but also reduces the substrate etch pit density and hence shows good promise of delivering high quality substrates.

On the influence of etch pits in the overall dissolution rate of apatite basal sections

Determination of efficiencies for particle detection plays a central role for proper estimation of reaction rates. If chemical etching is employed in the revelation of latent particle tracks in solid-state detectors, dissolution rates and etchable lengths are important factors governing the revelation and observation. In this work, the mask method, where a reference part of the sample is protected during dissolution, was employed to measure step heights in basal sections of apatite etched with a nitric acid, HNO\(_3\), solution at a concentration of 1.1 M and a temperature of 20 °C. We show a drastic increase in the etching velocity as the number of etch pits in the surface augments, in accordance with the dissolution stepwave model, where the outcrop of each etch pit generates a continuous sequence of stepwaves. The number of etch pits was varied by irradiation with neutrons and perpendicularly incident heavy ions. The size dependence of the etch-pit opening with etching duration for ion (200–300 MeV 152Sm and 238U) tracks was also investigated. There is no distinction for the etch pits between the different ions, and the dissolution seems to be governed by the opening velocity when a high number of etch pits are present in the surface. Measurements of the etchable lengths of these ion tracks show an increase in these lengths when samples are not pre-annealed before irradiation. We discuss the implications of these findings for fission-track modelling.

HVPE법으로 성장시킨 GaN 단결정의 wet etching에 의한 표면 변화

In this paper, we investigated characteristics of etching induced surface morphology variation by wet etching of GaN epilayer were grown on sapphire (0001) substrate by hydride vapor phase epitaxy (HVPE). As a results of scanning electron microscope (SEM) observation, three types of hexagonal etch pits (Edge, Screw, Mixed) were formed by the GaN epilayer thickness variations. A lot of etch pits, attributed to screw and mixed type TD, were observed at thinner epilayer, leading to high etch pit density. On the other hand, the thickness of GaN epilayer increased with the number of etch pits corresponding to edge and mixed dislocations, which are the majority of TDs are observed.

초음파를 이용한 전처리가 알루미늄의 전기화학적 에칭 및 정전용량에 미치는 효과

Aluminum was electrochemically etched in acid solution and the surface area was magnified by the formation of etch pits. Etched aluminum was covered with a compact and dense dielectric oxide film by anodization and applied to the aluminum electrolytic capacitor electrode. Capacitance of aluminum electrolytic capacitor is closely related with surface area, which depends on size and number of etch pits. Size of etch pits need to be controlled because inside of the pits can be buried by the formation of dielectric oxide film. In this work, the effect of ultrasound pretreatment on the aluminum etch pit formation and capacitance were investigated. Additionally, the relationship between the second etching effect on pit size and capacitance was studied.

Surface preparation of ZnO single-crystal substrate for the epitaxial growth of ZnO thin films

The surface treatment method using chemical etching for Zn-polar zinc oxide (ZnO) single-crystal substrates without annealing is proposed. The wet-chemical etching of Zn-polar ZnO had a serious issue that led to the formation of a large number of etch pits at the surface together with the formation of step structure. After various experiments, the pH control of the solution during wet-etching at first stage of the etching is found to be very important to obtain the straight step-edges without formation of etch-pit. Atomically flat substrates without etch pits were able to be obtained by controlling the pH in BHF solution. Eventually, homoepitaxial ZnO thin films with atomically flat surface were formed as well.

WEATHERING MECHANISM OF SILICATE PHENOCRYSTS IN TEPHRAS, INFERRED FROM SEM OBSERVATIONS OF SURFACE ETCHING

In the present study we describe the surface etching features of plagioclase, pyroxene, olivine, amphibole, and biotite phenocrysts in tephras from Hachijo-Higashiyama, Daisen, and Niijima volcanoes with progress in weathering. The variations in the size and number of etch pits were quantified by image analysis as a function of depth in tephra column from Hachijo-Higashiyama. In Hachijo-Higashiyama tephras, pyroxene and plagioclase phenocrysts were completely covered with glassy materials and etching did not occur during the early weathering duration of about 10 ky after deposition. After the glassy cover disappeared, etching began selectively at dislocations. The etch-pit shapes are crystallographically controlled on different faces, particularly in plagioclase. The etch-pit density decreased, the size increased with increase in depth of tephra column. This change is an overall result of etch-pit coalescence and neoformation of small etch pits. Eitching of phenocrysts is preceded by halloysitization of glass, which results in the increase of saturation levels in porewaters infiltrating through tephra column. Consequently, it is implied that mineral dissolution rates are strongly controlled by the saturation level of porewaters with respect to solute species supplied from rapid dissolution of glasses during chemical weathering of tephras.

Characterization of threading dislocations in GaN epitaxial layers

We investigated Si-doped GaN epitaxial layers on a (0001)-sapphire substrate using a HCl vapor-phase etching technique, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. Three kinds of distinctive etch pits correspond to three different types of threading dislocations, edge, mixed, and screw types. Photoluminescence intensity increases with the decrease in the number of etch pits corresponding to mixed and screw dislocations. The number of etch pits corresponding to edge dislocations, however, did not change. We concluded, therefore, that threading dislocations having a screw-component burgers vector act as strong nonradiative centers in GaN epitaxial layers, whereas edge dislocations, which are the majority, do not act as nonradiative centers.

Physicochemical properties of the surface and near-surface region of epitaxial n-GaAs layers modified by atomic hydrogen

Changes in the static electrical parameters of the Au-GaAs Schottky barriers in the (n-n+)-GaAs structures treated with atomic hydrogen are closely related to modification of the chemical properties of the surface layers in these structures, including changes in the rate of n-GaAs etching in a DMF-monoethanol amine (1:3) solution, in the electrochemical deposition rate and the structure of the resulting Au layer, and in the degree of passivation of linear defects emerging on the surface. The unprotected surface of epitaxial n-GaAs(100) layer exhibited virtually no etch pits upon the treatment in atomic hydrogen at 100°C. For n-GaAs protected with a 50-A-thick SiO2 film, a drop in the etching rate and a considerable decrease in the number of etch pits, as well as a decrease in the thickness of electrochemically deposited gold layer and a change in is structure, were observed for the samples treated in atomic hydrogen at all temperatures in the range studied (100–400°C).

In situ real-time study of chemical etching process of Si(100) using light scattering

We report the development of an in situ real-time light scattering technique to study the wet chemical etching process of Si(100). Based on a simple scattering theory, the number of etch pits and other statistical parameters such as correlation length and interface width on a pitted surface are extracted from the scattering profile. The time evolution of the surface morphology can be interpreted by a simple rate equation.

Atmospheric photoassisted chemical vapor deposition of Si using ultraviolet-light irradiated H2 carrier gas and nonexcited SiH2Cl2

We have proposed a new photoassisted chemical vapor deposition (photo-CVD) process of Si, in which only a hydrogen carrier gas is excited by UV light from low-pressure Hg lamps and a reactant gas of SiH2Cl2 is not irradiated at all. In this type of photo-CVD, it is found that (1) the number of pyramidal hillocks on orientation-just surfaces is drastically suppressed, (2) the number of etch pits, corresponding to the stacking fault and the precipitation of contaminants, is also decreased, (3) the growth rate is significantly enhanced, and (4) the surface roughness is decreased. In particular it should be emphasized that these effects are more apparent at atmospheric pressure. It is suggested that the UV-light irradiated hydrogen plays an important role in removing chlorine atoms adsorbed on the surface.

Automatic counting of etch Pits in InP

A computer algorithm for automatic EPD-counting (etch-pit density) with an optical microscope is presented. Several dislocation etchants proposed in the literature to reveal structural defects on InP were employed and improved. Their reliability for automatic counting was proven. For a considerable number of samples exhibiting an EPD between 104 and 106 cm−2 it is shown that the automatically counted number of etch pits agrees with the visually determined value within less than ±30%. Using a modified H3PO4:HBr etchant good results for automatically determined EPDs beyond 107 cm−2 were obtained on InP layers epitaxially grown on Si substrates.

Direct electron microscopic imaging of surface topography by diffraction and phase contrast

Surface imaging in a transmission electron microscope by diffraction contrast is compared with imaging by focus-dependent phase contrast. With both techniques surface steps of atomic height can be imaged with high resolution. At high magnification, kinks along the atomic steps become visible. Advantages and disadvantages of both methods are discussed. By combining the two methods, the initial stage of etching on the surface due to the interaction of a surface layer with the electron beam could be observed. The final etch structure shows a dynamic behavior which indicates that the number of etch pits is approximately constant but their position changes during the observation.

Fast-neutron dosimetry by solid-state track detectors

Various plastic Solid-State Track Detectors (SSTDs) commonly used for the detection of light charged particles have been examined for their use in fast-neutron dosimetry. It is observed that more and more etched tracks are accumulated as the etching process is prolonged and that this increase in number of etchpits is quite sensitive to etching interruptions. The detection sensitivity of these detectors for various combinations of energy, etching time and angle of incidence of neutrons has been determined. Also, attempts have been made to explore the neutron spectrometric characteristics of these detectors.

Orientation-dependent etchpit penetration and dissolution of fluoroapatite.

In this study, fluoroapatite crystals were etched with citric acid (pH 2) at 60 °C parallel and perpendicular to Apatite the c-axis. Quantitative measurements on a number of etchpits, visualized with the scanning electron microscope were combined with accurate chemical solubility studies with an atomic absorption spectrophotometer, pertaining to the <i>same</i> crystal surface. Whereas the difference in chemical solubility with respect to the prism or basal plane is small, the velocity of etchpit penetration is 5 times quicker parallel to the c-axis than perpendicular to it. Etchpits and dislocations existing in a one-to-one relation, these experiments strongly indicate that the dislocations present in apatite crystallites in enamel, are the sites where the very first dissolution during the caries process occurs.

Prolonged etching factor in solid state track detection and its applications

Abstract It has been observed that the number density of etch pits resulting from spontaneous or induced fission within a solid state track detector (SSTD) is a function of the duration of etching, other conditions being constant. As the etching proceeds, the net number of etch pits observed per unit area continues to increase. This necessitates a modification of the conventional equations governing the observed etch-pit densities in SSTD. A prolonged etching factor f(t) is defined, and its value measured as a function of time under various specific etching conditions, in a number of materials of interest, including ‘reference glass’. Furthermore, the theoretical relationship of this factor with the general velocity of etching in a given material, and with the average range R of fission fragments in it, is utilized in deriving self-consistent and very satisfactory values of R in the above-mentioned materials.

Detection of Fast Neutrons by Etch-Pit Method of Nuclear Track Registration in Plastics

Plastics, such as polycarbonate, cellulose nitrate and cellulose acetate were irradiated with fast neutrons (2.5, 14 MeV) and a count was made of the number of etch-pits on the surfaces of the irradiated material after etching with suitable chemical reagents. The experiments proved that the number of etch-pits increases with the etching time, and that at least during the early period of etching, a close correlation seems to exist between ΔP the increment in the number of etch-pits per unit area and Δl the increment of thickness of layer removed for a common increment of etching time Δt. In other words, an approximate relation ΔP/Δl=ρ was observed to hold during this early etching period, ρ being a constant that seems to correspond to the number of etchable damages produced by fast neutron irradiation per unit volume. The value of ρ was found to correspond roughly to the estimated number of recoil carbon and oxygen atoms in a unit volume in the case of polycarbonate which consists of carbon, oxygen and hyd...

Etching Behavior of In2O3 Grown from PbO–B2O3

Single crystals of In2O3 grown from a PbO–B2O3 solution are etched by HNO3 or HNO3–HCl solutions. Characteristic etch pits and etch tubes are described. The number of etch pits is found to be related to the growth history of the crystals. The relationship of the etch tubes to crystal growth is discussed.