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1.
Effect of rogue particles on the sub-surface damage of fused silica during grinding/polishing 总被引:5,自引:0,他引:5
T. Suratwala R. Steele M.D. Feit L. Wong P. Miller J. Menapace P. Davis 《Journal of Non》2008,354(18):2023-2037
The distribution and characteristics of surface cracks (i.e., sub-surface damage or scratching) on fused silica formed during grinding/polishing resulting from the addition of rogue particles in the base slurry has been investigated. Fused silica samples (10 cm diameter × 1 cm thick) were: (1) ground by loose abrasive grinding (alumina particles 9-30 μm) on a glass lap with the addition of larger alumina particles at various concentrations with mean sizes ranging from 15 to 30 μm, or (2) polished (using 0.5 μm cerium oxide slurry) on various laps (polyurethane pads or pitch) with the addition of larger rogue particles (diamond (4-45 μm), pitch, dust, or dried Ceria slurry agglomerates) at various concentrations. For the resulting ground samples, the crack distributions of the as-prepared surfaces were determined using a polished taper technique. The crack depth was observed to: (1) increase at small concentrations (>10−4 fraction) of rogue particles; and (2) increase with rogue particle concentration to crack depths consistent with that observed when grinding with particles the size of the rogue particles alone. For the polished samples, which were subsequently etched in HF:NH4F to expose the surface damage, the resulting scratch properties (type, number density, width, and length) were characterized. The number density of scratches increased exponentially with the size of the rogue diamond at a fixed rogue diamond concentration suggesting that larger particles are more likely to lead to scratching. The length of the scratch was found to increase with rogue particle size, increase with lap viscosity, and decrease with applied load. At high diamond concentrations, the type of scratch transitioned from brittle to ductile and the length of the scratches dramatically increased and extended to the edge of the optic. The observed trends can be explained semi-quantitatively in terms of the time needed for a rogue particle to penetrate into a viscoelastic lap. The results of this study provide useful insights and ‘rules-of-thumb’ relating scratch characteristics observed on surfaces during optical glass fabrication to the characteristics of the rogue particles causing them and their possible source. 相似文献
2.
X. F. Chen D. Siche M. Albrecht C. Hartmann J. Wollweber X. G. Xu 《Crystal Research and Technology》2008,43(6):651-655
The Al‐polar surfaces of AlN wafers cut from physical vapor transport grown crystals were lapped and polished. Polishing procedures were developed to produce surfaces for epitaxial growth. The surface scratches and subsurface damage caused by mechanical polishing were removed by a final chemical mechanical polishing (CMP) process, which yielded a perfect surface ready for epitaxial growth. After CMP the average root mean square surface roughness on a 5 µm × 5 µm area was 0.1 nm. Characterization of the polished surfaces by electron back scatter diffraction and cathodoluminescence showed no subsurface damage. The difference of orientation dependent material removal rate during CMP went up with the increase of the misorientation from (0001) surface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
3.
《Journal of Non》2005,351(52-54):3861-3865
The subsurface damage in ground optical glasses was characterized using the ball-dimple technique. At the same lapping conditions, larger abrasive size introduced deeper subsurface damage, and the surface damage was proportional to the surface roughness. Surface degradation in the ground glasses due to the formation and propagation of the subsurface damage was evaluated using microindentation method. A two parameters empirical equation was used to describe the indentation behavior of the ground glasses. It was found that the nominal near-surface elastic constant decreases with the indentation load, suggesting the propagation and formation of surface cracks during the indentation. 相似文献
4.
M. Bickermann S. Schmidt B.M. Epelbaum P. Heimann S. Nagata A. Winnacker 《Journal of Crystal Growth》2007,300(2):299-307
We investigated defect-selective wet chemical etching of freestanding aluminum nitride (AlN) single crystals and polished cuts in a molten NaOH–KOH eutectic at temperatures ranging from 240 to 400 °C. Due to the strong anisotropy of the AlN wurtzite structure, different AlN faces get etched at very different etching rates. On as-grown rhombohedral and prismatic facets, defect-related etching features could not be traced, as etching these facets was found to mainly emphasize features present already on the un-etched surface. On nitrogen polar basal planes, hexagonal pyramids/hillocks exceeding 100 μm in diameter may form within seconds of etching at 240 °C. They sometimes are arranged in lines and clusters, thus we attribute them to defects on the surface, presumably originating in the bulk material. On aluminum polar basal planes, the etch pit density which saturates after approx. 2–3 min of total etching time at 350 °C equals the density of a certain type of dislocations (presumably screw dislocations) threading the surface. Smaller etch pits form around annealed indentations, in the vicinity of some bigger etch pits after repeated etching, and sometimes also isolated on the surface area. Although alternate explanations exist, we attribute these etch pits to threading mixed and edge dislocations. This paper features etching parameters optimized for different planes and models on the formation of etching features especially on the polar faces. Finally, the issue of reliability and reproducibility of defect detection and evaluation by wet chemical etching is addressed. 相似文献
5.
A. Bensouici V. Carcelen J.L. Plaza S. De Dios N. Vijayan J. Crocco H. Bensalah E. Dieguez M. Elaatmani 《Journal of Crystal Growth》2010,312(14):2098-2102
The effect of surface preparation on CdZnTe properties was investigated. Surface etching using bromine solutions enhances Te elemental composition, resulting in a Te rich surface layer that is prone to oxidize. This oxidation degrades the performance of the fabricated CZT gamma detector. Roughness results were identical for samples polished with 1 and 3 μm and subsequently etched in 2% Br-MeOH. The optimal concentration of etching was 2% Br-MeOH. 相似文献
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The reactive ion etch process (RIE) of silicon in a CF4/O2 gas mixture is described. The dependence of the etch rate and the surface quality on used mask material (photoresist, aluminium) is studied. A silicon etch rate of about 1.5 times higher than with resist mask is reached using aluminium as mask material. The free etched surfaces are very rough due to micromasking effects during the etch process. Using a phtoresist mask the surfaces remain clean. The silicon etch depth depends on the thickness of the mask. 相似文献
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J.L. Weyher F.D. Tichelaar D.H van Dorp J.J. Kelly A. Khachapuridze 《Journal of Crystal Growth》2010,312(18):2607-2610
A recently developed photoetching system for n-type GaN, a KOH solution containing the strong oxidizing agent potassium peroxydisulphate (K2S2O8), was studied in detail. By careful selection of the etching parameters, such as the ratio of components and the hydrodynamics, two distinct modes were defined: defect-selective etching (denoted by KSO-D) and polishing (KSO-P). Both photoetching methods can be used under open-circuit (electroless) conditions. Well-defined dislocation-related etch whiskers are formed during KSO-D etching. All types of dislocations are revealed, and this was confirmed by cross-sectional TEM examination of the etched samples. Extended electrically active defects are also clearly revealed. The known relationship between etch rate and carrier concentration for photoetching of GaN in KOH solutions was confirmed for KSO-D etch using Raman measurements. It is shown that during KSO-P etching diffusion is the rate-limiting step, i.e. this etch is suitable for polishing of GaN. Some constraints of the KSO etching system for GaN are discussed and peculiar etch features, so far not understood, are described. 相似文献
10.
Yen-Hsien Yeh Kuei-Ming Chen Yin-Hao Wu Ying-Chia Hsu Wei-I. Lee 《Journal of Crystal Growth》2011,314(1):9-12
The morphology of GaN etched in hydrogen atmosphere is investigated. It is found that GaN surfaces have different profiles after being etched at different pressures. The profile resembles a surface that has been decorated with columns or mooring posts at high pressure and with deep cavities at low pressure. Etch pit density (EPD) experiment shows all dislocations have been etched to form cavities at low pressure, but not all the cavities result from etched dislocations. A model has been developed to explain the mechanism of H2 etching. Patterned structure with a flat surface and porous inside has been produced by two-step etching which is designed according to the model. 相似文献
11.
Glass surfaces were damaged in a defined manner by sandblasting with an adjustable sand blasting machine and subsequent etching with HF. Investigations with the scanning electron microscope (SEM) showed surface defects with an ellipsoidal shape. A quantitative evaluation of the exact profile of these defects was made using mathematical evaluation of stereographic pairs. A new method is described for characterizing surfaces with optical light scattering. In contrast to the usual method of a fixed specimen and a photocell moving on a circle around it, here the specimen revolves on an axis perpendicular to a laser beam and rotates on an axis parallel to it in order to average the scattering over a large area of the surface, thus preventing interferences of the coherent laser beam with surface defects. A theory is described which enables a numerical estimation of roughness parameters using a distribution function of angles of small mirrors to the average surface. In this special case the theory was extended for the special type of defects having an ellipsoidal shape. The results are discussed with respect to creation of surface defects by sandblasting, which are accompanied by subsurface cracks. 相似文献
12.
利用化学气相沉积法在抛光铜衬底上制备出六角形石墨烯晶畴,并对石墨烯晶畴进行氧气刻蚀.刻蚀完成后,利用光学显微镜和扫描电子显微镜观察到石墨烯晶畴表面的褶皱被刻蚀成网络状和短线状形貌的刻蚀条纹,并且刻蚀条纹的密度分布差异较大.通过电子背散射衍射测试证明了铜衬底的晶向与褶皱的形貌和密度分布有密切关系,不同的铜衬底晶向会影响褶皱的形貌和密度分布.通过改变刻蚀时间和刻蚀温度,发现刻蚀温度对石墨烯的氧气刻蚀具有更重要的影响,当刻蚀温度高于250 ℃时,刻蚀速率明显提高.这种氧气刻蚀方法,为观察石墨烯表面褶皱的形态和密度分布提供了一种便捷的途径. 相似文献
13.
Duk-Yong Choi Steve Maden Andrei Rode Rongping Wang Barry Luther-Davies 《Journal of Non》2008,354(27):3179-3183
Chalcogenide glasses are good candidate materials for ultra-fast non-linear optic devices. In this work, we present the photolithographic process and the plasma etching of arsenic tri-sulphide (As2S3) film. The films were deposited on thermally oxidized silicon substrates by ultra-fast pulsed laser deposition. To protect As2S3 film from photo-resist developer, thin resist layer ∼100-200 nm was remained on the UV exposed area by controlling resist development time. After removing the protective layer in oxygen plasma, As2S3 waveguides were patterned in inductively coupled plasma reactive ion etching (ICP-RIE) system using CF4-O2 gas mixture. We investigated the etch rate and the etch selectivity to photo-resist of As2S3 as a function of bias power, induction power, operating pressure, and gas flow rate ratio of CF4 and O2. The film is mainly etched by the chemical reaction with fluorine radicals. The content of oxygen in the plasma determines the etched sidewall profiles and nearly vertical profile was obtained at high oxygen content plasma. 相似文献
14.
《Journal of Non》2007,353(8-10):953-955
We present evidence of nano-scale phase separation in amorphous arsenic tri-sulphide films prepared by ultra-fast pulsed laser deposition based on Raman spectroscopy, X-ray photo-electron spectroscopy, and atomic force microscopy. We also show the results from plasma etching this material and conclude that the grainy structure of etched surfaces comes from the differential chemical etch rates of the different phases. 相似文献
15.
Etching of {111} cleavage faces of CaF2 crystals in aqueous solution of 50% HCl is carried out in citric acid set silica gel, and the kinetics of growth of etch pits at the sites of dislocations is investigated as a function of temperature, time of etching and height of gel column above the crystal surface. It is observed that the transient period required to initiate etch pit at the sites of a dislocation decreases (1) at particular temperature, with a decrease in gel height, and (2) for a particular gel height, with an increase in the temperature of etching. It is also observed that the morphology of dislocation etch pits remains triangular irrespective of the gel height and the temperature of etching. The results are compared with those of solution etching and discussed. 相似文献
16.
P. N. Kotru 《Crystal Research and Technology》1978,13(1):35-41
Some results of microtopographical investigations on various habit faces of hydrothermally grown cultured quartz crystals are reported. Circular hillocks with a background of minor rhombohedral surface as dull as the surface surrounding the hillocks are illustrated. The dullness of the surfaces is attributed to microetching of bulk quartz crystals. Unusual etch patterns on major rhombohedral faces are illustrated. Oriented raised humps on rhombohedral faces are explained to be as a result of interaction of etch fronts from different etch nuclei surrounding the humps. Rare observations of oriented depressions on trigonal trapezohedron and prism faces are reported. Possibilities that may lead to etching of bulk quartz crystals both inside as well as outside the growing chambers are discussed. From the considerations of various facets of the processes involved, it emerges that the etch patterns are indicative of quartz crystals getting etched in the growing chambers itself when the supply quartz is exhausted and where the growing chambers is the hottest. 相似文献
17.
The quality of an optical glass component is influenced by the presence of surface and subsurface defects generated by machining processes, especially lapping. However, the damaged area is characterized by roughness and crack layers that contribute to reduce the component's mechanical and optical performances. Evaluation of these defects leads to the obtainment of the best finishing technique for optical glass components.In this work, the effect of the lapping technological parameters (lapping time and alumina abrasive grain size) on the glass surface roughness as well as the depth of the damaged layer were determined. Furthermore, a proportionality constant between the total height of the roughness profile (Rt) and the subsurface damage layer was calculated. The damaged depth was characterized using mechanical techniques and microscopic analysis. The obtained results show an important damage of the glass surface, since the first few seconds of contact time between the surface and the grains. The increase of the lapping time gives rise to the propagation of this damage to reach its maximum and then a material removal rate is observed. At the end of the operation, a defined final surface roughness and a subsurface damaged layer are obtained. The proportionality constant between the subsurface damage layer and the total height of the roughness profile (Rt) was found to be 6.7 ± 0.8. 相似文献
18.
Characterization of the epitaxial defect known as the carrot defect was performed in thick 4H-SiC epilayers. A large number of carrot defects have been studied using different experimental techniques such as Nomarski optical microscopy, KOH etching, cathodoluminescence and synchrotron white beam X-ray topography. This has revealed that carrot defects appear in many different shapes and structures in the epilayers. Our results support the previous assignment of the carrot defect as related to a prismatic stacking fault. However, we have observed carrot defects with and without a visible threading dislocation related etch pit in the head region, after KOH etching. Polishing of epilayers in a few μm steps in combination with etching in molten KOH and imaging using Nomarski optical microscope has been used to find the geometry and origin of the carrot defects in different epilayers. The defects were found to originate both at the epi-substrate interface and during the epitaxial growth. Different sources of the carrot defect have been observed at the epi-substrate interface, which result in different structures and surfaces appearance of the defect in the epilayer. Furthermore, termination of the carrot defect inside the epilayer and the influence of substrate surface damage and growth conditions on the density of carrot defects are studied. 相似文献
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Studies on etching of (110) cleavages of natrolite crystals in organic acids (viz., succinic acid, formic acid, and phthalic acid) and stream under high hydrostatic pressures have been made. It is observed that on successive etching of matched cleavages in any of these organic etchants, the pits get bigger both in regard to depth as well as lateral dimensions. Study of matched cleavages etched in any of these etchants indicates 1:1 correspondence of point bottomed pits. Similar results are obtained when matched cleavages are etched by the hydrothermal method. In contrast to such results, it is observed that the etch pit density on a cleavage etched by the hydrothermal method is always higher when compared with its matched cleavage etched in any of the given organic acids. Through a series of experiments, it is found that while corresponding to every etch pit due to any of these organic acids there is a pit due to hydrothermal etching, the converse is not true. It is suggested that the hydrothermal etching is more reliable so far as dislocation density estimation on (101) cleavages of natrolite is concerned. 相似文献