Groove Profile Research Articles

Micromachined silicon grisms for infrared optics

We demonstrate the successful fabrication of large format (approximately 50 mm × 50 mm) gratings in monolithic silicon for use as high-efficiency grisms at infrared wavelengths. The substrates for the grisms were thick (8-16 mm) disks of precisely oriented single-crystal silicon (refractive index, n ~ 3.42). We used microlithography and chemical wet etching techniques to produce the diffraction gratings on one side of these substrates. These techniques permitted the manufacture of coarse grooves (as few as 7 grooves/mm) with precise control of the blaze angle and groove profile and resulted in excellent groove surface quality. Profilometric measurements of the groove structure of the gratings confirm that the physical dimensions of the final devices closely match their design values. Optical performance of these devices exceeds the specifications required for diffraction-limited performance (RMS wave surface error <λ/20) in the near- and mid-infrared (1-40 μm). Peak diffraction efficiencies measured in the reflection range from 70-95% of the theoretical maximum. Tests of our grisms in the near infrared indicate transmission efficiencies of 30-48% uncorrected for Fresnel losses and confirm excellent performance. In infrared wavelength regions where silicon transmits well, the blaze control and high index permit high-resolution, high-order dispersion in a compact space. The first application of these grisms is to provide FORCAST, a mid-infrared camera on NASA's airborne observatory, with a moderate resolution (R=100-1000) spectroscopic capability.

Thermal grain-boundary grooving in bicrystal thin solid films having strong anisotropic surface Gibbs free energy represented by the modified cycloid-curtate function

The variational non-equilibrium thermodynamic method is further extended to give full coverage for the tilted grain-boundary (GB) configuration with respect to the sidewalls of a bicrystal thin solid film having strong anisotropic specific surface Gibbs free energy associated with the singular directions (faceting, vicinal planes). A set of critical computer simulation experiments supported by the generalized longitudinal force diagrams is performed on the asymmetrically disposed (inclination) bicrystal thin metallic films having four- and six-fold anisotropic specific surface Gibbs free energy to demonstrate the various GB-groove root topologies caused by the grain-boundary grooving under the surface drift-diffusion driven by the capillarity forces (thermal grooving). In the computer simulations, the strongly anisotropic surface-specific Gibbs free energy associated with the cusp regions is represented by the modified cycloid-curtate function (MCCF) as a basis (generator) for the Dirac delta distribution function on the Wulff construction, which involves not only the Wulff surface roughness (WSR) parameter (anisotropy constant) but also the Wulff surface topography (WST) index (shape parameter) that may be used as a metric for the temperature roughening phenomenon. A special computer run is also designed using the realistic structural and physicochemical properties in order to simulate the thermal groove profiles of cube-textured pure nickel tape {Ni—99.99 wt%} annealed four hours in vacuum at 800 °C, and observed by the atomic force microcopy (AFM). The experimental line width fitting procedure applied to the simulation profile subjected to the self-similarity transformation, which resulted in almost perfect replication of the experimental digitized AFM photography, has yielded a mean surface (mass) diffusivity of nickel about 5.7×10 −13 m 2/s (800 °C), which is in excellent quantitative agreement with the diffusivity relationship at T⩾1300 K reported in the literature on relatively contaminated surfaces, and obtained by high-precision profilometry measurements of the decay of capillary modes associated with the wide surface scratches.

Characteristics of the acoustic emission during horizontal single grit scratch tests: Part 1 characteristics and identification

Material process in grinding involves three phenomena namely: rubbing, ploughing and cutting. Rubbing and ploughing, which usually occur before or after cutting, essentially mean the energy is being applied less efficiently in terms of material removal. It is therefore important to identify the effects of these different phenomena experienced during grinding. To identify the different phenomena, two channel Acoustic Emission (AE) signals were extracted by two AE sensors which would give verified energy information relating to the horizontal groove profile in terms of the material plastic deformation and material removal. With the use of a Fogale Photomap Profiler, accurate material surface profile measurements of the cut groove would be made and compared against the corresponding AE signal scratch hit data. A combination of filters, Short-Time Fourier Transform (STFT) would provide the salient components for comparison and classification of the three different levels of Single Grit (SG) processing phenomena. Verified classification was achieved from both Neural Networks and Fuzzy-c Genetic Algorithm Clustering Techniques and is discussed in the second part of this work.

Frequency selective characteristics of gratings with arbitrary profiles composed of left-handed materials

The frequency selective surface (FSS) of gratings with arbitrary profiles composed of left-handed materials is systematically analysed by a method that combines the staircase approximation and the multimode network theory with the rigorous mode matching procedure. The effects of different periodic groove profiles, such as rectangle, ellipse and trapezoid on the reflection characteristics of the FSS are carefully studied and compared with each other. The variations of the frequency selective characteristics with dielectric loss and the comparisons between left-handed and right-handed gratings are also presented with the physical explanations of the related phenomena.

A wet abrasive blasting process for smooth micromachining of glass by ductile-mode removal

This paper describes the ductile removal behavior of a Pyrex glass substrate in a wet blasting process with an aqueous fine abrasive slurry of 4 µm Al2O3 particles in water. Glass was removed in a ductile cutting mode when the blasting was carried out with low applied pressure or with a long nozzle distance. Although the removal rate in the ductile mode was much lower than with brittle-mode blasting, a smooth surface within a roughness of 50 nm Ra was obtained. Using ductile-mode blasting, a micro groove with a smooth surface (roughness <50 nm Ra) was successfully obtained. The profile of the micro groove was U-shaped, in contrast to the V-shaped profile obtained with conventional brittle-mode blasting. Ductile-mode blasting was also used for surface finishing after a rough pre-blasting process. The roughness of the pre-blasted surface was reduced from 200 nm Ra to about 100 nm Ra by the finishing process.

Biotribological behavior of ultra high molecular weight polyethylene composites containing bovine bone hydroxyapatite

Abstract Wear particles of ultrahigh molecular weight polyethylene (UHMWPE) are the main cause of long-term failure of total joint replacements. Therefore, increasing its wear resistance or bioactivity will be very useful in order to obtain high quality artificial joints. In our study, UHMWPE composites filled with the bovine bone hydroxyapatite (BHA) were prepared by the method of compression moulding. A ball-on-disc wear test was carried out with a Universal Micro-Tribometer to investigate the friction and wear behavior of a Si3N4 ceramic ball, cross-sliding against the UHMWPE/BHA composites with human plasma lubrication. At the same time, the profiles of the worn grooves on the UHMWPE/BHA surface were scanned. The experimental results indicate that the addition of BHA to UHMWPE had a significant effect on the biotribological behavior of UHMWPE cross-sliding against the Si3N4 ceramic ball. The addition of BHA powder enhanced the hardness and modulus of elasticity of these composites and decreased the friction coefficients and wear rates under conditions of human plasma lubrication. When the added amount of BHA powders was up to 20%∼30%, UHMWPE/BHA composites demonstrated the designed performance of the mechanical properties and biotribological behavior.

Static and Dynamic Characteristics of Oil Lubricated Beveled-Step Herringbone-Grooved Journal Bearings

Recently, herringbone-grooved journal bearings (HGJBs) have important applications in high-speed rotating machinery. The groove action in pumping the lubricating fluid inward generates supporting stiffness and improves the stability of the bearing when operating concentrically. Several researchers have investigated the static and dynamic characteristics of HGJBs and grooved thrust bearings. Most of these investigations were theoretical and concentrated on HGJBs with rectangular-profile grooves. In the present work, the static and dynamic characteristics of the beveled-step HGJBs are experimentally investigated. The bearing attitude angle, pressure distribution, and bearing friction torque were measured on a hydrodynamic lubrication unit, and then the static and dynamic characteristics were determined. The obtained experimental results are compared to the obtained experimental results for plain journal bearing. The merits as well as the demerits of the groove profile were discussed through comparisons with plain journal bearings.

Fabrication of extreme-ultraviolet blazed gratings by use of direct argon-oxygen ion-beam etching through a rectangular photoresist mask

We present a simple method to fabricate blazed gratings used in the extreme-ultraviolet wavelength region. The method uses an argon and oxygen ion beam to etch directly the fused silica substrate through a rectangular profile photoresist grating mask. The blaze angle can be significantly reduced by using oxygen, and the profile evolution under ion-beam bombardment can be simplified when a rectangular mask is used. A simple geometric model is built to analyze the etching process. The etched grating groove profile is approximately triangular with a sharp apex angle provided the aspect ratio of the mask ridge is properly chosen; the blaze angle is directly proportional to the ion-beam grazing incident angle for a fixed oxygen partial pressure. Gratings of a 2400 line/mm groove density and 0.5-3 degrees blaze angles have been fabricated, which confirms the convenience of this method and the effectiveness of the etching model.

Grazing incidence off-plane lamellar grating as a beam splitter for a 1-Å free electron laser

A beam splitter based on the diffraction grating working in the grazing incidence conical diffraction is proposed for x-ray free-electron laser (XFEL) experiments with coherent beams in plasma and atomic physics. Such a beam splitter can provide undistorted wavefronts, high-power radiation scattering, and split beams with equal intensities, which propagate with delay along different paths to the target chamber of the XFEL end station. Using the PCGrate software based on rigorous electromagnetic theory and developed for the short-wavelength range, it is shown that the plane grating with lamellar groove profile of a certain depth, operating in grazing conical incidence mount (grooves are parallel to the incident beam), separates three beams in the −1, 0, and +1 orders with close diffraction efficiency. Numerical simulation predicts 23–27% absolute efficiency for 0.1-nm incident radiation in each separated order of a bulk or multilayer grating, taking into account the atomic level roughnesses and interdiffusion. When using a multilayer coating based on Ru/C or Ru/B4C pairs, the optimum grazing angle providing approximately equal efficiencies is ∼1.038° which is four times higher than for the Pt-coated grating. Such optimization of radiation geometry, groove profile shape, and multilayer coating parameters can be performed for various XFEL wavelengths. The proposed grating, in addition to diffraction, technological, and design advantages over the beam splitter based on a set of perfect crystals, can be fabricated and tested using currently available methods.

Parametric Design on 3D Complex Groove of Turning Inserts Using Pro/Engineer

One main method of chip breaking is to use the grooves which can make chips be broken. 3D complex grooves meet the requirements of controllable chip breaking. It is too complicated to design 3D complex grooves using AutoCAD in short periods because each section of them is intricacy. Thus the author established the parametric model of the groove based on the advanced functions of Pro/Engineer, in which parameters can be obtained, transferred and modified through setting up parameter relations and compiling control programs. The combination of representative elements constituting the solid model of 3D complex grooves can be achieved by just inputting parameters, which can be directly transformed into 2D drawing accordingly; the heavy work of drawing complex surfaces using AutoCAD can be avoided; and the curvature of each normal profile of grooves are gotten. All such work lays a foundation for the groove design and optimization.

Profile control of a borosilicate-glass groove formed by deep reactive ion etching

We investigated the deep reactive ion etching (DRIE) of borosilicate glass and profile control of an etched groove. We carried out DRIE using an anodically bonded silicon wafer as an etching mask. We controlled the glass-groove profile, namely improving its sidewall angle, by removing an excessive polymer film produced by carbon-fluoride etching gases during DRIE. We experimentally compared two fabrication processes for effective removal of the polymer film: (1) DRIE with the addition of argon (Ar) to the etching gases and (2) a novel combined process in which DRIE and subsequent ultrasonic cleaning in DI water were alternately carried out. Both processes improved the sidewall angle, reaching 85° independent of the mask-opening width. The results showed that the processes remove the excessive polymer film on sidewalls. Accordingly, the processes are an effective way to control the groove profile of borosilicate glass.

Investigation of Nanoscratch Processes in Semiconductor Materials for Application to Maskless Patterning

Features of nanoscratching processes with a diamond 90 degrees cube corner tip in semiconductor materials have been studied with different tip orientations and scratch procedures: constant and linearly increasing normal load during scratching, multi-scratching and the direct analysis of the generated scratch by re-scanning the scratch with a strongly reduced normal load. These scratch functions allowed a detailed investigation of the materials response due to the mechanical deformation process. Elastic material recovery, plastic deformation and material removal contribute to the generation of scratch groove profiles. For low applied normal loads mainly elastic deformation occurs whereas for larger normal loads stick-slip processes with periodic hillocks at the groove bottom and irregular pile-up along the scratch rim dominate the process. From the analysis of the scratch groove profile in Si(100), GaAs(100) and thin InSb films, quantitative values for the elastic deformation, the friction coefficient, stick-slip pattern, material removal and scratch depth as a function of the applied normal load are obtained. With multi-scratching a definite removal pattern with a reproducible scratch depth is obtained. These results can be used to optimise the scratch technique for application to maskless patterning.

High-efficiency multilayer-coated ion-beam-etched blazed grating in the extreme-ultraviolet wavelength region

We describe a simple method to fabricate blazed gratings used in the extreme ultraviolet wavelength region. The method uses an argon and oxygen mixed-gas ion beam to directly etch the grating substrate through a rectangular profile photoresist grating mask. With this method the etched grating groove profile can be well controlled. An Mo/Si multilayer-coated specimen with a blaze angle of 1.9 degrees was fabricated and measured. At an incident angle of 10 degrees and a wavelength of 13.62 nm, the diffraction efficiency of the negative second order reaches 36.2%.

A Large Measuring Range Profilometer for Three-Dimensional Surface Topography Measurement

A novel profilometer for three-dimensional (3D) surface topography measurement is presented. The profilometer has large measuring range, high precision and small measuring touch force. It is composed of a two-dimensional (2D) displacement sensor, a 3D platform based on vertical scanning, measuring and control circuits and an industrial control computer. When a workpiece is measured, the vertical undulation of the profile at a sampling point leads to a zero offset of the 2D displacement sensor. According to the zero offset, a piezoelectric actuator and a servo motor drive the vertical scanning platform to move vertically to ensure that the lever returns to its balance position. So the non-linear error caused by the rotation of the lever is very small even if the measuring range is large. When the stylus barges up against a steep wall, the horizontal resistance force results in another zero offset of the 2D displacement sensor. If the zero offset exceeds a quota, the vertical scanning platform descends to make the stylus climb the steep wall successfully. According to the theoretical and experimental analysis, the profilometer can measure roughness, profile of sphere, step, groove and other 3D surfaces with curvature precisely.

Dirichlet extremum problem associated with the asymmetric grain-boundary thermal grooving under the Dirac δ-type anisotropic surface stiffness in bicrystal thin solid films

A generalized Rayleigh-Ritz (RR) method combined with the Galerkin (RRG) functional space approximation is elaborated by using the extended and modified Laguerre functions manifold for the weak solution of the asymmetric grain-boundary thermal grooving problem with the Dirichlet boundary. This new hybrid RRG approach, which resembles the front-tracking method, reveals the fine features of the grain boundary groove-root topography (rough or faceted regions) more accurately than the previous approach under the severe nonanalyticity of the surface stiffness anisotropy, and showing almost excellent in accord with the experimental observations made by atomic force microscopy and scanning tunneling microscopy. The large deviations from Mullins’ t1/4 scaling law combined with the self-trapping (quasifaceting) are observed especially at low values of the normalized longitudinal mobilities, where the kinetics rather than the energetic considerations are found to be the dominating factor for the whole topographic appearances. For very high longitudinal mobilities, the smooth and symmetric groove profiles (no faceting) are found to be represented by the Mullins’ function for the fourfold symmetry in the stationary state with great precision, if one modifies the rate parameter by the anisotropy constant and simultaneously utilizes the anisotropic complementary dihedral angle in the calculation of the slope parameter. A recently developed analytical theory fully supports this observation rigorously, and furnishes the quantitative determination of the threshold level of the anisotropy constant for the ridge formation, and as well as the penetration depth evaluation.

Evaluation of the profile of the taper ball-end milling cutter with a cylindrical shank

This paper presents a model for evaluating the quality of the actual working profile of a taper ball-end milling cutter with a cylindrical shank. The cutter is attached to the cylindrical surface of the shank, and is then mounted on a machine tool. The analysis presented within this paper takes the axis of the minimum circumscribed cylindrical surface (MCCS) of the shank as the datum axis. This paper provides revised equations for defining the minimum circumscribed taper surface (MCTS) and the minimum circumscribed sphere (MCS), which may be used to calculate the profile of the spiral groove on the taper part and the ball-end part of the cutter, respectively. This paper serves as a basis for evaluation of the profile of the taper ball-end milling cutter with a cylindrical shank.

Quantifying cation grain boundary diffusion

Evolution in the shape of grooves formed at grain boundaries at the air/aluminum oxide interface is analyzed for the case in which there is both diffusion along the oxide surface and oxidation-induced mass flow along grain boundaries of the already-formed oxide. The shape evolution is compared with atomic force microscope measurements of the groove profiles produced when thermally grown alumina on FeCrAl alloys is polished flat and reoxidized. A method of quantifying the grain boundary flux, based upon the shape of the surface profile, is presented.

The effect of bismuth segregation on the faceting of Σ3 and Σ9 coincidence boundaries in copper bicrystals

Abstract The faceting of a cylindric tilt grain boundary (GB) in Cu and Cu-160 ppm Bi bicrystals was studied. The crystal lattices of both grains form a superlattice called a coincidence site lattice (CSL) with an inverse density of coincidence sites relating to the density of lattice sites Σ = 3 and Σ = 9. The Σ3 and Σ9 &lt;110&gt; tilt GBs became faceted upon annealing at 0.95 Tm. The ratio of GB energy σGB and surface energy σsur of the specimen was measured, applying atomic force microscopy, from the profile of the GB thermal groove formed upon additional annealing. The 160 ppm Bi concentration in the Bi-containing bicrystal is between GB and bulk solidus lines in the Cu – Bi phase diagram. In this concentration region GBs contain a multilayer Bi-rich film which is supposed to be liquid-like. Wulff – Herring diagrams were constructed using the measured σGB/σsur values, revealing stable and metastable GB facets.

Off-plane grazing-incidence blazed grating with radial grooves as an efficient spectral purity filter for EUV lithography

It was found that the high-blaze-angle reflective diffraction grating operating in the off-plane grazing-incidence configuration allows the separation and focusing of a 2% wavelength band in the vicinity of 13.5 nm. A model of a cooled multiple grating with a fan-groove geometry was used to separate the desired spectral range and to achieve a record efficiency and stigmatic focusing of images at high dispersion of adjacent orders. The highest relative efficiency in the range of 0.96–0.99 and reflectances from 0.71 to 0.96 can be achieved for an off-plane fine-pitch grating irradiated at angles of 70°–85° with a converging unpolarized light beam from a EUV collector. Such efficiency is higher than that of the corresponding in-plane configuration. The absolute efficiency of 0.72 was achieved in the minus-first order of a Mo-coated test Si grating with 5000 grooves/mm in unpolarized light using the PCGrate®-SX™ code and the AFM-measured groove profile.

Effect of replication on the groove shape of a sinusoidal holographic grating

We study the changes in groove shape and depth that occur when holographic gratings are replicated in plastic. Specifically, we measure the groove profiles and spatial frequencies of electroplated metal shims made from sinusoidal holographic gratings, and also the same properties of the replicas made of polymethylmethacrylate (also metal shims). Nine samples are studied that have spatial frequencies in the range 600 to 2000 mm−1. The shims of the replicated gratings have up to 30% shallower grooves and 13% lower diffraction efficiencies than the shims of the originals. The maximum measured diffraction efficiency for shims of the original gratings having 525- to 620-mm−1 spatial frequencies correspond to a 0.22-µm groove depth, which agrees with the calculated value. We use this information to modify the groove shapes on the holographic gratings to make better plastic replicas.