Smooth Surface Profile Research Articles

Characterization of low temperature deposited atomic layer deposition TiO2 for MEMS applications

TiO2 is an interesting and promising material for micro-/nanoelectromechanical systems (MEMS/NEMS). For high performance and reliable MEMS/NEMS, optimization of the optical characteristics, mechanical stress, and especially surface smoothness of TiO2 is required. To overcome the roughness issue of the TiO2 films due to crystallization during deposition at high temperatures (above 250 °C), low temperature (80–120 °C) atomic layer deposition (ALD) is investigated. By lowering the deposition temperature, the surface roughness significantly decreases from 3.64 nm for the 300 °C deposited crystalline (anatase phase) TiO2 to 0.24 nm for the 120 °C amorphous TiO2. However, the layers deposited at low temperature present different physical behaviors comparing to the high temperature ones. The refractive index drops from 2.499 to 2.304 (at 633 nm) and the stress sharply decreases from 684 to 133 MPa. Superhydrophilic surface is obtained for the high temperature deposited TiO2 under ultraviolet illumination, while little changes are found for the low temperature TiO2. The authors demonstrate that by suitable postdeposition annealing, all the properties of the low temperature deposited films recover to that of the 300 °C deposited TiO2, while the smooth surface profile (less than 1 nm roughness) is maintained. Finally, micromachining of the low temperature ALD TiO2 by dry etching is also studied.

Design and fabrication of novel microlens-micromirrors array for infrared focal plane array

A simple method on fabricating a novel structure of microlens–micromirrors array (MMA) with 100% fill factor and smooth surface profile is presented. The MMA has a special structure, which has a microlens array with foot diameter of 35 μm on the upper layer and a micromirrors array with top width of 50 μm and bottom width of 30 μm on the lower layer. These two arrays are connected by a thin layer of silicon. The new structure has potential to integrate with infrared focal plane arrays (IRFPAs). An analytical optical model is established and experimentally verified; results show that all of the incident infrared lights within a certain range can be absorbed by the photosensitive surface of IRFPAs with this structure. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:879–884, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26722

Surface investigation on prototype cavities for the European X-ray Free Electron Laser

The accelerating gradient Eacc of X-ray Free Electron Laser (XFEL) prototype cavities manufactured at the industry and treated at DESY demonstrates wide-range scattering from 15 to $41\text{ }\text{ }\mathrm{MV}/\mathrm{m}$. Most cavities satisfy the XFEL specification. Few cavities with low performance ($15--17\text{ }\text{ }\mathrm{MV}/\mathrm{m}$) are limited by quench without field emission. The T-map analysis detected quench areas mainly close to the equator. Optical control by a high resolution camera has been applied and allowed to monitor the defects in some cases with good correlation to T-map observation. In order to understand the cause of reduced performance and get more detailed information of the origin of defects, some samples have been extracted from two cavities and investigated by light microscope, digital light microscope with 3D profile measurement, scanning electron microscope SEM, energy dispersive x-ray analysis, and Auger spectroscopy. The electron backscattered diffraction method in a SEM is used to make localized measurements of the lattice curvature. Several surface flaws with sizes from a few $\ensuremath{\mu}\mathrm{m}$ to hundreds of $\ensuremath{\mu}\mathrm{m}$ detected by microscopy. The defects can be separated into two categories. The first category of defects consists of foreign elements (often an increased content of carbon). Inclusions with increased content of carbon adhere on the surface and presumably have a hydrocarbon nature. Deviation from a smooth surface profile characterizes the second type of defects (holes, bumps, and pits). Some holes and bumps were found directly in the welding seam. The hot spots in the heat-affected zone (HAZ) of the equator welds have been partially associated with pits too. The study correlates the location of pits with the presence of plastic strain found to remain after welding. Pits near the HAZ were found either coincident with or near areas of high strain. Pits away from the weld were often found at grain boundary triple junctions.

Impact of localized surface preheating on the microstructure and crack formation in laser direct deposition of Stellite 1 on AISI 4340 steel

Crack formation in laser cladding of the hardfacing alloy Stellite 1 on AISI-SAE 4340 steel was prevented through locally preheating the substrate prior to the deposition process. Numerical analysis showed that the preheating process helps developing a relatively steadier melt temperature as well as decreasing the cooling rates and consequently the thermal stresses during the subsequent deposition process. Microstructural analysis revealed a thicker cross-section with smoother surface profile, more uniform surface hardness and even distribution of a dendritic morphology in the preheated sample. This confirmed the presence of a well-developed melt pool with a homogeneous composition at solidification. The microstructure of non-preheated sample was, however, considerably non-uniform consisting of macro-scale colonies of dendritic and lamellar (eutectic) structures. The experimental observations, as implied through the numerical results, showed that the preheated sample, in general, reveals more uniform structure and properties making it less prone to cracking during the deposition process.

Fabricating micro-structured surface by using single-crystalline diamond endmill

A ball endmill made of single-crystalline diamond was used for cutting micro-structures on two kinds of mold materials, oxygen-free copper, and reaction-bonded silicon carbide (RB-SiC). The cutting performance of the ball endmill was investigated by examining surface roughness and form accuracy of the machined workpiece as well as tool wear characteristics. Micro-dimple arrays, micro-grooves, and micro-pyramid arrays with extremely smooth surface and high-accuracy profile could be obtained on oxygen-free copper without remarkable tool wear. When machining RB-SiC, however, tool flank wear takes place, leading to a rough surface finish. After the tool has worn off, the cutting performance of the endmill significantly depended on the tool feed direction. The optimum tool feed direction for micro-grooving was experimentally investigated.

Tumor suppressor protein SMAR1 modulates the roughness of cell surface: combined AFM and SEM study

BackgroundImaging tools such as scanning electron microscope (SEM) and atomic force microscope (AFM) can be used to produce high-resolution topographic images of biomedical specimens and hence are well suited for imaging alterations in cell morphology. We have studied the correlation of SMAR1 expression with cell surface smoothness in cell lines as well as in different grades of human breast cancer and mouse tumor sections.MethodsWe validated knockdown and overexpression of SMAR1 using RT-PCR as well as Western blotting in human embryonic kidney (HEK) 293, human breast cancer (MCF-7) and mouse melanoma (B16F1) cell lines. The samples were then processed for cell surface roughness studies using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The same samples were used for microarray analysis as well. Tumors sections from control and SMAR1 treated mice as well as tissues sections from different grades of human breast cancer on poly L-lysine coated slides were used for AFM and SEM studies.ResultsTumor sections from mice injected with melanoma cells showed pronounced surface roughness. In contrast, tumor sections obtained from nude mice that were first injected with melanoma cells followed by repeated injections of SMAR1-P44 peptide, exhibited relatively smoother surface profile. Interestingly, human breast cancer tissue sections that showed reduced SMAR1 expression exhibited increased surface roughness compared to the adjacent normal breast tissue. Our AFM data establishes that treatment of cells with SMAR1-P44 results into increase in cytoskeletal volume that is supported by comparative gene expression data showing an increase in the expression of specific cytoskeletal proteins compared to the control cells. Altogether, these findings indicate that tumor suppressor function of SMAR1 might be exhibited through smoothening of cell surface by regulating expression of cell surface proteins.ConclusionTumor suppressor protein SMAR1 might be used as a phenotypic differentiation marker between cancerous and non-cancerous cells.

Microfabrication of colloidal scanning probes with controllable tip radii of curvature

We report the first batch-fabrication method to create colloidal scanning probes based on standard micromachining processes. Microfabrication of colloidal probe arrays having smooth surface profiles with radius of curvature ranging from nanometers to tens of microns is successfully demonstrated. A new mold filling technology is developed where bulk-etched cavities with sharp endpoints are transformed into cavities with curved endings via spin coating of a liquid filling material (photoresist). The curved profile is then replicated into a stable metallic mold by evaporating a layer of aluminum, after which mold-transfer scanning probe (SP) fabrication is conducted to create colloidal probes. Multiple control knobs were developed and characterized for accurate control of the tip radius of curvature. By adjusting the solid content of the filling material, the number of spin-coat cycles, and the cavity geometry, different mold profiles and thereby tip radii of curvature were achieved. The new controllable technology allows rapid microfabrication of singular or arrayed colloidal scanning probes with different tip radii of curvature which will be useful for many biological and nanotechnology applications.

C24 Cutting Performance of a Single-crystalline Diamond Ball Endmill in Fabricating Micro Lens Arrays and Grooves(Ultra-precision machining)

A ball endmill made of single-crystalline diamond was used for cutting two kinds of mold materials, oxygen-free copper and reaction-bonded silicon carbide (RB-SiC). The cutting performance of the ball endmills was investigated by examining surface roughness and form accuracy of the machined workpiece as well as tool wear characteristics. It was found that micro lens arrays and grooves with extremely smooth surface and high-accuracy profile could be obtained on oxygen-free copper without detectable tool wear. When machining RB-SiC, although ductile cutting was realized, a few fine streaks were observed on the machined surface, which were attributed to the flank wear of the diamond tool. The effects of tool feed condition on cutting performance of a worn tool was investigated by performing micro grooving tests.

Influence of metal organic and inorganic precursors on spray pyrolyzed ceramic MgO (2 0 0) thin films for epitaxial over layers

The MgO (2 0 0) surface is widely used as a substrate for epitaxial growth of superconducting and ferro-electric films. Highly oriented, single crystalline, extremely flat and transparent MgO films have been successfully deposited on quartz substrates by the chemical spray pyrolysis technique using economically viable metal organic and inorganic precursors under optimized conditions at the substrate temperature of 600 °C. Thermal analysis (TGA/DTA) in the temperature range 30–600 °C with the heating rate of 10 °C/min revealed the decomposition behavior of the precursors and confirmed the suitable substrate temperature range for film processing. The heat of reaction, Δ H due to decomposition of metal organic precursor contributed additional heat energy to the substrate for better crystallization. The intensity of the (2 0 0) peak in X-ray diffraction (XRD) measurements and the smooth surface profiles revealed the dependency of precursor on film formation. The compositional purity and the metal–oxide bond formation were tested for all the films. UV–Vis–NIR optical absorption in the 200–1500 nm range revealed an optical transmittance above 80% and the absorption edge at about 238 nm corresponding to an optical band gap E g = 5.25 eV. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) micrographs of MgO films confirmed better crystallinity with larger grain size (0.85 μm) and reduced surface roughness (26 nm), respectively.

A histopathologic evaluation of the plasma skin regeneration system (PSR) versus a standard carbon dioxide resurfacing laser in an animal model

A variety of high energy, pulsed, and scanned carbon dioxide lasers are available to perform cutaneous resurfacing. Rhytec has developed a device for skin regeneration that utilizes energy delivered via a burst of nitrogen plasma. This study was undertaken to benchmark the energy outputs of the plasma skin regeneration device as compared to an ultra-short pulsed carbon dioxide laser (the control device). The two systems were compared for time to complete healing, and the healing response post-treatment. Three Yucatan mini-pigs were utilized for this study. Following anesthesia, five experimental sites were marked along the skin atop the psoas muscle on each side of the spine. Treatment was applied using either the plasma skin regeneration system or the carbon dioxide laser, with one site remaining untreated as a control. Biopsies were taken from all treatment sites 0, 2, 7, 14, 30, and 60 days following treatment and processed to hematoxylin-eosin staining. Histopathologic examination was performed by observers blinded as to the treatment conditions. Skin treated with the plasma skin regeneration device showed a wider range of tissue effects across the energy settings used as compared to the laser treatment. All treatment sites had clinically regenerated epidermis by 7 days after treatment, with active cellular response below the D/E junction noted at the day 30 time-point at energies ranging from 2 to 4 J. The Rhytec PSR system provides an attractive alternative to standard CO2 laser with good remodeling of tissue architecture. Epidermis regenerated after PSR treatment shows a smoother surface profile than adjacent untreated tissue.

Nanoimprint of gratings on a bulk metallic glass

The authors demonstrate that optical gratings with 600 and 1500nm periods on a Pd40Ni40P20 bulk metallic glass (BMG) can be faithfully imprinted in air from Si dies. Results of scanning electron microscopy, atomic force microscopy, and optical diffraction analysis show the fine line feature of ∼150nm. The gratings have smooth and uniform surface profiles with comparable optical properties as the original Si dies. The BMG gratings can be further used to imprint the second-generation replicas on polymethylmethacrylate. Thereby, BMG is a suitable material not only for imprinting nanostructured parts such as gratings, but also as a good die material for nanoimprints.

Spherical and Aspheric Microlenses Fabricated by Excimer Laser LIGA-like Process

This paper presents an effective and low-cost method for fabricating spherical and aspheric microlenses based on excimer laser LIGA-like processes. It is based on a newly developed excimer laser micromachining technique that can accurately machine a 3D microstructure with a predetermined continuous surface profile. The method is called the planetary scanning method since it is based on a combination of sample rotation and revolution and a concept of laser machining probability. Spherical and aspheric microlenses with precise and smooth surface profiles are fabricated by direct laser machining on polymer materials. Laser-machined microlenses are replicated by electroforming to obtain inverse metal molds. Finally, plastic microlenses are replicated from these metal molds using hot embossing method. The profile accuracy and surface roughness of the produced microlenses at each stage have been measured and monitored. The average surface profile accuracy is better than 1μm and average surface roughness is less than 10nm. Optical performance of the fabricated microlenses is evaluated by measuring the light intensity distribution at the focal plane and the focal length. Experimental data show that the characteristics of fabricated spherical and aspheric microlenses are well matched to the theoretical predictions, which demonstrates the controllability and accuracy of this micromachining process. Potential applications and further developments will be addressed.

Blueshift of surface plasmon resonance spectra in anneal-treated silver nanoslit arrays

Silver nanoslit arrays were anneal treated in vacuum, and the effects on the surface morphology of silver and the surface plasmon resonance characteristics were investigated. Optical transmission through nanoslit arrays shows a distinctive change in the spectral profiles after annealing: A clear blueshift of the transmission peaks and dips (20nm shift for an anneal temperature of 150°C). Scanning electron microscopy reveals a morphological change of silver: Increased grain sizes, and smooth and round surface profiles after the anneal treatment. The observed blueshift of transmission spectra correlates well with the geometrical and dimensional changes of silver islands defined between slits, which are found to alter the surface plasmon resonance conditions involving various mechanisms in different regimes.

The development of a dynamic amplification estimator for bridges with good road profiles

The paper considers the influence of the surface profile on the dynamic amplification of a simply supported bridge when subject to a quarter-car vehicle model. The effect of the profile irregularities on the bridge dynamic amplification is characterized with a ‘response surface’ giving dynamic amplification due to a ‘unit ramp’ at any location. Even though the dynamic interaction problem is nonlinear, the effects of all ramps which together make up a road profile can be calculated separately and added using the ‘response surface’. This superposition process achieves reasonable accuracy for ‘good’ (moderately smooth) surface profiles. An accurate estimate of dynamic amplification for bridges is demonstrated with a wide range of good profiles.

Smooth Mixed Geometry Profiles of Nozzles and Transition Ducts

Parametric equations are derived that characterize smooth surface profiles for two general classes of nozzles and nonbranching transition ducts: straight sections for axial flow and curved sections (elbows) for in-plane or out-of-plane flow. For each profile, the terminal cross sections are specified as rectangular, elliptical, circular, or a combination of those shapes. At each terminal and in line with the flow, the displacement, slope, and curvature with its respective intersecting uniform section is maintained. Included is a design example of a 90deg elbow duct whose cross section remains constant between terminals of elliptical and circular cross sections.

Low-loss multimode waveguides using organic-inorganic hybrid materials

Multimode channel waveguides were fabricated using a direct UV patterning technology from thick films deposited by the one-step dip-coating of an organic/inorganic hybrid material (ORMOCER®). The core size of the covered ridge waveguide was 43 × 51 μm2; the waveguides can be readily prepared for multimode applications by direct UV patterning. The waveguides exhibited smooth surface profiles and a low optical loss of 0.07 dB/cm at the most important wavelength (850 nm) used for optical interconnects.

Fabrication of Multimode Polymeric Waveguides by Hot Embossing Lithography

The fabrication of polymeric waveguides and the loss of waveguides were investigated for optical interconnection. Multimode polymeric waveguides were fabricated by hot embossing process. The replication of waveguide channels with hot embossing technology is of interest for single step processes that have to deliver a surface roughness far below the wavelength. Resulting waveguides exhibited a smooth surface profile and the square cross section of the core. The average propagation loss of these waveguides was approximately 0.2 dB/cm at 850 nm wavelength.

Deposition of nanocrystalline diamond and titanium oxide coatings onto pyrolytic carbon using CVD and sol–gel techniques

In this paper, we report the deposition of freestanding nanocrystalline diamond (NCD) films and dense nanocrystalline titanium oxide (nc-TiO 2) coatings onto pyrolytic carbon (PyC) using advanced chemical vapour deposition (CVD) and sol–gel techniques, respectively. The micro-structural properties, such as surface morphology and crystallinity, of PyC, NCD and nc-TiO 2 were characterised using XRD, Raman spectroscopy and SEM analysis. Freestanding NCD films were prepared using our newly introduced time-modulated CVD (TMCVD) process. Furthermore, conventional sol–gel technique was used to uniformly coat PyC with dense nc-TiO 2 coatings. The as-grown nc-TiO 2 coatings were found to display smooth surface profiles and the average crystallite size was in the range approximately 30–50 nm.

Time-modulated CVD on 0.8 μm-WC–10%-Co hardmetals: study on diamond nucleation and coating adhesion

In this study, we investigate the deposition of diamond films onto 0.8 μm-WC–10%-Co hardmetals using chemical vapour deposition (CVD). Polycrystalline diamond films were deposited using (i) constant methane (CH 4) flow, at 3 and 4.5 sccm, and (ii) modulated CH 4 flow at 4.5 sccm and 3 sccm for 8 min and 10 min, respectively. Constant flow of CH 4 into the vacuum chamber, during diamond CVD is the conventional approach to deposit diamond films onto a range of materials. The timed CH 4 modulations are an integral part of our recently proposed process, called time-modulated CVD (TMCVD). The TMCVD process increased drastically the number of diamond crystallites nucleating onto WC–Co. Furthermore, the time-modulated films exhibited (i) smooth surface profile, (ii) improved film coverage and (iii) better coating adhesion. The adhesion was characterised using conventional indentation tests. Data obtained from the micro-Raman spectroscopy technique was used to calculate the biaxial stresses. It is expected that the TMCVD process increases both the diamond nucleation processes and the coating adhesion possibly due to the secondary nucleation processes occurring during the high CH 4 bursts. It is highly likely that the mechanical interlock at the coating/substrate interface increases during the CH 4 pulse cycles.

Time-modulated CVD on 0.8 μm-WC–10%-Co hardmetals: study on diamond nucleation and coating adhesion

In this study, we investigate the deposition of diamond films onto 0.8 μm-WC–10%-Co hardmetals using chemical vapour deposition (CVD). Polycrystalline diamond films were deposited using (i) constant methane (CH 4 ) flow, at 3 and 4.5 sccm, and (ii) modulated CH 4 flow at 4.5 sccm and 3 sccm for 8 min and 10 min, respectively. Constant flow of CH 4 into the vacuum chamber, during diamond CVD is the conventional approach to deposit diamond films onto a range of materials. The timed CH 4 modulations are an integral part of our recently proposed process, called time-modulated CVD (TMCVD). The TMCVD process increased drastically the number of diamond crystallites nucleating onto WC–Co. Furthermore, the time-modulated films exhibited (i) smooth surface profile, (ii) improved film coverage and (iii) better coating adhesion. The adhesion was characterised using conventional indentation tests. Data obtained from the micro-Raman spectroscopy technique was used to calculate the biaxial stresses. It is expected that the TMCVD process increases both the diamond nucleation processes and the coating adhesion possibly due to the secondary nucleation processes occurring during the high CH 4 bursts. It is highly likely that the mechanical interlock at the coating/substrate interface increases during the CH 4 pulse cycles.