Search

An anti-sticking patterned metallic stamp for imprinting has been successfully fabricated in this study. Firstly, the amorphous phase transformation films of Ge2Sb2Te5 (GST) were deposited on the cleaned silicon substrates by DC sputtering system. The as-deposited GST film was then irradiated with femtosecond laser pulse through a photomask to induce the crystalline mark on the surface. The patterns were well-defined while the thermal diffusion length of the irradiated GST film was less than 1 nm. Due to the fact that the chemical properties between the amorphous region and crystalline mark were varied, the crystalline mark was etched by using nitric acid mixed with ethanol, and consequently a μm-patterned GST stamp was fabricated. For the purpose of reducing patterned GST stamp’s surface roughness to under Ra 5 nm, and for the fact that the bottom of the trench was fairly flat, the optimized processing parameters which use Taguchi methods were found to be within the irradiation time of 1 min, in the concentration of etching of 25 vol%, and etching time of 1 min. Owing to the patterned GST stamp has low surface energy than the patterned silicon stamp thus the SU-8 polymeric patterns were more successfully replicated and easily demolded.

Energy-yield loss caused by soiling of photovoltaic modules and concentrated solar power (CSP) mirrors in utility-scale power plants installed in semiarid lands and deserts would result in unsustainable demands for fresh water needed for cleaning. This paper reviews the progress of the electrodynamic screen (EDS) film technology for frequent water-free cleaning with low-energy requirements. Results presented here, based on laboratory-scale EDS-film-laminated solar panel cleaning, show that the output power can be restored higher than 95% of the initial power under clean conditions. For solar mirrors, the specular reflection efficiency can be maintained over 90% ensuring high efficiency of the CSP plants. Operation of the EDS film for maintaining high optical efficiency of solar collectors requires less than 0.2 Wh/m ${}^2$ /cleaning cycle. Principles, optical modeling, construction, lamination of the EDS films on modules and mirrors, and experimental data showing optical efficiency restoration without water consumption are presented. Current challenges in developing electrodes that would meet optical and conduction properties, low-cost production, and meeting long-term outdoor durability of the EDS films are discussed.

A 1064 nm fiber laser and a 355 nm ultraviolet solid-state laser with galvanometer scanners and F-theta lenses are used to rapidly etch the silver electrode pattern of a cholesteric liquid crystal display. These results of the two laser processes are that the 1064 nm laser effectively reduces the damage to the liquid crystal layer and underlying indium tin oxide layer, and reduces the heat-affected zone of the ablated silver electrode.

When ethylene/ammonia (C2H4/NH3) mixtures are used to deposit carbon films by thermal chemical vapor deposition (CVD), effects of C2H4/(C2H4+NH3) ratios on the deposition rate and microstructures of carbon films are investigated. Experimental results reveal that the deposition rate of carbon films increases with the C2H4/(C2H4+NH3) ratio, and also, raises with the residence time, deposition temperature, and working pressure. The kinetics of this thermal CVD process is discussed. The deposition rate of carbon films is proportional to the C2H4/(C2H4+NH3) ratio with a power of first order, which is resulted from the adsorption of remaining precursor gas C2H4 on the silica glass plate substrate. Few nitrogen and hydrogen atoms are incorporated into carbon films. The activation energy (=152 kJ/mole) of carbon deposition is related to the activation energy of C2H4 dissociation. The crystallinity, degree of ordering, and nano-crystallite size of carbonfilms decrease with increasing theC2H4/(C2H4+NH3) ratio, while the fraction of sp 3 carbon sites of carbon films increase. Finally, the results of thermal CVD carbon deposition using C2H4/NH3 mixtures are

This paper gives a detail presentation of a fully pseudo-differential open-loop BiCMOS track-and-hold amplifier THA for 9-b operation up to 1 GSample/s. The proposed THA not only uses a double sampling technique to increase the achievable sampling frequency by a factor of two, but also employs a linearization technique to reduce the gain dependence of the THA input stage upon the input level. Moreover, timing mismatch between the clock signals of the two interleaved paths is minimized by means of a timing mismatch insensitive clock generator controlled by a common master sampling clock. The post-layout simulation results using TSMC 75GHz fT, 0.35-µm SiGe BiCMOS technology show that the proposed architecture achieve a signal to noise and distortion ratio of 53.92dB, equivalent to the effective number of bits of 8.66-b for 58.11MHz input frequency at 1 GSample/s. The power dissipation of the whole THA is 161.1mW. Copyright © 2012 John Wiley & Sons, Ltd.

Compared to the OLED with planar substrate, the luminous current efficiency and luminous power efficiency of the device are shown 25% and 36% enhancement, respectively, by attaching the microlens array film (MAF) having a fill factor of 0.788 and a height ratio of 0.46. Both the luminous current efficiency and luminous power efficiency of the organic light-emitting device (OLED) increased monotonically with increasing the fill factor of MAFs, regardless of their arrangements. However, the curve-fitting equation of the luminous power efficiency has a negative second-order term, which shows a saturation phenomenon. Based on the experimentally verified configuration, simulation showed that the luminous current and power efficiencies also increase along with increasing height ratio and they were found to have more pronounced saturation phenomena. As for the spectral characteristics, the peak wavelength of the planar OLED spectra got blue-shift and the full-width-at-half-maximum (FWHM) of its spectra decreased with increasing the viewing angles due to the microcavity theories. After MAFs are attached to the OLED, the FWHM of the OLED spectra decreased linearly by increasing the fill factor of the MAFs. We also observe blue shifts at different viewing angles which is the evidence that the waveguiding modes are being extracted. The saturation phenomena of efficiency enhancement imply that high fill factor and large height ratio of MAFs will certainly benefit for efficiency enhancement, however, full factor cases are not always the most desirable. Optimal fill factor and height ratio, which may be less than unity, will gain the best efficiency enhancement, suffer from less color deviation, and make fabrication easier.

Carbon nanotubes (CNTs) have potential as a transparent conductive material with good mechanical and electrical properties. However, carbon nanotube thin film deposition and etching processes are very difficult to pattern the electrode. In this study, transparent CNT film with a binder is coated on a PET flexible substrate. The transmittance and sheet resistance of carbon nanotube film are 84% and 1000 Ω/□, respectively. The etching process of carbon nanotube film on flexible substrates was investigated using 355 nm and 1064 nm laser sources. Experimental results show that carbon nanotube film can be ablated using laser technology. With the 355 nm UV laser, the minimum etched line width was 20 μm with a low amount of recast material of the ablated sections. The optimal conditions of laser ablation were determined for carbon nanotube film.

Characteristics of carbon coatings on optical fibers prepared by radio-frequency plasma enhanced chemical vapor deposition with different H 2 /C 2 H 2 ratios are investigated. Five kinds of carbon coatings are prepared with H 2 /C 2 H 2 ratios of 2, 4, 6, 8, and 10. Experimental results show that the deposition rate and surface roughness of carbon coatings decrease as the H 2 /C 2 H 2 ratio increases. When the H 2 /C 2 H 2 ratio changes from 2 to 8, the increase of H 2 /C 2 H 2 ratios detrimentally yields sp 3 carbon atoms and sp 3 -CH 3 bonds in the carbon coatings. However, when the H 2 /C 2 H 2 ratio exceeds 8, the hydrogen retards the growth of the graphite structure. Moreover, the redundant hydrogen radicals favor bonding with the dangling bonds in the coating surface. Therefore, when the H 2 /C 2 H 2 ratio increases from 8 to 10, the amounts of sp 3 carbon atoms and sp 3 -CH 3 bonds in the carbon coatings increase. At an H 2 /C 2 H 2 ratio of 8, the carbon coating exhibits excellent water-repellency and thermal-loading resistance, and so this ratio is the best for producing a hermetically sealed optical fiber coating.

In high-gain fully differential operational amplifier (FD op-amp) design, the output common-mode (CM) voltage of the FD op-amp is quite sensitive to device properties and mismatch. It is, therefore, necessary to add an additional control circuit, referred to as the common-mode feedback (CMFB) circuit, to stabilize the output CM voltage at some specified voltage. In this paper, we present a high linear CMOS continuous-time CMFB circuit based on two differential pairs and the source degeneration using MOS transistors. Theoretical analysis and SPICE simulation results are provided to validate our proposed ideas. Finally, we present two design applications of the proposed configuration, one is the FD folded-cascode op-amp and the other is the Multiply-by-Two circuit which is the key component in the popular 1.5 bit/stage pipelined analog-to-digital converter. Comparison with conventional topologies shows that the new configuration has attractive characteristics concerning their implementation in high linear analog integrated circuits. Copyright © 2010 John Wiley & Sons, Ltd.

In this study, we used diffuser lithography to fabricate microlens arrays with the height smaller or larger than the radius of curvature of microlenses. The experimental results showed that the fill factor of the duplicated microlens arrays can be adjusted not only by the gap distance of clear holes on the photomask but also by the UV exposure dose. The surface morphology of the duplicated microlenses can also be altered by the exposure dose, the gap distance, and the thickness of the photomask. For example, a spherical microlens array having a fill factor very near 100% could be fabricated by using a 10-@mm gap distance and an exposure dose of 300mJ/cm^2.

The effect of the substrate size on the properties of carbon coatings that are deposited on the glass cylinder substrates by thermal chemical vapor deposition is investigated. Experimental results show that the deposition rate of carbon coatings decreases as the diameter of the glass cylinder increases, because the residence time of the precursor gas in the deposition zone decreases and the deposition area of the substrate increases. Experimental results also reveal that the surface roughness and electrical resistivity of carbon coatings decrease as the diameter of the glass cylinder increases, while the degree of ordering and crystallite size of the carbon coatings increase.

When carbon films are prepared using thermal CVD, the properties of carbon films are affected by many factors, such as the precursor gas, deposition temperature, and working pressure. It is believed that the substrate size is also an important factor in preparing carbon films by thermal CVD. Hence, this study investigates the effect of substrate size on the properties of carbon coatings that are deposited on glass plate substrates in a quartz tube furnace using thermal CVD. Experimental results show that the deposition thickness decreases with increasing silica glass-plate width, indicating that the deposition rate of carbon coatings decreases with increasing deposition area of the glass plate substrate. Meanwhile, the ordered degree and crystallite size of carbon films increase with increasing glass-plate width, while the number and size of particles on carbon-coating surfaces, surface roughness, and electrical resistivity of carbon films decrease. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of high (∼1000 ppm) and low (∼200 ppm) hydroxyl (OH) content on second-order optical nonlinearity (χ (2) ) in thermally poled type-III fused silica (KU-1) are studied. Type-III fused silica with low OH content poled under 275 °C with 6 kV for various poling durations shows much stronger intensity of second-harmonic generation (SHG) signals compared with that with high OH content poled under the same condition. A near-anodic uniform surface and uniform bulk χ (2) profiles which are opposite in sign are calculated to be formed in the fused silica poled longer than the optimum poling duration. A two-charge-carrier model with charge injection and non-blocking electrodes is given to explain the creation of the χ (2) profile. More OH is believed to decrease the mobility of alkali ions during poling.

In this paper, we present and analyze the influences of the fill factor and the height ratio of square-based microlens arrays on the optical characteristics of an organic light-emitting device (OLED). These properties include spectral shift, CIE coordinates, viewing-angle dependence, luminous current efficiency and luminous power efficiency. Both the luminous current efficiency and luminous power efficiency of the OLED were found to increase linearly with increasing the fill factor of microlenses. It is also found that the full width at half maximum (FWHM) of the OLED spectra and CIE coordinate decreased linearly with increasing the fill factor of the microlenses. Besides, the efficiency improvement of the OLED increased with the height ratio of attached microlenses. Compared to the OLED, the luminous current efficiency and luminous power efficiency of the device can be enhanced by 42% and 47%, respectively, by attaching the microlens array having a fill factor of 90% and a height ratio of 0.57. We also observed blue shifts at different viewing angles when microlens arrays were attached to the OLED, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifted and the FWHM decreased with increasing the viewing angles due to the microcavity effect.

The effect of substrate temperature on the properties of carbon-coated optical fibers prepared by plasma enhanced chemical vapor deposition is studied. The substrate temperatures were set at 20, 150, 300, and 450 °C. The deposition rate of carbon films decreases with increasing substrate temperature, while the self-bias voltage during deposition increases. The results of analysis by Fourier transform infrared spectroscopy and determination of the optical band gap show that sp 2 carbon sites in the coating structure increase as the substrate temperature increases. When the substrate temperature changes from 20 to 300 °C, the carbon coating surface becomes more compact. Alternatively, when the substrate temperature is increased to 450 °C, many nano-scale hillocks appear on the carbon coating surface. The carbon coating prepared at the substrate temperature of 300 °C has the highest water contact angle of 90° and an excellent ability to sustain the thermal loading, so it is the best for production of carbon-coated optical fibers.

We report a unique approach for producing one-dimensional gold-nanoparticle patterns with single-particle resolution in which the linewidth is only limited by the particle size. In this approach, a focused electron beam was first utilized to generate a positive charge layer on a SiO 2 surface. Biotinated DNA molecules attracted by these positive charges were subsequently used to grasp Au-nanoparticles revealing the e-beam exposure patterns. Due to repulsive force between Au colloidal particles, the particles in the single-line patterns were orderly separated. We further show that the single-line patterns hold potential in nano-photonics and nano-electronics. For the latter, we demonstrate that the line patterns can serve as a template for conductive nanowires of high or low resistance. While low resistance wires showed linear current-voltage characteristics with an extremely high maximum allowed current density, the high resistance wires exhibited charging effect with clear Coulomb oscillation behavior at low temperatures. This demonstrates that the technique is capable of producing interconnects as well as single-electron-transistors, and opens up possibilities for fabrication of integrated circuits.

In this paper, we present and analyse the optical characteristics, such as spectral shift, CIE coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency, of an organic light-emitting device (OLED) with a commercial diffuser film or a brightness-enhancement film (BEF) attached. Compared to a planar green OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 29% and 23%, respectively. The overall luminous power efficiencies are enhanced by 28% and 7%. Compared to the planar green device, we observe blue shifts at different viewing angles when microstructured films are attached, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifts and the full width at the half maximum (FWHM) decrease with increasing viewing angles due to the microcavity effect. When the diffuser is attached, the spectral peak has a constant blue shift (6 nm) compared to that of the planar OLED. On the other hand, in the BEF case, the spectral shift depends on the viewing angle (2–12 nm blue shifts from 0 to 80°). This is due to the different operating principles (scattering and redirected light) of the diffuser and BEF. Since the transmittance spectra of both the diffuser film and the BEF are flat over the visible range, it is suitable for lighting applications by using white OLED. When attaching the films on a commercial white OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 34% and 31%, respectively. The overall luminous power efficiencies are enhanced by 42% and 8%.

The bulge test was used to measure the mechanical properties of polymer thin films with thickness in the range of 77 nm to 352 nm. The mechanical properties of polymeric thin films were extracted by comparing differences between curves of load vs. bulge height obtained from composite film configurations with and without the polymer layer. Both square and long rectangular windows were used to obtain the Poisson ratio and Young's Modulus. Composite film with 230 nm silicon nitride layer and 30 nm Al layer has a composite Poisson ratio of 0.29 and a Young's Modulus of 234 ± 0.8 GPa. The Poisson ratio extracted for a 352 nm Poly(methyl methacrylate)-based thermoplastic polymeric thin film was 0.39. The Young's Modulus extracted for the 77 nm thick polymeric film is 4.9 ± 0.8 GPa and for the 352 nm thick film is 5.8 ± 0.2 GPa. In the thickness range investigated, no clear thickness dependence of the Young's modulus was observed using the Bulge test.

The stress-induced supporting mechanism consisting of stress-induced bending beams and novel locking component used to assemble the micromachined optical devices has been realized. The tip deflection of the stress-induced bending beams has been exploited to lift up the micromachined devices. Based on the MUMPs platform, this study has successfully established an improved surface micromachining process (MUMPs-like process) to enhance the reliability of the stress-induced beams. According to the reliability test, the variation of the tip displacement is <

A novel micromachined torsional mirror for use as an optical scanner is reported in this study. The proposed micromachined torsional mirror exploits novel electrostatic actuators and a reinforced thin-film mirror plate to improve the performance of the device. The electrostatic actuator is actuated by near gap-closing electrodes so as to decrease the driving voltage. Moreover, the actuator employs a lever mechanism to magnify its output displacement. A torque generator is implemented by combining two electrostatic actuators, which prevents the mirror plate from wobbling. A reinforced rib is used to stiffen the thin-film mirror plate to improve the optical performance of the scanner. In order to demonstrate the proposed concept, micromachined torsional mirrors were fabricated through the integration of DRIE, surface, and bulk micromachining processes. Measurements revealed that the proposed torsional mirror could operate at a low driving voltage, the scanning frequency of the mirror can reach 17.7 kHz, and the optical scan angle is 5°.

The undercut process of the micromachined structures on a (1 1 1) oriented silicon wafer is studied in this paper. As observed in the experiment, the undercut of a cantilever on (1 1 1) wafer is along the width of the beam. According to the undercut mechanism, the advantages of fabricating a cantilever on (1 1 1) wafer are three-fold: (1) significantly reduce the etching time and obtain an ideal clamped boundary in the mean time; (2) the thickness as well as the moment of inertia of the cantilever is closer to the ideal case; (3) the flexural rigidity of the cantilever is constant along the beam axis. Consequently, the micromachined cantilever on a (1 1 1) wafer is more appropriate in various applications. For instance, it is more appropriate to fabricate the diagnostic microstructures on the (1 1 1) wafer than on the (1 0 0) wafer in determining the thin film residual stress.

The stiffness of a micromachined beam is usually restricted to the thickness of the thin-film materials. In this research, the rib-reinforced beam is proposed to increase the bending stiffness of thin-film micromachined structures. The increase of the bending stiffness of micromachined cantilevers has been demonstrated through analytical and experimental approaches. The fabrication processes required for the structure are compatible with the standard bulk micromachining processes. The primary contribution of the proposed design is that it can remarkably increase the bending stiffness of the micromachined structure without changing the thickness of the films. Hence, the design of the micromachined structure becomes more flexible. In application of the rib-reinforced structure, a micromachined lever mechanism is also designed and fabricated.

The vertical comb-drive actuator (VCA) is a promising component to drive analog as well as scanning micromirrors. This work demonstrates the concept of using ldquosequential engagement of vertical comb electrodesrdquo to improve the linearity and to maximize the deflection for analog micromirror. This concept is achieved by varying the in-plane distribution of comb electrodes. The simulation and experiment results of vertical comb-drive actuator VCA with four different electrode-distribution designs demonstrated the feasibility of this study. In comparison, a modified (curved-profile) VCA was remarkably improved the performance of conventional (straight-profile) VCA. Experiments show that the curved-profile VCA improves the nonlinearity by 34% and increases the maximum angular motion for 2.3-fold.

This work presents a novel two-axis gimbaled mirror for optical scanning applications. This scanner has been implemented using the molded surface-micromachining and bulk etching release (MOSBE II) process. Thus, the vertical comb-drive actuators are employed to realize the large stroke. The thin-film electrical routings are employed to drive the actuators individually. The rib-reinforced structures are exploited to increase the stiffness of mirror plate and supporting frame. In addition, the moving space created by backside deep reactive ion etching enables the mirror to perform large out-of-plane angular motion. The measured radius of curvature of reinforced mirror plate is 0.43 m. The maximum scanning angle of two driving axis are plusmn3.8deg at 55 V and plusmn2.4deg at 100 V, respectively. The resonant frequencies associated with the scanning modes are 5.8 and 7.8m kHz, respectively. In addition, the two-dimensional scanning images such as Lissajous patterns are also demonstrated

In order to increase the recording capacity of optical disc, electron beam (EB) mastering technology is used to replace the traditional laser beam mastering technology. Without the optical diffraction limit, EB mastering is one of the most possible candidates that can reach the demand of going beyond 100 GB/layer in capacity of an optical disc. Although this technology can satisfy the requirement of ultra-high recording density, a poor throughput, however, is the main drawback. In our work, a chemically amplified resist, which has much lower required dosage for exposure than the traditional Polymethylmethacrylate resist, was adopted to increase the recording velocity. The stamper of newly announced optical disc, Blu-ray disc (BD, 25-27 GB/layer) and even higher capacity (50 GB) have been successfully manufactured in our work. Because of the advanced technology, it has great possibility that the next generation optical disc, BD and the following ultrahigh-capacity disc will be manufactured by EB mastering technology.

A series of Parylene C film/silicon substrate bilayer microcantilever beams were fabricated by microelectromechanical processes for the study of residual stresses. The Parylene C films of 2 µm thickness were deposited on the Si substrates with various thicknesses. After deposition at room temperature, deflection of the beam was observed with deposited Parylene C on the concave side. While Parylene C has a higher coefficient of thermal expansion than Si, this deflection is believed to result from the thermal mismatch between Parylene C and Si, and the temperature of monomer gas (which is formed at 690 °C) flowing across the sample could be higher than 25 °C. It is estimated to be 73 °C based on the fitting of the curvature versus substrate thickness relation between the measurements and analytical solutions. In this case, Parylene C films are subjected to tension. In addition, the residual stress in the Parlyene C film decreases with decreasing substrate thickness.

This study reports a novel micro electrostatic vertical comb-drive actuator (VCA) driven by the photovoltaic effect that results from incident light. The vertical comb electrodes have a pn junction structure (named pn-combs). The VCA with pn-combs can be driven by the photovoltaic effect. The combination of the photovoltaic effect and reverse bias can further increase the driving amplitude of the VCA. To demonstrate the feasibility of the proposed concept, the VCA with pn-combs was fabricated on an epitaxial silicon wafer (epi-wafer) and successfully driven resonantly by intensity-modulated laser light. The first torsional mode of a typical fabricated VCA is at 1.46 kHz. Moreover, VCA driven using (1) optical driving, and (2) optical driving with dc reverse bias, were also demonstrated. The angular displacement of the VCA was ±3.8 m deg by optical driving. The angular displacement of the VCA significantly increased to ±41 m deg after applying an additional dc reverse bias of 5 V. (Some figures in this article are in colour only in the electronic version)