silicon and potassium-hydroxide

Microfluidics is an emerging field with various applications. In situ analysis of liquids inside microfluidic channels is an important research subject for any of these applications. On the other hand, attenuated total reflectance infrared spectroscopy (ATR-IR) is a strong surface detection method. Recently, there have been various attempts to use ATR-IR for detection of liquids inside microfluidic channels. Micromachined silicon ATR-IR (μSi-ATR-IR) is an emerging analytical tool for micro/nanofluidics. This paper reviews μSi-ATR-IR micro/nanofluidics detection devices and discusses the application fields, capabilities, advantages, and disadvantages of the method.

Topics: Equipment Design; Hydroxides; Microfluidic Analytical Techniques; Nanotechnology; Potassium Compounds; Silicon; Spectroscopy, Fourier Transform Infrared

The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells.

Topics: Acids; Electric Power Supplies; Equipment Design; Equipment Failure Analysis; Hydroxides; Nanoparticles; Potassium Compounds; Silicon; Solar Energy; Surface Properties; Wettability

Three-dimensionally structured gold membrane films with nanopores of defined, periodic geometries are designed and fabricated to provide the spatially localised enhancement of electric fields by manipulation of the plasmons inside nanopores. Square nanopores of different size and orientation relative to the pyramid are considered for films in aqueous and air environments, which allow for control of the position of electric fields within the structure. Designs suitable for use with 780 nm light were created. Here, periodic pyramidal cavities produced by potassium hydroxide etching to the {111} planes of (100) silicon substrates are used as templates for creating a periodic, pyramidal structured, free-standing thin gold film. Consistent with the findings from the theoretical studies, a nano-sized hole of 50 nm square was milled through the gold film at a specific location in the cavity to provide electric field control which can subsequently used for enhancement of fluorescence or Raman scattering of molecules in the nanopore.

Topics: Electricity; Fluorescence; Gold; Hydroxides; Models, Theoretical; Nanopores; Potassium Compounds; Silicon; Spectrum Analysis, Raman

A novel technique based on silicon micromachining for fabrication of linear arrays of high-frequency piezoelectric micromachined ultrasound transducers (pMUT) is presented. Piezoelectric elements are formed by deposition of lead zirconia titanate into etched features of a silicon substrate such that the depth of these features determine the element thickness and hence the resonance frequency. The process leaves a near planar surface which is ideal for further wafer level processing such as top electrode and interconnect formation. A fabricated element is characterized by pulse echo response.

Topics: Algorithms; Hydroxides; Lead; Potassium Compounds; Silicon; Titanium; Transducers; Ultrasonography; Zirconium

It is shown that the resonant frequencies and the transmission spectra of ring resonators can be adjusted by depositing or etching the cladding nitride layer on the ring waveguide without introducing an extra loss or extra variations of channel spacing. The cladding nitride layer increases the minimum width of the gap in the coupling region to larger than 150nm which makes it possible to consider photolithography instead of E-beam lithography for the typical design rule of ring filters. KOH silicon etching can also adjust not only the resonance frequencies but also coupling coefficients with a small sacrifice of guiding loss.

Topics: Algorithms; Equipment Design; Hydroxides; Materials Testing; Models, Statistical; Optics and Photonics; Potassium Compounds; Silicon; Silicon Compounds; Spectrum Analysis, Raman; Temperature; Time Factors

The anisotropic wet micromachining of silicon, based on a water solution of potassium hydroxide (KOH), is a standard fabrication process that is extensively exploited in the realization of very complex microsystems, which comprise cantilevers, membranes, and bridges. A nanostructured self-assembled biofilm of amphiphilic proteins, the hydrophobins, was deposited on crystalline silicon by solution deposition and characterized by variable-angle spectroscopic ellipsometry (VASE). This procedure formed chemically and mechanically stable mono- and multilayers of self-assembled proteins. The biomolecular membrane has been tested as masking material in the KOH wet etch of the crystalline silicon. The process has been monitored by VASE and atomic force microscopy measurements. Because of the high persistence of the protein biofilm, the hydrophobin-coated silicon surface is perfectly protected during the standard KOH micromachining process.

Topics: Anisotropy; Biofilms; Fungal Proteins; Hydroxides; Membranes, Artificial; Potassium Compounds; Silicon

Silicon surface hydrophobicity has been varied by using silane treatments on silicon pyramid surfaces generated by KOH anisotropic etching. Results demonstrated that by altering the surface hydrophobicity, the apparent contact angle changed in accord with the Wenzel equation for surface structures with inclined side walls. Hierarchical structures were also constructed from Si pyramids where nanostructures were added by Au-assisted electroless HF/H2O2 etching. Surface hydrophobicity and superhydrophobicity were achieved by surface modification with a variety of silanes. Stability of the Cassie state of superhydrophobicity is described with respect to the Laplace pressure as indicated by the water droplet meniscus in contact with the hierarchical structures. The contact angle hysteresis observed is also discussed with respect to water/substrate adhesion.

Topics: Anisotropy; Hydrofluoric Acid; Hydrogen Peroxide; Hydrophobic and Hydrophilic Interactions; Hydroxides; Microscopy, Electron, Scanning; Models, Statistical; Potassium Compounds; Pressure; Silanes; Silicon; Substrate Specificity; Surface Properties; Temperature; Time Factors; Water

To develop x-ray mirrors for micropore optics, smooth silicon (111) sidewalls obtained after anisotropic wet etching of a silicon (110) wafer were studied. A sample device with 19 microm wide (111) sidewalls was fabricated using a 220 microm thick silicon (110) wafer and potassium hydroxide solution. For what we believe to be the first time, x-ray reflection on the (111) sidewalls was detected in the angular response measurement. Compared to ray-tracing simulations, the surface roughness of the sidewalls was estimated to be 3-5 nm, which is consistent with the atomic force microscope and the surface profiler measurements.

Topics: Anisotropy; Hydroxides; Microscopy, Atomic Force; Optics and Photonics; Physics; Potassium Compounds; Scattering, Radiation; Semiconductors; Silicon; Surface Properties; X-Rays