W. Kern

Bio: W. Kern is an academic researcher. The author has contributed to research in topics: Semiconductor & Hydrogen peroxide. The author has an hindex of 1, co-authored 1 publications receiving 920 citations.

Etch rates for micromachining processing

Abstract: The etch rates for 317 combinations of 16 materials (single-crystal silicon, doped, and undoped polysilicon, several types of silicon dioxide, stoichiometric and silicon-rich silicon nitride, aluminum, tungsten, titanium, Ti/W alloy, and two brands of positive photoresist) used in the fabrication of microelectromechanical systems and integrated circuits in 28 wet, plasma, and plasmaless-gas-phase etches (several HF solutions, H/sub 3/PO/sub 4/, HNO/sub 3/+H/sub 2/O+NH/sub 4/F, KOH, Type A aluminum etchant, H/sub 2/O+H/sub 2/O/sub 2/+HF, H/sub 2/O/sub 2/, piranha, acetone, HF vapor, XeF/sub 2/, and various combinations of SF/sub 6/, CF/sub 4/, CHF/sub 3/, Cl/sub 2/, O/sub 2/, N/sub 2/, and He in plasmas) were measured and are tabulated. Etch preparation, use, and chemical reactions (from the technical literature) are given. Sample preparation and MEMS applications are described for the materials.

Gas detection by means of surface plasmon resonance

Abstract: A theoretical and experimental investigation of the possibilities of using surface plasmon resonance for gas detection is presented. The system used in the experiments was an organic layer that reversibly absorbs the anaesthetic gas halothane. The method was shown to be sensitive to variations in the optical properties of the film upon gas exposure down to the ppm range. Possible developments of the method are also discussed.

Self assembled monolayers on silicon for molecular electronics.

Abstract: We present an overview of various aspects of the self-assembly of organic monolayers on silicon substrates for molecular electronics applications. Different chemical strategies employed for grafting the self-assembled monolayers (SAMs) of alkanes having different chain lengths on native oxide of Si or on bare Si have been reviewed. The utility of different characterization techniques in determination of the thickness, molecular ordering and orientation, surface coverage, growth kinetics and chemical composition of the SAMs has been discussed by choosing appropriate examples. The metal counterelectrodes are an integral part of SAMs for measuring their electrical properties as well as using them for molecular electronic devices. A brief discussion on the variety of options available for the deposition of metal counterelectrodes, that is, soft metal contacts, vapor deposition and soft lithography, has been presented. Various theoretical models, namely, tunneling (direct and Fowler-Nordheim), thermionic emission, Poole-Frenkel emission and hopping conduction, used for explaining the electronic transport in dielectric SAMs have been outlined and, some experimental data on alkane SAMs have been analyzed using these models. It has been found that short alkyl chains show excellent agreement with tunneling models; while more experimental data on long alkyl chains are required to understand their transport mechanism(s). Finally, the concepts and realization of various molecular electronic components, that is, diodes, resonant tunnel diodes, memories and transistors, based on appropriate architecture of SAMs comprising of alkyl chains (sigma- molecule) and conjugated molecules (pi-molecule) have been presented.

Comparison of chemical cleaning methods of glass in preparation for silanization

Abstract: The uniform deposition of a silane monolayer upon glass has been shown to require small amounts of water along with hydroxyl groups in an isolated or geminal configuration on the substrate surface. In order to expose these groups, organic compounds at the surface must be removed. We present a qualitative evaluation of eight chemical methods commonly used to clean glass microscope slides in preparation for silanization. Mean contact angle of deionized water was measured before covalent attachment of (3-mercaptopropyl)triethoxysilane to assess the efficacy of each procedure. Contact angles were also measured after silanization as a means of determining the uniformity and reproducibility of the silane monolayer. The results indicate that a 1:1 methanol/HC1 wash followed by a bath in concentrated H2SO4 removes surface contaminants most effectively and allows for a very even silanization of the glass surface.

Vascularized and Complex Organ Buds from Diverse Tissues via Mesenchymal Cell-Driven Condensation

Abstract: Transplantation of in-vitro-generated organ buds is a promising approach toward regenerating functional and vascularized organs. Though it has been recently shown in the context of liver models, demonstrating the applicability of this approach to other systems by delineating the molecular mechanisms guiding organ bud formation is critical. Here, we demonstrate a generalized method for organ bud formation from diverse tissues by combining pluripotent stem cell-derived tissue-specific progenitors or relevant tissue samples with endothelial cells and mesenchymal stem cells (MSCs). The MSCs initiated condensation within these heterotypic cell mixtures, which was dependent upon substrate matrix stiffness. Defining optimal mechanical properties promoted formation of 3D, transplantable organ buds from tissues including kidney, pancreas, intestine, heart, lung, and brain. Transplanted pancreatic and renal buds were rapidly vascularized and self-organized into functional, tissue-specific structures. These findings provide a general platform for harnessing mechanical properties to generate vascularized, complex organ buds with broad applications for regenerative medicine.