Metal electrodes patterning methods

The lift-off process is usually employed to fabricate metal electrodes. This method, as opposed to the wet-etch process, allows the dual-composition electrode to be patterned in a single step [747]. In order to achieve well-defined metal electrodes in a channel recess using the lift-off technique, the metal (Pt/Ta) will not be deposited onto the sidewalls of the photoresist structure (see Figure 2.32). This discontinuity of the deposited metal layer around the sidewalls allows metal on the resist to be removed cleanly from the surface without tearing away from the metal on the surface. Thus negative resists were used because they can be easily processed to produce negatively inclined sidewalls. To achieve this, the photoresist is subjected to underexposure, followed by overdevelopment [141]. 

Another interesting method for generating single-electron transistors is to prestructure the substrate surface, followed by deposition of the nanoparticles, and finally to place two or more metal electrodes across the nanoparticle chain. This method was described by Coskun et al. [67], who first spin-coated a cleaned silicon substrate with PMMA, and then structured the surface with EBL to define the desired patterns, treated the substrate vhth a aminopropyltriethoxysilane (APTES) solution. 

Fig. 1 Three different methods to pattern the CP layers. (A) Etching, e.g., using RIE A1 deposition of the patterned photoresist, A2 etching of the CP layer, A3 (wet chemical) etching of the metal layer, and finally A4 stripping of the photoresist. (B) Patterned electrodes Bl deposition of the patterned photoresist, B2 (wet chemical) etching of the metal layer, B3 stripping of the photoresist, B4 electrosynthesis of CP on the patterned metal electrode. (C) Resist holes Cl deposition of the patterned photoresist, C2 electrosynthesis of CP in the patterned photoresist layer, C3 stripping of the photoresist, C4 (wet chemical) etching of the metal layer, depending on the etchant a protective photoresist layer similar to A2 might be needed in this step...

Theoretically, electrical patterning is one the simplest method to structure materials since they can be patterned directly on the surface of an electrode. Creating conducting microelectrodes is, nowadays, fast and simple using micro and nanotechnology tools. Deposition and etching, or deposition followed by lift-off, are the conventional methods [35], Other solutions based on electrodeposition of metals... 

Detector elements 11 are formed on a ceramic substrate 1. Each detector element includes a photosensitive zone 9, an output terminal 4 and a common terminal S. The detector elements are arranged in an array protruding from a common metal line 3, which is connected to a terminal pad 6. The terminal electrodes and the common metal line are formed on a comb-like patterned photo-conductive layer 2. An aperture plate 7 of silicon or ZnS having apertures 8 formed therein by an anisotropic etching method is prepared. The purpose of the aperture plate is to restrict the field of view of the photosensitive zones. An auxiliary electrode 30 is formed on the aperture plate. When the aperture plate is assembled with the substrate using an adhesive, the auxiliary electrode is pressed against the common metal line and the common terminal, which together reduce the electrical resistance. 

The driving force behind the rapid development of powder diffraction methods over the past 10 years is the increasing need for structural characterization of materials that are only available as powders. Examples are zeolite catalysts, magnets, metal hydrides, ceramics, battery and fuel cell electrodes, piezo- and ferroelectrics, and more recently pharmaceuticals and organic and molecular materials as well as biominerals. The emergence of nanoscience as an interdisciplinary research area will further increase the need for powder diffraction, pair-distribution function (PDF) analysis of powder diffraction pattern allows the refinement of structural models regardless of the crystalline quality of the sample and is therefore a very powerful structural characterization tool for nanomaterials and disordered complex materials. 

Metal oxide nanocomposites were synthesized by electrical discharge method using a combination of aluminum and copper electrodes submerged into water. The crystal structure, lattice parameters and grain size of the nanopowders were determined by XRD using Cu K radiation (Fig. 3b). The XRD pattern exhibited the presence of cubic copper with a lattice constant of 0.3615 nm, as well as aluminum and copper oxide and hydroxide phases. The positions of all peaks were in agreement with the JCPDS standards. 

---