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Purpose -Nanogap electrodes have important applications in power saving devices, electrochemical sensors and dielectric detections of biomolecules. The purpose of this paper is to report on the fabrication and characterization of polysilicon nanogap patterning using novelties technique. Design/methodology/approach -Polysilicon material is used to fabricate the nanogap structure and gold is used for the electrode and two chrome masks are used to complete this work; the first mask for the nanogap pattern and a second mask for the electrode. The method is based on the control of the coefficients (temperature and time) with an improved pattern size resolution thermal oxidation. Findings -Physical characterization by scanning electron microscopy (SEM) demonstrates such nanogap electrodes could be produced with high reproducibility and precision. Electrical characterization shows that nanogap enhanced the sensitivity of the device by increase the capacitance and the conductivity as well. They have also good efficiency of power consumption with high insulation properties. Originality/value -With this technique, there are no principal limitations to fabricating nanostructures with different layouts down to several different nanometer dimensions. The paper documents the fabrication of nanogaps electrodes on a polysilicon, using low-cost techniques such as vacuum deposition and conventional lithography. Polysilicon is a low-cost materials and has desirable properties for semiconductor applications. A method of preparing a nanogap electrode according to the present innovation has an advantage of providing active surface that can easily be modified for immobilizations of biomolecules.

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We have demonstrated a simple and low-cost method to fabricate poly-silicon microwire by conventional photolithography technique. There are two different steps process flow were involved in the conventional photolithography technique which are employed the positive resist as a mask and aluminium (Al) as hard mask. Low pressure chemical vapour deposition (LPCVD) was used to deposit 50 nm poly-silicon layer on the Si-SiO 2 -Si 3 N 4 layer. Wire mask must be first designed using AutoCAD before patterning onto chrome mask. Initially the 300 nm thick layer of positive resist is coated on the sample. Subsequently, the coated sample were exposed to UV light for 10 seconds and followed by development process. The critical part in this development process is to control the development time and resist profile. There are three types of resist profile problems such as underdevelopment, incomplete development and overdevelopment resist profile. These resist profiles problems can negatively affect in the subsequent etch process. Next process is an etching process. For positive resist as a mask process flow, the developed sample was loaded into SAMCO Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) 10iP to anisotropic etching of poly-silicon for 7 seconds. Meanwhile, for Al as a hard mask, the developed sample was dipped into Aluminium (Al) etchant for 3 minutes then followed by resist stripping and anisotropic etching of poly-silicon as similar to the resist mask process flow. Finally, the dimensions and etch profiles of < 1um poly-silicon microwire were morphologically characterized using optical microscopy.

We report a thermal oxidation process for the fabrication of nanogaps of less than 50 nm in dimension. Nanogaps of this dimension are necessary to eliminate contributions from double-layer capacitance in the dielectric detection of protein or nucleic acid. The method combines conventional photolithography and pattern-size reduction techniques. The gaps are fabricated on polysilicon-coated silicon substrate with gold electrodes. The dimensions of the structure are determined by scanning electron microscopy (SEM). An electrical characterization of the structures by dielectric analyzer (DA) shows an improved conductivity as well as enhanced permittivity and capacity with the reduction of gap size, suggesting its potential applications in the detection of biomolecule with very low level of power supply. Two chrome Masks are used to complete the work: the first Mask is for the nanogap pattern and the second one is for the electrodes. An improved resolution of pattern size is obtained by controlling the oxidation time. The method expected to enable fabrication of nanogaps with a wide ranging designs and dimensions on different substrates. It is a simple and cost-effective method and does not require complicated nanolithography process for fabricating desired nanogaps in a reproducible fashion.

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Food contamination has become critical issue and is being worse due to the insensitive detection devices. One of the dangerous food contaminations is by Escherichia coli (E.coli) O157:H7, one of the harmful bacterial pathogens which is distributed in soil, marine and estuarine waters, the intestinal tract of animals, or water contaminated with fecal matter. A small amount of E.coli with the dose fewer than 100 organisms in food products or water is enough to cause serious gastrointestinal illness to human. Hence, the ultra-high sensitive, label free biosensors have been designed in this research for the low concentration E.coli detection. Surface acoustic waves (SAW) devices have been initially developed and used for the high-volume low-cost TV component. Due to the ultra-sensitivity to the surface perturbation, SAW based devices have been modified to be sensors. Initially, SAW sensors were developed for gas detections and have been moving towards biological detections recently. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based types is most suitable for the liquid based application as it has the advantage of acoustic energy is not being radiated into liquid. However, the main SHSAW design components are the operating frequency and wave length. These are strictly depended on the inter digital transducers (IDTs) design. Therefore, this paper is presenting the IDTs design concept and pattern development by using computer aid design (CAD) software.

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