In this thesis, the development of a novel experimental technique for measuring the spontaneous, stochastic work function (WF) fluctuations of conducting polymer films, at equilibrium, is discussed. Polyaniline (PANI) is studied as a representative conducting polymer. This technique utilizes an insulated-gate field-effect transistor (IGFET) with PANI gate electrode (PANI-IGFET). The fluctuations of PANI WF are transduced into measurable drain current fluctuations of the device. By analyzing these fluctuations while systematically controlling the temperature, electric field and doping level, a model of WF fluctuations in PANI films is developed. These experiments suggest that the source of WF fluctuations is the hopping of charge carriers, or trapping/detrapping of charge carriers, around the Fermi level of the PANI film at the PANI-insulator interface. This process is thermally activated with a field and doping dependent activation energy in the range of 0.1 to 0.5 eV. Thus, this new technique provides detailed information about charge-carrier dynamics in the space-charge region of the PANI film, at equilibrium. These results have important implications for organic electronics and furthering fundamental understanding of the relationship between doping, disorder and work function in organic semiconductors.

<p>Controlling the properties of single walled carbon nanotubes (SWNTs) is the major challenge toward their future applications. This dissertation describes several contributions to this chanllenge. </p><p>This dissertation begins with the brief review on carbon nanotubes (CNTs), including discovery, structure, properties, challenges, synthesis and applications. The remaining parts can be divided into three sections. They demonstrate the control of SWNT properties as well as their devices by direct synthesis and metal decoration. </p><p>Two studies are described on the control of SWNT properties by direct synthesis. The first demonstrates the controlled synthesis of SWNTs in terms of their diameter, uniformity, and density by the chemical vapor deposition (CVD) method. The approaches employed include using uniform nanoparticles with specific sizes as catalysts to grow different diameter SWNTs, specially small diameter tubes less than 1 nm; using laser irradiation to grow uniform and high quality SWNTs; and changing the gas flow pattern to obtain different density. The second study demonstrates the growth of aligned SWNTs by flow and substrate guidance. Horizontally aligned ultralong nanotubes are synthesized on Si substrate by both high flow and low flow. The guided growth by the quartz substrate is shown by a large variety of metal catalysts to further the understanding of the growth mechanism. Moreover, top gated FETs have been explored for the selective growth of purely semiconducting, horizontally aligned SWNTs grown on quartz by a ethanol/methanol mixture. </p><p>The control of SWNT device performance is also described, in particular, the correlation between the SWNT field effect transistor (FET) configuration and its gate dependence response. The effects of FET channel length, nanotube density and diameter on the device performance are demonstrated. A model has been constructed in order to simulate the electronic behavior. An interesting metallic behavior has been observed. </p><p>Finally, control of SWNT properties by Palladium decoration after growth is used to manipulate their properties. Moreover, two novel applications including improvement of carbon nanotube film conductivity and catalysis of nanostructure growth are developed.</p> / Dissertation

A high aspect ratio epoxy mask has been built with Taiyo PSR4000BN on chemical sensing array chip. Thickness up to 200 and #61549;m and aspect ratio up to 16:1 have been achieved with this material. It is demonstrated that this material satisfies the mechanical and chemical requirements. A three-electrode system has been designed and built for electrochemistry in micro-cell on chip. Tests with poly(phenylenesulfide-phenyleneamine) (PPSA) demonstrates that it is possible to precisely tune the properties (Work function and resistance) of conducting polymer that has been cast on chip surface. A new test platform GT03 has been fabricated and used to characterize the chemical effects on organic electronics. It is demonstrated that the chemical species in ambient environment can affect organic electronics properties on bulk, interface and electric contact. The contact resistance in organic field-effect transistors (OFETs) has been characterized with modified interdigitated structure (IDS). It is demonstrated that drain and source contact resistances can be calculated separately with modified four-point-probe measurements, and contact resistance and material bulk resistance are actually modulated by the gate electric field. Furthermore, the influence from oxygen doping in poly(3-hexylthiophene) (P3HT) based OFETs has been investigated. A new model of oxygen doping has been suggested and it is demonstrated that oxygen doping can affect all the resistance components in P3HT OFETs.

In recent years, as biological information analysis technology rapidly develops in hematology, biochemistry and microbiology areas, demand for portable measurement systems become more and more important. This study makes efforts in developing disposable hydrogen and potassium ion sensor and microsystem for analysis application. The measured ion concentration data by this analysis microsystem provide people a judgement on their health condition, and furthermore an important reference for medical treatment for patients. There are several advantages in using IC or MEMS technology to manufacture portable measurement system, the advantages are down-scaling, short reaction time, trace chemical analysis, low power dissipation, and low cost. So the thesis uses extended gate field effect transistor, in order to measure multiple ions at the same time, multiple transistors are manufactured on the same chip with an ion selective membrane on top of the gate sensitive layer. This allows the measurement result of the multiple ion be shown at the same time. The main processing steps of the ion sensor developed in this study involve at least four photolithographic and three thin-film deposition processes. Based on the measurement result, the hydrogen ion sensor¡¦s sensitivity is 30.7 mV/decade for a sensing range pH1 ~ pH13. The sensitivity of the potassium ion sensor is 11.5 mV/decade for a sensing range 10-1M to 10-3M.

Human blood reflects the health of internal organs and tissues, the constituent can be affected on account of abnormal health status. Moreover, the ion concentration of chloride and ammonium in human blood relates to the functionality of our kidney and liver, which is one of the most important health indicators. For real-time monitoring and detecting applications, this study uses micro-electromechanical systems (MEMS) surface micromachining process technology to develop an extended-gate field-effect transistors (EGFET), and by combining two different ion-selective membranes (ISM), a disposable silicon-based chloride and ammonium micro ion sensor was fabricated. The main process steps include four photolithography process and two thin film deposition. In order to probe into the influences on modulating three designing parameters: (i) channel width to length ratio; (ii) channel shape; (iii) mixing ratio of the sensing film additives, the size of the sensing area is fixed to 1¡Ñ1 mm2 while the device is fixed to 6 mm3. In this thesis, the optimization of the development chloride and ammonium micro ion sensors, according to the measuring results from the commercial semiconductor analyzer (Agilent B1500A), when measuring range of 10-1~10-5 mol/L, the sensitivity and linearity for the chlorine ion sensor is 47.5 mV/pCl and 99.13%, as for the ammonium ion sensor are 41.2 mV/pNH4 and 99.28%, the interfering ion selectivity coefficients (log KCl,OH, log KNH ,Na) are -4.71 and 0.53 respectively.

Water resource is one of the most important natural resources on earth. In recent years, due to the discharges of large industrial and domestic waste-water into the nature, water pollution problem is getting more and more serious and how to monitor the quality of water in real time has become a very important research issue. The dissolved oxygen is one of the critical indexes for evaluating the quality of water. Although the conventional dissolved oxygen detectors presented a high sensitivity and high accuracy, the high cost, large dimension, low capability of batch fabrication and real-time monitoring will limit their applications. In this thesis, an extended-gate field-effect transistor (EGFET) based dissolved oxygen microsensor is developed utilizing micro-electromechanical system (MEMS) technology. The gate voltages of EGFET under different concentrations of dissolved oxygen can be detected by the Cr/Au sensing electrode. To further enhance the sensitivity of the proposed microsensor, a polystyrene layer with very high permeation rate of the dissolved oxygen gas is adopted and coated on the surface of Cr/Au layer. The main processing steps of the presented microsensor involve four photolithographic and four thin-film deposition processes. The influence of the channel¡¦s width/length ratio, source/drain geometry and polystyrene additional layer on the sensitivity of the EGFET based dissolved oxygen microsensor are investigated in this study. The chip size of the implemented dissolved oxygen microsensor is 11 mm¡Ñ13 mm¡Ñ 0.5 mm and the sensing area is 1 mm¡Ñ1 mm. As the dissolved oxygen concentration varies from 2 ppm to 6 ppm, a very high sensitivity (35.36 mV/ppm) and sensing linearity (98.83%) of the proposed EGFET microsensor can be demonstrated. In addition, the response time of the presented dissolved oxygen microsensor is only about III 180~200 seconds, hence it is very suitable for developing a real-time monitoring microsystem.

The large carbon dioxides produced by highly developed industries not only result in serious air pollution and health problems, but also cause ocean acidification and decrease the survival rate of fry in aquaculture. Therefore, to develop a system for real-time detection of the concentration of carbon dioxide in aquaculture has become a very important research issue. Optical analysis and gas-chromatography are the two main methods adopted in conventional gas detection. Although the conventional carbon dioxide detectors presented high sensitivity and accuracy, the high fabrication cost, large dimension, low capability of batch fabrication and without real-time monitoring function will limit their applications. This thesis utilizes MEMS technology to implement an extended-gate field-effect transistor (EGFET) with an integrated gas permeable membrane for development of a high-sensitivity, small size and low cost carbon dioxide microsensor. The main material of the carbon dioxide gas permeable membrane adopted in this research is dioctyl sebacate. The main processing steps of the proposed microsensor include four photolithography and four thin-film deposition processes. In addition, the influences of the channel width/length ratio of EGFET and the coating of gas permeable membrane on the sensing performances of presented microsensor are also investigated in this study. The chip size of the implemented carbon dioxide microsensor is 11 mm¡Ñ13 mm¡Ñ 0.5 mm and the sensing area is 1 mm¡Ñ1 mm. As the carbon dioxide concentration varies from 0.25 mM to 50 mM, a very high sensitivity (42.3 mV/ppm) and sensing linearity (99.2%) of the proposed EGFET microsensor can be demonstrated. In addition, the response time of the presented carbon dioxide microsensor is only about 100 seconds, hence it is very suitable for developing a real-time monitoring microsystem.

Abstract ¡@¡@Biosensor chip has a lot of advantages, such as label-free, ultra-sensitive, highly selective, fast and real-time detection. Fabricating biosensor chip has great benefits for gene-detection, protein-detection, medical diagnosis and development of new medicine. This research will integrate the biomedical, chemistry, and physics, and also combined with biochemical technology and semiconductor technology to produce biosensor chip. ¡@¡@We use microelectronic semiconductor process technology to fabricate silicon nanowire field effect transistors (SiNW-FET). The source-drain current versus the voltage curve (Isd-Vsd) shows that the contact pad and the silicon nanowire form ohmic contact. And then we use chemical surface modification technologies to modified biotin on SiNW-FET to detect streptavidin. ¡@¡@In addition, we also grow AlGaN/GaN film by MBE, and fabricate nitride¡Vbased high electron mobility transistor (HEMT) by microelectronic semiconductor process technology. In this study, we apply HEMT in biosensor for pancreatic cancer marker CA19-9 antigen. And we modify pancreatic cancer marker CA19-9 antibody on the biosensor chip surface to detect pancreatic cancer marker CA19-9 antigen molecule. ¡@¡@Most of biomolecules are with weak charges, which can form chemical gating effect and change the conductance of p-type SiNW. And according to the streptavidin microfluidic measurement of biotin-modified SiNW-FET, the detection limit of streptavidin was 10-9 M. And the detection limit of pancreatic cancer marker CA19-9 antigen for N-HEMT biosensor was 150 U/mL.

Over the last decade, immobilization of proteins onto inorganic materials is becoming more crucial to extend a deep understanding of interaction between proteins and nanoparticles. With understanding of the real interaction lying under the protein-nanoparticle relations, it is possible to organize the conformation and orientation of surface and framework species of nanoparticles to generate ideal surfaces for potential biotechnological applications. Due to their unique properties such as large clean surface, tunable surface properties, adjustable surface charge, and dispersibility in aqueous solutions, zeolite and zeo-type materials are one of the remarkable classes of inorganic materials that are widely studied in the literature. These properties make zeolites promising alternative candidates for the immobilization of enzymes and incorporation into biosensing devices. In the current study, a new approach was developed for direct determination of urea, glucose, and butyrylcholine where zeolites were incorporated to the electrode surfaces of a conductometric biosensor and Ion Sensitive Field Effect Transistors were used to immobilize the enzymes. Biosensor responses, operational stabilities, and storage stabilities of the new approach were compared with results obtained from the standard membrane methods for the same measurements. For this purpose, different surface modification technique, which are simply named as Zeolite Modified Transducers (ZMTs) were compared with Standard Membrane Transducers (SMTs). During the conductometric measurements ZMT electrodes were used, which allowed the direct evaluation of the effect of zeolite morphology on the biosensor responses for the first time. It was seen that silicalite added electrodes lead to increased performances with respect to SMTs. As a result, the zeolite modified urea and glucose biosensors were successfully applied for detecting urea and glucose, which can offer improved possibilities to design biosensors. The results obtained show that zeolites could be used as alternatives for enzyme immobilization in conductometric biosensors development. Furthermore, the sensitivities of urease and butyrylcholinesterase biosensors, prepared by the incorporation of zeolite Beta crystals with varying acidity on the surface of pH-sensitive

As working time increases for most people, dining out and staying up late is inevitable, resulting in bad health conditions. The concentrations of calcium and sodium ion in human blood not only respond directly to health conditions, but can also obtain symptoms of different diseases by observing it. This shows that the concentrations of calcium and sodium ion in human blood are an important index of health. In order to manufacture disposable ion sensor and make it easy to measure, this study uses extended gate field effect transistor (EGFET) with an ion selective membrane(ISM) on top of the gate sensitive layer to replace traditional ion sensitive field effect transistor (ISFET). The ISM adsorbs the appointed ion by means of ion selective medicament which is covered by a macromolecule. The main processing steps of the extended gate field effect transistor developed in this study involve at least four photolithographic and two thin-film deposition processes. The influence of the channel¡¦s width to length ratio, the design of channel, the area of the gate sensitive layer, the energy and dose of ion implantation used for the transistor and ion sensor were investigated. Based on the measurement results of the ion sensor, a sensitivity of 40mV/decade with linearity of 98.589 % is measured for calcium ion concentration in human blood ranging from 5 ¡Ñ 10-3 mol/L to 5 ¡Ñ 10-4 mol/L. On the other hand, a sensitivity of 56 mV/decade with linearity of 98.589 % is measured for sodium ion concentration in human blood ranging from 1 mol/L to 10-1 mol/L.