Transparent oxide semiconducting films have continued to receive considerable attention, from a fundamental and application-based point of view, primarily because of their useful fundamental properties. Of particular interest is zinc oxide (ZnO), an n-type semiconductor that exhibits excellent optical, electrical, catalytic and gas-sensing properties, and has many applications in various fields. In this work, thin film transistor (TFT) arrays based on ZnO have been prepared by reactive radio frequency (RF) magnetron sputtering. Prior to the TFT fabrication, ZnO layers were sputtered on to glass and silicon substrates, and the deposition parameters optimised for electrical resistivities suitable for TFT applications. The sputtering process was carried out at room temperature with no intentional heating. The aim of this work is to prepare ZnO thin films with stable semiconducting electrical properties to be used as the active channel in TFTs; and to understand the role of intrinsic point defects in device performance and stability. The effect of oxygen (O2) adsorption on TFT device characteristics is also investigated. The structural quality of the material (defect type and concentration), electrical and optical properties (transmission/absorption) of semiconductor materials are usually closely correlated. Using the Vienna ab-initio simulation package (VASP), it is predicted that O2 adsorption may influence film transport properties only within a few atomic layers beneath the adsorption site. These findings were exploited to deposit thin films that are relatively stable in atmospheric ambient with improved TFT applications. TFTs incorporating the optimised layer were fabricated and demonstrated very impressive performance metrics, with effective channel mobilities as high as 30 cm2/V-1s-1, on-off current ratios of 107 and sub-threshold slopes of 0.9 – 3.2 V/dec. These were found to be dependent on film thickness (~15 – 60 nm) and the underlying dielectric (silicon dioxide (SiO2), gadolinium oxide (Gd2O3), yttrium oxide (Y2O3) and hafnium oxide (HfO2)). In this work, prior to sputtering the ZnO layer (using a ZnO target of 99.999 % purity), the sputtering chamber was evacuated to a base pressure ~4 x 10-6 Torr. Oxygen (O2) and argon (Ar) gas (with O2/Ar ratio of varying proportions) were then pumped into the chamber and the deposition process optimised by varying the RF power between 25 and 500 W and the O2/Ar ratio between 0.010 to 0.375. A two-level factorial design technique was implemented to test specific parameter combinations (i.e. RF power and O2/Ar ratio) and then statistical analysis was utilised to map out the responses. The ZnO films were sputtered on glass and silicon substrates for transparency and resistivity measurements, and TFT fabrication respectively. For TFT device fabrication, ZnO films were deposited onto thermally-grown silicon dioxide (SiO2) or a high-k dielectric layer (HfO2, Gd2O3 and Y2O3) deposited by a metal-organic chemical deposition (MOCVD) process. Also, by using ab initio simulation as implemented in the “Vienna ab initio simulation package (VASP)”, the role of oxygen adsorption on the electrical stability of ZnO thin film is also investigated. The results indicate that O2 adsorption on ZnO layers could modify both the electronic density of states in the vicinity of the Fermi level and the band gap of the film. This study is complemented by studying the effects of low temperature annealing in air on the properties of ZnO films. It is speculated that O2 adsorption/desorption at low temperatures (150 – 350 0C) induces variations in the electrical resistance, band gap and Urbach energy of the film, consistent with the trends predicted from DFT results.

Nas últimas décadas, o interesse na eletrônica flexível tem aumentado. Sistemas que apresentam benefícios, tais como: baixo custo, melhor desempenho, transparência, confiabilidade e melhores credenciais ecológicas, estão sendo extensivamente pesquisados por vários grupos. Os transistores de filmes-finos possuem potencial para alcançarem essas características. Dispositivos baseados em óxido de zinco (ZnO) tem atraído pesquisadores devido as suas propriedades elétricas, sensoriais e ópticas. Neste trabalho, nanopartículas de ZnO foram utilizadas como semicondutor ativo e cross-linked PVP (polivinilfenol) e PECVD-SiO2 (plasma enhanced chemical vapor deposition silicon dioxide) como dielétricos de porta para integrar transistores de filmes-finos. Este processo de integração tem por objetivo os pré-requisitos de baixo custo e baixa temperatura (<200°C). Por esta razão, a utilização de técnicas de integração simples, como o spin-coating ou a técnica de sidewall-etchback, foram utilizadas. Infelizmente, existem problemas relacionados à confiabilidade em dispositivos baseados em ZnO, entre eles a degradação no tempo ou a histerese. Após uma investigação experimental da histerese na característica de transferência, um modelo qualitativo para o comportamento observado é proposto. Observou-se que a direção da histerese é afetada pela variação da temperatura quando o dielétrico polimérico é usado. Baseando-se na caracterização dos transistores, a polarização do PVP, as armadilhas na superfície das nanopartículas e na interface com o dielétrico, bem como a liberação de moléculas de oxigênio da superfície das nanopartículas foram atribuídas como as principais causas da histerese. Além disso, uma flutuação discreta da corrente é observada em testes de estresse devido à captura e liberação de portadores em determinados caminhos de corrente no transistor, semelhante a random telegraph signal (RTS), relatado em MOSFET nanométricos. Este resultado suporta o hipotético mecanismo de transporte de elétrons (caminhos de percolação) em filmes compostos por ZnO nanoparticulado. / During the last decades, the interest in flexible electronics has arisen. Systems that present benefits such as low cost, improved performance, transparency, reliability and better environmental credential are being extensively researched by several groups. Thin-film transistors (TFT) have good potential concerning these technologies. Therefore, zinc oxide (ZnO) based devices have been attracting researchers for its electrical, sensory and optical properties. In this work, ZnO nanoparticles were used to integrate thin-film transistors, in which cross-linked PVP (Poly(4-vinylphenol)) and PECVD-SiO2 (plasma enhanced chemical vapor deposition silicon dioxide) were used as gate dielectric layer. The complete integration process targets low cost and low temperature requirements (< 200°C). For this reason, simple process techniques as spin-coating or sidewall-etchback were used. Unfortunately, there are different reliability concerns in ZnO devices, among them aging or hysteresis. An experimental investigation of the hysteresis in the transfer characteristic is performed, and a qualitative model for the observed behavior is proposed. It was observed that the hysteresis direction is affected by temperature variation when the polymeric dielectric is used. The PVP bulk polarization, the traps in nanoparticles and at the polymeric dielectric interface, as well as the desorption of oxygen molecules in the surface of the nanoparticles, were attributed as the main cause of the hysteretic behavior. Moreover, capture and release of charge carriers by traps at determined current paths in the transistor lead to discrete current fluctuations in stress tests, similar to random telegraph signal (RTS) reported in nanoscale MOSFET. This result supports the hypothesis of charge transport mechanism (percolation paths) in nanoparticulate ZnO.

This thesis presents the development of all-inkjet-printed low-voltage organic thin-film transistors. Organic thin-film transistors (OTFTs), taking advantage of low-temperature printability, mechanical flexibility, and multi-functionality, are promising for a wide range of emerging applications such as wearable electronics. Printed OTFTs provide great benefits in fabrication cost reduction, but they need a very high operating voltage and exhibit severe instability during storage and operation in ambient environment. In this study, all-inkjet-printed OTFTs with a low operating voltage of less than 3 V are demonstrated through reducing trap density in the fabricated devices. The transistors use 6,13-bis(triisopropylsilylethynyl)pentacene as the semiconductor, poly(4-vinylphenol) as the dielectric, silver as the electrodes, and CYTOP as the encapsulation. Several aspects of physical and chemical properties of polymer dielectrics are studied to achieve this goal, including cross-linking, wetting, and moisture affinity. Through the careful selection of device architecture and control of the inkjet-printing processes, the semiconductor-dielectric interface trap density of the fabricated OTFTs is significantly reduced. The applicability of this approach to different materials is also investigated and confirmed, including polyvinyl cinnamate as the dielectric, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene as the semiconductor, and anisole as the solvent for semiconductor inks. Based on the investigation of different materials, the characteristics and parameters of all-inkjet-printed OTFTs are optimised, demonstrating an ultra-steep subthreshold of 60.2 mV/decade approaching the theoretical limit and a low operating voltage of 1 V. In order to explore their feasibility in real-world applications, the stability of all-inkjet-printed OTFTs is investigated and the factors of instability are analysed. Based on these findings, the stability of the fabricated device is improved, such that the threshold voltage shift is less than 0.1 V in ambient environment storage for 3 months and operation for 1 hour. The electrical characteristics of OTFTs in the subthreshold regime are studied for analogue circuit design. Based on the developed low-voltage stable transistors, an ultra-low-power (< 1 nW) high-gain (> 200 V/V) amplifier is presented and utilised to detect electrophysiological signals from the human body.

The focus of this thesis involves development of highly transparent, n-channel, accumulation- mode thin-film transistors employing a zinc tin oxide (ZTO) channel layer. ZTO-based transparent thin-film transistors (TTFTs) show improved device performance compared to ZnO-based TTFTs. An estimated peak effective mobility for these devices as high as ~100 cm² V⁻¹sec⁻¹ has been observed, although effective mobilities in the range of 20-50 cm²V⁻¹sec⁻¹ are more common. This performance inconsistency may be due, in part, to the large device dimensions employed in developmental test structures and/or to shadow mask misalignment. Typical drain current on-to-off ratios are > 10⁶. Variation in the post-deposition annealing cycle is found to be an effective means to control the threshold voltage and to improve device performance. Optical characterization of these devices indicates ~84% transparency in the visible spectrum as viewed through the source/drain. Another aspect of this thesis research involves the utilization and extension of quantitative polycrystalline TFT device models with the intention of guiding the design and optimization of future TFTs. In particular, subthreshold conduction is assessed in order to estimate the bulk (and/or grain boundary) and interface trap densities. This leads to a consideration of threshold voltage and channel mobility extraction, as well as establishment of the turn-on voltage, V[subscript turn-on] Finally, a third aspect of this thesis research involves a new radio-frequency (RF) magnetron sputtering system, custom-designed and constructed at OSU by Chris Tasker. Contributions to the development of this tool include assisting in the design and implementation of the computer-controlled interlocks utilized for operation of the tool. The experimental flexibility of this new tool is discussed with respect to its applicability in the design and fabrication of future TTFTS. / Graduation date: 2004

The objective of this work is to understand how the thin film characteristics of p-type organic and polymer semiconductors affect their electronic properties in microelectronic applications. To achieve this goal, three main objectives were drawn out: (1) to create single-crystal organic field-effect transistors and measure the intrinsic charge carrier mobility, (2) to develop a platform for measuring and depositing polymer thin films for organic field-effect transistors, and (3) to deposit polythiophene thin films for inorganic-organic hybrid solar cells and determine how thin film properties effect device performance. Pentacene single-crystal field-effect transistors (OFETs) were successfully manufactured on crystals grown via horizontal vapor-phase reactors designed for simultaneous ultrapurification and crystal growth. These OFETs led to calculated pentacene field-effect mobility of 2.2 cm2/Vs. During the sublimation of pentacene at atmospheric pressure, a pentacene disporportionation reaction was observed whereby pentacene reacted with itself to form a peripentacene, a 2:1 cocrystal of pentacene:6,13-dihydropentacene and 6,13-dihydropentacene. This has led to the proposal of a possible mechanism for the observed disproportionation reaction similar to other polyaromatic hydrocarbons, which may be a precursor for explaining the formation of graphite. Several silicon-based and PET-based field-effect transistor platforms were developed for the measurement of mobility of materials in the thin film state. These platforms were critically examined against one another and the single-crystal devices in order to determine the optimal device design for highest possible mobility data, both theoretically based on silicon technology and commercially based on individual devices on flexible substrates. Novel FET device designs were constructed with a single gate per device on silicon and PET as well as the commonly used common-gate device. It was found that the deplanarization effects and poor gate insulator quality of the individual gate devices led to lower overall performance when compared to the common gate approach; however, good transistor behavior was observed with field modulation. Additionally, these thin films were implemented into inorganic-organic hybrid and purely organic solid-state photovoltaic cells. A correlation was drawn between the thin film properties of the device materials and the overall performance of the device. It was determined that each subsequent layer deposited on the device led to a planarization effect, and that the more pristine the individual layer, the better device performance. The hybrid cells performed at VOC = 0.8V and JSC = 55A/cm2.

In first part, the supercritical CO2 (SCCO2) fluid technology is employed to improve the device properties of ZnO TFT. The SCCO2 fluid exhibits liquid-like property, which has excellent transport ability. Furthermore, the SCCO2 fluid has gas-like and high-pressure properties to diffuse into the nanoscale structures without damage. Hence, the SCCO2 fluid can carry the H2O molecule effectively into the ZnO films at low temperature and passivate traps by H2O molecule at low temperature. The experimental results show that the on current, sub-threshold slope, and threshold voltage of the device were improved significantly. Next, the electrical degradation behaviors and mechanisms under drain bias stress of a-IGZO TFTs were investigated. A current crowding effect and an obvious capacitance-voltage stretch-out were observed after stress. During the drain-bias stress, the oxygen would be absorbed on the back channel near the drain region of IGZO film. Therefore, the carrier transport is impeded by the additional energy barrier near drain region induced by the adsorbed oxygen, which forms a depletion layer to generate the parasitism resistance. We also investigated the RRAM device based on IGZO film, and proposed the related physical mechanism models. The IGZO RRAM will be very promising for integration with IGZO TFTs for advanced system-on-panel display applications to be a transparent embedded system. In this part, the transparent RRAM device with ITO/IGZO/ITO structure was fabricated. The proposed device presents an excellent bipolar resistive switching characteristic and good reliability. The bipolar switching mechanism of our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path. The influence of electrode material on resistance switching characteristic is investigated through Pt/IGZO/TiN and Ti/IGZO/TiN structure. As the bias applied on the Ti or TiN, the Ti or TiN electrode can play the role of oxygen reservoir to absorb/discharge oxygen ions. Therefore, the device presents a bipolar resistive switching characteristic. However, as the bias applied on the Pt electrode, the device presents a unipolar resistive switching characteristic. Because the Pt electrode can¡¦t store the oxygen ion, the device should use the joule heating mode to rupture the conduction path and present the unipolar resistive switching characteristic. Finally, the resistive switching properties of IGZO film deposited at different oxygen content were investigated, since the resistance switching behaviors are related to the formation and rupture of filaments composed of oxygen vacancies in the IGZO matrix. Experiment results show that the HRS current decreases when the oxygen partial pressure gradually increases. Based on the XPS analysis, these phenomena are related to the non-lattice oxygen concentration. With increasing oxygen ratio, the filaments will rupture completely through the abundant non-lattice oxygen inducing oxidation, which leads to HRS current decrease and an increase in the memory window.

Thin-film transistors (TFTs) capable of low-voltage and high-frequency operation will be required to reduce the power consumption of next generation electronic devices driven by microelectronic components such as inverters, ring oscillators, and backplane circuits for mobile displays. To produce high performance TFTs, transparent oxide-semiconductors are becoming an attractive alternative to hydrogenated amorphous silicon (a-Si:H)- and organic-based materials because of their high electron mobility vlaues and low processing temperatures, making them compatible with flexible substrates and opening the potential for low production costs. Practical electronic devices are expected to use p- and n-channel TFT-based complementary inverters to operate with low power consumption, high gain values, and high and balanced noise margins. The p- and n-channel TFTs should yield comparable output characteristics despite differences in the materials used to achieve such performance. However, most oxide semiconductors are n-type, and the only high performance, oxide-based TFTs demonstrated so far are all n-channel, which prevents the realization of complementary metal-oxide-semiconductor (CMOS) technologies. On the other hand, ambipolar TFTs are very attractive microelectronic devices because, unlike unipolar transistors, they operate independently of the polarity of the gate voltage. This intrinsic property of ambipolar TFTs has the potential to lead to new paradigms in the design of analog and digital circuits. To date, ambipolar TFTs and their circuits, such as inverters, have shown very limited performance when compared with that obtained in unipolar TFTs. For instance, the electron and hole mobilities typically found in ambipolar TFTs (ATFTs) are, typically, at least an order of magnitude smaller than those found in unipolar TFTs. Furthermore, for a variety of circuits, ATFTs should provide balanced currents during p- and n-channel operations. Regardless of the selection of materials, achieving these basic transistor properties is a very challenging task with the use of current device geometries. This dissertation presents research work performed on oxide TFTs, oxide TFT-based electronic circuits, organic-inorganic hybrid complementary inverters, organic-inorganic hybrid ambipolar TFTs, and ambipolar TFT-based complementary-like inverters in an attempt to overcome some of the current issues. The research performed first was to develop low-voltage and high-performance oxide TFTs, with an emphasis on n-channel oxide TFTs, using high-k and/or thin dielectrics as gate insulators. A high mobility electron transporting semiconductor, amorphous indium gallium zinc oxide (a-IGZO), was used as the n-channel active material. Such oxide TFTs were employed to demonstrate active matrix organic light emitting diode (AMOLED) display backplane circuits operating at low voltage. Then, high-performance hybrid complementary inverters were developed using unipolar TFTs employing organic and inorganic semiconductors as p- and n-channel layers, respectively. An inorganic a-IGZO and pentacene, a widely used organic semiconductor, were used as the n- and p-channel semiconductors, respectively. By the integration of the p-channel organic and n-channel inorganic TFTs, high-gain complementary inverters with high and balanced noise margins were developed. A new approach to find the switching threshold voltage and the optimum value of the supply voltage to operate a complementary inverter was also proposed. Furthermore, we proposed a co-planar channel geometry for the realization of high-performance ambipolar TFTs. Using non-overlapping horizontal channels of pentacene and a-IGZO, we demonstrate hybrid organic-inorganic ambipolar TFTs with channels that show electrical properties comparable to those found in unipolar TFTs with the same channel aspect ratios. A key characteristic of this co-planar channel ambipolar TFT geometry is that the onset of ambipolar operation is mediated by a new operating regime where one of the channels can reach saturation while the other channel remains off. This allows these ambipolar TFTs to reach high on-off current ratios approaching 104. With the new design flexibility we demonstrated organic-inorganic hybrid ambipolar TFT-based complementary-like inverters, on rigid and flexible substrates, that show a significant improvement over the performance found in previously reported complementary-like inverters. From a materials perspective, this work shows that future breakthroughs in the performance of unipolar n-channel and p-channel semiconductors could be directly transposed into ambipolar transistors and circuits. Hence, we expect that this geometry will provide new strategies for the realization of high-performance ambipolar TFTs and novel ambipolar microelectronic circuits.

Compared with its inorganic counterpart, organic thin-film transistor (OTFT) has advantages such as low-temperature fabrication, adaptability to large-area flexible substrate, and low cost. However, they usually need high operating voltage and thus are not suitable for portable applications. Although reducing their gate–dielectric thickness can lower the operating voltage, it increases their gate leakage. A better way is making use of high-κ gate dielectric, which is the main theme of this research. Firstly, pentacene OTFTs with HfO2 gate dielectric nitrided in N2O or NH3 at 200 oC were studied. The NH3-annealed OTFT displayed higher carrier mobility, larger on/off current ratio, smaller sub-threshold swing and smaller Hooge?s parameter than the N2O-annealed device. All these advantages were attributed to more nitrogen incorporation at the dielectric surface by the NH3 annealing which provided stronger passivation of surface traps. The incorporation of lanthanum to hafnium oxide was demonstrated to realize enhanced interface in the pentacene OTFTs. Therefore, pentacene OTFTs with HfLaO gate dielectric annealed in N2, NH3, O2 or NO at 400 oC were investigated. Among the 4 devices, the NH3-annealed OTFT obtained the highest carrier mobility, smallest sub-threshold swing and smallest 1/f noise. All these should be attributed to the improved interface between the gate dielectric and the organic semiconductor associated with the passivation effects of the NH3 annealing on the dielectric surface. The processing temperature of OTFTs is a big concern because use of flexible or glass substrate is the trend in organic electronics. Therefore, the HfLaO gate dielectric was annealed in N2, NH3, or O2 at two different temperatures, 200 oC and 400 oC. For all the annealing gases, the OTFTs annealed at 400 oC achieved higher carrier mobility, which could be supported by SEM image that pentacene tended to form larger grains (thus less carrier scattering) on HfLaO annealed at 400 oC. Furthermore, the HfLaO film annealed at 400 oC achieved much smaller leakage because more thermal energy at higher annealing temperature could remove oxide defects more effectively. Fluorination of the HfLaO film (annealed in N2 or NH3 at 400 oC) in a plasma based on CHF3 and O2 was also proposed. For both annealing gases, the OTFT with a 100-s plasma treatment achieved higher carrier mobility and smaller 1/f noise than that without plasma treatment. All these improvements should be due to fluorine incorporation at the dielectric surface which passivated the traps there. By contrast, for longer time (300 s or 900 s) of plasma treatment, the performance of the OTFTs deteriorated due to damage of dielectric surface induced by excessive plasma treatment. Lastly, a comparative study was done on pentacene OTFTs with HfLaO or La2O3 as gate dielectric. For the same annealing gas (H2, N2, NH3, or O2 at 400 oC), the OTFT with La2O3 gate dielectric obtained lower carrier mobility, smaller on/off current ratio, and larger threshold voltage than that based on HfLaO. The worse performance of the OTFTs with La2O3 gate dielectric was due to the degradation of La2O3 film caused by moisture absorption. / published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

The filtered cathodic vacuum arc (FCVA) technique is a well established deposition method for wear resistant mechanical coatings. More recently, this method has attracted attention for growing ZnO based transparent conducting films. However, the potential of FCVA deposition to prepare ZnO layers for electronic devices is largely unexplored. This thesis addresses the use of FCVA deposition for the fabrication of active ZnO based electronic devices. The structural, electrical and optical characteristics of unintentionally doped ZnO films grown on different sapphire substrates were systematically investigated. The potential of FCVA to grow both polar and non-polar ZnO films was demonstrated. The resulting films showed considerable promise for device applications with properties including high transparency(> 90%), moderate intrinsic carrier concentrations (10¹⁷ - 10¹⁹ cm⁻³), electron mobilities up to 110 cm⁻²/Vs, low surface roughness (< 5 nm) and well-structured photoluminescence. Post-growth annealing in oxygen at temperatures up to 800 C produced significant improvements in the electronic and optical properties of these films, due to the formation of larger grains with lower inter-grain potential barriers. Silver oxide (AgOᵪ ) and iridium oxide (IrOᵪ) Schottky diodes fabricated on annealed FCVA ZnO films showed ideality factors as low as 1.20, barrier heights up to 0.85 eV and high sensitivity to ultraviolet light (up to ̴ 10⁻⁵ at -2 V). Transparent and opaque MESFETs fabricated on these films showed well defined field effect characteristics, channel mobilities up to 70 cm⁻²/Vs and insensitivity to 1 mW/cm⁻² visible light. These devices were further subjected to extensive bias and temperature stress tests. MESFET stability appeared to be strongly dependent on Schottky gate type, bias conditions and ZnO film morphology. Positive bias stress of AgOᵪ gated devices resulted in irreversible damage, that is thought to be due to Ag electromigration across the gate interface. Mapping of the surface potential of the ZnO channel material with Kelvin probe force microscopy suggested a strong relationship between the defect density at grain boundaries and both channel mobility and current stability. Interval growth techniques were found to reduce the density of defects at grain boundaries and produced MESFETs with higher current stability. IrOᵪ gated devices showed superior bias stability and temperature resilience from 25 C-195 C.

There is significant need to improve the sensitivity and selectivity for detecting chemical and biological agents. This need exists in a myriad of human endeavors, from the monitoring of production of consumer products to the detection of infectious agents and cancers. Although many well established methodologies for chemical and biological sensing exist, such as mass spectrometry, gas or liquid phase chromatography, enzymelinked immunosorbent (ELISA) assays, etc., it is the goal of the work described herein to outline aspects of two specific platforms which can add two very important features, low cost and portability. The platforms discussed in this dissertation are organic semiconductor field-effect transistors (OFETS), in various architectural forms and chemical modifications, and ion channels immobilized in tethered lipid bilayers integrated with solid state devices. They take advantage of several factors to make these added features possible, low cost manufacturing techniques for producing silicon and organic circuits, low physical size requirements for the sensing elements, the capability to run such circuits on low power, and the ability of these systems to directly transduce a sensing event into an electrical signal, thus making it easier to process, interpret and record a signal. In the most basic OFET functionality, many types of organic semiconductors can be used to produce transistors, each with a slightly different range of sensitivities. When used in concert, they can produce a reversible chemical "fingerprint". These OFETS can also be integrated with silicon transistors - in a hybrid device architecture - to enhance their sensitivity while maintaining their reversibility. The organic semiconductors themselves can be chemically altered with the use of small molecule receptors designed for specific chemicals or chemical functional groups to greatly enhance the interaction of these molecules with the transistor. This increases both sensitivity and selectivity for discrete devices. Specially designed nanoscale OFET configurations with individually addressable gates can enhance the sensitivity of OFETS as well. Finally, ion channels can be selected for immobilization in tethered lipid bilayer sensors which are already inherently sensitive to the analyte of choice or can be genetically modified to include receptors for many kinds of chemical or biological agents. / text