Ce travail de thèse porte sur les divers aspects de l'application de la microscopie à force atomique (AFM), pour la caractérisation de semi-conducteurs organiques et de réseaux d’ADN, pour des applications en électronique organique et en biologie. Sur ces surfaces molles, le mode de fonctionnement Amplitude modulation de l’AFM a été choisi. Ce choix est argumenté par une étude des processus dissipatifs, réalisée sur un échantillon particulier, une puce à ADN. Nous avons montré l’influence des paramètres expérimentaux d’amplitude sur la qualité des images topographique et de phase. A partir du calcul de l’énergie dissipative, il a été montré que la dissipation sur la puce ADN était principalement induite par une interaction pointe-échantillon de type viscoélastique. L’étude par AFM de la croissance “thickness-driven“ du pentacène a été réalisée afin de relier sa morphologie à la nature du substrat et aux performances électriques pour la réalisation de transistors organiques à effet de champ, OFET (Organic Field EffectTransistor). Déposé sur deux substrats de polymères, le parylène et le benzocyclobutène (BCB), le pentacène a été caractérisé à l’échelle nanométrique pour des épaisseurs de film entre 6 et 60nm. Il a été démontré que les grains créés par le dépôt étaient les plus étendus pour une épaisseur déposée de 30nm. La spectroscopie AFM en mode contact a été utilisée, comme une alternative à la méthode des angles de contact, pour mesurer localement l'énergie de surface. Une énergie de surface minimale caractéristique d’une surface mieux ordonnée a été mesurée pour l’épaisseur de pentacène déposée de 30nm pour les deux substrats. Des méthodes spectrales d'analyse statistique d’images, à base de PSD (Power Spectrum Density), ont été utilisées pour expliquer la morphologie des films de pentacène. En outre, ces modèles ont fourni une description exhaustive non seulement de la surface accessible de l’échantillon, mais aussi de ses propriétés structurales intérieures. Mise en évidence dans les modèles, cette épaisseur critique de 30nm correspond à une transition de la phase orthorhombique à la phase triclinique pour les molécules de pentacène déposées surparylène. De même, une transition polymorphique se produit sur le BCB. Sur des OFET créés à base de pentacène sur BCB, la mobilité la plus importante de 3.1x10-2cm²/Vs correspond à la couche de pentacène de 30nm, ce qui montre l'avantage de l'moléculaire orthorhombique en comparaison du triclinique. L’assemblage moléculaire de structures en X et en Y à base d’ADN a été observé par AFM à l’air et dans deux solutions buffer de Tris et HEPES sur un substrat de mica. Il a été montré que le traitement du mica par des ions Ni2+ augmente la force d’interaction ADN/substrat et réduit la diffusivité des molécules. A l'air, des macromolécules filaires contenant une seule structure double brin sont observées sur le mica non traité et des macromolécules avec une géométrie 2D ramifiée, sur le mica prétraité. Sur une surface non-traitée, l’agitation thermique suffit à déplacer les molécules d’ADN faiblement liées au mica, ce qui conduit à la formation de structures plus simples 1D. L’organisation est différente dans les solutions de Tris et d’HEPES. Dans la solution deTris, contenant des cations Mg2+, les arrangements conduisent à une architecture 2D, bien organisée. Dans la solution d’HEPES, contenant des cations Ni2+, la force ionique est 10 fois plus faible, qui conduit à une rupture des liaisons préalablement formées entre le mica et l'ADN. Cependant, les molécules d'ADN restent les unes près des autres en raison d'une substitution partielle des cations de Mg2+ déjà adsorbés par les cations de Ni2+ de plus grande affinité avec le mica. [...] / This work reports the various aspects of the application of atomic force microscopy (AFM), for the characterization of organic semiconductors and DNA-based arrays, for organic electronics and biological applications. On these soft surfaces, the amplitude modulation AFM mode was chosen. This choice is argued by a study of dissipative processes, performed on a particular sample, a DNA chip. We showed the influence of experimental parameters on the topographic and phase image quality. By calculating the dissipative energy, it was shown that the dissipation on the DNA chip was mainly induced by a viscoelastic tip-sample interaction.The AFM study of the "thickness-driven” pentacene growth was made to link the morphology to the nature of the substrate and to the electrical performance of created pentacene-based Organic Field Effect Transistor (OFET). Deposited on two polymer substrates, parylene and benzocyclobutene (BCB), pentacene has been characterized for nanoscale film thicknesses between 6 and 60nm. It has been shown that the larger grains were created for a deposited thickness of 30nm. Spectroscopic AFM mode was used as an alternative to the method of contact angles, to measure local surface energy. Decrease of surface energy is characteristic of a more ordered surface and was measured for a thickness of 30 nm of pentacene deposited on both substrates. Models of statistical analysis of spectral images, based on the Power Spectrum Distribution (PSD) have been used to explain the morphology of pentacene films. In addition, these models have provided a comprehensive description not only of the accessible surface of the sample, but also of its internal structural properties. Highlighted in the models, the critical thickness of 30 nm corresponds to a transition from the orthorhombic phase to the triclinic phase for pentacene molecules deposited on parylene. Similarly, a polymorphic transition occurs on the BCB. On OFETs, based on pentacene on BCB, the largest mobility of 3.1x10-2 cm²/Vs corresponds to the pentacene layer of 30nm, that shows a better ordering of the orthorhombic molecular packing in comparison with the triclinic packing.The molecular arrangement of X and Y structures based on DNA was observed, by AFM, in air and in two buffer solutions of Tris and HEPES on a mica substrate. It was shown that the treatment of the mica by Ni2 + ions increases the strength of the DNA/substrate interaction and reduces the diffusivity of the molecules. In air, wired macromolecules containing one double-stranded structure are observed on untreated mica and macromolecules with a 2D geometry on pretreated mica. Onto a non-treated, the greater thermal motion of weakly bounded to mica DNA molecules leads to the rupture of intermolecular bonding and the forming structures are more simple and not branched. The organization is different in solutions of Tris and HEPES. In the Tris solution, containing Mg2+ cations, the arrangement leads to a well-organized 2D architecture. In the HEPES solution, containing Ni2+ cations, the ionic strength is 10 times lower, this leads to a breaking of the bonds previously formed between DNA and mica. However, DNA molecules are near each other due to a partial substitution of already adsorbed Mg2 + cations by Ni 2 + cations of higher affinity with the mica. These results show that the two liquids promote a 2D assembly. In air, the networks are not stable and the few observed ones remain in a dendritic structure on the surface of pretreated mica and as a linear macromolecule on the untreated mica.

Ce travail de thèse porte sur l'étude de dérivés du pérylène-3,4:9,10-tétracarboxylique acide diimide comme semi-conducteurs pour l'électronique organique, et plus particulièrement pour la réalisation de transistors organiques à effet de champs. Les objectifs de ce travail sont la synthèse de dérivés du pérylène à l'aide entre autres de réactions d'halogénation ou de couplage de Suzuki-Miyaura, et la fabrication de transistors organiques à effet de champs. Dans un premier temps, une large gamme de dérivés du pérylène a été synthétisée et caractérisée. Des études spectroscopiques et électrochimiques ont pu être menées, notamment afin de déterminer les énergies des orbitales frontières de nos molécules. Puis dans un second temps, la réalisation de transistors organiques à effet de champs a été mise en oeuvre, en commençant par un gros travail d'optimisation des conditions de formulation des encres, de dépôt et de traitement du film. Puis ces transistors ont été caractérisés en mesurant les courants drain-source. Mots-clés : semi-conducteur, pérylène, transistor organique à effet de champs, couplage de Suzuki-Miyaura, impression jet d'encre. / This study deals with the synthesis of perylene-3,4:9,10-tetracarboxylic acid bisimide derivatives and their use as semi-conductors for organic electronics, and more specifically for the realization of organic field-effect transistors. The goals of this study are the synthesis of perylene derivatives, using halogenation reactions or Suzuki-Miyaura coupling, and the fabrication of organic field-effect transistors.In the first part of the work, a wide variety of perylene derivatives has been obtained and fully characterized. Spectroscopic and electrochemical studies have been performed to determine energy levels of the frontier orbitals.In the second part, the making of organic field-effect transistors was realized, beginning with the research of optimal conditions for ink formulation, deposition and annealing of the film. Then those devices have been characterized by measuring the source-drain current.Keywords: semi-conductor, perylene, organic field-effect transistor, Suzuki-Miyaura coupling, ink jet printing.

Orientadora: Mônica Alonso Cotta / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-31T00:06:01Z (GMT). No. of bitstreams: 1 Silva_AldelianeMariada_M.pdf: 11574559 bytes, checksum: 5c39733d3a4441b98e7edbef8adbd795 (MD5) Previous issue date: 2016 / Resumo: Este trabalho apresenta resultados de nossa investigação sobre as propriedades elétricas do biossensor do tipo transistor de efeito de campo (FET, do inglês Field Effect Transistor) baseado em fosfeto de índio (InP). A estrutura deste biossensor consiste em um filme fino de InP do tipo-n crescido por Epitaxia de Feixe Químico (CBE, do inglês Chemical Beam Epitaxy) sobre um substrato de InP semi-isolante. No nosso biosensor, o contato da porta foi substituído por uma camada de biomoléculas carregadas de interesse para a detecção, funcionalizadas na camada de óxido do InP. O campo elétrico associado a estas biomoléculas pode modular o canal de condução. O sistema de interação específica utilizado foi a hibridização de fitas de ssDNA (single stranded DNA) complementares, onde os oligonucleotídeos receptores (probe) ssDNA foram imobilizados covalentemente na superfície da amostra. Este procedimento foi realizado através da oxidação com plasma de O2, seguida da funcionalização utilizando etanolamina e polietileno glicol (PEG), que serve como linker para a imobilização de receptores na superfície. As medidas elétricas de detecção foram feitas com as moléculas de target diluídas em buffer TRIS. A hibridização do DNA provoca um aumento na densidade de cargas na superfície, que consequentemente aumenta a largura da região de depleção no semicondutor, variando a resistência medida. A resposta do biossensor corresponde à variação da resistência em função da concentração de target. O biossensor apresentou sensibilidade para medidas de concentrações entre 10 pM e 30 pM, onde ocorre a saturação, e o tempo de resposta, no qual encontramos a estabilização do sinal medido, foi de aproximadamente 20 min. Variando a concentração de portadores e a espessura da camada semicondutora, verificamos alterações no limite de saturação (até ?M) e na sensibilidade do dispositivo. O controle destas propriedades, porém, mostrou-se limitado devido à variações na dopagem residual do semicondutor, e por isso discutimos aqui alternativas à geometria do dispositivo. Analisamos também a camada funcionalizada através de medidas de topografia e potencial de superfície usando métodos de microscopia de varredura por sonda (SPM, do inglês Scanning Probe Microscopy). Pudemos identificar a variação no potencial de superfície associada à imobilização do PEG e do DNA probe, mas não obtivemos resolução para o DNA target. Esta técnica permitiu porém verificar a estratificação de quatro níveis de potencial de superfície, no caso onde a funcionalização resultou em camadas mais espessas do que os valores típicos (~2 nm de espessura), em pequenas áreas do semicondutor / Abstract: This dissertation presents our results for the electrical properties investigation of Indium Phosphide (InP) based Field Effect Transistor (FET) biosensor. The structure of this biosensor consists of a thin n-type InP film grown by Chemical Beam Epitaxy (CBE) on a semi-insulating InP substrate. In our biosensor, the gate contact has been replaced by charged biomolecules of interest for detection, functionalized to the InP oxide layer. The electric field associated with these biomolecules provides the conduction channel modulation. The specific interaction system used here was the hybridization of single stranded-DNA (ssDNA) complementary oligonucleotides, for which the ssDNA receivers (probes) were covalently immobilized on the sample surface. The functionalization was carried out by oxidation with O2 plasma, followed by grafting biomolecules using ethanolamine and polyethylene glycol (PEG), which act as a linker for immobilizing the receptors on the surface. Electrical detection measurements were made with the target molecules diluted in TRIS buffer. DNA hybridization causes an increase in the surface charge density; consequently the semiconductor depletion width increases, affecting the measured resistance. The biosensor response function corresponds to the resistance variation as a function of target concentration. Our biosensor showed measured sensitivity to concentrations between 10 pM and 30 pM, for which signal saturation occurs. The response time, for which the measured signal stabilization was observed, was approximately 20 min. By varying the carrier concentration and the thickness of the semiconductor layer, we observed changes in the saturation limit (up ?M) and device sensitivity. The control of these properties, however, is limited due to variations in the residual doping of the semiconductor. Therefore we discuss here alternative device geometries. We also analyzed the functionalized layer by topography and surface potential measurements obtained using scanning probe microscopy (SPM) methods. We were able to identify the change in surface potential associated with the immobilization of PEG and probe DNA, but not for the target DNA. These techniques have however shown four surface potential levels in the case when the functionalization resulted in non-uniform layers, thicker than the typical values (~ 2 nm), in small areas of the semiconductor / Mestrado / Física / Mestra em Física / 165741/2014-7 / CNPQ

Enormous demands for fast and low-power computing and memory building blocks for consumer electronics, such as smartphones or tablets, have led to the emergence of silicon nanowire transistors a decade ago. Along with the Si-based nanotechnology, the silicon compatible optical and chemical sensing applications have boosted the research on hybrid devices that combine the organic and inorganic materials. Apart from the revolution in the device dimensions, the rapid growth of artificial intelligence in the software industry brunch requires the next generation’s computers with the revolutionized hybrid device architecture. Implementing such new devices can effectively perform machine learning tasks without the massive consumption of energy. The hybrid Si nanowire devices have an excellent capability to replace the conventional computing element by providing new functionalities of combined materials to the traditional transistor devices preserving the advantage of CMOS technology. A goal of this thesis is to develop functional hybrid Si nanowire-based transistors modulated by the stimuli-dependent gate to go beyond the current digital building blocks. The hybrid devices converge semiconductor channel and various materials from organic molecules to silicate composite as a gate of the transistor. External stimuli change the electronic state of the gate materials which is transformed to the gate potential of the transistors. First, this thesis studies the electronic characteristics of the Si nanowire FETs under the optical stimulus. Optical stimulus induces the strong conductance change on bare Si nanowire FETs. Under the light with low power intensity, the transistor shows an unconventional negative photoconductance (NPC) which is dependent on the doping concentration of the nanowire and the wavelength of the incident light. The dopants ions and surface states cause photo-generated hot electrons trapping which restricts conventional photoconductance in the semiconductor. In the hybrid device, however, the gate material on the Si dioxide layer plays a significant role in the optoelectronic modulation of the FET device. This thesis demonstrates that an organic photochromic material, porphyrin, wrapping around the nanowire channel acts as an optical gate of the Si nanowire transistor. The diffusive property of electrons in the molecular film decides the optical switching dynamics and efficiency. Further, this thesis introduces new functional gate material, sol-gel derived ion-doped silicate film, based on the availability of stimulus-dependent gate modulation. This amorphous and transparent silicate film shows memristive property due to the ionic redistribution in the film under bias condition. Interestingly, the sol-gel film-coated Si nanowire FETs the devices show a double gate effect cooperating with a back gate under light illumination which is due to the channel separation in the fin structure of the nanowire. In addition, the sol-gel silicate film-coated Si nanowire transistor emulates the neuronal plasticity with pulsed gate stimulation, namely “neurotransistor.” Because of the mobile ions in the silicate film, the transistor has a short-term memory and mimics membrane potential change of the neuron cell. The neurotransistor could be used as a computing node in the physical neural network for hardware machine learning. This work demonstrates that the physical properties of the gate material decide the transfer characteristics and time-dependent dynamics of the hybrid Si nanowire transistors. The optical and neuromorphic gate features of the hybrid transistors would accelerate the advancement of an optical or brain-like computing machine.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22072号 / 工博第4653号 / 新制||工||1725(附属図書館) / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 川上 養一, 准教授 杉山 和彦 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Solution-processed organic field effect transistors (OFETs) have emerged in recent years as promising contenders to be part of electronic and optoelectronic circuits owing to their compatibility with low-cost high throughput roll-to-roll manufacturing technology. The stringent performance requirements for OFETs in terms of carrier mobility, switching speed, turn-on voltage and uniformity over large areas require the performance of single crystal-based OFETs, but these suffer from major scale-up challenges. To achieve device performance approaching that of single crystals with scalable, high throughput and industry-compatible solution coating of OFETs requires understanding and ultimately controlling the crystallization of organic semiconductors (OSCs), and producing very low defect-density thin films. In this thesis, we develop an understanding of the process-structure-property-performance relationship in OSCs that bring fresh insights into the nature of solution crystallization and lead to novel ways to control OSC crystallization, and finally help achieve fabrication of high-performance OFETs by scalable, high throughput and industry-compatible blade coating method. We probe the solution crystallization of OSCs by employing a suite of ex & in situ characterization techniques. This leads us to an important finding that OSC molecules aggregate to form a dense amorphous intermediate state and nucleation happens from this intermediate state during blade coating under a wide window of coating conditions. This phenomenon resembles the so-called two-step nucleation model. Two-step nucleation mediates the crystallization of a wide range of natural and synthetic products ranging from soft materials, such as proteins, biominerals, colloids and pharmaceutical molecules, to inorganic compounds. We go on to show that this nucleation mechanism is generally applicable to achieve formation of high-quality polycrystalline films in a variety of small molecule OSCs and their polymer blends. This phenomenon results in highly textured and well-connected domains, which exhibit reduced interfacial and bulk trap-state densities, helping raise the carrier mobility by one to two orders of magnitude in OFETs in comparison to direct nucleation. We extend the understanding developed for solution crystallization of various acenes and thiophene-based small molecule OSCs to the high-performance benzothieno-benzothiophene (BTBT) based small molecule OSCs. On this end, we develop protocols to fabricate high-quality thin films of BTBT based OSCs by blade coating at industrially compatible coating speeds (>100 mms-1). These films show massive single-domains with very few apparent defects when crystallized via multiple liquid-crystalline phases in two-step nucleation conditions, resulting in an average carrier mobility of ~10 cm2V-1s-1. To sum up, this thesis develops an understanding of OSC solution crystallization and efficient protocols to control polycrystalline thin film quality for high-performance OFETs. These protocols involve a combination of two-step nucleation pathway, solvent mixtures, polymer blends and device-manufacturing conditions. Our efforts enable to realize high-performance OFETs based on high-quality polycrystalline OSC thin films at industry-compatible conditions.

Understanding and control of interactions between biological environment (cells, proteins, tissues, membranes, electrolytes, etc.) and solid-state surfaces is fundamental for biomedical applications such as bio-sensors, bio-electronics, tissue engineering and implant materials as well as for environmental monitoring, security and other fields. Diamond can provide unique combination of semiconducting, chemical, optical, biocompatible and other properties for this purpose. In this thesis we characterize electronic properties of protein-diamond interface by employing a solution-gated field-effect transistor (SGFET) based on hydrogen-terminated diamond, surface of which is exposed to biological media. We elucidate the role of adsorbed protein layer on the electronic response of the diamond transistor. We investigate effects of cells (using mainly osteoblast cells as model) on diamond SGFETs transfer characteristics and gate currents. We employ nanocrystalline diamond (NCD) thin films of different grain sizes (80 - 250 nm) to characterize and discuss influence of grain boundaries and sp2 phase on bio- electronic function of SGFETs. We investigate effects of gamma irradiation on function and stability of hydrogen-terminated diamond SGFETs interfaced with proteins and cells, showing feasibility of...

1998 publizierten die Arbeitsgruppen von S. J. Tans und R. Martel die Herstellung des Prototypen eines Kohlenstoffnanoröhren Feldeffekttransistors. Dabei bilden halbleitende Kohlenstoffnanoröhren den aktiven, feldgesteuerten Bereich des Transistors. Aufgrund der herausragenden Eigenschaften der Kohlenstoffnanoröhren wurde den Bauelementen ein großes Anwendungspotential in Halbleiterindustrie und Sensorik vorhergesagt. Dass die Verwendung von Kohlenstoffnanoröhren in der Industrie heute hinter den Erwartungen zurückbleibt, liegt vor allem an den Problemen bei der Sortierung und Integration der Kohlenstoffnanoröhren: Trotz intensiver Bemühungen entsteht bei der Synthese eine Mischung aus halbleitenden und metallischen Kohlenstoffnanoröhren. Eine postsynthetische Separation der Spezies ist daher notwendig. In dieser Arbeit wurden verschiedene Wege zur Separation der Kohlenstoffnanoröhren in eine halbleitende und metallische Fraktion verfolgt: (i) Die Dichtegradientenzentrifugation differenziert zwischen unterschiedlichen Schwimmdichten der Kohlenstoffnanoröhren in einer Lösung mit einem Dichtegradienten. Durch die selektive Assemblierung unterschiedlich polarisierbarer Tenside werden Dichteunterschiede zwischen den halbleitenden und metallischen Röhren hergestellt. In einem Zwei-Schritt-Verfahren konnte so eine hohe Reinheit an halbleitenden Kohlenstoffnanoröhren erzielt werden. (ii) Die dielektrophoretische Auftrennung der Kohlenstoffnanoröhren erfolgt aufgrund von Unterschieden in der Polarität und der Leitfähigkeit der metallischen und halbleitenden Spezies. Durch die Wahl des Tensidsystems können dabei die Unterschiede zwischen den beiden Spezies verstärkt und somit die Sortierung effizienter gestaltet werden. Die Erfahrungen mit statischen Dielektrophorese-Experimenten wurden in ein kontinuierliches mikrofluidisches System übertragen. Damit eröffnet sich die Möglichkeit der Separation der Kohlenstoffnanoröhren im größeren Maßstab. Im Anschluss an die Sortierung ist ein Prozess notwendig, der die parallele Integration vieler Kohlenstoffnanoröhren in mikroelektronische Strukturen auf einem Wafer ermöglicht. Die Dielektrophorese erlaubt die ortsspezische parallele Assemblierung der Kohlenstoffnanoröhren in vorgefertigte Strukturen. Damit können auf Waferebene Kohlenstoffnanoröhren-Feldeffekttransistoren aufgebaut werden. In dieser Arbeit kann gezeigt werden, dass mit der Integration sortierter halbleitender Röhren die übliche selektive Zerstörung metallischer Strompfade überflüssig ist. Im letzten Teil dieser Arbeit soll der aufgebaute Kohlenstoffnanoröhren-Feldeffekttransistor für einen zukünftigen Einsatz als membranbasierter Biosensor modifiziert werden. Dafür wird eine Doppellipidschicht über den Kohlenstoffnanoröhren assembliert werden, welche als Modell für eine Biomembran dient. Es werden erste Messungen in Flüssigkeit gezeigt und die Interaktion der Lipidmoleküle mit den dispergierten Kohlenstoffnanoröhren charakterisiert.

Les transistors organiques à effet de champ (OFETs) dans lesquels le transport des charges se fait à travers un film mince de molécules organiques représentent une transformation de la technologie des transistors à effet de champ au regard de la technologie au silicium. Ils permettent notamment d’envisager le développement d’une électronique flexible à bas coût. Ce travail porte sur la synthèse, l’étude et l’utilisation en tant que couche active dans des OFETs de type n de couples d’isomères para- et méta-indacénodithiophènes (para- et méta-IDT) appauvris en électrons inédits. Une introduction aux OFETs de type n est tout d’abord présentée. Elle est suivie par la présentation de la synthèse des dérivés IDT et de l’analyse comparée de leurs propriétés physico-chimiques. La fabrication des OFETs, leur caractérisation et l’optimisation de leur architecture est enfin décrite, leurs performances montrant l’intérêt des IDTs pour les OFETs de type n. Différentes fonctionnalisations menant à des IDTs d’architecture 3π-2spiro sont également synthétisées afin d’étudier les propriétés intrinsèques de ces dérivés π-conjugués et d’envisager leur incorporation comme matrice hôte dans des diodes électrophosphorescentes organiques. / Organic Field Effect Transistors (OFETs), in which the charge transport is carried through a thin film made of organic molecules represent a transformation of the FET technology regarding that based on Silicon. They offer in particular the possibility to manufacture low cost flexible electronics. This work is focused on the synthesis, the study and the use as active layer in n-type OFETs of novel, electron poor, couples of para- and meta-indacenodithiophenes isomers (para- and meta-IDT). First of all, an introduction to the field of n-type OFETs is presented, followed by the presentation of the synthesis of the IDT derivatives and the comparative analysis of their properties. Finally, the fabrication of the OFETs, their characterization and the optimization of their architecture is described. The performances recorded attest that these derivatives are of great interest for the n-type OFETs. Different 3π-2spiro IDT derivatives are also presented in order to study the IDTs intrinsic properties and to envisage their incorporation as host in phosphorescent organic light-emitting diodes.

With the end of Si based Metal Oxide Semiconductor Field Effect Transistor scaling paradigm approaching fast as predicted by the Moore’s Law, and the technological advancements as well as human needs in many ways pushing for faster devices, graphene has emerged as a powerful alternative solution. This is so because of its very special properties like high charge carrier mobility, highly linear dispersion relation, high current carrying capacity and so on. However, since we have a finite resistance at Dirac point, the on/off ratio in graphene devices is sufficiently low, making graphene devices not so suitable for logical applications. At the same time, the 1/f noise, which is understood till now to originate from surface disorders like those observed in a two-dimensional electron gas system like graphene and is a major unwanted outcome in mesoscopic regime devices, reduces very much at high frequencies, making these devices good candidates for high frequency analogue applications. Motivated by these observations, this work explores fabrication and characterization of graphene field effect transistors operating at microwave frequencies, and compares a double gated device performance to a mono-gated device having the same geometry, dielectric layer thickness and gate length. A simple electrostatic finite element simulation model has also been developed to support our experimental observations by fitting simulated gate coupling capacitance values to the measured data. The model helps us in understanding the level of interface trap charge densities introduced into the device channel during fabrication, and the effect of quantum capacitance on device performance, and is in line with the experimental observations. Our results show that a double gated graphene FET has superior performance compared to a mono-gated FET.