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6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) films are prepared by spin coating on commercial prefabricated bottom gate-bottom contact (BGBC) configuration organic field effect transistors (OFETs). The commercial prefabricated OFET offers a less time consuming in order to prepare other multilayer compared to custom made prefabricated OFET. In this study, the fabricated OFET shows mobility, threshold voltage and on/off current ratio of 0.08 cm2/Vs, 5.0 V and 102 respectively. Compared to previous study on custom made fabricated substrate, this commercial prefabricated substrate shows an increased mobility of 1-2 order of magnitude for bottom gate-bottom contact OFET. Furthermore, the threshold voltage of our work was improved compared to the Ossila report based on same BGBC devices. This commercial prefabricated OFET offers a suitable substrate to fabricate organic semiconductor OFET compared to custom made prefabricated OFET with less preparation time of the multilayer. [ABSTRACT FROM AUTHOR]

Ionization potential and electron affinity of organic semicondutors are important quantities, which are relevant to charge injection barriers. The electrostatic and dynamical contributions to the polarization energies for the injected charges in pentacene polymorphs were investigated. While the dynamical polarization induced narrowing of the energy gap, the electrostatic effect shifted up or down the frontier energy levels, which is sensitive to the molecular orientation at the surface. [ABSTRACT FROM AUTHOR]

Using the molecular dynamics and the Monte Carlo methods, we have studied the structural features and growth mechanism of the pentacene film on graphite and polymethylmethacrylate /graphite surfaces. Monolayer capacity and molecular area, optimal angles between the pentacene molecules and graphite and PMMA/graphite surfaces as well as the characteristic angles between the neighboring pentacene molecules in the adsorption layer were estimated. It is shown that the orientation of the pentacene molecules in the film is determined by a number of factors, including the surface concentration of the molecules, relief of the surface, presence or absence of the polymer layer and its thickness. The pentacene molecules adsorbed on the graphite surface keep a horizontal position relative to the long axis at any surface coverage/thickness of the film. In the presence of the PMMA layer on the graphite, the increase of the number of pentacene molecules as well as the thickness of the PMMA layer induce the change of molecular orientation from predominantly horizontal to vertical one. The reason for such behavior is supposed to be the roughness of the PMMA surface. [ABSTRACT FROM AUTHOR]

Charge carrier transport in organic semiconductors is dominated by positional and energetic disorder in Gaussian density of states (GDOS) and is characterized by hopping through localized states. Due to the immobilization of charge carriers in these localized states, significant non-uniform carrier distribution exists, resulting diffusive transport. A simple, nevertheless powerful technique to determine diffusion coefficient D in disordered organic semiconductors has been presented. Diffusion coefficients of charge carriers in two technologically important organic molecular semiconductors, Pentacene and copper phthalocyanine (CuPc) have been measured from current-voltage (J-V) characteristics of Al/Pentacene/Au and Al/CuPc/Au based Schottky diodes. Ideality factor g and carrier mobility μ have been calculated from the exponential and space charge limited region respectively of J-V characteristics. Classical Einstein relation is not valid in organic semiconductors due to energetic disorders in DOS. Using generalized Einstein relation, diffusion coefficients have been obtained to be 1.31x10-6and 1.73x10-7cm2/s for Pentacene and CuPc respectively. [ABSTRACT FROM AUTHOR]

3,16-bis triisopropylsilylethynyl (Pentacene) (TIPS-Pentacene) compactable interface property is important in order to have a good arrangement of molecular structure. Comparison for TIPS-Pentacene deposited between two different surface layers conducted. 0.1wt% TIPS-Pentacene diluted in chloroform were deposited onto poly(methylmeaclyrate) (PMMA) layered transparent substrates using slide coating method. X-ray diffraction (XRD) used to determine crystallinity of thin films. Series of (00l) diffraction peaks obtained with sharp first peaks (001) for TIPS-Pentacene deposited onto PMMA layer at 5.35° and separation of 16.3 Å. Morphology and surface roughness were carried out using scanning electron microscope (SEM) and surface profilemeter LS500, respectively.TIPS-Pentacene deposited onto PMMA layer formed needled-like-shape grains with 10.26 nm surface roughness. These properties were related as thin film formed and its surface roughness plays important role towards good mobility devices. [ABSTRACT FROM AUTHOR]

Investigation on the physical characterization and comparison of organic thin film based on a soluble 6,13- bis(triisopropylsilylethynyl) (TIPS) pentacene is reported. Oriented thin-films of pentacene have been successfully deposited by flow-coating method, in which the chloroform solution is sandwiched between a transparent substrate and a slide glass, followed by slow-drawing of the substrate with respect to the slide glass. Molecular orientation of flowcoated TIPS-pentacene is comparable to that of the thermal-evaporated pentacene thin film by the X-ray diffraction (XRD) results. XRD results showed that the morphology of flow-coated soluble pentacene is similar to that of the thermal-evaporated pentacene thin films in series of (00l) diffraction peaks where the (001) diffraction peaks are strongest in the nominally out-of-plane intensity and interplanar spacing located at approximately 20 = 5.33° (d-spacing, d001 = 16 Å). Following that, ITO/p-TIPS-pentacene/n-ZnO/Au vertical diode was fabricated. The diode exhibited almost linear characteristics at low voltage with nonlinear characteristics at higher voltage which similar to a pn junction behavior. The results indicated that the TIPS-pentacene semiconductor active thin films can be used as a hole injection layer for fabrication of a vertical organic transistor. [ABSTRACT FROM AUTHOR]

In this study we analyzed one of the environmental factors that could affect organic materials. Pentacene thin film samples were fabricated and the degradation of their electrical characteristics was measured when the devices were exposed to ultraviolet light irradiation. The results have been reported in terms of a trap density model, which provides a description of the dynamics of light induced electrically active defects in an organic semiconductor. [ABSTRACT FROM AUTHOR]

Organic electronics have immense potential over a wide spectrum of applications. In the present scenario, an abundance of investigations are being followed on the transistor operation and its characterization. However, circuit level research focus is not that common. Therefore, we sensed the urgency to provide a complete assessment of the different circuit styles, which are, the diode-load, zero-Vgs, pseudo-E and pseudo-D, in ratioless and ratioed logic. A comparative evaluation of the collective circuit behavior of each design style is critical. The major parameters, such as, power consumption, noise margin of high and low level signal, circuit speed, on current and output voltage swing were measured and thereupon, analyzed to decide upon the optimum circuit style for cascading. The inverter, NAND and NOR logic gates, and a 5-inverter ring oscillator were further analyzed, using the pentacene OTFT model file, to realize the best architecture for integration in large scale circuits. Based on our evaluations, the lowest power consumption was in case of the zero-Vgs and pseudo-D design style, along with, a fast circuit operation speed. The pseudo-D circuit configuration, not only provides the maximum Vout swing, but it has the best performance. [ABSTRACT FROM PUBLISHER]

This paper describes a feasibility study of a fully organic, low cost, frequency doubler for harmonic RFID applications. The proposed structure is formed by two antennas (RX and TX) printed on paper and an organic Shottky diode able to double the frequency of the received signal. To the author knowledge this contribution proofs for the first time the feasibility of a fully organic non linear electronic circuit for RFID applications. [ABSTRACT FROM PUBLISHER]

We report on the fabrication and characterization of a pentacene and poly(4-vinyl phenol) (PVP) based metal-insulator-semiconductor (MIS) memory structures. The surface morphology of pentacene grown on a thin layer of PVP showed the largest polycrystalline grains as compared to other dielectric materials such as polymethyl-metacrylate (PMMA) or SU8. The effect of larger grain size of pentacene was reflected in the capacitance-voltage (C-V) characteristics of the devices, where devices with larger pentacene grains showed lower operating voltages and a steeper slope of the depletion region of the C-V curve. The introduction of solution-processed gold nanoparticles (AuNPs) embedded within the PVP layer induced the memory characteristics as it served as a floating gate in the MIS Al/PVP/AuNPs/PVP/Pentacene/Au structure. The C-V characteristics of the memory devices exhibit a clockwise hysteresis due to the charging and discharging of AuNPs from the aluminium gate through the PVP insulator layer. A memory window of 8.5V was achieved at a ±10V voltage sweep range; wider memory windows were achieved at higher voltage sweep ranges. The memory devices have hysteresis centred close to 0V and a short depletion region which make it favourable for low voltage and fast operation in organic and flexible electronics applications. [ABSTRACT FROM PUBLISHER]

We introduce a charge-accepting layer on a gate dielectric to investigate the reversible threshold voltage (Vth) shifts in both p-channel and n-channel organic field-effect transistors (OFETs) using organic semiconductors of pentacene and poly-naphthalene dicarboximide [P(NDI2OD-T2)], respectively. Bottom gate with top drain-source contact structure of both devices exhibited a unipolar property of field-effect transistor behavior. Furthermore, the existence of fullerene (PCBM) and poly(3-hexylthiophene) (P3HT) films as a charge-accepting-like storage layers in p-channel and n-channel devices, respectively, resulted in a reversible Vth shifts upon the application of external gate bias (Vbias). Hence, p-channel OFETs exhibited a memory window of 2.4 V and n-channel OFETs exhibited a memory window of 10.7 V for program and erase electrically upon application of gate bias. [ABSTRACT FROM PUBLISHER]

This study reports the performance improvement of pentacene-based organic thin-film transistor (OTFT) with the proposed planar bottom-contact structure and the bi-layer gate dielectric. The planar bottom-contact (pBC) structure can provide a continuous plane to enhance the grain growth continuity of pentacene layer, further improving the charge carriers injection or/and transportation near the edge of source/drain electrodes; hence, the pBC structure reduces the contact resistance between the organic semiconductor and the source/drain metals, resulting in the improved field-effect mobility. In addition, the bi-layer gate dielectric is used for the etching selectivity to control the planarization process well. [ABSTRACT FROM PUBLISHER]

We have fabricated a top contact pentacene-based organic thin-film transistors (OTFTs) with bi-layer WO3/Au electrodes. We have obtained that the performance and the field-effect mobility of the devices with bilayer WO3/Au electrode was highly improved by comparing with pentacene based transistor without WO3 layer. The field-effect mobility was increased from 0.47 cm2/Vs to 0.69 cm2/Vs in the device with bilayer WO3/Au electrodes. From temperature dependence characteristics and surface morphology of pentacene, the improved device performance was due to the reduction in barrier height and surface roughness after inserting a suitable transitions metal oxide layer between the pentacene and the gold electrodes. [ABSTRACT FROM PUBLISHER]

The flow in conical supersonic micronozzles and behind them by deposition of pentacene accelerated by helium was studied with the use of direct simulation Monte-Carlo method. The Knudsen number in critical cross-section of nozzles is 0.0043. A directedness of resulting accelerated pentacene flow was studied as a function of cone angle and geometrical Mach number of the nozzle. The intensity of heavy gas flow in the hypersonic region can be elevated by one order using supersonic nozzles. [ABSTRACT FROM AUTHOR]

The performance of thin-film transistors based on an aluminum oxide gate dielectric and a pentacene semiconductor have been systematically enhanced by modification of the oxide surface. The oxide layer was formed at room temperature using a standard anodization technique. The effects of surface modification of the oxide layer on device performance have been investigated. Higher mobility transistors were fabricated by passivating the oxide layer with a self-assembled molecular monolayer of an alkyl phosphonic acid or a spin-coated acrylic film. In both cases the normalized sub-threshold swing was reduced by a factor of 1.9 and 1.5, and the maximum charge-carrier mobility was increased by one and two orders of magnitudes respectively. The much increased mobility for transistors modified by a thin film of polymethylmethacrylate (PMMA) is attributed to the larger pentacene grain size. [ABSTRACT FROM PUBLISHER]

The electrical behavior of an organic memory device based on a pentacene thin film metal-insulator-semiconductor (MIS) and transistor structures incorporating a layer of thermally evaporated metallic floating gate is demonstrated. The devices have been realised using thermally evaporated pentacene (semiconductor) and spin-coated polymethylmethacrylate (PMMA) (insulator). The drain and source electrodes have been fabricated by evaporating 50 nm gold, and the gate electrode was made from 50 nm evaporated aluminium on a clean glass substrate. The devices containing the floating gate exhibited clear hysteresis in their electrical characteristics (output and transfer characteristics for transistors and also capacitance-voltage (C-V) characteristics of MIS structures). Under an appropriate gate bias (2s pulses), the floating gate is charged and discharged, resulting in significant threshold voltage shifts. Pulses of as low as 1 V resulted in a clear write and erase states. The hysteresis in C-V characteristics and shifts in the threshold voltage of the transfer characteristics were attributed to the charging and discharging of the floating gate. The detailed programming and erasing procedures are reported. [ABSTRACT FROM PUBLISHER]

We consider a trapping—detrapping noise model to explain the recently observed maximum in the spectral density of current fluctuations in organic semiconductors (tetracene, pentacene), under space-charge-limited-current conditions. The ratio u = nt/Nt of filled to total traps is obtained from the current-voltage characteristics and is used to evaluate the current noise spectral density at the trap-filling transition. [ABSTRACT FROM AUTHOR]

Charge transfer properties of pentacene adsorbed on silver is investigated using DFT methods. Optimized geometry of pentacene after adsorption on silver indicates distortion in hexagonal structure of the ring close to the silver cluster and deviations in co-planarity of carbon atoms due to the variations in bond angles and dihedral angles. Theoretically simulated absorption spectrum has a symmetric surface plasmon resonance peak around 486nm corresponding to the transfer of charge from HOMO-2 to LUMO. Theoretical SERS confirms the process of adsorption, tilted orientation of pentacene on silver surface and the charge transfers reported. Localization of electron density arising from redistribution of electrostatic potential together with a reduced bandgap of pentacene after adsorption on silver suggests its utility in the design of electro active organic semiconducting devices. [ABSTRACT FROM AUTHOR]

Organic thin-film transistors (OTFTs) with bottom-gate top-contacts architecture have been fabricated on glass substrates using solution-processed TIPS-pentacene (triisopropylsilyl pentacene) as semiconductor and cross-linked PVP (poly(4-vinylphenol)) as insulator, with Gold contacts evaporated through shadow masks. Applying constant electrical stress for short time on both gate and drain, an increase of drain current respect just finished devices have been observed in output and transfer characteristics. [ABSTRACT FROM AUTHOR]

Metal-insulator-semiconductor (MIS) capacitors based on pentacene semiconductor and CYTOP polymeric dielectric were realized and characterized by capacitance-frequency measurements (C-F) under dark and light conditions at different aging times. The devices showed good responses under light radiation at zero time and a strong degradation of the performances during the time due to a modification of the impedance of the dielectric layer. [ABSTRACT FROM AUTHOR]

In this work we demonstrate that the unified model and parameter extraction method (UMEM) can be used to describe the behavior of hybrid complementary metal-oxide-semiconductor thin film transistors (CMOS TFTs) fabricated with cadmium sulfide (CdS) and pentacene as n-type and p-type active layer, respectively. Both devices were fabricated using a bottom gate configuration and top source-drain (SD) contacts. In particular, we describe the effect of semiconductor defects using the effective medium approximation, which considers a localized charge distribution in the bandgap of the semiconductor. Extracted parameters from UMEM were used in HSPICE to simulate the CMOS inverters fabricated previously by our group. [ABSTRACT FROM PUBLISHER]

A temperature analysis of the OTFT having pentacene as channel semiconductor and PMMA as gate dielectric has been performed. The experimental results have been studied by extracting the field-effect mobility of the TFTs and relating it to the sample’s temperature. We have found the mobility to follow the Meyer-Neldel rule. This behavior can be considered imputable to the channel carrier hopping. The gate voltage effect on the thermal activation energy for the mobility and the asymptotic parameter has been also taken into account. [ABSTRACT FROM AUTHOR]

With the aim of investigating the effect of alkyl chain orientation of self-assembled monolayers (SAMs) on the pentacene growth mode and the performances of organic thin-film transistors (OTFT), pentacene films were deposited on octadecyltrichlorosilane (ODTS) with different alkyl chain orientation. The alky chain orientation of ODTS was controlled by adjusting the reaction temperature. Pentacene films on ordered ODTS were found to have higher crystallinity and better device performances than those on the disordered ODTS, and their differences increased with the substrate temperature. These results can be explained by (1) lattice matching effect between the pentacene crystals and ODTS, and (2) temperature-dependent alkyl chains mobility of ODTS. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We fabricated inorganic-organic hybrid heterojunction between indium phosphide (InP) and pentacene for photodetector application. InP layer was grown on n-Si substrate by atmospheric pressure metal organic chemical vapour deposition (MOCVD) technique. Morphological properties of InP and pentacene thin film were characterized by atomic force microscopy (AFM). Current-voltage characteristics were investigated in dark and under illumination condition at room temperature. During illumination, different wavelengths of visible and infrared light source were employed to perform the electrical measurement. Enhancement of photocurrent was observed with decreasing in wavelength of incident photo radiation. Ideality factor was found to be 1.92. High rectification ratio of 225 was found at ± 3 V in presence of infrared light source. This study provides new insights of inorganic-organic hybrid heterojunction for broadband photoresponse in visible to near infrared (IR) region under low reverse bias condition. [ABSTRACT FROM AUTHOR]

In the present work, an examination of the electronic properties of pentacene, dinaphtho[2,3-b:2',3'-f ]thieno[3,2- b]thiophene (DNTT) and dianthra[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DATT) using ab initio methodology is reported. According to the results, the herringbone packing and p-stack orientation play an important role in the hole mobilities for DNTT and DATT. Band structure of pentacene crystals is more anisotropic than DNTT and DATT and the highest values for the dispersion are found in the herrigbone plane. For the band transport regime, it is demonstrated that the DATT must have carrier mobilities larger than pentacene and smaller than that found in DNTT. [ABSTRACT FROM AUTHOR]

We had fabricated the pentacene organic thin-film transistor (OTFT) with very thin film thickness and investigated the electrical characteristics. When the film thickness decreased, the on current of OTFT increased. It is considered that the quantum level is formed in the triangle potential. The mobility of OTFT is improved by using quantum effect. In order to fabricate uniformly ultrathin OTFT without pinhole, the size of pentacene island must be smaller. We tried to fabricate pentacene island using atomic hydrogen annealing (AHA). It is found that pentacene and resist can be etched by AHA without damage. It is expected that this method is a promising technique for fabrication of ultrathin OTFT with small island. [ABSTRACT FROM PUBLISHER]

The performance of multi-layer graphene (MLG) films as alternative electrodes for pentacene organic field effect transistors (OFETs) was investigated and compared to conventional OFETs with Au electrodes. We observed the enhancement of charge injection for graphene-electrode pentacene OFETs (GR-pentacene OFET), as evidenced by decreased contact resistance and lower barrier height than in the case of Au-electrode pentacene OFETs (Au-pentacene OFET). Our results show that the beneficial orientation of the interfacial dipole layer is responsible for the improved performance of the graphene-electrode OFETs compared to Au-pentacene OFETs. This study will help to establish graphene-based thin films as efficient electrode materials for organic electronic devices. [ABSTRACT FROM AUTHOR]

We report on the solution-processed thin-film transistors (TFTs) fabricated by the vertical flowing of the viscous 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and isotatic (i-) poly-(methyl methacrylate) (PMMA) blend. This vertical flowing method provide us with phase-separated film (TIPS pentcene (up)/ i-PMMA(down) after drying. As fabricated on a highly capacitive 20 nm-thick Al2O3 dielectric, our device displayed a high mobility of 0.20 cm2/V s, a low operation voltage of -10 V, and little hysteresis. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors (OFETs) were fabricated using pentacene thin layer, and the effects of inserted Lewis-acid thin layers on electrical properties were investigated. The OFETs have active layers of pentacene and vanadium pentoxide (V2O5) as a Lewis-acid layer. Typical source-drain current (IDS) vs. source-drain voltage (VDS) curves were observed under negative gate voltages (VGS) application, and the shift of the threshold voltage for FET driving (Vt) to positive side was also observed by V2O5 layer insertion, that is, -2.5 V for device with V2O5 layer and -5.7 V for device without V2O5 layer. It was thought that charge transfer (CT) complexes which were formed at the interface between pentacene and V2O5 layer were dissociated by the applied gate voltage, and the generated holes seem to contribute to drain current and the apparent Vt improvement. [ABSTRACT FROM AUTHOR]

The current-gain cutoff frequency for bottom contact p-channel pentacene thin-film transistors (TFTs) with channel lengths of 2-10 μm has been investigated. A maximum cutoff frequency of 11.4 MHz was obtained from a pentacene TFT with a channel length of 2 μm and a saturation mobility of 0.73 cm2/Vs. [ABSTRACT FROM AUTHOR]

An anthracene-2-thiol treatment of the electrodes in bottom-contact pentacene field-effect transistors is used to improve the performance of organic transistors. Transistors with different channel lengths are prepared in order to separate the sheet resistance from the parasitic series resistance of the contacts and leads. The treatment results in a reduced sheet resistance of more than one order of magnitude whereas the parasistic resistance is nearly unaffected. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

We investigated the structural properties and transfer properties of pentacene thin films fabricated by thermal deposition and transfer printing onto SiO2 and plastic substrates, respectively. The dependence of the crystallite size on the printing time, temperature and pressure were measured. The increases of crystalline size were observed when pentacene thin films were printed under specific conditions, e.g. 120°C & 600 psi and can be correlated with the improvement of the field effect mobility of pentacene thin-film transistors. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Resonant enhancements of Raman scattering intensities offer the sensitivity required to study nanoscale pentacene films that reach into monolayer thickness. In the results reported here structural characterization of ultra-thin layers and of their fundamental optical properties are investigated by resonant Raman scattering from intra-molecular and inter-molecular vibrations. In this work Raman methods emerge as ideal tools for the study of physics and characterization of ultra-thin nanoscale films of molecular organic materials fabricated on diverse substrates of current and future devices. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We irradiated Organic Thin-Film Transistors with wavelengths ranging in the visible and near ultraviolet parts of the solar spectrum, reporting strong degradation in few hours. We modeled the sunlight-induced permanent degradation, taking into account the mobility reduction. The model closely fits the experimental data, allowing the prediction of the device permanent degradation under sunlight exposure. [ABSTRACT FROM PUBLISHER]