Showing papers by "Tobin J. Marks published in 2006"
TL;DR: Thiophene-based n-type semiconductors exhibiting similar film morphologies and microstructures on various bilayer gate dielectrics therefore provide an incisive means to probe TFT performance parameters versus semiconductor-dielectric interface relationships.
Abstract: This study describes a general approach for probing semiconductor−dielectric interfacial chemistry effects on organic field-effect transistor performance parameters using bilayer gate dielectrics. Organic semiconductors exhibiting p-/n-type or ambipolar majority charge transport are grown on six different bilayer dielectric structures consisting of various spin-coated polymers/HMDS on 300 nm SiO2/p+-Si, and are characterized by AFM, SEM, and WAXRD, followed by transistor electrical characterization. In the case of air-sensitive (generally high LUMO energy) n-type semiconductors, dielectric surface modifications induce large variations in the corresponding OTFT performance parameters although the film morphologies and microstructures remain similar. In marked contrast, the device performance of air-stable n-type and p-type semiconductors is not significantly affected by the same dielectric surface modifications. Among the bilayer dielectric structures examined, nonpolar polystyrene coatings on SiO2 having ...
451 citations
TL;DR: The device operational lifetime is comparable to that of devices with Sn-doped In(2)O(3) (ITO)/PET anodes, and the advantages of this novel type of anode over conventional ITO are discussed.
Abstract: Single-walled carbon nanotube (SWNT) films on flexible PET (polyethyleneterephthalate) substrates are used as transparent, flexible anodes for organic light-emitting diodes (OLEDs). For polymer-based OLEDs having the structure: SWNT/PEDOT-PSS:MeOH/TFB (poly(9,9dioctylfluorene-co-N-(4-butylphenyl)diphenylamine)) + TPD-Si2 (4,4′-bis[(p-trichlorosilylpropylphenyl)phenylamino]biphenyl) /BT (poly(9,9dioctylfluorene-co-benzothiadiazole))/CsF/Al, a maximum light output of 3500 cd/m 2 and a current efficiency of 1.6 cd/A have been achieved. The device operational lifetime is comparable to that of devices with Sn-doped In 2O3 (ITO)/PET anodes. The advantages of this novel type of anode over conventional ITO are discussed.
357 citations
TL;DR: Transparent inorganic–organic hybrid n-type TFTs fabricated at room temperature by combining In2O3 thin films grown by ion-assisted deposition, with nanoscale organic dielectrics self-assembled in a solution-phase process are reported, suggesting new strategies for achieving ‘invisible’ optoelectronics.
Abstract: High-performance thin-film transistors (TFTs) that can be fabricated at low temperature and are mechanically flexible, optically transparent and compatible with diverse substrate materials are of great current interest. To function at low biases to minimize power consumption, such devices must also contain a high-mobility semiconductor and/or a high-capacitance gate dielectric. Here we report transparent inorganic-organic hybrid n-type TFTs fabricated at room temperature by combining In2O3 thin films grown by ion-assisted deposition, with nanoscale organic dielectrics self-assembled in a solution-phase process. Such TFTs combine the advantages of a high-mobility transparent inorganic semiconductor with an ultrathin high-capacitance/low-leakage organic gate dielectric. The resulting, completely transparent TFTs exhibit excellent operating characteristics near 1.0 V with large field-effect mobilities of >120 cm2 V(-1) s(-1), drain-source current on/off modulation ratio (I(on)/I(off)) approximately 10(5), near-zero threshold voltages and sub-threshold gate voltage swings of 90 mV per decade. The results suggest new strategies for achieving 'invisible' optoelectronics.
348 citations
TL;DR: OfETs based on this polymer class exhibit excellent ambient operational stability and have low turn-on voltages and current on/off ratios.
Abstract: The synthesis and physicochemical properties of a new class of thiophene/arenesilole-containing π-conjugated polymers are reported. Examples of this new polymer class include the following: poly(2,5-bis(3‘,3‘ ‘-dihexylsilylene-2‘,2‘ ‘-bithieno)thiophene) (TS6T1), poly(2,5‘-bis(3‘ ‘,3‘ ‘‘-dihexylsilylene-2‘ ‘,2‘ ‘‘-bithieno)bithiophene) (TS6T2), poly(2,5‘-bis(2‘ ‘,2‘ ‘‘-dioctylsilylene-1‘ ‘,1‘ ‘‘-biphenyl)thiophene) (BS8T1), and poly(2,5‘-bis(2‘ ‘,2‘ ‘‘-dioctylsilylene-1‘ ‘,1‘ ‘‘-biphenyl)bithiophene) (BS8T2). Organic field-effect transistors (OFETs) with hole carrier mobilities as high as 0.02−0.06 cm2/V s in air, low turn-on voltages, and current on/off ratios >105−106 are fabricated using solution processing techniques with the above polymers as the active channel layer. OFETs based on this polymer class exhibit excellent ambient operational stability.
325 citations
TL;DR: Field-effect transistor (FET) measurements demonstrate that all of these materials are FET-active and, depending on the molecular architecture, exhibit comparably good p- or n-type mobility when optimum film microstructural order is achieved.
Abstract: We present here the systematic synthesis and comparative physicochemical characterization of a series of regiochemically varied and core size extension-modulated arene(perfluoroarene)-thiophene oligomers. The molecules investigated are: 5,5''-diphenyl-2,2':5',2'':5'',2'''-quaterthiophene (1), 5,5'-bis[1-[4-(thien-2-yl)phenyl]]-2,2'-dithiophene (2), 4,4'-bis[5-(2,2'-dithiophenyl)]-biphenyl (3), 5,5''-diperfluorophenyl-2,2':5',2'':5'',2'''-quaterthiophene (4), 5,5'-bis[1-[4-(thien-2-yl)perfluorophenyl]]-2,2'-dithiophene (5), 4,4'-bis[5-(2,2'-dithiophenyl)]-perfluorobiphenyl (6), 5,5''-diperfluorophenyl-2,2':5',2''-tertthiophene (7), 5,5'-diperfluorophenyl-2,2'-dihiophene (8), and 5,5-diperfluorophenylthiophene (9). Trends in optical absorption and emission parameters, molecular structures as defined by single-crystal X-ray diffraction, as well as electrochemical redox processes are described. The morphologies and microstructures of the vapor-deposited films grown over a range of growth temperatures have also been characterized. Field-effect transistor (FET) measurements demonstrate that all of these materials are FET-active and, depending on the molecular architecture, exhibit comparably good p- or n-type mobility when optimum film microstructural order is achieved. A very large n-channel mobility of approximately 0.5 cm2/Vs with I(on)/I(off) ratios > 10(8) is achieved for films of 4.
296 citations
TL;DR: In this article, a two-component layered structure of organic light-emitting transistors (OLETs) with balanced ambipolar transport and mobility as large as 3 × 10 cm V s is presented.
Abstract: Today organic materials are routinely employed for the fabrication of light-emitting devices (OLEDs) and thin-film transistors (OTFTs), with the first technological realizations already having reached the market. Moreover, OTFTs with unipolar mobility values comparable to those of amorphous silicon (1 cm V s) have now been demonstrated. Applications impacting display technologies and those sectors where low cost is a key factor and low performance is acceptable include electronic paper and radio-frequency identification (RF-ID) products. In a recent development, OTFTs also exhibiting electroluminescence (EL) have been successfully demonstrated. Organic light-emitting transistors (OLETs) represent a significant technological advance by combining two functionalities, electrical switching and light emission, in a single device, thus significantly increasing the potential applications of organic semiconductors. In particular, if appropriate materials can be introduced, OLETs offer an ideal structure for improving the lifetime and efficiency of organic light-emitting heterostructures due to the intrinsically different driving conditions and charge-carrier balance compared to conventional OLEDs. Potential applications of OLETs include flat-panel display technologies, lighting, and, ultimately, easily fabricated organic lasers. The first OLET prototypes were unipolar transport devices, and recombination was expected to take place in close proximity to the metallic drain electrode where efficiency-depleting exciton quenching is also likely to occur. To avoid this significant device deficiency and to instead generate EL nearer the center of the channel, OLETs with ambipolar charge transport would be highly desirable. Furthermore, balanced ambipolar conduction is crucial for maximizing exciton recombination through efficient electron–hole balancing. Up to now various solutions have been proposed: single ambipolar materials and two-component coevaporated or layered structures. In coevaporated films, two materials are simultaneously sublimed to form bulk heterojunctions. However, carrier transport is unbalanced and the mobility values are below 10 cm V s. Devices employing a polymer film showing intrinsic ambipolar transport have also been reported but with mobility values for both charge carriers around 10 cm V s. In this paper we report OLETs based on two-component layered structures that have balanced ambipolar transport and mobility values as large as 3 × 10 cm V s. These devices are realized by sequentially depositing p-type (a,x-dihexyl-quaterthiophene, DH4T) and n-type films (N,N′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide, PTCDIC13H27, P13). The combination with the highest mobility and most-balanced transport is obtained with DH4T grown in direct contact with the dielectric. For comparison, we have also employed pentacene in place of DH4T as the p-type material and showed that unbalanced ambipolarity is obtained. Morphological analysis of the outermost and buried layers, performed by laser scanning confocal microscopy (LSCM), allows selective imaging of materials with energetically separated photoluminescence (PL) spectra. Importantly, it is shown that ‘growth compatibility’ between the nand p-type materials is essential in forming a continuous interface and thereby controlling the resulting OLET optoelectronic-response properties. Each OLET material was first evaluated in a single layer in a top source–drain contact OTFT. As substrates we employed heavily doped silicon wafers with thermally grown oxides. Surface treatments such as octadecyltrichlorosilane or hexamethyldisilazane did not result in substantial improvement in the device performance. Parameters such as substrate temperature (Tsub) and evaporation rate were varied to optimize electrical characteristics. The optimum growth conditions were found to be: Tsub = 90 °C and rate = 0.1 A s –1 for DH4T, and Tsub = 25 °C and rate = 0.1 A s –1 for P13. In Table 1, the mobility (l) and threshold-voltage (Vth) values obtained are summarized. These are comparable to the highest values reported in the literature. The DH4T devices were stable even C O M M U N IC A TI O N S
220 citations
Abstract: A series of bimetallic organo-group 4 “constrained geometry” catalysts and binuclear bisborane and bisborate cocatalysts have been synthesized to probe catalyst center–catalyst center cooperativity effects on olefin enchainment in homogenous olefin polymerization and copolymerization processes. Significant nuclearity effects are found versus mononuclear controls, and the effect can be correlated with metal–metal approach distances and ion pairing effects. Novel polymer structures can be obtained by using such binuclear catalyst/cocatalyst systems.
219 citations
TL;DR: In this article, the synthesis of delafossite-type oxides from their constituent binary metal oxides, oxide hydroxides, by low temperature (<210 °C) and low pressure (<20 atm) hydrothermal reactions are described.
Abstract: The syntheses of copper and silver delafossite-type oxides from their constituent binary metal oxides, oxide hydroxides and hydroxides, by low temperature (<210 °C) and low pressure (<20 atm) hydrothermal reactions are described. Particular emphasis is placed on how the acid−base character of a constituent oxide determines its solubility and therefore whether a particular delafossite-type oxide can be synthesized, a strategy utilized by geologists and mineralogists to understand the conditions necessary for the synthesis of various minerals. Thus, the geochemical and corrosion science literature are shown to be useful in understanding the reaction conditions required for the syntheses of delafossite-type oxides and the relationship between reactant metal oxide acid−base character, solubility, aqueous speciation, and product formation. Manipulation of the key parameters, temperature, pressure, pH, and reactant solubility, results in broad families of phase-pure delafossite-type oxides in moderate to high y...
202 citations
TL;DR: In this article, the electrical characteristics of bottom contact organic field effect transistors fabricated with the air-stable n-type semiconductor N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis (dicarboximide) (PDI-8CN2) are described.
Abstract: The electrical characteristics of bottom-contact organic field-effect transistors fabricated with the air-stable n-type semiconductor N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN2) are described. The mobility, threshold voltage, subthreshold swing, and Ion∕Ioff ratio(VDS=40V, VG=0∼40V) are 0.14cm2∕Vs, 1.6V, 2.0V/decade, and 1.2×103, respectively. The effect of electrode/dielectric surface treatment on these devices is also examined, with a combination of 1-octadecanethiol and hexamethyldisilazane. Organic complementary five-stage ring oscillators were fabricated using pentacene and PDI-8CN2, and operated at an oscillation frequency of 34kHz and a propagation delay per stage of 3μs.
133 citations
TL;DR: A novel type of "X-shaped" two-dimensional electro-optic chromophore with extended conjugation with remarkably blue-shifted optical maximum while maintaining a very large first hyperpolarizability (beta) is found.
Abstract: A novel type of “X-shaped” two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH2Cl2) while maintaining a very large first hyperpolarizability (β). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a βzzz value of 1840 × 10-30 esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (χ(2)333 ∼ 232 pm/V at 1064 nm; r33 ∼ 45 pm/V at 1310 nm). This work demonstrates an attractive approach to...
124 citations
TL;DR: In this paper, the exothermic hydroamination/cyclization of a prototypical aminoalkyne, H2N(CH2)3C⋮CR, was investigated.
TL;DR: Thin-film characterization by a variety of techniques underscore the importance of the chromophore molecular architecture as well as film growth method on film microstructure and optical/electrooptic response.
Abstract: The new dibranched, heterocyclic "push-pull" chromophores bis{1-(pyridin-4-yl)-2-[2-(N-methylpyrrol-5-yl)]ethane}methane (1), 1-(pyrid-4-yl)-2-(N-methyl-5-formylpyrrol-2-yl)ethylene (2), {1-(N-methylpyridinium-4-yl)-2-[2-(N-methylpyrrol-5-yl)]ethane}{(1-(pyridin-4-yl)-2-[2-(N-methylpyrrol-5-yl)]ethane}methane (3), N-methyl-2-[1-(N-methylpyrid-4-yl)ethen-2-yl]-5-[pyrid-4-yl]ethen-2-yl]pyrrole iodide (4), bis{1-(N-methyl-4-pyridinio)-2-[2-(N-methylpyrrol-5-yl)]ethane}methane iodide (5), and N-methyl-2,5-[1-(N-methylpyrid-4-yl)ethen-2-yl]pyrrole iodide (6) have been synthesized and characterized. The neutral (1 and 2) and monomethyl salts (3 and 4) undergo chemisorptive reaction with iodobenzyl-functionalized surfaces to afford chromophore monolayers SA-1/SA-2 and SA-3/SA-4, respectively. Molecular structures and other physicochemical properties have been defined by (1)H NMR, optical spectroscopy, and XRD. Thin-film characterization by a variety of techniques (optical spectroscopy, specular X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and angle-dependent polarized second harmonic generation) underscore the importance of the chromophore molecular architecture as well as film growth method on film microstructure and optical/electrooptic response.
TL;DR: In this paper, double-layer transparent conducting oxide thin film structures containing In-doped CdO (CIO) and Sndoped In2O3 (ITO) layers were grown on glass by metal-organic chemical vapor deposition and ion-assisted deposition (IAD), respectively, and used as anodes for polymer light-emitting diodes (PLEDs).
Abstract: Double-layer transparent conducting oxide thin film structures containing In-doped CdO (CIO) and Sn-doped In2O3 (ITO) layers were grown on glass by metal-organic chemical vapor deposition and ion-assisted deposition (IAD), respectively, and used as anodes for polymer light-emitting diodes (PLEDs). These films have a very low overall In content of 16at.%. For 180-nm-thick CIO/ITO films, the sheet resistance is 5.6Ω∕◻, and the average optical transmittance is 87.1% in the 400–700nm region. The overall figure of merit (Φ=T10∕Rsheet) of the double-layer CIO/ITO films is significantly greater than that of single-layer CIO, IAD-ITO, and commercial ITO films. CIO/ITO-based PLEDs exhibit comparable or superior device performance versus ITO-based control devices. CIO/ITO materials have a much lower sheet resistance than ITO, rendering them promising low In content electrode materials for large-area optoelectronic devices.
TL;DR: This study demonstrates that the DFH-4T film growth transition from monolayer to multilayer on Au is accompanied by dramatic morphology and molecular orientation changes, starting from an amorphous, pitted, and disordered monolayers to crystalline and smooth bi/tetralayers but with the molecules reoriented by 90 degrees.
Abstract: The evolution in growth morphology and molecular orientation of n-type semiconducting α,ω-diperfluorohexyl-quaterthiophene (DFH-4T) on Au(111) is investigated by scanning tunneling microscopy and scanning tunneling spectroscopy as the film thickness is increased from one monolayer to multilayers. Monolayer-thick DFH-4T films are amorphous and morphologically featureless with a large pit density, whereas multilayer films exhibit drastically different terraced structures consisting of overlapping platelets. Large changes in DFH-4T molecular orientation are observed on transitioning from two to four monolayers. Parallel electrical characterization of top-versus-bottom contact configuration DFH-4T FETs with Au source/drain electrodes reveals greatly different mobilities (μTOP = 1.1 ± 0.2 10-2 cm2V-1s-1 versus μBOTTOM = 2.3 ± 0.5 10-5 cm2V-1s-1) and contact resistances (RC-TOP = 4−12 MΩcm vs RC-BOTTOM > 1 GΩcm). This study provides important information on the organic semiconductor-source\drain electrode inter...
TL;DR: It is shown that NN* influences the spin dynamics of the photogenerated triradical states (2,4)(MeOAn(+)*-6ANI-Ph(NN*)-NI(-)*), resulting in slower charge recombination within the trIRadical compared to the corresponding biradical lacking NN*.
Abstract: Appending a stable radical to the bridge molecule in a donor−bridge−acceptor system (D−B−A) is potentially an important way to control charge- and spin-transfer dynamics through D−B−A We have attached a nitronyl nitroxide (NN•) stable radical to a D−B−A system having well-defined distances between the components: MeOAn−6ANI−Ph(NN•)−NI, where MeOAn = p-methoxyaniline, 6ANI = 4-(N-piperidinyl)naphthalene-1,8-dicarboximide, Ph = phenyl, and NI = naphthalene-1,8:4,5-bis(dicarboximide) MeOAn-6ANI, NN•, and NI are attached to the 1, 3, and 5 positions of the Ph bridge Using both time-resolved optical and EPR spectroscopy, we show that NN• influences the spin dynamics of the photogenerated triradical states 2,4(MeOAn+•−6ANI−Ph(NN•)−NI-•), resulting in slower charge recombination within the triradical compared to the corresponding biradical lacking NN• The observed spin−spin exchange interaction between the photogenerated radicals MeOAn+• and NI-• is not altered by the presence of NN•, which only accelerates
TL;DR: In this article, a series of ITO anode-linked silyltriarylamine precursors are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure and charge-injection/electroluminescence properties.
Abstract: Molecule-scale structure effects at indium tin oxide (ITO) anode−hole transport layer (HTL) interfaces in organic light-emitting diode (OLED) heterostructures are systematically probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine precursors differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure and charge-injection/electroluminescence properties. These precursors form conformal and largely pinhole-free self-assembled monolayers (SAMs) on the ITO anode surface with angstrom-level thickness control. Deposition of a HTL on top of the SAMs places the probe molecules precisely at the anode−HTL interface. OLEDs containing ITO/SAM/HTL configurations have dramatically varied hole-injection magnitudes and OLED responses. These can be correlated with the probe molecular structures and electrochemically derived heterogeneous electron-transfer rates for such triarylamine fragments. ...
TL;DR: A series of mononuclear and polynuclear trityl (perfluoroaryl)borate, -aluminate, and gallate reagents, potential cocatalysts/activators for metallocene-mediated olefin polymerization, have been synthesized via fluoride abstraction from trithl fluoride (Ph3CF) by the organo Lewis acid reagents as mentioned in this paper.
TL;DR: In this paper, an organic complementary D flip-flop using PDI-8CN2 n-channel transistors and pentacene p-channel Transistors is described, and the measured clock-to-output delay is 25 mus for 1 kHz and 14 mus for 5 kHz.
Abstract: The development of organic complementary circuits has been largely limited by the development of suitable organic n-channel transistors. However, recent advances have led to materials such as the high-mobility air-stable n-channel organic semiconductor, N,N'-bis(n-octyl)-dicyanoperylene-3, 4 : 9, 10-bis(dicarboximide), PDI-8CN2. Here, the fabrication of an organic complementary D flip-flop using PDI-8CN2 n-channel transistors and pentacene p-channel transistors is described. The measured clock-to-output delay is 25 mus for 1 kHz, and 14 mus at the clock frequency of 5 kHz. This is the fastest clock speed for an organic complementary circuit yet achieved
TL;DR: The present study represents the first case in which a functionalized comonomer is efficiently used to effect both propagation and chain transfer chemistry during olefin polymerization.
Abstract: The comonomer 5-hexenylsilane is introduced into organotitanium-mediated ethylene polymerizations to produce silane-terminated ethylene/5-hexenylsilane copolymers. The resulting polymers were characterized by 1H and 13C NMR, GPC, and DSC. High activities (up to 107 g polymer/(mol Ti·atm ethylene·h)) and narrow polydispersities are observed in the polymerization/chain transfer process. Ethylene/5-hexenylsilane copolymer molecular weights are found to be inversely proportional to 5-hexenylsilane concentration, supporting a silanolytic chain transfer mechanism. Control experiments indicate that chain transfer mechanism by 5-hexenylsilane is significantly more efficient than that of n-hexylsilane for organotitanium-mediated ethylene polymerization. The present study represents the first case in which a functionalized comonomer is efficiently used to effect both propagation and chain transfer chemistry during olefin polymerization.
TL;DR: In this paper, an n-channel and ambipolar organic field-effect transistors with a few tens of nanometer channel length were fabricated and characterized, and the shortest channel length of 15nm was obtained.
Abstract: N-channel and ambipolar organic field-effect transistors (OFETs) with a few tens of nanometer channel length were fabricated and characterized. N,N′-bis(n-octyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDI-8CN2) was employed as the active semiconductor and yielded a linear regime electron mobility of 2.3×10−3cm2∕Vs at 5×105V∕cm in an OFET with channel length of 15nm. An ambipolar heterostructure transistor consisting of thin layers of PDI-8CN2 and pentacene was fabricated with channel length of about 23nm. Field-effect hole and electron mobilities of 9.2×10−3 and 4.0×10−3cm2∕Vs, respectively, are obtained at 5×105V∕cm. These results represent the shortest channel length n-channel and ambipolar organic transistors that have been fabricated.
TL;DR: From the calculated carrier effective masses, it is found that sterically governed molecular planarity plays a crucial role in the transport properties of these semiconductors.
Abstract: Density-functional theory (DFT) is employed to investigate the structural, electronic, and transport properties of several isomeric fluoroarene-oligothiophene-based semiconductors. Three oligothiophene systems varying in the perfluoroarene group positions within the molecule are studied to understand the electronic structure leading to the observed mobility values and to the n- or p-type behavior in these structures. Analyses of both intermolecular interactions in dimers and extended interactions in crystalline structures afford considerable insight into the electronic properties and carrier mobilities of these materials, as well as the polarity of the charge carriers. From the calculated carrier effective masses, we find that sterically governed molecular planarity plays a crucial role in the transport properties of these semiconductors. Our calculations correlate well with experimentally obtained geometries, highest-occupied molecular orbital (HOMO)/lowest-unoccupied molecular orbital (LUMO) energies, and the experimental carrier mobility trends among the systems investigated.
TL;DR: In this paper, the effects of bias stress (gate stress or drain stress) on nanowire field effect transistor (NW-FET) stability were investigated as a function of stress bias and stress time.
Abstract: The effects of bias stress (gate stress or drain stress) on nanowire field-effect transistor (NW-FET) stability were investigated as a function of stress bias and stress time. The n-channel NW-FETs used a nanoscopic self-assembled organic gate insulator, and each device contained a single ZnO nanowire. Before stress, the off current is limited by a leakage current in the 1nA range, which increases as the gate to source bias becomes increasingly negative. The devices also exhibited significant changes in threshold voltage (Vth) and off current over 500 repeated measurement sweeps. The leakage current was significantly reduced after gate stress, but not after drain stress. Vth variations observed upon successive bias sweeps for devices following gate stress or drain stress were smaller than the Vth variation of unstressed devices. These observations suggest that gate stress and drain stress modify the ZnO nanowire-gate insulator interface, which can reduce electron trapping at the surface and therefore redu...
TL;DR: A series of divinylbenzene cross-linked, amino-functionalized polystyrene resins such as aminomethylated polystyrenes of varying mesh size, piperazinomethodododecanetrityl....
TL;DR: In this paper, electron beam lithography (EBL) is used to write patterns directly onto cured poly(dimethylsiloxane) stamps, thus overcoming the need for multiple patterning steps.
Abstract: Poly(dimethylsiloxane) (PDMS) has become a ubiquitous material for microcontact printing, yet there are few methods available to pattern a completed PDMS stamp in a single step. It is shown here that electron beam lithography (EBL) is effective in writing patterns directly onto cured PDMS stamps, thus overcoming the need for multiple patterning steps. Not only does this method allow the modification of an existing lithographic pattern, but new 3D features such as cones, pits, and channels can also be fabricated. EBL can also be used to fabricate PDMS masks for photolithography whereby 1:1 pattern transfer into a photoresist is achieved. Additionally, direct EBL writing of surface chemical features has been achieved using a PDMS stamp coated with a self-assembled monolayer. An electrostatic mechanism appears to be operative in the EBL patterning process, as supported by calculations, thermogravimetric analysis, time-of-flight secondary ion mass spectroscopy, optical and atomic force microscopy, and chemica...
Patent•
20 Dec 2006TL;DR: Inorganic semiconducting compounds, composites and compositions thereof, and related device structures are discussed in detail in this paper, where the authors propose a method to construct a semiconductor device.
Abstract: Inorganic semiconducting compounds, composites and compositions thereof, and related device structures.
TL;DR: In this paper, the frequency dependent charge transport in organic light-emitting diodes, including marked negative capacitance (NC), is reproduced through an equivalent circuit model, and the robustness of the model is tested through impedance spectroscopy characterization as a function of bias changes and layer thickness modifications.
Abstract: Frequency dependent charge transport in organic light-emitting diodes, including marked negative capacitance (NC), is reproduced through an equivalent circuit model. The robustness of the model is tested through impedance spectroscopy characterization as a function of bias changes and layer thickness modifications. Correlations with current-voltage measurements reveal that the NC occurs once trap assisted space charge limited transport is reached. Through variation of the organic layer thicknesses, the magnitude of the NC response can be precisely tuned. In particular, increasing the thickness of the electron transport layer increases the NC magnitude, whereas hole transport layer thickness modifications have little effect on the magnitude of NC. Subsequent modeling indicates that alterations in the distribution of the electric field across the individual organic layers account for the observed variations in NC. In addition, it is found that the time constants for the inductive elements of the model increase with applied bias, unlike their capacitive counterparts, suggesting that an accumulation of charge at the organic/organic interface is responsible for both the increasing NC and redistribution of the applied field.
TL;DR: In this paper, a simple strategy of using thin, highly (100)-oriented MgO films as template layers for CdO thin film growth by metal-organic chemical vapor deposition on amorphous glass substrates is presented.
Abstract: A simple strategy of using thin, highly (100)-oriented MgO films as template layers for CdO thin film growth by metal-organic chemical vapor deposition on amorphous glass substrates is presented. For comparison, CdO films are grown simultaneously on clean glass, on a 50nm MgO(100) template layer on glass, and on single-crystal MgO(100). X-ray diffraction as well as four-probe conductivity and Hall-effect measurements reveal that the 50nm MgO(100) template layer significantly improves the microstructural texture and charge carrier mobility of the overlying CdO thin films. Thus, highly textured CdO thin films with an x-ray diffraction rocking curve full width at half maximum of 2.1° and large carrier mobilities of 160cm2∕Vs can be achieved on amorphous glass. Substrate effects, film microstructures, optical properties, and surface morphologies of the CdO films on the different substrates are discussed.
Patent•
20 Dec 2006TL;DR: In this paper, methods of using inorganic moieties for dielectric modulation, and related device structures are discussed. But they do not cover the use of inorganic materials.
Abstract: Compositions, methods of using inorganic moieties for dielectric modulation, and related device structures.
TL;DR: In the area of synthetic abiotic organic polymers, the past two decades have witnessed a dramatic explosion in research activity, driven by appreciation for the remarkable properties that synthetic polymers can have and the desire to productively put the creation and understanding of their properties on a firm scientific footing.
Abstract: The Oxford English Dictionary defines polymer in its broadest sense as “a substance with a molecular structure formed from many identical small molecules bonded together.” Polymers, in their many diverse forms, are the remarkable materials constituting the essential “stuff” from which everything, from living organisms to computer components to common household goods, is formed. In the area of synthetic abiotic organic polymers, the past two decades have witnessed a dramatic explosion in research activity, driven by appreciation for the remarkable properties that synthetic polymers can have and the desire to productively put the creation and understanding of their properties on a firm scientific footing. The ultimate goal is to synthesize …