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  • 1
    Electronic Resource
    Electronic Resource
    Molecular beam deposited thin films of pentacene for organic field effect transistor applications (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 2501-2508 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pentacene films deposited with molecular beam deposition have been fabricated and characterized with respect to structure and morphology using x-ray diffraction and scanning electron microscopy. Metal-insulator semiconductor field-effect transistor devices based on such films were used to study their transport properties. A maximum field-effect mobility of 0.038 cm−2 V−1 s−1 is reported for devices incorporating pentacene films deposited at room temperature. The structural characterization revealed the coexistence of two phases: the thermodynamically stable single-crystal phase and the kinetically favored, metastable thin-film phase. Such mixed phase films were produced when low deposition rates were used in combination with a substrate temperature of 55 °C. Mixed phase films had transport properties inferior to films consisting solely of one phase, while amorphous films deposited at low surface mobility conditions had extremely low conductivity. Use of prepurified pentacene as source material resulted in an order of magnitude lower free-carrier concentration in the pentacene film as compared to films made with as-received pentacene. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363032
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen loss during thermal donor formation in Czochralski silicon: New insights into oxygen diffusion mechanisms (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1427-1442 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As-grown Czochralski silicon samples with different oxygen concentrations have been heated at temperatures in the range 350–500 °C. Oxygen loss during anneals at low temperatures (T≤400 °C) is shown to follow second-order kinetics and measurements led to values of oxygen diffusivity that were larger than normal by a factor of ∼3, assuming the capture radius for dimer formation was 5 A(ring). Variations in the rate of [Oi] loss during more extended anneals could be explained if oxygen diffusion was initially enhanced but tended to its normal value as the anneals progressed. Much greater initial enhancements were derived from similar measurements for samples which had been hydrogenated by a heat treatment in H2 gas at 1300 °C for 30 min followed by a rapid quench to room temperature, and the enhancements were consistent with values derived from measurements of the relaxation of stress-induced dichroism. At higher temperatures (T≥450 °C) the measured rates of [Oi] loss were less than the expected rate of Oi-Oi interaction and tended to vary with increasingly high powers of [Oi]. Modeling of the clustering process demonstrated that the reductions could be explained if the oxygen dimers were present in a quasiequilibrium concentration throughout the anneals. The establishment of this equilibrium appears to require that oxygen dimers diffuse much more rapidly than isolated Oi atoms. The kinetics of oxygen loss over the whole range of temperatures can then be explained if dimer clustering leads mainly to increases in concentrations of agglomorates containing large numbers (≥8) of oxygen atoms. It is therefore possible to account for thermal donor (TD) formation based on the formation of different sizes of oxygen clusters, although the possibility that self-interstitials are involved in TD formation is not excluded. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358890
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  • 3
    Electronic Resource
    Electronic Resource
    Precursor route pentacene metal-insulator-semiconductor field-effect transistors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2136-2138 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Metal-insulator-semiconductor field-effect transistors have been constructed with pentacene as the active semiconductor. The pentacene is processed by spin coating from a soluble precursor. A simple thermal conversion yields transistors with carrier mobilities as high as 9×10−3 cm2 V−1 s−1 and current modulations of the order of 105. Depletion of charge is essential to the device operation. Data for an invertor exhibiting voltage amplification are presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361071
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  • 4
    Electronic Resource
    Electronic Resource
    Field effect measurements in doped conjugated polymer films: Assessment of charge carrier mobilities (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 6289-6294 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conductivity and field-effect mobility measurements using metal-insulator-semiconductor field-effect-transistor devices and acceptor density measurements using metal-insulator- semiconductor (MIS) diodes are presented. The measurements were made on thin polymer films of the organic semiconductor, poly(β'-dodecyloxy-α,α',-α',α‘terthienyl), which were doped to different conductivities using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an oxidizing agent. It is found that both the field-effect mobility and the conductivity of these films increases superlinearly upon doping while the transistor amplification, the on/off ratio, decreases. Acceptor densities as obtained from MIS diode measurements are in close agreement with the bulk charge density as calculated from the DDQ content. However, the product of this bulk charge density, field-effect mobility, and the elementary charge e is a factor of 100 larger than the polymer conductivity. This indicates that the average mobility for charge carriers in the bulk is considerably lower than the field-effect mobility. It is considered that the bulk charge carriers are trapped by the Coulomb interaction with their parent charge compensating counter-ions, whereas charges in accumulation have no associated counter-ions and, therefore, are more mobile. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359096
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  • 5
    Electronic Resource
    Electronic Resource
    Potential fluctuations in metal–oxide–semiconductor field-effect transistors generated by random impurities in the depletion layer (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 4326-4334 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the magnitude and length scale of potential fluctuations in the channel of metal–oxide–semiconductor field-effect transistors due to the random positions of ionized impurities in the depletion layer. These fluctuations effect the threshold voltage of deep submicron devices, impede their integration, and reduce yield and reliability. Our simple, analytic results complement numerical, atomistic simulations. The calculations are based on a model introduced by Brews to study fluctuations due to charges in the oxide. We find a typical standard deviation of 70 mV in the potential below threshold, where the channel is empty, falling to 40 mV above threshold due to screening by carriers in the channel. These figures can be reduced by a lightly doped epitaxial layer of a few nm thickness. The correlation function decays exponentially in an empty channel with a length scale of 9 nm, which screening by carriers reduces to about 5 nm. These calculations of the random potential provide a guide to fluctuations of the threshold voltage between devices because the length of the critical region in a well-scaled transistor near threshold is comparable to the correlation length of the fluctuations. The results agree reasonably well with atomistic simulations but detailed comparison is difficult because half of the total standard deviation comes from impurities within 1 nm of the silicon–oxide interface, which is a single layer of the grid used in the simulations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1450031
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  • 6
    Electronic Resource
    Electronic Resource
    Hydrogen diffusion and the catalysis of enhanced oxygen diffusion in silicon at temperatures below 500 °C (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3061-3070 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The relaxation of stress-induced dichroism of the 9-μm oxygen infrared absorption band has been investigated for Czochralski silicon annealed isothermally at various temperatures in the range 225–350 °C while the material was immersed in a hydrogen plasma. The in-diffusion of hydrogen atoms enhanced the rate of oxygen diffusion so that the dichroism was lost progressively from the external surfaces of samples. Comprehensive ancillary measurements demonstrated that the oxygen diffusion jumps were catalyzed by collisions with diffusing hydrogen atoms, rather than some other fast-diffusing species. The measurements allowed the hydrogen diffusion coefficient to be estimated as 1.7 × 102 exp( − 1.2 eV/kT) cm2 s−1 for the range of temperatures investigated. Increased rates of thermal donor formation were also found due to enhanced long-range oxygen diffusion. The new data are related to previous reports of enhanced oxygen diffusion jumps found in Czochralski silicon given post-growth heat treatments in hydrogen gas. It is implied that concentrations of hydrogen atoms as low as 108 cm−3 may significantly enhance oxygen diffusivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349338
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of oxygen concentration on the kinetics of thermal donor formation in silicon at temperatures between 350 and 500 °C (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1525-1526 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Early measurements of the initial rate of thermal donor formation in Czochralski silicon at 450 °C revealed a dependency on the fourth power of the oxygen concentration. This result has led to the view that the core of the defects contained four oxygen atoms. We now show that this dependency is observed only for anneals close to 450 °C. Our results indicate that oxygen dimerization controls the thermal donor formation kinetics but that the dimers become increasingly unstable above 400 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108628
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  • 8
    Electronic Resource
    Electronic Resource
    Poly(p-phenylenevinylene) light-emitting diodes: Enhanced electroluminescent efficiency through charge carrier confinement (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2793-2795 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated light-emitting diodes with poly(p-phenylenevinylene) as the emissive layer, and with an electron-transporting layer formed from a solid state dispersion of 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole in poly(methyl methacrylate), placed between this and the negative electrode. These structures show typically a tenfold improvement in efficiency in the low-voltage regime and an eightfold improvement in the high-voltage regime over devices without the electron-transporting layer. Typical efficiencies are about 0.8% photons/electron. We consider that the role of the electron-transport layer is to confine holes to the emissive layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108094
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  • 9
    Electronic Resource
    Electronic Resource
    A STRATIGRAPHIC CASE HISTORY USING THREE-DIMENSIONAL SEISMIC DATA IN THE GULF OF THAILAND (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 29 (1981), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: A three-dimensional marine seismic survey was conducted in the Gulf of Thailand to aid in the development of a gas field indicated by three wildcat wells. The results and interpretation reported previously demonstrated improved fault resolution and better structural definition.Five successful appraisal wells have now been drilled, and these show that most of the sands have limited extent. Widespread character changes in the seismic data also support stratigraphic variations in many of the sands.Several new methods of 3D stratigraphic interpretation have been developed while investigating the depositional history of this area. Anomalous seismic amplitudes, tied to sands penetrated by wells and mapped from SeiscropTM horizontal sections in time and depth, have indicated the distribution of bars and channels. Horizon Seiscrop sections, each sliced through a single bed, have been used to delineate these depositional features directly. G-LOGTM sections, displaying seismic logs derived by rigorous wave equation inversion, confirm the existence of these features. Sands greater than 10 m thick have proved mappable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.1981.tb01017.x
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  • 10
    Electronic Resource
    Electronic Resource
    Meaning and Scope of Social Anthropology (1944)
    [s.l.] : Nature Publishing Group
    Nature 154 (1944), S. 257-260 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] THE name 'social anthropology' came into use some sixty years ago to distinguish the subject from ethnology. The avowed aim has always been to apply the inductive method of the natural sciences to the study of human society, its institutions and its evolution. But it is only gradually that we can ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/154257a0
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