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1

Digitale Medien

Interactions between fullerene (C60) and endohedral alkali atoms (1992)

Dunlap, B. I. ; Ballester, J. L. ; Schmidt, P. P.

s.l. : American Chemical Society

The @journal of physical chemistry 〈Washington, DC〉 96 (1992), S. 9781-9787

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Quelle: ACS Legacy Archives

Thema: Chemie und Pharmazie , Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1021/j100203a038

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2

Digitale Medien

Semiconductor analysis using organic-on-inorganic contact barriers. II. Application to InP-based compound semiconductors (1986)

Forrest, S. R. ; Kaplan, M. L. ; Schmidt, P. H.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 60 (1986), S. 2406-2418

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Organic-on-inorganic (OI) contact barrier devices have been applied to the study of InP and In0.53Ga0.47As surfaces. The characteristics of these devices differ from OI diodes fabricated using Si or Ge substrates in that the contact barriers for InP-based devices are relatively small (≤0.55 eV), and the diode characteristics are governed by a high density of states at the organic/inorganic interface. We present current-voltage and frequency-dependent admittance-voltage characteristics for OI diodes employing 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA) and related compounds as the organic thin-film material. Analysis of characteristics using a theory presented previously [S. R. Forrest and P. H. Schmidt, J. Appl. Phys. 59, 513 (1986)] indicates that the surface state density is (i) independent of the organic material employed, and (ii) sensitive to the exposure of the surface to chemical treatment prior to the organic thin-film deposition. Using techniques derived previously, we determine the magnitude and energy distribution of the density of states at InP and In0.53Ga0.47As surfaces. It is found that the densities of states can vary between mid-1011 and 1015 cm−2 eV−1, depending on the surface treatment employed. Furthermore, some surface treatments result in an organic/In0.53Ga0.47As barrier height that is strongly dependent on applied voltage due to the presence of a high density of interface states.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.337153

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Digitale Medien

Semiconductor analysis using organic-on-inorganic contact barriers. I. Theory of the effects of surface states on diode potential and ac admittance (1986)

Forrest, S. R. ; Schmidt, P. H.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 59 (1986), S. 513-525

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A new method for measuring the density of states at semiconductor surfaces using organic-on-inorganic (OI) semiconductor contact barriers is suggested. This work is an extension of previous models of OI diode behavior which includes the ac admittance characteristics, and which considers the range of validity of approximations to OI diode capacitance used in previous experiments. The theory describes the potential distribution across the device. We consider the case of ideal OI diodes, as well as diodes with significant densities of states at the inorganic semiconductor surface. This analysis leads to a technique whereby the low-frequency conductance and capacitance characteristics can be used to obtain information about the magnitude and the energy distribution of surface states in the inorganic semiconductor bandgap. Also, the carrier concentration profiles of the substrate can be conveniently obtained. Due to the noninvasive nature of the organic/inorganic contact, information about the density of states at relatively undisturbed semiconductor surfaces obtained via this technique may prove useful in determining the processes involved in Schottky barrier formation and metal-insulator-semiconductor diode surface properties. This theory has been applied to the investigation of surfaces of III-V alloy semiconductor-based OI diodes, and the experimental results will be presented in a subsequent paper. In addition, an expression for the OI diode n value obtained from the forward current-voltage characteristics is derived. It is found that the n value depends on surface states which are in equilibrium with the organic as well as the inorganic materials. Estimates of the surface state densities obtained from previously reported n values are consistent with expectations for the semiconductors under test.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336662

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4

Digitale Medien

Organic-on-GaAs contact barrier diodes (1985)

Forrest, S. R. ; Kaplan, M. L. ; Schmidt, P. H. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 58 (1985), S. 867-870

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Thin films of the organic compound 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) were deposited on n- and p-type GaAs substrates, and were found to form high contact barriers. Barrier energies of 0.64 eV on n-type substrates and 0.75 eV on p-type material yielded organic-on-inorganic (OI) contact barrier diodes characterized by exponentially increasing forward current with voltage, and a reverse dark current leakage limited by generation and recombination of carriers in the GaAs bulk. The Fermi level does not appear to be pinned at the OI interface, contrary to what is commonly observed in metal/GaAs Schottky barrier diodes. In addition, we have made OI contact barriers using N,N'-dimethyl 3,4,9,10-perylenetetracarboxylic diimide (DIME-PTCDI) deposited on n- and p-type GaAs. These devices have contact barriers of 0.85 eV for substrates of either majority-carrier-type. The n values obtained from the forward biased characteristics of the GaAs/DIME-PTCDI structures are n=1.19, and are the lowest obtained to date for OI devices.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336157

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5

Digitale Medien

Electrical characterization of InxGa1−xAs/Al0.4Ga0.6As/GaAs pseudomorphic semiconductor/insulator/semiconductor heterostructures (1991)

Collot, P. ; Barbier, E. ; Schmidt, P. E. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 58 (1991), S. 367-369

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Two pseudomorphic InxGa1−xAs/Al0.4Ga0.6As/GaAs semiconductor/insulator/ semiconductor heterostructures (PM-SIS) with indium mole fractions x=0.15 and 0.25 were investigated and compared to a conventional GaAs/AlGaAs/GaAs SIS structure by means of current-temperature and capacitance-voltage characterizations. High reduction in gate leakage current is observed in the pseudomorphic structures compared with the conventional one. The conventional SISs is normally off, while the PM-SISs are normally on with a sheet carrier density at 0 V of 1.8×1011 cm−2 and 2.2×1011 cm−2 with x=0.15 and 0.25, respectively.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.104636

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6

Digitale Medien

Low-temperature magnetotransport experiments in pseudomorphic GaAs/Ga0.87In0.13As/Al0.40Ga0.60As semiconductor-insulator-semiconductor field-effect transistors (1991)

Schmidt, P. E. ; Barbier, E. ; Rossmanith, M. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 59 (1991), S. 1320-1322

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Low-temperature magnetotransport measurements on a molecular-beam-epitaxy-grown pseudomorphic GaAs-Ga0.87In0.13As-AlxGa1−xAs-GaAs semiconductor-insulator-semiconductor field-effect transistor are reported. In magnetic fields up to 12 T, the sample reveals clearly the integer quantum Hall effect. By varying the gate voltage, the sheet electron concentration of the two-dimensional electron gas can be tuned from depletion to 2×1012 cm−2. The dependence of the electron concentration and the mobility is studied as a function of the gate voltage.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.105487

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7

Digitale Medien

A Raman spectroscopic study of naphthalene:octafluoronaphthalene at high pressure and low temperature (1985)

Desgreniers, S. ; Kourouklis, G. A. ; Jayaraman, A. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 83 (1985), S. 480-485

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The crystalline 1:1 complex naphthalene:octafluoronaphthalene has been investigated at high pressure under ambient temperature, and down to 10 K at ambient pressure, by Raman spectroscopy. The complex is stable in the pressure range studied, 1 to 80 kbar. The lattice mode frequencies show a strong positive pressure dependence, while the internal modes are only weakly affected. The temperature and pressure dependencies of the phonon frequencies suggest that the bonding interaction between the molecular partners is of the usual van der Waals type, and the results are in agreement with the "sublattice'' model proposed by Chen and Prasad. The mode Grüneisen γi's have been obtained from the pressure data. From the measured (∂ν/∂T)p and (∂ν/∂P)T, the "explicit,'' "implicit'' contributions have been extracted.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.449563

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8

Digitale Medien

A general treatment of environmental effects on molecular vibrations (1987)

Severson, M. W. ; Schmidt, P. P. ; McKinley, John M.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 86 (1987), S. 5392-5404

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Vibrational spectroscopy is increasingly used as a selective and sensitive probe of the interaction between a given molecule and its environment. For electrochemistry, in particular, vibrational spectroscopy has been useful in the process of sorting reactive intermediates and mechanisms out of the many possibilities which present themselves. In this paper we discuss a general approach to the analysis of environmental effects on molecular vibrations. The objective is to use vibrational spectroscopy to determine values of specific parameters in a set of intra- and intermolecular pair potentials. In the body of this paper, we discuss in detail how one can manipulate a variety of model potential energy functions in order to account for environmental effects. We then apply the method to the adsorption of tetrahedral molecules on a metal surface. We report infrared spectra for sulfate ion adsorbed on a platinum electrode, and we make use of our analysis of the spectra to suggest that the sulfate anion associates with the metal through only one oxygen atom.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.452563

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9

Digitale Medien

A theoretical analysis of the vibrational spectrum of carbon monoxide on platinum metal electrodes (1986)

Korzeniewski, Carol ; Pons, Stanley ; Schmidt, P. P. ; [weitere]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 85 (1986), S. 4153-4160

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: The vibrational frequencies of carbon monoxide adsorbed on a platinum metal electrode are obtained in terms of discrete interatomic interactions. We show that for linear changes in the binding energy of carbon and oxygen to the surface there is a linear dependence of the shift in CO vibrational frequency. Based on our model, we suggest that there is a direct, linear relationship between the binding energy and the applied electrostatic potential. As a result, we predict a linear dependence of the frequency on electrochemical potential in accord with experiment. Further, we calculate a Stark tuning rate of 9.0×10−9 cm−1/(V/m). We also demonstrate that the application of a relatively large external electric field (of the order of 3×109 V/m) is necessary to account for the observed vibrational frequency shift. Because the surface charge of the electrode must change in order to give rise to changes in the electric field, we conclude that a combination of chemical bonding and electric field interactions are required to account for the observed spectral shifts.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.450888

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10

Digitale Medien

Measurement of hyperfine polarization quantum beats in a polyatomic molecule (1986)

Dubs, M. ; Schmidt, P. ; Huber, J. Robert

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 85 (1986), S. 6335-6339

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: Polarization quantum beats between hyperfine components of perturbed rotational states in the S1→S0 fluorescence of propynal (HC≡CCHO) have been measured. The quantum beats are explained by a periodic transfer of molecular alignment to nuclear spin polarization.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.451463

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