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  • 1
    Electronic Resource
    Electronic Resource
    Room-temperature midwavelength two-color infrared detectors with HgCdTe/CdTe multilayer structures by metal-organic chemical-vapor deposition (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4787-4789 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two-color photoconductive detectors in the 3–5 μm wavelength range using multilayer undoped n-type Hg1−xCdxTe heterostructures have been demonstrated at room temperature. These heterostructures, consisting of three or four Hg1−xCdxTe layers separated with CdTe layers, were grown by the metal-organic chemical-vapor-deposition (MOCVD) technique. The quality of MOCVD films was verified by near-theoretical values of the minority-carrier lifetime at 300 K, ranging from 0.8 to 4.7 μs depending on the x value. The Hg1−xCdxTe layers are either detectors or filters, and the CdTe layers serve as insulating separators. The concept of using the exponential absorption tails of two Hg1−xCdxTe layers with different band gaps to form an absorption band was verified by the difference in the photoconductive spectral responses between backside and frontside illumination. Two different multilayer heterostructures with two-color peaks at 3.2/3.8 μm and 3.7/4.6 μm, respectively, were studied. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359759
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  • 2
    Electronic Resource
    Electronic Resource
    A density functional study of clean and hydrogen-covered α-MoO3(010): Electronic structure and surface relaxation (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6854-6860 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report extensive density functional theory calculations, using pseudopotentials with a plane-wave basis, for the properties of the (010) face of molybdenum trioxide (α-MoO3). The surface is modeled by a one-layer slab. Calculated bond lengths compare favorably with experimental measurements. The bonding of the different oxygen species to molybdenum is analyzed using the crystal orbital overlap population. This analysis indicates that the bonding is a combination of ionic and covalent character for all oxygen species. The terminal oxygen exhibits covalent bonding to Mo which is stronger than either of the two bridging oxygens. We also study the adsorption of hydrogen on this surface. Hydrogen is most strongly adsorbed over the terminal oxygen, followed by the asymmetric bridging oxygen, and then the symmetric bridging oxygen. This trend is explained in terms of simple chemical concepts. The inclusion of full surface relaxation is important for even a qualitative description of adsorbate bonding. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477252
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  • 3
    Electronic Resource
    Electronic Resource
    Magnetic and crystallographic structure of Nd5Fe17 (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5693-5695 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Neutron diffraction has been used to refine the crystallographic and magnetic structure of Nd5Fe17. The results of Rietveld refinement yield improved precision for the Fe coordinates relative to the x-ray study. The magnetic moments are refined by assuming that all Fe atoms in comparable environments have the same moment or by grouping sites by average Fe–Fe bond length. Each model leads to five distinct moments, in which the magnitude of the moment is correlated with both the average Fe–Fe bond lengths and the near-neighbor distribution. The results of the refinement are in reasonable agreement with the analysis of the Mössbauer spectra. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370254
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  • 4
    Electronic Resource
    Electronic Resource
    Studies of V, Nb, Cr, and Zr substituted 2:17 compounds and their carbides using neutron diffraction : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4542-4544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of Nd2Fe17−xTxCy with T=V, Nb, Cr, and Zr were prepared by melting of the constituent elements including C and studied by neutron diffraction. Comparing with their uncarbided counterparts, we found that the substituents transfer, more or less, from the 6c site to the 18f and 18h sites with the introduction of C atoms. This behavior appears to relate to the electronegativities between the C atoms and the early transition series elements because the 18f and 18h sites are near neighbors of the interstitial C site. However, the C effects in the V, Nb, Cr, and Zr samples are not as strong as those in Ti samples. SQUID measurements show that the Curie temperatures of these samples depend on both the interstitial C atoms and the substituents. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365421
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  • 5
    Electronic Resource
    Electronic Resource
    High-quality p - type Hg1−xCdxTe prepared by metalorganic chemical vapor deposition (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3450-3452 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An arsenic source, tris-dimethylaminoarsine (TDMAAs), was used as a p-type dopant for Hg1−xCdxTe prepared by metalorganic chemical vapor deposition (MOCVD). The Hg1−xCdxTe layers were grown using the interdiffused multilayer process (IMP) at 360 °C with dimethylcadmium, di-isopropyltelluride and elemental mercury. Hole concentrations at 77 K in the range of 2×10+16–7×10+17 cm−3 were obtained in Hg1−xCdxTe with x=0.2–0.35, and ∼30%–50% of the arsenic was electrically active based on the data from secondary ion mass spectrometry (SIMS) measurements. These MOCVD Hg1−xCdxTe layers show minority carrier lifetimes at 77 K in the range of 3 ns–4 μs, which compare favorably with those from the best arsenic-doped Hg1−xCdxTe films prepared by liquid phase epitaxy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115276
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  • 6
    Electronic Resource
    Electronic Resource
    On the geometric structure of thermodynamics (1999)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 40 (1999), S. 830-837 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this paper we consider symmetry transformations of the generalized entropy function that preserve the Gibbs one-form (Gibbs relation). We show that this symmetry consideration naturally leads to the geometric structure of thermodynamics in terms of contact geometry. We also construct an example based on the van der Waals' fluid to illustrate the method discussed in the paper. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532688
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  • 7
    Electronic Resource
    Electronic Resource
    On the moment methods and irreversible thermodynamics (1997)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 3589-3602 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this paper we investigate the kinetic foundation of irreversible thermodynamics by means of the moment methods proposed by Grad and by Eu, respectively. First we show that the moment methods yield a weak solution of the Boltzmann equation. On the other hand, the entropy balance equation can be satisfied only by the strong solution of the Boltzmann equation. Second, we reformulate the energy balance equation in an alternative form where dissipative energy as well as a generalized work 1-form are included in this new equation. Assume that the dissipative energy is semi-positive definite. The local form of the second law of thermodynamics is then formulated in terms of the inaccessibility condition of Caratheodory. We then show that our new formulation of the second law is equivalent to Kelvin's principle and Clausius' principle. Finally we obtain a calotropy balance equation where the calotropy density function is a state function in the thermodynamic space. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532072
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  • 8
    Electronic Resource
    Electronic Resource
    On the second law of thermodynamics and contact geometry (1998)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 39 (1998), S. 329-344 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this paper we consider the second law of thermodynamics for a dissipative system and its symmetry property in terms of contact geometry. We first show that the inaccessibility condition of Caratheodory and the assumption of semipositive definite property of the dissipative energy are equivalent to Clausius' inequality. The inaccessibility condition then gives rise to a generalized Gibbs relation (GGR). By means of the GGR a 1-form ω can be defined such that the zero of ω reproduces the GGR. Such 1-form ω has the property ω∧(dω)n≠0 and ω∧(dω)n+1=0. The integral surface of the GGR is an n-dimensional 1-graph space G (Legendre submanifold) of a 1-jet space J1(En,R), where En is the base space of J1(En,R) with thermodynamic variables as its coordinates. The (2n+1)-dimensional J1(En,R) equipped with the 1-form ω is also called a contact bundle K, where the intensive thermodynamic variables are considered as the contact elements to K at every x. Next we construct an isovector field Xf such that the inaccessibility condition is invariant under the contact transformations generated by Xf. Finally, suppose under some specific assumptions the dynamical equations of the thermodynamic variables x can be approximated by the flow equations of a vector field XG on G. We can lift XG to Xf such that the 1-graph space G as well as the inaccessibility condition are preserved under the contact transformations generated by Xf. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532316
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  • 9
    Electronic Resource
    Electronic Resource
    On the second law of thermodynamics for a dissipative system (1997)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 5153-5166 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: In this paper we consider dissipative fluxes as well as the conserved variables as a set of independent variables characterizing the thermodynamic state of a nonequilibrium system. We then generalize the traditional internal energy balance equation so that contributions due to the dissipative fluxes are taken into consideration. On the other hand, the second law is formulated in terms of Caratheodory's inaccessibility condition in conjunction with the assumption that dissipative energy associated with internal work arising from irreversible processes be semipositive definite. We show that the second law formulated in this manner is equivalent to Kelvin's principle and Clausius's principle, as well as Clausius's inequality. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.531934
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  • 10
    Electronic Resource
    Electronic Resource
    Photoreflectance spectroscopy of strained-layer (111)B InGaAs/GaAs quantum well diodes (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 1595-1601 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaAs/GaAs (111)B quantum well p-i-n structures grown by gas source molecular beam epitaxy have been investigated with a photoreflectance technique. Using the reduced mass deduced from experiments, the built-in electric field is obtained from the above band-gap Franz–Keldysh oscillations (FKOs). The strain-induced piezoelectric field is then determined directly from the comparison of the periods of FKOs in different samples. Numerical solutions for exciton transition energies with the experimentally derived potentials are in good agreement with experimental results. Hence, the piezoelectric constant can be determined using the piezoelectric field. The temperature dependences of the quantized energy levels indicate that the influence of temperature on exciton transitions is essentially the same as that of the gaps of the relevant bulk constituent materials. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368229
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