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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics and structure of irreversibly adsorbed polymer layers (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 11319-11325 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The kinetics of formation and the structure of an adsorbed layer formed by homopolymer chains irreversibly adsorbed onto a flat wall are studied by Monto Carlo simulation using the bond fluctuation model. The rapid initial adsorption is followed by slow kinetics at later times. The surface coverage can be described by an empirical law of stretched exponential approach to the final value. The formation time constant τ can be interpreted by scaling theories of diffusion inside a dense pseudo-brush. The detailed structure of the layer in a good solvent saturated by the adsorbed chains is also measured. The extension of the layer and the distributions of the loops and tails are also analyzed in light of recent scaling theories. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472872
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  • 2
    Electronic Resource
    Electronic Resource
    Increased angiotensin-converting enzyme and type 1 angiotensin receptors in cortical vasculature and tubulointerstitium of chronically rejected human kidney allografts (2001)
    Melbourne, Australia : Blackwell Science Pty
    Nephrology 6 (2001), S. 0 
    Details
    ISSN: 1440-1797
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: SUMMARY: Chronic rejection of human renal allografts after transplantation is characterized by interstitial infiltration, arteriosclerosis and glomerulosclerosis in the grafts. Apart from tissue HLA compatibility, angiotensin II (AII) may be implicated in accelerating the processes of chronic rejection. In the present study, the cellular distribution of angiotensin-converting enzyme (ACE) and type 1 AII (AT1) receptors was mapped and compared in non-rejected human kidneys (n = 8) and chronically rejected renal allografts (n = 9) using complementary immunohistochemistry and quantitative in vitro autoradiography. Chronically rejected allografts showed typical histopathological characteristics of tissue rejection, including concentric intimal thickening of intrarenal arteries, extensive or focal glomerulosclerosis, tubular atrophy and severe tubulointerstitial fibrosis. In rejected allografts, total ACE binding in the cortex was decreased to 46% of that in non-rejected kidneys (P 〈 0.01), whereas AT1 receptor binding in the glomeruli and the inner stripe of the outer medulla was maintained. However, ACE and AT1 receptor binding were increased in the cortical tubulointerstitium of chronically rejected allografts. In non-rejected kidneys, strong ACE immunostaining occurred in proximal tubules and vascular endothelium, whereas AT1 receptors occurred in vascular smooth muscle cells, as expected. In rejected allografts, intense ACE and AT1 receptor immunostaining were detected not only in the same sites as those non-rejected kidneys, but also in cortical tubulointerstitium between atrophied tubules and surrounding the glomeruli. AT1 receptors were markedly up-regulated in vascular smooth muscle cells of thickened atherosclerotic vessels. These results provide novel morphological evidence that increased expression and/or altered distribution of ACE and AT1 receptors in cortical tubulointerstitium and in the neointima of intrarenal arteries may play an important role in the progression of chronic rejection of human renal allografts after transplantation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1797.2001.00045.x
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  • 3
    Electronic Resource
    Electronic Resource
    Ta-based interface ohmic contacts to AlGaN/GaN heterostructures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5543-5546 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Al/Ti based metallization is commonly used for ohmic contacts to n-GaN and related compounds. We have previously reported an ohmic contact scheme specially designed for AlGaN/GaN heterostructure field-effect transistors (HFETs) [D. Qiao et al., Appl. Phys. Lett. 74, 2652 (1999)]. This scheme, referred to as the "advancing interface" contact, takes advantage of the interfacial reactions between the metal layers and the AlGaN barrier layer in the HFET structure. These reactions consume a portion of the barrier, thus facilitating carrier tunneling from the source/drain regions to the channel region. The advancing interface approach has led to consistently low contact resistance on Al0.25Ga0.75N/GaN HFETs. There are two drawbacks of the Al/Ti based advancing interface scheme, (i) it requires a capping layer for the ohmic formation annealing since Ti is too reactive and is easily oxidized when annealing is performed in pure N2 or even in forming gas, and (ii) the atomic number of Al and that of Ti are too low to yield efficient backscattered electron emission for e-beam lithographic alignment purposes. In this work, we investigated a Ta based advancing interface contact scheme for the HFET structures. We found that the presence of Ta in this ohmic scheme leads to (1) a specific contact resistivity as low as 5×10−7 Ω cm2, (2) efficient electron emission for e-beam lithographic alignment, and (3) elimination of the capping layer for the ohmic annealing. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1365431
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  • 4
    Electronic Resource
    Electronic Resource
    Study of Schottky barrier of Ni on p-GaN (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4536-4538 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Schottky barrier characteristics of Ni on p-GaN have been investigated using current–voltage–temperature (I–V–T) and capacitance–voltage characteristics (C–V) measurements. Barrier height values ranging from 2.68 to 2.87 eV were obtained from C–V measurements. The temperature dependence of I–V characteristics clearly indicated the dominance of tunneling current in the transport mechanism of the diodes, therefore, barrier height determination using I–V measurements can lead to erroneous results, as indicated by the wide range of barrier heights reported in the literature. Acceptor concentration, deduced from C–V measurements, was found to be of 1019/cm3 within 200 Å of the sample surface, and tapered off to be ∼1018/cm3. These values are 10–100 times higher than the hole concentration of ∼1017/cm3 obtained from Hall measurements. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428773
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  • 5
    Electronic Resource
    Electronic Resource
    Polarization charges and polarization-induced barriers in AlxGa1−xN/GaN and InyGa1−yN/GaN heterostructures (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2916-2918 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polarization charges are measured and the formation of large electrostatic barriers arising primarily as a consequence of the presence of polarization-induced charge densities is deduced from capacitance–voltage analysis of n-type AlxGa1−xN/GaN and InyGa1−yN/GaN heterostructures. In structures consisting of 5–10 nm AlxGa1−xN or InyGa1−yN surrounded by n-GaN, capacitance–voltage profiling studies combined with elementary electrostatic analysis yield experimental estimates of polarization charge densities, which are compared with values expected based on the combined effects of spontaneous and piezoelectric polarization. These results imply the existence of electrostatic barriers that are due primarily to the large polarization charge densities at each heterojunction interface and the resulting potential difference maintained across the thin AlxGa1−xN or InyGa1−yN layers. The electrostatic barriers formed in these structures are large in comparison to the heterojunction conduction-band offsets, demonstrating the utility of polarization-based engineering of electrostatic barriers in nitride semiconductor heterostructures. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412594
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  • 6
    Electronic Resource
    Electronic Resource
    Transport properties of the advancing interface ohmic contact to AlGaN/GaN heterostructures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 992-994 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport properties of the advancing interface ohmic contact to AlGaN/GaN heterostructure field-effect transistors have been investigated. We found that carrier transport across the AlGaN barrier layer is dominated by the tunneling of electrons that originate from the two-dimensional electron gas located at the AlGaN/GaN interface. The observed temperature dependence of the specific contact resistivity is different from that of the contact on highly doped bulk semiconductors, although tunneling current dominates the carrier transport in both cases. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1447591
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: "Further evidence for the quantum confined electrochemistry model of the formation mechanism of p−-type porous silicon" [Appl. Phys. Lett. 69, 3399 (1996)] (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 912-912 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119267
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  • 8
    Electronic Resource
    Electronic Resource
    Photoluminescence of ozone oxidized and HF etched porous silicon and the multiple source quantum well model (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1391-1393 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Porous silicon (PS) samples were alternately oxidized in an ozone atmosphere and etched in HF solution. The variation of the corresponding photoluminescence (PL) implies that there is more than one origin responsible for the PL of PS. These results are explained by a multiple source quantum well model, where the nanoscale Si units and their covering oxide layers both contribute to the PL in different situations. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119902
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  • 9
    Electronic Resource
    Electronic Resource
    Further evidence for the quantum confined electrochemistry model of the formation mechanism of p−-type porous silicon (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3399-3401 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two types of p− porous silicon (PS) were formed in HF solutions of different concentrations. One type with nanoscale (NS) dimensions of about 3 nm and the other with dimensions of about 5 nm. PS samples formed in the lower concentration of HF were anodized again in the higher concentration of HF and vice versa. The photoluminescence peak position and, thus, the size of NS units of PS were found to be related to the concentration of HF in which the PS is formed, independent of the forming time. The larger NS units of PS can be further electrochemically etched by anodization, while the smaller ones cannot. These results give a confirming evidence for the quantum confined electrochemistry model of the formation mechanism of PS based on the quantum confinement effect and classical electrochemical theory [S. L. Zhang, K. S. Ho, Y. T. Hou, B. D. Qian, P. Diao, and S. M. Cai, Appl. Phys. Lett. 62, 642 (1993)]. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117272
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  • 10
    Electronic Resource
    Electronic Resource
    Three-dimensional development of electron beam exposed resist patterns simulated by using ray tracing model
    Amsterdam : Elsevier
    Microelectronic Engineering 6 (1987), S. 147-151 
    Details
    ISSN: 0167-9317
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0167-9317(87)90030-X
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