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  • 1
    Electronic Resource
    Electronic Resource
    Microstructure of U–Mo and U–W oxides investigated by means of high-resolution electron microscopy (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 821-827 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The potential of high-resolution electron microscopy (HREM) is demonstrated by the investigation of complex oxides with a general formula [UnMmO]- [MpO3p + l], M = (Mo, W). The HREM structure images of β-UMo2O8 agree well with the model derived from X-ray data. It is found that the γ- U3Mo20O64 sample considered earlier as a monophase appears in fact as a set of isostructural phases. The structure of these phases with MoO3 octahedral block width varying within p = 1-7 is derived from electron microscope images. Both regular and irregular substitution of cations and the formation of uranium vacancies in M-O rows are detected in γ-U3Mo20O64. Interstitial sites in the structures are detected, which can be occupied by extra U and W cations. The electron microscope images of vacancy rows give evidence for the finite length of some M-O rows. In this case oxygen dangling bonds at the ends of rows are supposed to be saturated by interstitial tungsten atoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388004374
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  • 2
    Electronic Resource
    Electronic Resource
    Physical and electrical characterization of Hafnium oxide and Hafnium silicate sputtered films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6466-6475 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hafnium oxides and hafnium silicate films were investigated as a possible replacement for the SiO2 gate dielectric. Hafnium oxide films were formed by reactive sputtering from a single Hf oxide target in a predominantly Ar atmosphere containing small additions of oxygen. Hafnium silicates were made by adding a He-diluted silane gas for Si incorporation. By changing the silane gas flow, different Si atomic concentrations were incorporated into the Hf oxide films. Depositions were performed with the substrate held at temperatures of 22 °C and 500 °C. The chemical composition of the films was determined with nuclear techniques. Optical reflectivity was used to measure the optical band gap. The film morphology was investigated by transmission electron microscopy (TEM) and the electrical properties were measured with capacitance–voltage and current–voltage measurements using aluminum gate capacitors. TEM and electrical measurement showed that a SiO2 interfacial layer of about 3 nm formed at the Si interface due to the oxidizing sputter ambient. This precluded the growth of Hf based high-K films with small equivalent thickness. After correction for the interfacial oxide layer, the dielectric constant was found to decrease from about 21 for Hf oxide to about 4–5 for the Hafnium silicates with low Hf content (3 at. % Hf and 32 at. % Si). The optical band gap was found to increase from 5.8 eV for Hf oxide to about 7 eV for the silicate films. After annealing at 1000 °C followed by a 300 °C postmetallization anneal, negligible flat band voltage shift were measured on hafnium silicate films and good interface passivation was observed. However, leakage currents increased due to the high temperature processing. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1417991
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of Mo doping on accelerated growth of C-54 TiSi2: Evidence for template mechanism (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2571-2575 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase sequence of the rapid thermal processing induced reaction at T=650 °C has been studied by a combination of high resolution transmission electron microscopy and image simulations. We found that pre-amorphization of poly-Si substrates does not change the reaction path, i.e., Ti5Si4 and C-49 TiSi2 phases were formed with the latter growing upon further annealing. In the Mo doped poly-Si/Ti system the C-54 TiSi2 phase forms along with Ti5Si4 and two Mo silicide phases, MoSi2 and Mo5Si3; no C-49 TiSi2 was observed. We provide direct evidence that the Ti–Si reaction in the Mo doped system follows the template mechanism with MoSi2 and Mo5Si3 based phases acting as template phases for accelerated growth of C-54 TiSi2. Direct formation of C-54 TiSi2 at lower temperatures bypassing C-49 TiSi2 is very promising for application of the Ti salicide process in the future generation of deep-submicron complementary metal–oxide–semiconductor devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371094
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  • 4
    Electronic Resource
    Electronic Resource
    Interface reactions in ZrO2 based gate dielectric stacks (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 1232-1237 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interface reactions in Si/SiOx(Ny)/ZrO2 and Si/SiOx(Ny)/ZrO2/poly-Si gate stacks have been studied by high-resolution transmission electron microscopy. In the case of an uncapped stack ZrSi and ZrSi2 phases form during an ultrahigh vacuum anneal at temperatures above 900 °C. Both phases show an island-type growth with an epitaxial relationship with Si (100). Gate dielectric stacks with a poly-Si cap are found to be thermally unstable at T=1000 °C, so that the reaction is initiated at the ZrO2/poly-Si interface. Here a different reaction mechanism is identified, which involves the reduction of ZrO2 and the growth of a bottom interfacial layer between ZrOx and Si. Replacement of the bottom SiO2 layer by an ultrathin Si oxinitride does not completely suppress these interfacial reactions at T≥1000 °C. We suggest that control of the poly-Si/ZrO2 interfacial reactions may be an important factor in modifying the thermal stability of a stack. These results shed a new light on understanding the material challenges involved in the integration of ZrO2 for the next generation of complementary metal–oxide–semiconductor technologies. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1486036
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  • 5
    Electronic Resource
    Electronic Resource
    Atomic beam deposition of lanthanum- and yttrium-based oxide thin films for gate dielectrics (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2710-2712 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the electrical and microstructural characteristics of La- and Y-based oxides grown on silicon substrates by ultrahigh vacuum atomic beam deposition, in order to examine their potential as alternate gate dielectrics for Si complementary metal oxide semiconductor technology. We have examined the issues of polycrystallinity and interfacial silicon oxide formation in these films and their effect on the leakage currents and the ability to deposit films with low electrical thickness. We observe that polycrystallinity in the films does not result in unacceptably high leakage currents. We show significant Si penetration in both types of films. We find that the interfacial SiO2 is much thicker at ∼1.5 nm for the Y-based oxide compared to the La-based oxide where the thickness is 〈0.5 nm. We also show that while the Y-based oxide films show excellent electrical properties, the La based films exhibit a large flat band voltage shift indicative of positive charge in the films. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1320464
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanism of low temperature C54 TiSi2 formation bypassing C49 TiSi2: Effect of Si microstructure and Mo impurities on the Ti–Si reaction path (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 900-902 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray diffraction, high resolution transmission electron microscopy, and resistivity measurements were used to demonstrate a modification of the Ti/Si reaction path consisting of direct nucleation followed by diffusion limited growth of low resistivity C54 TiSi2 without nucleation of high resistivity C49 TiSi2, for the reaction of Ti with Mo doped polycrystalline or Mo doped amorphous Si by rapid thermal processing at 650 °C. We also report the mechanism of early C54 nucleation. We demonstrate that MoSi2 and an unidentified silicide phase lattice matched to C54 TiSi2, with spacings of 4.15 and 2.26 Å, nucleate along the Ti/Si interface at early stages of the reaction and act as templates on which C54 TiSi2 nucleates and grows epitaxially. In contrast, the conventional phase sequence, nucleation and growth of C49 TiSi2 preceding nucleation of C54 TiSi2, was observed for the Ti/Mo doped single crystal (100) Si reaction and for all samples without Mo. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122032
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  • 7
    Electronic Resource
    Electronic Resource
    Microstructure of chain silicates investigated by HRTEM (1988)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 135-142 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768187010899
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  • 8
    Electronic Resource
    Electronic Resource
    Structure retrieval in HREM (1991)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 715-723 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A new iteration method for direct structure retrieval starting from the exit plane-wave function Ψe(r) is proposed and tested on models. The imaginary part of the potential cannot be retrieved. The effects of the limited resolution of Ψe(r) as well as neglect of high-order Laue-zone effects and the choice of the starting potential on the result are discussed. The procedure is found to be preferable to that based on the subsequent approximation method with respect to a higher convergence rate. It is shown that an error as low as 10% may be obtained for the real part of the retrieved potential up to |σV(r)t| 〈 5.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767391006001
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