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  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 533-535 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Novel nonlinear composite thin films containing 4-dialkylamino-4'-nitro-stilbene (DANS) and Teflon AF 1600 have been deposited by vacuum evaporation techniques. Pure DANS thin film, due to its centrosymmetric crystal structure, does not exhibit any electro-optic effect. However, composite thin films of DANS and Teflon AF 1600 with a DANS concentration of 5%–25% (by volume) do exhibit an electro-optic effect after poling. Their electro-optical coefficients are measured to be as large as 2.4 pm/V. X-ray diffraction shows that these composite thin films are in an amorphous state as-deposited as well as after poling. It is argued that the DANS molecules are in their molecular form embedded in the Teflon AF amorphous matrix, thereby allowing the effect of their large molecular hyperpolarizability to be detected. The characterization of the thin films using scanning electron microscopy is also presented.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2258-2263 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear optical films were vapor deposited onto Si(100) and indium-tin-oxide-coated glass. These films are guest-host-type polymer and showed electrooptical (EO) properties after poling. The host polymer is Teflon AF 1600 (AF) and the guest is dimethylaminonitrostilbene (DANS). Deposition is done by coevaporation. EO effects were found in films containing 5–25 vol % DANS. The EO coefficient r33, is found to be a function of composition, poling temperature, and cooling rate during poling. The highest EO coefficient obtained is 2.4 pm/V from a film with 10 vol % DANS and poled at a temperature of 130 °C. Very little or no EO effects were found for films with (approximately-greater-than)25 vol % DANS. This is found to be a result of phase separation and subsequent crystallization of DANS. A decrease of EO effect at higher poling temperature is possibly a result of thermal disorder which was "frozen'' during cooling. DANS was also found to react with Teflon AF 1600 at a higher DANS concentration. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1392-1396 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diffusion of Ag from epitaxial layers into Si(111) is studied under an anneal of 450–500 °C using the secondary ion mass spectrometry depth profiling tool. The measurements yielded values of the diffusion constant (0.80–1.6 × 10−15 cm2/s) which fall short of literature values extrapolated from higher-temperature Arrhenius laws. Diffusion of Ag into SiO2 was also measured directly. The observed diffusivity of 1.0 × 10−15 cm2/s is a factor of ∼ 105 smaller than expected from previous determinations of the diffusivity of Ag+ in SiO2 obtained from anneals in forming gas. The discrepancy may be due to changes in the local electrostatic environment in the absence of acceptor levels in SiO2 from dissolved gases which are absent in vacuum.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 773-777 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The observation of room-temperature epitaxy of vapor-deposited thin Ag films on Si(111) accomplished under conventional vacuum conditions is reported. Epitaxy was also observed at 350 °C. The films were deposited using a partially ionized beam deposition system, and were typically 1500 A(ring) thick. Epitaxy was confirmed via pole-figure analysis. Scanning electron microscopy revealed excellent surface flatness even for the room-temperature films. Contrary to previous observations, the growth was found to proceed by the layer mode, even at the elevated temperature. This change in morphology is attributed to the enhanced density of nucleation sites due to the energetic ions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3313-3316 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SiO2 film of 1500-A(ring) thickness has been grown by a conventional thermal dry oxidation process on commercial Si(111) and Si(100) wafers. A secondary-ion mass spectrometry study of the SiO2/Si structure showed that a gettering of Cu atoms, which were present in the Si wafers as residual impurities, has occurred at the SiO2/Si interface due to the thermal dry oxidation process. The areal concentration of the Cu atoms at the interface has been found to depend on the Cu concentration in the Si wafers. Areal concentrations in order of 1×1012/cm2 were measured at the interfaces. Facilitated by the high diffusivity of Cu in SiO2 and Si, the gettering is thermodynamically driven by the low solid solubility of Cu, either in SiO2 at the temperature range up to the oxidation temperature, or in Si at low temperatures as the wafers cool down. The defects generated at the SiO2/Si interface provide the nucleation sites for the Cu gettering.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6719-6721 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Evidence is presented for the blocking of Cu diffusion into SiO2 and Si by Ta and Ta/W barriers. The anneal was performed at 450 °C for 30 min. Here, W is rejected as a potential barrier for Cu technology. A Cr layer as thin as 200 A(ring) is shown to limit diffusion into Si to ∼600 A(ring). The study also demonstrates the utility and versatility of secondary ion mass spectrometry for evaluating potential diffusion barriers, and the need for such corroborative characterization in light of the lesser sensitivity of Rutherford backscattering spectroscopy.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3619-3624 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cu thin films have been deposited on Si(111) substrate using partially ionized deposition technique in which the self-ions, i.e., the ions derived from the depositing materials themselves, are being used to concurrently bombard the substrate surface during thin film growth. The ion percentage in the deposition beam is in the range from 0% to 5% with the ion energy varying between a few eV and several keV. The Si(111) substrates are chemically cleaned by a RCA cleaning process before loading into the vacuum chamber of deposition. No in situ cleaning of the substrate surface is performed prior to deposition. A reduction of impurities such as oxygen, carbon, and hydrogen at the Cu/Si interface is observed as a function of the ion bombardment parameters using secondary-ion mass spectrometry. The estimates of the sputtering cross section of oxygen, carbon and hydrogen at the Cu/Si interface by Cu ions and their energy dependence are discussed in the framework of mechanisms of the impurity sputtering by low-energy ions.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4519-4521 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have shown that high-purity Cu films can be deposited on the Si substrate at room temperature in a conventional vacuum condition using the partially ionized beam technique. The beam contains about 2% of Cu self-ions and a bias potential of 1 kV is applied to the substrate during deposition. By using the secondary ion mass spectrometry technique we show that the Cu/Si interface is free of contaminants such as oxygen, carbon, and hydrogen, despite the fact that no in situ surface cleaning has been performed on the substrate prior to deposition. These phenomena are attributed to the self-cleaning effect induced by the energetic Cu ions bombardment during deposition.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1846-1847 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we study Ta/parylene-F (PA–F) buried interfaces using x-ray photoelectron spectroscopy. We found that the Ta–F bond was formed at the Ta/PA–F interface after depositing a layer of thin Ta film (〈50 Å). For the Ar+ or O2 plasma pretreated PA–F surface, in addition to the Ta–F bond, a Ta–C bond was observed at the buried interface after Ta metallization. The Ta–C bond may be responsible for the enhancement of Ta/PA–F adhesion. © 1998 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 399-401 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Buried interfaces of thin Al/Ta2O5 and Ta2O5/Al films were studied using the x-ray photoelectron spectroscopy technique. The peak decomposition technique was employed to identify the composition and chemical states at the interface region. It was observed that there is an "intermixing layer" at the Al/Ta2O5 interface, where Ta2O5 has been reduced to lower binding energy states due to the reaction of Al with Ta2O5 during deposition. On the other hand, the Ta2O5/Al interface is relatively stable, consisting of Ta2O5 and Al2O3 interfacial layers. Based on a uniform multilayer structure model, the thickness of the interfacial layers was estimated by using the relative photoelectron intensities. © 1997 American Institute of Physics.
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