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  • 1
    Electronic Resource
    Electronic Resource
    Profiling nitrogen in ultrathin silicon oxynitrides with angle-resolved x-ray photoelectron spectroscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4449-4455 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Angle-resolved x-ray photoelectron spectroscopy (AR–XPS) is utilized in this work to accurately and nondestructively determine the nitrogen concentration and profile in ultrathin SiOxNy films. With furnace growth at 800–850 °C using nitric oxide (NO) and oxygen, 1013–1015 cm−2 of nitrogen is incorporated in the ultrathin (≤4 nm) oxide films. Additional nitrogen can be incorporated by low energy ion (15N2) implantation. The nitrogen profile and nitrogen chemical bonding states are analyzed as a function of the depth to understand the distribution of nitrogen incorporation during the SiOxNy thermal growth process. AR–XPS is shown to yield accurate nitrogen profiles that agree well with both medium energy ion scattering and secondary ion mass spectrometry analysis. Preferential nitrogen accumulation near the SiOxNy/Si interface is observed with a NO annealing, and nitrogen is shown to bond to both silicon and oxygen in multiple distinct chemical states, whose thermal stability bears implications on the reliability of nitrogen containing SiO2. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373090
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared spectroscopic analysis of the Si/SiO2 interface structure of thermally oxidized silicon (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1322-1330 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nature of the silicon oxide transition region in the vicinity of the Si/SiO2 interface is probed by infrared and x-ray photoelectron spectroscopies. The layer-by-layer composition of the interface is evaluated by uniformly thinning thermal oxide films from 31 Å down to 6 Å. We find that the thickness dependence of the frequencies of the transverse optical and longitudinal optical phonons of the oxide film cannot be reconciled by consideration of simple homogeneous processes such as image charge effects or stress near the interface. Rather, by applying the Bruggeman effective medium approximation, we show that film inhomogeneity in the form of substoichiometric silicon oxide species accounts for the observed spectral changes as the interface is approached. The presence of such substoichiometric oxide species is supported by the thickness dependence of the integrated Si suboxide signal in companion x-ray photoelectron spectra. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372017
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  • 3
    Electronic Resource
    Electronic Resource
    Material and electrical characterization of carbon-doped Ta2O5 films for embedded dynamic random access memory applications (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 308-316 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work is a systematic study of carbon incorporation in Ta2O5 and its effect on the material and electrical properties of Ta2O5, a promising replacement for silicon oxide in embedded dynamic random access memory applications. Using pulsed-dc reactive and rf-magnetron sputtering of Ta2O5 performed in an argon/oxygen/carbon-dioxide plasma, we have methodically doped the Ta2O5 films with carbon. In thick (70 nm) Ta2O5 films, an optimal amount (0.8–1.4 at. %) of carbon doping reduced the leakage current to 10−8 A/cm2 at +3 MV/cm, a four orders of magnitude reduction compared to a leakage current of 10−4 A/cm2 in an undoped Ta2O5 film grown in similar conditions without CO2 in the plasma. This finding suggests that carbon doping can further improve the dielectric leakage property at an optimal concentration. X-ray Photoemission Spectroscopy analysis showed the presence of carbonate (carbon bonded to three oxygen) in these electrically improved carbon-doped films. Analysis by high-resolution transmission electron microscopy and Nomarsky microscopy exhibited no morphological or structural changes in these carbon-doped thin films. Moreover, carbon doping showed no improvement in the leakage current in thin (10 nm) Ta2O5 films. This phenomenon is explained by a defect compensation mechanism in which the carbon-related defects remove carriers at low concentrations but form a hopping conduction path at high concentrations. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418420
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal stability of Ta2O5 in metal–oxide–metal capacitor structures (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3705-3707 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry, we have studied structures used in metal–oxide–metal capacitors including Ta2O5/TiN/Ti, Ta2O5/Ti, Ta2O5/TaN/Ti, Ta2O5/WN/Ti, and Ta2O5/M, where M=Ta, Pt, W, Al, and Si. We find that Ti and Al are able to reduce the Ta2O5 to Ta, forming oxides of Ti and Al, respectively. The diffusion barriers TiN, TaN, and WN hamper the diffusion of oxygen and therefore postpone the reduction of Ta2O5 to higher temperatures. As judged by the temperatures at which the reduction of Ta2O5 occurs, TaN and WN are more effective oxygen-diffusion barriers than TiN. We observe no oxygen remaining in the diffusion barrier when a Ti layer is present underneath. We observe no reduction of Ta2O5 when M=Pt, W, or Si. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123227
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  • 5
    Electronic Resource
    Electronic Resource
    Dielectric property and conduction mechanism of ultrathin zirconium oxide films (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3666-3668 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Stoichiometric, uniform, amorphous ZrO2 films with an equivalent oxide thickness of ∼1.5 nm and a dielectric constant of ∼18 were deposited by an atomic layer controlled deposition process on silicon for potential applications in metal–oxide–semiconductor (MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole–Frenkel emission at high electric fields. The MOS devices showed low leakage current, small hysteresis (〈50 mV), and low interface state density (∼2×1011 cm−2 eV−1). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of α-ZrO2 and an amorphous interfacial ZrSixOy layer which has a corresponding dielectric constant of 11. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1418265
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal stability of stacked high-k dielectrics on silicon (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3824-3826 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of ZrO2/ZrSixOy and ZrO2/ZrSixOy/SiNx thin films on silicon was examined by synchrotron radiation ultraviolet photoemission spectroscopy. The ZrO2/ZrSixOy layer deposited by atomic-layer-controlled deposition is stoichiometric, uniform, amorphous, and has an equivalent oxide thickness of ∼1 nm and a dielectric constant of ∼18 with low leakage current. These ZrO2/ZrSixOy samples are thermally stable in vacuum up to 880 °C at which the film decomposed to form ZrSi2, the most thermodynamically stable metal silicide at a per zirconium atom basis, and the desorption of SiO(g) and ZrO(g) accounted for the greatly reduced oxygen and zirconium photoemission intensities. The thermal stability of ZrO2/ZrSixOy is improved to 950 °C when deposited on a 0.5–0.7 nm SiNx film. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1419030
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  • 7
    Electronic Resource
    Electronic Resource
    Intracellular Calcium Involvement in Pituitary Adenylate Cyclase-Activating Polypeptide Stimulation of Growth Hormone and Gonadotrophin Secretion in Goldfish Pituitary Cells (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 17 (2005), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The involvement of intracellular Ca2+ stores and their regulatory mechanisms in mediating pituitary adenylate cyclase-activating polypeptide (PACAP) stimulation of growth hormone (GH) and maturational gonadotrophin (GTH-II) secretion from goldfish pituitary cells was investigated using a cell column perifusion system. Pretreatment with caffeine abolished the GH and GTH-II responses to PACAP. Dantrolene attenuated PACAP-elicited GTH-II release but did not affect the GH response, whereas ryanodine and 8-bromo-cADP ribose did not alter PACAP-induced GH and GTH-II release. Two endoplasmic/sarcoplasmic reticulum Ca2+ ATPase (SERCA) inhibitors, thapsigargin and cyclopiazonic acid, augmented PACAP-induced GTH-II release; similarly, thapsigargin elevated GH responses to PACAP. Treatment with carbonyl cyanide m-chlorophenylhydrazone, a mitochondrial uncoupler, reduced PACAP-stimulated GH release; however, inhibition of the mitochondrial Ca2+ uniport by Ru360 did not affect GH and GTH-II responses. The phosphatidyl inositol (PI)-specific phospholipase C (PLC) inhibitor ET-18-OCH3 inhibited, whereas the phosphatidyl-choline (PC)-specific PLC inhibitor D609 enhanced, PACAP-stimulated GH and GTH-II responses. On the other hand, the IP3 receptor blocker xestospongin D had no effect on PACAP-induced GTH-II response and potentiated the GH response. These results suggest that, despite some differences between GH and GTH-II cells, PACAP actions in both cell types generally rely on a caffeine-sensitive, but a largely ryanodine receptor-independent, mechanism. PC-PLC and some SERCA negatively modulate PACAP actions but mitochondrial Ca2+ stores per se are not important. A novel PI-PLC mechanism, which does not involve the traditional IP3/Ca2+ pathway, is also suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.2005.01312.x
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  • 8
    Electronic Resource
    Electronic Resource
    Agonist-Specific and Sexual Stage-Dependent Inhibition of Gonadotropin-Releasing Hormone-Stimulated Gonadotropin and Growth Hormone Release by Ryanodine: Relationship to Sexual Stage-Dependent Caffeine-Sensitive Hormone Release (2002)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Differential utilization of intracellular Ca2+ stores with specific functional characteristics could be a potential mechanism for coupling various stimuli to specific cellular responses. In the goldfish pituitary, both gonadotropes and somatotropes possess multiple intracellular Ca2+ stores that are differentially coupled to agonist-evoked exocytosis. We investigated the role of ryanodine receptor/Ca2+-release channels (RyR) in basal and gonadotropin-releasing hormone (GnRH)-evoked hormone secretion from cultured gonadotropes and somatotropes using radioimmunoassay for gonadotropin (GTH-II) and growth hormone (GH). As is the case in vivo, the basal and evoked secretion of both hormones varied with seasonal reproductive status. GnRH-stimulated hormone release was three-fold higher in cells from sexually mature animals compared to those in a sexually regressed state. Nanomolar doses of ryanodine evoked significant GTH-II and GH secretion, suggesting that ryanodine-sensitive Ca2+ stores can couple to exocytosis in both cell types. In gonadotropes, 10 µM ryanodine abolished cGnRH-II-evoked GTH-II release in both sexually mature and sexually regressed fish, while sGnRH signalling was mediated by ryanodine-sensitive Ca2+ stores in cells from sexually regressed fish only. Ryanodine-sensitive Ca2+ stores in somatotropes were only involved in cGnRH-II-stimulated GH release during gonadal regression. In contrast, sGnRH-stimulated, but not cGnRH-II-stimulated, GH release was significantly reduced by 1 µM xestospongin C. Although hormone release stimulated by mobilizing caffeine-sensitive Ca2+ pools was also markedly seasonal, it was largely independent of ryanodine-sensitive Ca2+ stores. Ryanodine-sensitive Ca2+ stores in both cell types are not active downstream of ionomycin, BayK 8644, protein kinase C or cyclic adenosine monophosphate signalling pathways, suggesting difference from a classical Ca2+-induced Ca2+ release system. Ours study is the first to suggest that RyR2 may be involved in the seasonal plasticity of pituitary function, which may be related to cyclic changes observed in reproduction and growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0007-1331.2001.00756.x
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  • 9
    Electronic Resource
    Electronic Resource
    Modulation of Gonadotropin II Release by K+ Channel Blockers in Goldfish Gonadotropes: A Novel Stimulatory Action of 4-Aminopyridine (2001)
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 13 (2001), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The effects of K+ channel blockers on basal gonadotropin II (GTH-II) release were examined in cultured goldfish gonadotropes. Tetraethylammonium (TEA) inhibited basal GTH-II release, whereas 4-aminopyridine (4-AP) increased basal release, although both K+ channel blockers generated increases in [Ca2+]i. Other K+ channel blockers had no significant effect on GTH-II release. We examined whether Ca2+ entry that arises from blockade of K+ channels by 4-AP mediates the secretory response. Secretion evoked by 4-AP was slightly reduced by TEA but was unaffected by reducing Ca2+ entry using either an inhibitor of Ca2+ channels, verapamil, or nominally Ca2+-free medium. In contrast, the Ca2+ signal evoked by 4-AP was largely blocked by Ca2+-free medium, as predicted by its inhibitory action on K+ channels. Together, these data suggest that the hormone release response to 4-AP is independent of entry of extracellular Ca2+. Finally, the mechanism of hormone release evoked by 4-AP appeared to be independent of mechanism(s) evoked by caffeine since 4-AP did not affect caffeine-evoked release and caffeine did not affect 4-AP evoked release. That both 4-AP and TEA generated Ca2+ signals but affected hormone release in either an extracellular Ca2+ independent (4-AP) or inhibitory (TEA) manner suggests that Ca2+ entry is linked to GTH-II secretion in a highly nonlinear fashion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2826.2001.00710.x
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  • 10
    Electronic Resource
    Electronic Resource
    Somatostatin-14 Actions on Dopamine- and Pituitary Adenylate Cyclase-Activating Polypeptide-Evoked Ca2+ Signals and Growth Hormone Secretion (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 16 (2004), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Using single-cell Ca2+ imaging and a growth hormone (GH) radioimmunassay, we investigated somatostatin-14 (SS14) inhibition of cAMP-dependent, stimulated GH secretion from primary cultures of dispersed goldfish pituitary cells. The dopamine-D1 receptor agonist SKF-38393, and the hypothalamic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) both elevated intracellular Ca2+ concentration ([Ca2+]i) and stimulated GH release. When increases in [Ca2+]i were prevented by intracellular loading of BAPTA, a Ca2+ chelator, SKF-38393- and PACAP-stimulated GH release were inhibited, suggesting that these Ca2+ signals are required for stimulated GH release. SS14 inhibited SKF-38393- and PACAP-stimulated GH release, but did not prevent these Ca2+ signals. Kinetic analysis revealed that SS14 lowered the maximum amplitude of the SKF-38393- and PACAP-evoked Ca2+ responses, but had no effect on other aspects of the Ca2+ signal. We then examined the ability of SS14 to act subsequent to dopamine-D1 or PACAP receptor activation using the adenylate cyclase activator forskolin, or the membrane permeant cAMP analogue 8Br-cAMP. Forskolin and 8Br-cAMP both increased [Ca2+]i and GH secretion and, as expected, SS14 inhibited the resultant GH release. Although SS14 significantly increased the time to maximum amplitude of the forskolin-evoked Ca2+ signals, it had no detectable effect on any of the kinetic parameters used to describe the Ca2+ signals evoked by 8Br-cAMP. Taken together, these results establish that SS14 has the ability to suppress Ca2+-dependent exocytosis by acting distal to elevations in [Ca2+]i. Furthermore, it appears likely that the cellular mechanisms underlying the observed effects of SS14 on Ca2+ signalling are upstream of cAMP and may be unrelated to those responsible for inhibiting GH release.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.2004.01218.x
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