Direct evidence of the failure of electric-dipole approximation in second-harmonic generation from a chiral polymer film

Second-harmonic generation from Langmuir-Blodgett films of a polythiophene is strongly influenced by the chirality of the polymer. The polarization dependence of the process cannot be explained in the elec.-dipole approxn. Evidence of contributions beyond elec. dipoles is obtained directly from individual second-harmonic signal

Atomic layer deposition of high-k dielectric layers on Ge and III-V MOS channels

Ge and III-V semiconductors are potential high performance channel materials for future CMOS devices. In this work, we have studied At. Layer Deposition (ALD) of high-k dielec. layers on Ge and GaAs substrates. We focus at the effect of the oxidant (H2O, O3, O2, O2 plasma) during gate stack formation. GeO2, obtained by Ge oxidn. in O2 or O3, is a promising passivation layer. The germanium oxide thickness can be scaled down below 1 nm, but such thin layers contain Ge in oxidn. states lower than 4+. Still, elec. results indicate that small amts. of Ge in oxidn. states lower than 4+ are not detrimental for device performance. Partial intermixing was obsd. for high-k dielec. and GeO2 or GaAsOx, suggesting possible correlations in the ALD growth mechanisms on Ge and GaAs substrates. [on SciFinder (R)

Traveller Specific Drugs Initiative: annual report (November 2000- December 2001): an initiative to promote the inclusion of Travellers in the National Drugs Strategy Building on Experience 2001-2008.

Second-harmonic generation was used as a technique to examine different types of chiral materials. All materials studied showed large circular-difference effects in the 2nd-harmonic response, i.e., the efficiency of the process was different for left- and right-hand circularly-polarized light. Study of various chiral materials showed that a different quant. and qual. response can be expected depending on the compn. and structure. The existence of magnetic dipole contributions to the nonlinearity of those materials is demonstrate

Dysprosium scandate thin films as an alternate amorphous gate oxide prepared by metal-organic chemical vapor deposition

Dysprosium scandate (DyScO3) thin films were deposited on Si substrates using metal-organic chemical vapor deposition. Individual source precursors of Dy and Sc were used and deposition temperatures ranged from 480 to 700 degrees C. Films were amorphous with low root mean square roughness (<= 2 A) and were stable up to 1050 degrees C annealing. Electrical characterization yielded C-V curves with negligible hysteresis (< 10 mV), high dielectric constant (similar to 22), and low leakage currents. The electrical properties of the DyScO3/SiOx/Si stacks were stable up to 800 degrees C for films on native oxide; however, this limit increased to 900 degrees C for films on special chemically grown oxide, suggesting further improvement with proper diffusion barrier. (c) 2006 American Institute of Physics

Interdiffusion and crystallization in HfO2/Al2O3 superlattices

The interplay of interdiffusion and crystallization in HfO2/Al2O3 superlattices during spike annealing at 1050 degrees C was studied using x-ray reflectivity and x-ray diffraction. A transition in thermal stability was found as a function of HfO2 thickness between 2.3 and 3.2 nm. This transition is due to a crossover of HfO2 crystallization and amorphous HfO2/Al2O3 interdiffusion kinetics. For thin HfO2, amorphous HfO2 and Al2O3 interdiffuse and subsequently crystallize as HfAlOx into a cubic-HfO2-like phase. For thicker HfO2, HfO2 layers crystallize individually into the monoclinic phase. As a consequence, interdiffusion between HfO2 and Al2O3 is suppressed because of the immiscibility of Al2O3 in monoclinic HfO2

Metal gate work function tuning by Al incorporation in TiN

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Titanium nitride (TiN) films have been used as gate electrode on metal-oxide-semiconductor (MOS) devices. TiN effective work function (EWF) values have been often reported as suitable for pMOS. For nMOS devices, a gate electrode with sufficient low EWF value with a similar robustness as TiN is a challenge. Thus, in this work, aluminum (Al) is incorporated into the TiN layer to reduce the EWF values, which allows the use of this electrode in nMOS devices. Titanium aluminum (TiAl), Al, and aluminum nitride (AlN) layers were introduced between the high-k (HfO2) dielectric and TiN electrode as Al diffusion sources. Pt/TiN (with Al diffusion) and Pt/TiN/TiAl/TiN structures were obtained and TiN EWF values were reduced of 0.37 eV and 1.09 eV, respectively. The study of TiN/AlN/HfO2/SiO2/Si/Al structures demonstrated that AlN layer can be used as an alternative film for TiN EWF tuning. A decrease of 0.26 eV and 0.45 eV on TiN EWF values were extracted from AlN/TiN stack and AlN/TiN laminate stack, respectively. AlN/TiN laminate structures have been shown to be more effective to reduce the TiN work function than just increasing the AlN thickness. (C) 2014 AIP Publishing LLC.1157Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Medium energy ion scattering for the high depth resolution characterisation of high-k dielectric layers of nanometer thickness

Medium energy ion scattering (MEIS) using, typically, 100–200 keV H+ or He+ ions derives it ability to characterise nanolayers from the fact that the energy after backscattering depends (i) on the elastic energy loss suffered in a single collision with a target atom and (ii) on the inelastic energy losses on its incoming and outgoing trajectories. From the former the mass of the atom can be determined and from the latter its depth. Thus MEIS yields depth dependent compositional and structural information, with high depth resolution (sub-nm near the surface) and good sensitivity for all but the lighter masses. It is particularly well suited for the depth analysis of high-k multilayers of nanometer thickness. Accurate quantification of the depth distributions of atomic species can be obtained using suitable spectrum simulation. In the present paper, important aspects of MEIS including quantification, depth resolution and spectrum simulation are briefly discussed. The capabilities of the technique in terms of the high depth resolution layer compositional and structural information it yields, is illustrated with reference to the detailed characterisation of a range of high-k nanolayer and multilayer structures for current microelectronic devices or those still under development: (i) HfO2 and HfSiOx for gate dielectric applications, including a TiN/Al2O3/HfO2/SiO2/Si structure, (ii) TiN/SrTiO3/TiN and (iii) TiO2/Ru/TiN multilayer structures for metal–insulator–metal capacitors (MIMcaps) in DRAM applications. The unique information provided by the technique is highlighted by its clear capability to accurately quantify the composition profiles and thickness of nanolayers and complex multilayers as grown, and to identify the nature and extent of atom redistribution (e.g. intermixing, segregation) during layer deposition, annealing and plasma processing. The ability makes it a valuable tool in the development of the nanostructures that will become increasingly important as device dimensions continue to be scaled down