Characterization of the Si/SiO2 interface morphology from quantum oscillations in Fowler–Nordheim tunneling currents

As design rules shrink to conform with ULSI device dimensions, gate dielectrics for MOSFET structures are required to be scaled to below ~60A where some properties of the device, such as interface roughness, that are negligible for thicker films become critical. Microroughness at the interface of ultrathin MOS capacitors has been shown to degrade these devices. The present study focuses on the interfacial region of -50A. SiO, on Si, using the quantum oscillations in Fowler-Nordheim tunneling currents as a probe. The oscillations are sensitive to the electron potential and abruptness of the film and interfaces. In particular, inelastic scattering and/or thickness inhomogeneities in the film will reduce the amplitude of the oscillations. We are using the amplitude of the oscillations to examine the degree of microroughness at the interface that results from a pre-oxidation high temperature anneal in an inert ambient containing various amounts of H20. AFM imaging has shown correlations supporting a microroughness induced change in the quantum oscillation amplitudes

Thermoelectric effect in molecular electronics

We provide a theoretical estimate of the thermoelectric current and voltage over a Phenyldithiol molecule. We also show that the thermoelectric voltage is (1) easy to analyze, (2) insensitive to the detailed coupling to the contacts, (3) large enough to be measured and (4) give valuable information, which is not readily accessible through other experiments, on the location of the Fermi energy relative to the molecular levels. The location of the Fermi-energy is poorly understood and controversial even though it is a central factor in determining the nature of conduction (n- or p-type). We also note that the thermoelectric voltage measured over Guanine molecules with an STM by Poler et al., indicate conduction through the HOMO level, i.e., p-type conduction.Comment: 4 pages, 3 figure

Theoretical and experimental study of the coordination ability of 4,6-dimethylpyrimidinylhydrazone diacetylmonooxime towards Ni(ii), Mn(ii), Fe(iii) and Co(iii) ions

The ligand system diacethylmonooxime 4,6-dimethylpyrimidylhydrazone and its Ni(ii), Mn(ii), Fe(iii) and Co(iii) complexes with composition [Ni(H2L)2]Cl2·1.17H2O, [Mn(H2L)2](ClO4)2·0.75H2O, [Fe(H2L)2]·3Cl·H2O and [Co(HL)2]·ClO4 have been synthesized. The structure of both the ligand and complexes has been established through IR and 1H NMR spectroscopy, magnetic measurements and X-ray analysis. The acid-base properties of the hetarylhydrazone were studied with potentiometric and spectrophotometric methods. The protolytic equilibrium constants and energies of possible ligand tautomeric forms have been obtained with these data and from quantum-chemical calculations. These calculated pKa values are compared to the computational data. The structures of the hetarylhydrazone and its Ni(ii), Mn(ii) and Co(iii) complexes have been also determined by X-ray analysis. It was shown that the high-spin Ni(ii), Mn(ii), and Fe(iii) complexes possess a distorted-octahedral structure of the coordination unit. The low-spin Co3+ complex has been synthesized by the reaction between Co(ClO4)2 and the hetarylhydrazone, the ligand being reacted in the monodeprotonated pyrimidine tautomeric form. This diacethylmonooxime 4,6-dimethylpyrimidylhydrazone ligand shows potential in stabilizing different metal complexes with interesting reactivity, magnetic and electrochemical properties. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique