The sub-micrometer thickness n-InSb/i-GaAs epilayers for magnetoresistor applications at room temperatures of operation

Magnetotransport at fields up to 500 mT and LF-noise characteristics are reported for miniature magnetoresistors with ferrite concentrators based on Sn-doped n-InSb/i-GaAs heterostructures grown by MBE. The thickness of the InSb epilayers lie in the range 0.55–1.5 μm giving room temperature mobilities of 2.5–5.5 m² V⁻¹ s⁻¹ with carrier densities of (0.5–1.5)×10¹⁷ cm⁻³. The room temperature magnetoresistance (MR) for our two terminal devices could be as high as 115% at 50 mT which is comparable to the extraordinary MR (ExMR) recently reported in microscopic composite van der Pauw disks four terminal devices [Science 289 (2000) 1530]. In addition, a high signal-to-noise ratio and a good temperature stability of R(B)/R₀=0.5–0.83% K⁻¹ was observed for B<60 mT (below the saturation field B_sat for ferrite). Device resistance stability R₀(T) was equal to 0.27–0.66% K⁻¹ in zero field with a nominal device resistance R₀=197–224 Ω for DC currents in the range I=0.01–1.0 mA. The minimum detectable magnetic field is estimated from the reduced differential MR (∂R/∂B)/R=2000% T⁻¹ at B=31 mT and normalised 1/f current noise power spectral density measured at the same field. The resolution limit B_min=2.6 nT at 10² Hz and B_min=0.82 nT at 10³ Hz. These resolution limits are seven times better than those recently reported for the same material n-InSb/i-GaAs and ferrite fabricated Hall sensors [Magnetotransport and Raman characterization of n-InSb/i-GaAs epilayers, for Hall sensors applications over extremely wide ranges of temperature and magnetic field, Proceedings NGS 10, IPAP Conference Series 2, IPAP, Tokyo, 2001, pp. 151–154].     

Ultrafast multidimensional dynamics of strong hydrogen bonds

The laser driven dynamics of the OH(D) stretching vibration in phthalic acid monomethylester is investigated. The combination of a 55-dimensional all-Cartesian reaction surface Hamiltonian and the time-dependent self-consistent field approach is shown to provide a microscopic picture of intramolecular vibrational energy redistribution taking place upon interaction with an external laser field. Choosing suitable zeroth-order vibrational states and combinations thereof a quasi-periodic in-phase and out-of-phase oscillatory behavior is observed manifesting energy flow on different time scales. The fingerprints of this behavior in transient absorption spectroscopy are also discussed. Received 24 August 2000 and Received in final form 11 October 2000     

Electrochemical Catalysis of the Reduction of 1,1,2-Trifluorotrichloroethane (Freon 113) by Outer-Sphere Electron Transfer Mediators

Cyclic voltammetry and preparative electrolysis in DMF were used to study the electrochemical catalytic reduction of 1,1,2-trifluorotrichloroethane with aromatic electron transfer mediators (p-dicyanobenzene, p-diacetylbenzene, fluoranthen, perylene, and (E)-azobenzene), leading to trichloroethylene in high yield. The results of a kinetic study of these systems indicate that the efficiency of other mediators of this class may be estimated relative to their redox properties. In comparison with direct electrochemical reduction of Freon 113, the use of aromatic electron transfer agents significantly raises the efficiency of Freon conversion and permits us to perform the reaction at less negative potentials.     

Polarographic study of aliphatic nitro compounds

Conclusions Study bas shown that the first stage in the reduction of 1,1-dinitroethane and fluorodinitromethane in strongly acidic solution is a two-electron C-N bond rupture process, the subsequent stages of the reaction being determined by the relative rates of the competing processes of protonation, nitrosation, and Neff reaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 567–573, March, 1977.