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Papers by L. Krusin-Elbaum

configuration. Lithium doping was done with 1.69 mol BuLi solution (0.34 ml per 0.25 g of VO x na... more configuration. Lithium doping was done with 1.69 mol BuLi solution (0.34 ml per 0.25 g of VO x nanotubes, calculated to compensate each V 5þ with one Li). Iodine doping was done by submitting VO x nanotubes to iodine vapour for varying time intervals (0.5, 1, 1.5 and 2 h) from iodine crystals (0.125 g of VO x per 0.85 g of I) in evacuated (1.3 £ 10 26 torr) and sealed 125-cm 3 quartz tubes. After 1 h, the nanotubes visibly darkened, with no measurable change afterwards. All chemicals were from Aldrich. For magnetic measurements, doped nanotubes were weighed and sealed under nitrogen in gel capsules to avoid dopant oxidation (see ref. 8). Magnetic measurements were performed in a SQUID magnetometer (MPMS, Quantum Design) in fields up to 5 T. For two-probe transport measurements, the tubes were cast out of hexane solution onto oxidized silicon substrates, which were e-beam prepatterned with Pt/Ti or Au/Ti electrodes. The oxide thickness was 140 nm and the electrodes were 300 nm wide, with separation varied in the 200-800 nm range. All transport measurements were performed in vacuum (starting at 3.8 £ 10 27 torr and prebaking for 17 h to improve contact resistance), with the in situ Li doping from a commercial (SAES Getter) source, following an alkali-doping process used for carbon nanotubes 8. Li was added in fixed steps; in each step the source was heated by applying current I ¼ 6.7 A for 1.5 min (see Fig. 4c).

Physical Review B

We report local-magnetic-field measurements near a YBa2Cu307y crystal by a linear array of Hall p... more We report local-magnetic-field measurements near a YBa2Cu307y crystal by a linear array of Hall probes. Two distinct features are observed in the local-field hysteresis HI vs H, which are not present in the integrated magnetization measured by a SQUID: (1) a peak in HI right after the field reversal that we attribute to the field generated by the current liow in a platelike superconductor, and (2) a position-dependent suppression of HI near zero external field which may be linked to H, l. These local measurements suggest a relevant scale for the critical current variation of between 10 and 200 pm.

Physical Review Letters, 1998

... Vortex Liquid above the Critical Point of the First-Order Melting Transition: A Consequence o... more ... Vortex Liquid above the Critical Point of the First-Order Melting Transition: A Consequence of Pointlike Disorder D. L?,1, * L. Krusin-Elbaum,1 H. Safar,2 E. Righi,3 F. de la Cruz,3 S. Grigera,3 C. Feild,1 WK Kwok,4 L. Paulius,5 and GW Crabtree4 IBM TJ Watson Research Center ...

$Research paper thumbnail of Two-dimensional X-ray diffraction characterization of (Zn,Cd,Mg)Se wurtzite layers grown on Bi2Se3$

Journal of Crystal Growth, 2016

The wurtzite structure of ZnSe, Zn 0.49 Cd 0.51 Se and Zn 0.23 Cd 0.25 Mg 0.52 Se layers grown on... more The wurtzite structure of ZnSe, Zn 0.49 Cd 0.51 Se and Zn 0.23 Cd 0.25 Mg 0.52 Se layers grown on Bi 2 Se 3 /sapphire (0001) by Molecular Beam Epitaxy (MBE) is reported. Structure characterization is studied by two-dimensional X-ray diffraction. Pole figures are calculated for cubic and hexagonal planes of the (Zn,Cd,Mg)Se family and compared to their expected values. The targeted wurtzite plane was (11-22), while the cubic ones were the (220) and (311). The results show that, under our MBE growth conditions, ZnSe, Zn 0.49 Cd 0.51 Se and Zn 0.23 Cd 0.25 Mg 0.52 Se layers prefer to form the hexagonal (wurtzite) phase rather than the cubic one when grown on Bi 2 Se 3 /sapphire in (0001) direction. These results have implications for the next generation devices combining semiconductors and topological insulator materials.

Physical Phenomena At High Magnetic Fields IV, 2002

ABSTRACT We map the field-temperature (H-T) diagram of the pseudogap state in Bi2Sr2CaCu2O8+y cry... more ABSTRACT We map the field-temperature (H-T) diagram of the pseudogap state in Bi2Sr2CaCu2O8+y crystals in a wide range of hole doping. By probing the quasiparticle density-of-states with the c-axis interlayer resistivity measurements in fields up to 60 T we make a systematic evaluation of the pseudogap closing field Hpg that restores the superconductor to its ungapped state. In contrast to the characteristic fields of the superconducting state, Hpg(T) at low temperatures is temperature independent and scales with the pseudogap temperature T* by a simple Zeeman energy scale, indicating a predominant role of spins over the orbital effects in the formation of the pseudogap.

$Research paper thumbnail of Transport in refractory metals and their interaction with SiO2: Comparison of tungsten and molybdenum$

Thin Solid Films, 1987

ABSTRACT We have investigated sputtered and electron-beam-evaporated thin films of tungsten and m... more ABSTRACT We have investigated sputtered and electron-beam-evaporated thin films of tungsten and molybdenum deposited onto 100 Å SiO2. These two refractory metals have comparable room temperature resistivities (5–6 μΩ cm) and a work function at the midgap between n+ and p+ polycrystalline silicon. Therefore both can be considered for application as a gate electrode in submicron very large scale integration technology. We have probed their interaction with SiO2 using Auger spectroscopy, cross-sectional transmission electron microscopy (CTEM) and with current-voltage (I-V) characteristics of molybdenum and tungsten metal/oxide/ semiconductor (MOS) capacitors as a function of the annealing temperature. We have also measured electrical resistivity in the 4.2–300K temperature range to ascertain the differences and the similarities between the two. We find that, in terms of resistivity, the difference between the two metals is slight. Although at room temperature, ρMo is 10% higher than ρw, at liquid nitrogen, molybdenum is around 30% more conductive after a 900–1000°C anneal. The interface with SiO2 appears in CTEM to be very smooth for both. Auger depth profiling, however, reveals some interface interaction for molybdenum, but not tungsten. This is confirmed with leakage and breakdown measurements on an MOS capacitor structure 32 mm in diameter. After anneals at and above 900°C, molybdenum capacitors on 100 Å oxide are all shorted. The same annealing schedule produces a reasonable distribution of breakdown voltages for tungsten capacitors.

Magnetic Susceptibility of Superconductors and Other Spin Systems, 1991

Physics and Materials Science of High Temperature Superconductors, II, 1992

Mixed valent vanadium oxides belong to the class of strongly correlated systems that can host unu... more Mixed valent vanadium oxides belong to the class of strongly correlated systems that can host unusual quantum spin states. Here we report on magnetic behavior of VOx (x ˜ 2.4) nanotubes self-assembled using monoamines as structure-directing templates. In their `as-assembled' state, S = 1/2 spins in the VOx nanotubes form a (quantum) spin-liquid with a spin-gap Deltas ≈ 665 K. However, when the tubes are doped either with lithium (electrons) or iodine (holes) they develop a nonlinear hysteretic (ferromagnetic) response to the applied magnetic field. We discuss how this magnetic particle-hole complimentarity can arise from the low-dimensionality of the nanotube structure with crystal field splittings that enforce a Mott gap. The double-layer arrangement of vanadium ions allows for emptying or filling the Mott bands upon doping, removing the frustration in the undoped system responsible for the spin-gap.

The entire temperature dependence of the upper critical field Hc2 in the β-pyrochlore KOs2O6 is o... more The entire temperature dependence of the upper critical field Hc2 in the β-pyrochlore KOs2O6 is obtained from high-field resistivity and magnetic measurements. Both techniques identically give Hc2(T ≃ 0 K) not only surprisingly high (∼ 33 T), but also the approach to it unusually temperature-linear all the way below Tc (= 9.6 K). We show that, while Hc2(0) exceeds a

In phase-change materials (PCM), typically Ge-Te-Sb based glassy semiconductors, a reversible tra... more In phase-change materials (PCM), typically Ge-Te-Sb based glassy semiconductors, a reversible transformation between a highly resistive (amorphous) and a highly conductive (crystalline) phase is accomplished by Joule heating that melt-quenches PCM into the amorphous state, and thermally anneals it back to the crystalline state. Here we report a room-temperature pressure driven reversible phase change in a binary eutectic GeSb system.