InAs/GaSb/AlSb resonant tunneling spin device concepts

We discuss device concepts for creating spin-polarized current sources without external magnetic fields, using non-magnetic 6.1 Å semiconductor resonant tunneling structures. Spin filters, spin pumps, and spin transistors that exploit structural and bulk inversion asymmetries will be examined.     

Scanning probe microscopy characterization of gold-chemisorbed poplar plastocyanin mutants

Two poplar plastocyanin mutants adsorbed onto gold electrodes have been characterized at single molecule level by scanning probe microscopy. Immobilization of the two redox metalloprotein mutants on Au(1 1 1) surface was achieved by either a disulphide bridge (PCSS) or a single thiol (PCSH), both the anchoring groups having been introduced by site-directed mutagenesis. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) analysis gives evidence of a stable and robust binding of both mutants to gold. The lateral dimensions, as estimated by STM, and the height above the gold substrate, as evaluated by AFM, of the two mutants well agree with crystallographic sizes. A narrower height distribution is observed for PCSS compared to PCSH, corresponding to a more homogeneous orientation of the former mutant adsorbed onto gold. Major differences between the mutants are observed by electrochemical STM. In particular, the image contrast of adsorbed PCSS is affected by tuning the external electrochemical potential to the redox levels of the mutant, consistent with some involvement of copper active site in the tunneling process. On the contrary, no contrast variation is observed in electrochemical STM of adsorbed PCSH. Moreover, scanning tunneling spectroscopy experiments reveal asymmetric I–V characteristics for single PCSS proteins, reminiscent of a rectifying-like behaviour, whereas an almost symmetric I–V relation is observed for PCSH.     

Coherent quantum transport in normal-metal/d-wave superconductor/normal-metal double tunnel junctions

Taking into account the effects of quantum interference and interface scattering, combining the electron current with hole current contribution to tunnel current,we study the coherent quantum transport in normal-metal/d-wave superconductor/normal-metal (NM/d-wave SC/NM) double tunnel junctions by using extended Blonder-Tinkham-Klapwijk (BTK) approach. It is shown that all quasiparticle transport coefficients and conductance spectrum exhibit oscillating behavior with the energy, in which periodic vanishing of Andreev reflection (AR) above superconducting gap is found.In tunnel limit for the interface scattering strength taken very large, there are a series of bound states of quasiparticles formed in SC.     

Low energy properties of identical and strongly correlated particles

Interesting qualitative consequences can arise from the quantum mechanical identity among strongly correlated particles that carry spin. This is demonstrated for properties connected with the low energy excitations in molecular and electronic systems. Spatial permutations among the identical particles are used as the key features. The particular behaviour of rotational tunneling molecules or molecular parts under the influence of dissipation are discussed together with the consequences arising for conversion transitions. The relationship between the thermal shifting of the tunneling line and the conversion rate at low and at elevated temperatures is explicated. The valuable information, that can be extracted from the conversion behaviour after isotopical substitution, is explained in detail. At low temperatures qualitative changes are predicted for the conversion rate by deuteration. Weakly hindered rotors show, also experimentally, drastic isotopic effects. The second part is devoted to finite systems of strongly interacting electrons that appear in semi-conductor nano-structures. The lowest excitation energies are strongly influenced by the interaction. They can be understood and determined starting from the limit of crystallized electrons by introducing localized many particle ‘pocket states’. The energy levels show multiplet structure, in agreement with numerical results. The total electron spin, associated with the low energy excitations, is crucially important for the nonlinear transport properties through quantum dots. It allows for instance to explain the appearance of negative differential conductances.     

Characterization of heat-assisted magnetic probe recording on CoNi/Pt multilayers

A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2–7 V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260 nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments.     

XD－YES：IC功能成品率模拟器的实现

首先建立缺陷空间分布和粒径分布的模型，并讨论了缺陷通过版图产生电路错误的过程，给出了ＩＣ功能成品率模拟器ＸＤ－ＹＥＳ的实现。用ＸＤ－ＹＥＳ对微电子测试图和实际ＩＣ的功能成品率模拟和分析表明，其结果与实际符合很好，从而表明ＸＤ－ＹＥＳ的可行性和实用性。     

Nitroxyl free radical binding to Si(1 0 0): a combined scanning tunneling microscopy and computational modeling study

The ultra-high vacuum scanning tunneling microscope (UHV-STM) was used to investigate the addition of the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radical to the Si(1 0 0) surface. Room temperature studies performed on clean Si(1 0 0)-2 × 1 confirm the proposed binding of the unpaired valence electron associated with the singly occupied molecular orbital (SOMO) of the molecule with a Si dangling bond. A strong bias dependence in the topography of isolated molecules was observed in the range of −2.0 to +2.5 V. Semiempirical and density functional calculations of TEMPO bound to a three-dimer silicon cluster model yield occupied state density isosurfaces below the highest occupied (HOMO) and unoccupied state densities isosurfaces above the lowest unoccupied molecular orbital (LUMO) which trend in qualitative agreement with the bias dependent STM topography. Furthermore, the placement of TEMPO molecules on dangling bonds was controlled with atomic precision on the monohydride Si(1 0 0) surface via electron stimulated desorption of H, demonstrating the compatibility of nitroxyl free radical binding chemistries with nanopatterning techniques such as feedback controlled lithography.     

H andH NMR Relaxation in Hydrogen-Bonded Solids Due to a Complex Motion: Classical Jumps over a Barrier and Incoherent Tunneling

Equations for the temperature dependence of proton and deuteron spin–lattice relaxation rates and second moments due to a complex motion consisting of classical jumps over a potential barrier and quantum mechanical tunneling through the barrier have been derived. Asymmetric double and triple potential wells are considered. These equations have been employed to analyze proton spin–lattice relaxation data for solid naphthazarin in the laboratory and rotating frames as a function of temperature. It is shown that tunneling plays an important role in the proton transfer dynamics of this compound.     

STS investigations of temperature dependence of Au(1 1 1) surface state energy position

High temperature scanning tunneling spectroscopy (HT-STS) was used to investigate the electronic structure of Au(1 1 1) at different temperatures in the energy range 0-1 eV below the Fermi level. We concentrated on the influence of temperature on the Shockley surface state (SS) appearing on noble metals surface due to a surface projected bulk bang gap in [1 1 1] direction. The influence of temperature on the projected band gap edge (BE) was also investigated. The experiment was carried out in the temperature range 294-580 K. As the result of the experiment a delicate shift of the SS and the BE in direction of the Fermi level was reported.     

Matrix assisted pulsed laser evaporation processing of triacetate-pullulan polysaccharide thin films for drug delivery systems

We report the first successful deposition of triacetate-pullulan polysaccharide thin films by matrix assisted pulsed laser evaporation. We used a KrF* excimer laser source (λ = 248 nm, τ ≈ 20 ns) operated at a repetition rate of 10 Hz. We demonstrated by FTIR that our thin films are composed of triacetate-pullulan maintaining its chemical structure and functionality. The dependence on incident laser fluence of the induced surface morphology is analysed.