Issues on nanoimprint lithography with a single-layer resist structure

We summarize our key developments in nanoimprint lithography (NIL) that employs a single layer resist lift-off process: lowering of the imprint temperature (for thermal imprint) and pressure, achieving uniform resist thickness and low residual resist layer thickness in the trenches, and eliminating metal ‘rabbit ears’ for the single-layer lift-off. In thermal NIL, our requirements for lower operating temperature and pressure motivated us to develop an alternative resist that is a viscous fluid at room temperature and cures at a lower temperature of 70 °C than the operating temperature of the conventional thermal NIL (≈200 °C). For UV NIL, we devised a method to dispense the resist onto a hydrophobic mold and use the hydrophilic substrate surface to spread the resist via surface wetting to engineer a continuous and uniform film. We also explored the use of Si(110) substrates as molds to produce features with perfectly vertical side walls, and the use of aqua regia to directly etch away rabbit ears. PACS 86.65.+h; 81.16.Nd; 81.16.Rf     

Ultra-smooth platinum surfaces for nanoscale devices fabricated using chemical mechanical polishing

A technique involving two steps of chemical mechanical polishing (CMP) has been developed to produce ultra-smooth metal surfaces with an RMS roughness better than 0.1 nm. A figure of merit termed degree of smoothness (DOS) is proposed for the purpose of quantifying the extent of smoothness of a polished metal surface. A post CMP metal slurry cleaning solution was used for cleaning Pt slurry for the first time and by applying special techniques, a very high quality clean surface was attained. Applications of the polished Pt electrodes in interfacing molecular switching devices with self-assembled monolayers of molecules have been found to dramatically improve the packing and orientation of the molecular monolayer with a huge improvement in the molecular electronics device yields. These smooth metal surfaces may open doors for new opportunities in future nanoscale devices. PACS 81.05.Bx; 81.16.Rf; 81.65.Ps     

The Morrison rule in the ABFST multiperipheral model

The validity and consistency of the Morrison rule for the process ππ→πA₂ is considered at asymptotic energy in the context of the ABFST multiperipheral model. The Morrison rule turns out to be inconsistent with the model.     

PrimaryE2 transitions observed following neutron capture for the mass region 144≦A≦180

Values or upper limits for the radiative widths of 12 primaryE2 transitions observed in thermal neutron capture for nuclei with 144≦A≦180 are presented. The results are compared with the predictions of the Axel-Brink hypothesis using the systematics of the isoscalar and isovector quadrupole resonances. The strengths are on the average lower than expected. Analysis of previously reported average resonance data results in the same conclusion.     

Computer simulation of Fresnel diffraction from rectangular apertures and obstacles using the Fresnel integrals approach

In this paper, we describe a new computer simulation technique of generating Fresnel diffraction images from rectangular apertures of arbitrary dimensions by using Fresnel integrals instead of the more common fast Fourier transform methods. The simulation can be performed in almost any PC using the software MATLAB. Diffraction images can be generated for any wavelength of light and for any aperture–screen and aperture-source distances. Images for rectangular obstacles can also be simulated. Details of the algorithm and program are presented, as well as the interesting insights than can be gained from using the program. Finally, it is shown that the simulated images reduce to the simple Fraunhofer diffraction patterns for certain limiting situations.     

Fluctuations in the total cross sections of Y,Zr, La,Ce, Pr,Gd, Ho,Ta and Hg for 1.0 TO 2.0 MeV neutrons

Results of an analysis of the fluctuations observed in the neutron total cross sections of nine different nuclei in the energy range between 1.0 and 2.0 MeV are presented. It has been found that in general these may be explained to be due to fluctuations in the widths and spacings of the compound-nucleus level. The cross section data for some of the nuclei seem to indicate the presence of structures with widths much larger than the compound-nucleus width.     

Rates and equilibria in the reaction system Br + i-C4H10 ⇌ HBr + t-C4H9. The heat of formation of the t-butyl radical

The very low pressure reactor (VLPR) technique has been used to measure the bimolecular rate constant of the title reaction at 300 K. The rate constant is given by log k₁ (1/mol s) = (11.6 ± 0.4) ? (5.9 ± 0.6)/θ the equilibrium constant has also been measured at the same temperature and is given by K₁ = (5.6 ± 1) × 10^?3 and hence log k_?1 (1/mol s) = 9.5 ± 0.1. The results show that the reaction Br + t? C₄H₉ → HBr + i? C₄H₈ is unimportant under the present experimental conditions. Assigning the entropy of t-butyl radical to be 74 ± 2 eu which is in the possible range, the value of K₁ gives ΔH (t-butyl) = 9.1 ± 0.6 kcal/mol^?1. This yields for the bond dissociation, DH° (t-butyl-H) = 93.4 ± 0.6 kcal/mol. Both of these values are found to be in good agreement with recent VLPP studies.     

Effects of Zn on magnetic properties and pseudogap of optimally doped La2−xSrxCuO4

The effects of Zn substitution on the uniform (q = 0) magnetic susceptibility, χ(T), of optimally doped (x = 0.15) La_2?xSr_xCu_1?yZn_yO₄ sintered samples were investigated over a wide range of Zn contents (y). Non-magnetic Zn was found to enhance χ(T) systematically and depress T_c very effectively. We have extracted the characteristic pseudogap energy scale, ε_g, from the analysis of χ(T) data. Unlike T_c, ε_g was found to be fairly insensitive to the level of Zn substitution. This supports the scenario where the pseudogap phenomenon has non-superconducting origin. We have also analyzed the Zn-induced Curie-like enhancement of the χ(T) data using different models and discussed the various possible implications.     

A model for dimensional crossover temperature above the superconducting transition for high-temperature superconductors

We have developed a theoretical model for the calculation of dimensional crossover temperature above the mean-field transition temperature using paraconductivity approach. We have numerically estimated the dimensional crossover (2D–3D and 2D–1D) temperature for the recently reported polycrystalline sample of the type Hg, Tl-1223. Our numerical results indicate that the dimensional crossover temperature is a variable quantity and it depends on the parameter related to superconductivity and the range of temperature where the fluctuation effect is significant.     

Effect of a Floating Elastic Plate/Membrane on the Motion Due to a Ring Source in Water With Porous Bed

The velocity potentials due to the presence of a horizontal circular ring of wave sources of timedependent strength in water of finite constant depth with a floating elastic plate or a floating membrane are determined. The uniform bottom is composed of non-dissipative porous medium. The problems are formulated as the initial value problems and the Laplace transform method is used to solve these. For time-harmonic source strength, the steady-state analysis of the potentials reveals the existence of outgoing progressive waves. Graphs for the surface profiles are presented for different values of the tension parameter for the membrane, flexural rigidity of ice and the porous-effect parameter.