Electrostatic guiding of cold polar molecules on a chip

We propose a novel scheme to guide cold polar molecules on the surface of an insulating substrate (i.e. a chip) using an electrostatic field generated by the combination of a pair of parallel charged wires and a grounded metal plate. The spatial distributions of the electric fields from the above charged-wire layout and their Stark potentials for cold CO molecules and dipole forces are calculated, and the relationships between the electric field and the geometric parameters of our charged-wire system are analyzed. Our study shows that our charged-wire scheme can be used to guide cold polar molecules in the weak-field-seeking state, and to construct various molecular optical elements, such as a molecular funnel, a molecular beam splitter and a molecular interferometer and so on, to form various integrated molecular optical elements and their molecular chips, and even to generate a continuous wave (CW) cold molecular beam by using a low-pass energy filter based on bent two-wire guiding.     

Formation and Shape Transition of Nanostructures on Si(100) surfaces after MeV Sb Implantation

We have studied the formation of nanostructures on Si(100) surfaces after 1.5 MeV Sb implantation. Scanning Probe Microscopy has been utilized to investigate the ion implanted surfaces. We observe the formation of nanostructures after a fluence of 1×10¹³ ions/cm². These surface structures are elliptical in shape with an eccentricity of 0.86 and their major and minor axes having dimensions of about 11.6 nm and 23.0 nm, respectively. The area of the nanostructure is 210 nm²at this fluence. Although the nanostructures remain of elliptical shape, their area increase with increasing fluence. However, after a fluence of 5×10¹⁴ ions/cm² a transition in shape of nanostructures is observed. Nanostructures become approximately circular with an eccentricity of 0.19 and a diameter of about 30.1 nm. At this fluence we also observe a large increase in the area of the nanostructures to 726 nm². Surface morphology and surface roughness of the ion implanted surfaces has also been discussed.     

Investigation into defects occurring on the polymer surface during the photolithography process

With a view to improving the realisation of polymer optical waveguide some features relevant to the photolithography process are analysed. This paper focuses on defects that occur on the surface of polymer layers involved in the process. For example, depending on the heat treatment or the deposited material, some worm-like defects appear on the polymer surface. When they occur, the waveguide surface roughness becomes too high (about one hundred nm and more). This means that the optical performance of the waveguides is too poor. In this document, we show the changes in temperature on polymer film surfaces which are coated with a thin inorganic layer and the occurrence of these defects is observed. This work confirms that the defect occurrence is clearly linked to the glass transition temperature. The paper reports that, in some cases, the adjustment of thermal properties by annealing can advantageously shift the glass transition, without changing the target optical properties.     

Surface nano-structural modifications and characteristics in nitrogen ion implanted W as a function of temperature and N energy

The surface modifications of tungsten massive samples (0.5 mm foils) made by nitrogen ion implantation are studied by SEM, XRD, AFM, and SIMS. Nitrogen ions in the energy range of 16-30 keV with a fluence of 1 × 10¹⁸ N⁺ cm⁻² were implanted in tungsten samples for 1600 s at different temperatures. XRD patterns clearly showed WN₂ (0 1 8) (rhombohedral) very close to W (2 0 0) line. Crystallite sizes (coherently diffracting domains) obtained from WN₂ (0 1 8) line, showed an increase with substrate temperature. AFM images showed the formation of grains on W samples, which grew in size with temperature. Similar morphological changes to that has been observed for thin films by increasing substrate temperature (i.e., structure zone model (SZM)), is obtained. The surface roughness variation with temperature generally showed a decrease with increasing temperature. The density of implanted nitrogen ions and the depth of nitrogen ion implantation in W studied by SIMS showed a minimum for N⁺ density as well as a minimum for penetration depth of N⁺ ions in W at certain temperatures, which are both consistent with XRD results (i.e., I_{W (2 0 0)}/I_{W (2 1 1)}) for W (bcc). Hence, showing a correlation between XRD and SIMS results.     

Ferromagnetism and metallicity in the modulated Sr1−xThxCoO3−δ oxygen deficient perovskites with x∼0.1

The Th⁴⁺ for Sr²⁺ substitution in SrCoO_3−δ is found to be an efficient way to stabilize an oxygen deficient perovskite. The structural study reveals a Th⁴⁺ solubility limited to ∼10% so that the chemical formula, Sr_0.9Th_0.1CoO_2.79, is obtained. The comparison to the Y³⁺ for Sr²⁺ substitution shows that a lower oxygen content is obtained for the former according to the Sr_0.75Y_0.25CoO_2.55 formula. The higher oxygen content reached with Th⁴⁺ has a strong impact on the physical properties: Sr_0.9Th_0.1CoO_2.79 is an itinerant ferromagnet (T_C∼200 K, ρ_5 K=2 mΩ cm) whereas Sr_0.75Y_0.25CoO_2.55 is a robust insulating antiferromagnet (T_N∼320 K, ρ_5 K=10⁵ Ω cm). Clearly, the substitution of a tetravalent cation for Sr²⁺ appears to be a promising route to synthesize SrCoO_3−δ itinerant ferromagnets without the use of high oxygen pressure nor electrochemical oxidation.     

Effect of surface roughness on the development of protective Al2O3 on Fe-10Al (at.%) alloys containing 0-10 at.% Cr

The effect of alloy surface roughness, achieved by different degrees of surface polishing, on the development of protective alumina layer on Fe-10 at.% Al alloys containing 0, 5, and 10 at.% Cr was investigated during oxidation at 1000 °C in 0.1 MPa oxygen. For alloys that are not strong Al₂O₃ formers (Fe-10Al and Fe-5Cr-10Al), the rougher surfaces increased Fe incorporation into the overall surface layer. On the Fe-10Al, more iron oxides were formed in a uniform layer of mixed aluminum- and iron-oxides since the layer was thicker. On the Fe-5Cr-10Al, more iron-rich nodules developed on an otherwise thin Al₂O₃ surface layer. These nodules nucleated preferentially along surface scratch marks but not on alloy grain boundaries. For the strong Al₂O₃-forming Fe-10Cr-10Al alloy, protective alumina surface layers were observed regardless of the surface roughness. These results indicate that the formation of a protective Al₂O₃ layer on Fe-Cr-Al surfaces is not dictated by Al diffusion to the surface. More cold-worked surfaces caused an enhanced Fe diffusion, hence produced more Fe-rich oxides during the early stage of oxidation.     

Chemiluminescence of alkaline earth monohalides in the collisions of ground state Ca, Sr, and Ba atoms with Cl2, Br2, I2, ICl,, ICl, and IBr

Formation of electronically excited alkaline earth monohalides MX^* in the reactions of ground state Ca, Sr, and Ba atoms with Cl₂, Br₂, I₂, ICl, and IBr was studied in a beam-gas arrangement. The MX^* spectra were observed for all the reactive systems with the exception of Ca, . The energy balance indicates that MX^* can be formed in a single-collision exchange reaction; also the dependence of MX^*-chemiluminescence intensity on halogen gas pressure is typical of a bimolecular process. The MX^*-chemiluminescence cross sections and lower limits of photon yields are estimated. Received 17 April 2000 and Received in final form 18 July 2000     

Plasma modification of self-assembled structures of CoTMPP molecules

Plasma-treated cobalt metalloporphyrins have recently been proposed as electrocatalysts for the oxygen and oxygen peroxide reduction reaction. Whereas the effects of plasma treatment on the elemental composition of the surface of catalysts have been investigated, the effects of plasma treatment on the morphology of catalysts have not yet been studied. In this study, plasma modified nanosized structures of cobalt tetramethoxyphenylporphyrin (CoTMPP) molecules arising from the deposition of a porphyrin solution on an a-C:H film are investigated using an atomic force microscope (AFM). Additionally, the effects of plasma treatment on the structure of porphyrin molecules are studied by using ultra violet visible (UV-vis) absorption analysis. The investigations reveal the morphological changes which accompany the transformation of CoTMPP into the final catalytic material. First, the large CoTMPP aggregates are split into smaller ones. Second, the CoTMPP layer appears to be sublimated after plasma treatment. Sublimated CoTMPP molecules can be decomposed by plasma and after redeposition can form catalytic active fragments.     

Calorimetric Study of Crystalline and Liquid-Crystalline Polymorphism in the Homologues of Terephthal-bis-n-alkylaniline

The phase sequences of the homologues with n (the number of carbon atoms in the terminal alkyl chains) from 2 to 8 are obtained. At low temperatures, i) several crystalline modifications are found in each of the members with n = 4, 5, and 6 and ii) the monotropic transitions between crystal and smectic phase are observed in almost all the members. At intermediate temperature, iii) between the smectic H and C phases, the smectic F phase is found in the homologues with n ≥ = 5 by morphological observation or by a rheological method. The constancy of the temperature of the S_H(or S_F) – S_c transition with respect to “and broadening of the temperature range of S_H with increasing n in the expense of nematic phase are worthy of note. The even-odd effect of the end chain length n is observed very distinctively on the crystal melting and clearing point. Proton NMR measurement reveals a large mobility in the terminal alkyl chains in the crystal of the member with n = 6.