Ultra-thin films Subject

Meanwhile, study on ultra-thin film gas lubrication problems has become one of the most attractive subjects in the held of tribology during the past three decades. 

The conformation of polymer chains in an ultra-thin film has been an attractive subject in the field of polymer physics. The chain conformation has been extensively discussed theoretically and experimentally [6-11] however, the experimental technique to study an ultra-thin film is limited because it is difficult to obtain a signal from a specimen due to the low sample volume. The conformation of polymer chains in an ultra-thin film has been examined by small angle neutron scattering (SANS), and contradictory results have been reported. With decreasing film thickness, the radius of gyration, Rg, parallel to the film plane increases when the thickness is less than the unperturbed chain dimension in the bulk state [12-14]. On the other hand, Jones et al. reported that a polystyrene chain in an ultra-thin film takes a Gaussian conformation with a similar in-plane Rg to that in the bulk state [15, 16]. 

The vectors k are 3D, 2D, or ID for a crystal, slab, or periodic polymer respectively. Keep in mind that the nomenclature nD refers to the number of cartesian directions in which nuclei have periodic ordering. The electron density is three-dimensional, as is r, whatever the system periodicity. Thus, when we treat an ultra-thin film (UTF) with GTOFF, we are not doing a super-cell calculation on a fictitious crystal consisting of the UTF interspersed by layers of vacuum . GTOFF can do such super-cell calculations but more importantly, it can handle the UTF as a fi ee-standing object periodic in two Cartesian directions and of finite thickness in the third direction (conventionally z), subject to vacuum boundary conditions in z. Note also that a 2D GTOFF calculation does not require inversion s)mimetry with respect to z, hence can treat an even number of nuclear planes as readily as an odd number. 

SEIRA and SERS are powerful techniques for stmctural characterization of ultra thin films and well-ordered monolayer on metal surfaces. Thin films at interfaces are prepared by different procedures and developed for various applications. The fabrication and characterization of ultra thin films is a permanent area of research where some of the most interesting subjects are (a) bilayers and monolayers at liquid-liquid interface, (b) adsorption monolayers and Langmuir (water-insoluble) monolayers at air-water interface, (c) adsorption films and self-assembled monolayers (SAMs) at liquid-solid interface and Langmuir-Blodgett Alms, cast (deposit) films and spin-coat films at air-solid interface. Studies about molecular organization of monolayers of porphyrins derivatives, of azamacrocy-cles and their metallic derivatives among the many SEIRA applications to films and interfaces, were published . 

The present study focuses on mono-atomic steps on solid surfaces. Behaviours of lubricant molecules subject to high pressure and shear between two solid surfaces sliding very close to each other are examined by using MD simulations. On the basis of the results of the simulations, effects of atomic scale roughness on dynamic behaviour of lubricant molecules and traction between the sur ces in ultra-thin film lubrication are discussed. 

Thin films were prepared by physical vapor deposition in ultra-high vacuum (UHV) as described previously. A doser was constructed by tightly winding wires of the Pt and Co metals in small segments around a Ta filament. The filament is heated resistively at a current sufficiently high to initiate sublimation of subject metals onto a cold (Ru or Mo) substrate the latter is located close to the doser to enable a controllable deposition rate. 

Si02 films with different thicknesses are produced by oxidation (dry or wet) for different applications. Thick oxide films (0.1 to 1 pm), normally grown by wet oxidation, are used for device isolation and as masking layers thin oxide layers (< lOOnm) are finding applications as gate dielectrics, flash memory tunnel oxides and dynamic random access memory (DRAM) capacitor oxides. For reasons of space, only the literature on the fabrication of ultra-thin oxide films and the oxidation behaviour of low-dimensional Si nanostructures will be summarized in this chapter. Detailed discussions on the oxidation mechanisms and modelling of Si oxidation have been the subject of several excellent reviews [20-26]. 

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