High-vacuum environment, preparation

The SEXAFS teehnique is a partieular surface sensitive detection mode applied to an EXAFS measurement, performed in a particular environment, the Ultra High Vacuum, which is needed in order to prepare and protect the atomic-scale eleanliness of surface and interface systems for the whole time length of the experiment. As such the technique borrows equipment and procedures from the surface science spectroscopies, and exploitation procedures of the synchrotron radiation source from the conventional, non vacuum, EXAFS method. The studies described below have been performed at the Laboratoire pour T Utilisation du Rayonnement Electro-magnetique (LURE) exploiting synehrotron radiation from the storage ring DCI... 

Two preferred methods for preparing clean surfaces consist of generating the surfaces under high vacuum at the beginning. Using remote control manipulators to crush a sample under vacuum exposes fresh surface to an environment in which adsorption equilibrium is very slow. This technique produces a heterogeneous array of crystal faces, however. Far more suitable for the specific and localized examination that diffraction methods offer is crystal cleavage... 

In both preparative methods the integrity of the catalyst is compromised. Exposure to ambient conditions, exterior chemical environments, and exposure to high vacuum in the microscope may alter the catalyst properties. Employment of special chambers for redox pretreatments and/or environmental microscopes provides some assistance in overcoming these problems (9). It appears that regardless of the approach taken, compromises in specimen preparation or instrumental performance must be made. These factors must be kept in mind when interpreting results obtained from electron microscopic measurements. 

Monolayers and films of biomolecules on surfaces have been prepared in a variety of environments, including the liquid-liquid, solid-liquid, solid-gas and solid-ultra high vacuum interfaces. The interface between two immiscible liquids can be a useful model system for biomolecular adsorption at model membranes, but this interface is generally difficult to interrogate... 

Pentacene has all the qualities needed for an OTFT. The main challenge is the eontrol of the contact and dielectric interfaces to suppress the voltage drifts and hysteresis effects associated with trap states. Also the dependency of the injection efficiencies on contact preparation suggest that even if pentacene deposition technology can be applied under rather rough conditions, ultra high vacuum and clean environments may still be useful on the way of learning how to produce reliable devices. 

Here a method to prepare reflective metal holograms that does not require vacuum environment or masking is discussed. Despite the disadvantages inherent in many electroless deposition techniques, one particular approach will be described that produces high resolution reflective metal holograms. 

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