Surface potential detector

From the above discussion, it is evident that BR is a bifunctional electronic material [64] it is sensitive to light as well as to ions such as H+, Cl, and Ca. In the motion detector developed by Miyasaka etal, BR is configured as a photon sensor. In the cyclic-GMP cascade, a photon, via its action on rhodopsin, triggers the hydrolysis of cyclic-GMP, and thus in turn regulates the release of energy stored as a Na+ gradient. The hypothetical trigger mechanism based on the surface potential thus works like a field effect transistor (FET), or more precisely, a phototransistor. 

Spin analysis was carried out by a Mott-scattering detector with a spherically symmetric acceleration field operated at typically 70 keV without retarding potentials [3]. Surface barrier detectors were used as electron detectors. The figure of merit x ///q amounts to about 2.4 x 10 ". The advantages of this type of... 

Because of the very limited escape depths of conversion electrons (about 1.8 pm in water, 0.25 pm in metallic iron), their detection is somewhat difficult. This seeming drawback provides a unique surface sensitivity. In a rotating disc electrode arrangement Kordesch et al. [539] have used a disc-shaped electrode that slowly rotates with part of the disc immersed in the electrolyte solution. As a thin electrolyte film thin enough to permit escape of conversion electrons adheres to the metal surface, potential control is always maintained. Conversion electrons were detected using a suitable gas-filled detector mounted close to the upper emersed part of the disc. In a study of passive oxide films on iron, the advantage of this approach was demonstrated beyond an unmatched surface sensitivity, the measurement time was reduced to a small fraction of that needed for transmission measurements [543]. An inherent drawback of the setup is the poor current distribution inside the very thin electrolyte film (its thickness is around 4 nm as reported by Gordon [540]). 

The ability of XPS to detect surface potential changes provides a much needed tool for electrochemistry to simultaneously obtain information about the local chemistry and the electrical potential across interfaces and components of electrochemical devices. The great advantage of XPS is also that it is a local, noncontact probe for surface potentials, with a spatial resolution that is determined by either the beam spot of the incident X-rays or the resolution of a two-dimensional electron detector (for a detailed discussion of the latter case, see Ref. [71]). 

In the last decade or so, amorphous selenium has been applied as a photoconductor in X-ray image detectors, particularly for biomedical imaging. For this application, flat-panel detectors with large sensing areas (> 30 cm x 30 cm) have been developed. The coating of amorphous Se is typically 500 pm thick, and is deposited over a silicon thin film transistor layer. After applying an electrical potential to the surface, the detector is exposed to an X-ray beam and the electrons released are used to transmit information that ultimately provides an image. 

Classical ion trajectory computer simulations based on the BCA are a series of evaluations of two-body collisions. The parameters involved in each collision are tire type of atoms of the projectile and the target atom, the kinetic energy of the projectile and the impact parameter. The general procedure for implementation of such computer simulations is as follows. All of the parameters involved in tlie calculation are defined the surface structure in tenns of the types of the constituent atoms, their positions in the surface and their themial vibration amplitude the projectile in tenns of the type of ion to be used, the incident beam direction and the initial kinetic energy the detector in tenns of the position, size and detection efficiency the type of potential fiinctions for possible collision pairs. 

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