Synchrotron radiation, surface electronic structure determination

The availability of high-intensity, tunable X-rays produced by synchrotron radiation has resulted in the development of new techniques to study both bulk and surface materials properties. XAS methods have been applied both in situ and ex situ to determine electronic and structural characteristics of electrodes and electrode materials [58, 59], XAS combined with electron-yield techniques can be used to distinguish between surface and bulk properties, In the latter procedure X-rays are used to produce high energy Auger electrons [60] which, because of their limited escape depth ( 150-200 A), can provide information regarding near surface composition. 

The boranes nido-B and m do-BioHi4 and carbaboranes n/do-2,3-Et2C2B4H6 and c/oro-l,2-C2BioHi2 have been used as precursors for boron and boron carbide thin films. ISEELS has been used to characterise the molecular precursws at solid surfaces a comparison has been made between the bond lengths determined for the molecular clusters by MNDO calculations and results from X-ray or electron diffraction and from extended EELS fine structure. A study of the deposition of boron carbide films on Si(lll) surfaces from the synchrotron radiation induced decomposition of nido-2,3-diethyldicarbahexaborane has been described. The dissociation of the cluster is the rate determining step in the process. As with the deposition of boron from nido-BioHi4, it is found that thoe is an activation barrier to the dissociation of the boron carbide precursor on Si(l 11) surfaces.43... 

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