Photoelectric characteristics bands

The favorable characteristics of Si and Ge notwithstanding, both have low atomic number (hence low photoelectric absorption) and Ge requires cooling. Diamond can function as a detector and has been used, but it is expensive and has even lower atomic number. The most common alternatives to Si and Ge are the compound semiconductors Cdi cZn Je (CZT, or just CdTe when x = 0) and Hgl2. Their band gaps are sufficiently large for operation at or slightly below room temperature. Interested readers should consult specifications of available commercial devices. 

In the intrinsic part of the photoemission spectrum, that is, the elastic lines, there are basically three observables associated with each core-level or valence band peak line positions, line intensities, and line widths or line shapes. From these, different pieces of information can be gained. In core-level emission, the rough line positions reveal the elemental composition of the sample surface, whereas the exact positions are characteristic of the specific chemical environment of the atoms [6j. The intensities are determined not only by the atomic concentrations but also by the photoelectric cross sections and instrumental effects such as the photon flux and the transmission of the spectrometer. Finally, information on the many-body dynamics of the solid after the sudden creation of a photohole (the missing electron that has been ejected) is contained in the shape and width of the peak. In the simplest case, the line shape is Lorentzian and its width is a measure of... 

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