Free-electron bands diamond structure

We saw in detail in Section 16-D, and in Fig. 16-6 in particular, how nearly-free-electron bands are constructed. The diamond structure has the translational symmetry of the face-centered cubic structure, so the wave number lattice, the Brillouin Zone, and therefore the nearly-free-electron bands for the diamond structure are identical to the face-centered cubic nearly-free-electron bands and are those shown in Fig. 3-8,c. The bands that are of concern now are redrawn in Fig. 18-l,b. The lowest energy at X, relative to the lowest energy at F, is (fi /2m) x InjaY as shown clearly it is to be identified with the lower level... 

From the experimental side, the band-structure parameters are mainly determined from the cyclotron resonance (CR) spectra of electron and holes (see for instance [4]). Some of these parameters can also be obtained from the Zeeman splitting of electronic transitions of shallow impurities involving levels for which the electronic masses can be taken as those of free electrons or holes, or from the magnetoreflectivity of free carriers. Average effective masses can also be deduced from the Hall-effect measurements or from other transport measurements. Calculation methods that have been used to obtain band-structure parameters free from experimental input are the ab-initio pseudopotential method, the k-p method and a combination of both. These theoretical methods are presented in Chap. 2 of [107]. VB parameters at k = 0 including k and q have been calculated for several semiconductors with diamond and zinc-blended structures by Lawaetz [55]. 

In order to appreciate these and other results of yield spectroscopy on NEA diamond surfaces, it is best to recall briefly Spicer s three-step model of photoelectron emission, which is likely to be nowhere better suited than in the case at hand [109]. This model divides the photoelectron emission process up into three conceptually separate processes, (i) The bulk absorption of light generates photoexcited electrons and holes, and (ii) electrons travel to the surface with the possibility to suffer inelastic losses on their way before they (iii) escape into vacuum where they are being detected. In normal photoelectron spectroscopy interest lies in the so-called primary current, that is, in those electrons that leave the sample without energy loss on their way to the surface. In this case, the photoexcitation, transport, and escape processes are not entirely independent. For crystalline samples with well-ordered surfaces, the wave vector component parallel to the surface, k, is, for example, conserved from the initial electron state to the free electron in vacuum. In this case, a better description of the photoelectron emission is by a one-step excitation from an initial band structure state to a final state constructed as an inverse LEED state (Chapter 3.2.2). The inelastic mean free path of photoexcited electrons, is energy dependent and lies in the nanometer range (Chapter 3.2.3). 

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