Negative electron affinity silicon

Fig. S.3a-c. Band structure and photoemissive yield for (a) silicon activated to negative electron affinity (b) a thin layer of CSjO (values are approximate) and (c) metallic Cs. For Si, is the energy of intentionally added p-type dopants, while for CsjO, Eq is the energy level of native defects. The relationship between photoemissive threshold energy and the value of

Without reference to Figure 9.7, predict which of the following three elements, aluminum, silicon, or phosphorus, would have the most negative electron affinity. Verify your results by reference to the figure. Briefly explain the relative values of these electron affinities. 

Thermochemical information about neutral species can also be obtained from measurements of ions. Indeed, accurate bond dissociation energies for neutral molecules have been obtained from gas-phase ion chemistry techniques. In this section, we will summarize both the negative-ion and hydride-affinity cycles involving silicon hydrides (RsSiH) which are connected to electron affinity (EA) and ionization potential (IP) of silyl radicals, respectively [22-24]. 

In isolation such a tetrahedron has a strong electron affinity. Since the bond to the silicon atom employs only one of the bonding electrons of an oxygen atom, there is room in each for one more electron in an atomic orbital of principal quantum number 2. Hence an isolated Si04 group readily forms the negative orthosilicate ion, Si04 (Fig. 9.8). 

Surface bombardment by positive ions (particularly SiH ) plays a critical role in the growth of amorphous silicon films. The silane radicals SiHs and SiH2 have a positive electron affinity therefore, the silane discharge is essentially electronegative and dissociative attachment processes make a significant contribution in the balance of charged particles and production of negative silane ions ... 

Optimization of geometry for some silylenium cations was made (22,24). Such calculations predict that silylenium ions will adopt a planar structure in contrast to silyl anions, which are predicted to be pyramidal. It should be noted that theoretical studies also indicate a high ability of silicon to accommodate negative charge. The parent silyl anion H3Si was calculated to be more stable than its carbon analog by about 50 kcal/mol (24). This implies a remarkable affinity of silylenium ions toward electron-rich species. 

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