Other Chalcogen-Related Donors

Spectra due to other Ch-related donor complexes in silicon have also been reported [118,243,262] and these complexes have been denoted ChcXn where index c represents complex and n = 2, 3, 4, and 5. The spectroscopic data of the ChcXi complexes and of SCX3 are already included in Tables 6.14 and 6.15. The spectra of the other complexes show only a few lines and their main characteristics are given in Table 6.20. Each chalcogen is given in order of decreasing ionization energies and a correlation between the indices and the atomic structure of the complexes has not been established. 

2po (SCX2) must be close to a transition toward a 1 s excited state of ScXi and to 4/ i (SCX3), though it has not been identified with certainty. 

In silicon, the electrical activity of group-V donors can be passivated by hydrogen, when a Si — H bond involving the donor electron is formed on a Si atom nn of the donor. For double donors, IR absorption allows one to make a difference between full passivation of the electrical activity of the double donor centre, resulting in a decrease or a disappearance of the electronic spectra, and partial passivation of the centre, where the same effect is accompanied by the appearance of the spectrum of a new single donor. While 

The lines of the (S, H)c4-(S, H)c5 pair are close to those of SCX3 (see Table 6.20), but they do not show any 1H/2H isotope effect. The ionization energies of the above-discussed (S,H) complexes are summarized in Table 6.21. 

The first spectroscopic evidence of the presence of (S,H) and (S,D) centres in hydrogenated S-doped silicon was actually provided by Love et al. [155] in a study of spectral hole burning in the 2po and 2p lines of the (S, H)c2 and (S, H)c3 spectra inhomogeneously broadened in Si0.999Ge0.001 alloy samples. 

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The response to stress of the deep chalogen-related donors in silicon shows some differences due to the large separation of the deepest Is state from the other EM-like Is states, and also to the introduction of degeneracy of the chalcogen pairs, discussed in the following section. 

Intramolecular chalcogen interactions may also stabilize reactive functional groups enabling the isolation of otherwise unstable species or their use as transient intermediates, especially in the case of selenium and tellurium. For example, tellurium(II) compounds of the type ArTeCl are unstable with respect to disproportionation in the absence of such interactions. The diazene derivative 15.23 is stabilized by a Te N interaction. Presumably, intramolecular coordination hinders the disproportionation process. Other derivatives of the type RTeX that are stabilized by a Te N interaction include 8-(dimethylamino)-l-(naphthyl)tellurium bromide, 2-(bromotelluro)-A-(p-tolyl)benzylamine, and 2-[(dimethylammo)methyl]phenyltellunum iodide. Intramolecular donation from a nitrogen donor can also be used to stabilize the Se-I functionality in related compounds." ... 

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