Complex acceptor-doped case

The behaviour of group-II FAs in silicon is interesting. Mg behaves as an interstitial double donor and Zn as a substitutional double acceptor. Be shows an acceptor behaviour, but it has been stated that only T0% of the Be concentration in silicon is electrically active (quoted by Crouch et al. [45]). Discrete acceptor spectra have been reported at LHeT in Be- and Zn-doped silicon and they include many complexes. In the case of Be, EM acceptor-like spectra associated with four different centres have been reported [45,99]. They are sometimes denoted in the literature Be-I, Be-II, Be-III, and Be-IV, with ionization energies of 192, 146, 200, and 93meV, respectively. Spectra due to (Be, Lij) pairs have also been reported [45,137]. Only the first low-energy lines of these spectra are observed, but the line spacings are comparable to those observed for the group-III p3/2 spectra. Some of the p1/2 spectra associated with these centres have also been observed [99,137]. 

Relatively homogeneous fullerene LB films can be formed by mixing with arachidic acid [333]. This mixed film was used to construct a heterostructure with a PHT-arachidic acid layer, although no (bi)polaron formation was observed [341]. Donor-acceptor complexes of Cso with tetra(hexadecylthio)-TTF and BEDT-TTF were subjected to LB work. In both cases, multilayer film was formed at the air-water interface. Conductivity values of 4 and 20 S/cm for the tetra-(hexadecylthio)-TTF/C6o and the BEDT-TTF/Ceo system, respectively, were obtained after iodine doping of LB films [342]. 

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