Metastability, creation

As described above, there is a striking correlation between the creation and annealing kinetics of metastable defects in a-Si H and the motion of bonded hydrogen. There are essentially two classes of models proposed to both account for this agreement and to explain the microscopic mechanisms for hydrogen diffusion. One type of model assumes that the hydrogen is intrinsically mobile and moves from one bonded position to another... 

The systems described above are by deLnition metastable and are affected by temperature Luc-tuations. Two other factors inLuencing solubility are the effect of change in crystal morphology and the creation of a higher-energy surface on particles by mechanical stress (grinding). 

The AEs measured by our group are consistent with an ionization mechanism which involves the creation of the excited metastable argon atom Ar(3P2j0) via electron impact. After generation of this Ar 4s state, its excitation energy may then be transferred to the methanol component of the heterocluster. The excitation energies for the formation of Ar 4s 3P2 0 states are 11.55 and 11.72 eV, respectively. 

Thus obtained results show that the polyamorphic transitions occur not only at compression (Si02, H20, etc.) but at extension as well (C) in the systems having stable or metastable crystal analogs with a different density and a different coordination number z. At the minimal z=2 (chain structures) the transitions may occurs only at compression, at the maximal z=12 (close-packed structures) - only at extension, at the intermediate z (2structure-sensitive properties change and new metastable phases can appear. Amorphization under radiation (crystal lattice extension) can be associated with a softening of phonon frequencies. The transitions in the molecular glasses consisted from the molecules with unsaturated bonds are accompanied by creation of atomic or polymeric amorphous systems. 

Staebler and Wronski (1977) were the first to observe light-induced changes in the properties of a-Si H. The Staebler-Wronski effect is now known to affect the performance of a-Si H solar cells through the creation of recombination centers and charged traps (Carlson et al., 1983b). These light-induced centers are metastable and can be annealed out at temperatures of 150 - 200,C. 

Some representative light-soaking data are shown in Fig. 14 for a-Si H cells grown on both glass and steel substrates. Most a-Si H solar cells reach a steady-state condition after 102-103 hr of continuous AMI illumination ( 100 mW cm-2). The steady-state condition results from a balance between the rate of creation of new metastable centers and the rate of removal of old metastable centers by annealing. The efficiency of the cell in the... 

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