Uniaxial Stress Studies of H-Related Complexes

The uniaxial stress dependence of the IR absorption and Raman bands due to the B—H complex have been studied by Bergman et al. (1988b) and by Stutzmann and Herrero (1988a,b) and Herrero and Stutzmann (1988, 1989). The observed stress splittings and their interpretation for the two studies do not agree. Here, the two experiments and their interpretation will be summarized. While the differences between the experiments will be discussed, they will not be resolved. 

IR absorption spectra of the 1903 cm-1 stretching mode of the B—H complex were measured under stress (Bergman et al., 1988b) at low temperature where subsequent studies have found that the complex is static (Stavola et al., 1988b). Spectra are shown in Fig. 16 for different stress 

The stress parameters Aj and A2 for B—H are large for local vibrational modes. For example, they are an order of magnitude larger than was 

Values (in cm /MPa) for the parameters THAT CHARACTERIZE THE STRESS SPLITTINGS OF THE B-H AND As-H VIBRATIONAL MODES. [FROM Bergman et al. (1988b)]. 

The behavior of the Raman spectrum under stress of the stretching vibration of the B—H complex has been reported recently by Stutzmann and Herrero (1988a,b) and by Herrero and Stutzmann (1988a,b). Spectra measured at 100 K are shown in Fig. 18 for several values of [100] stress. The dependence of the mode frequency on [100] and [112] stress is shown in Fig. 19. There were stress induced splittings observed for [100], [112], and [110] stress directions. For the [111] stress direction the line broadened for low stresses but did not split. Further, the stress-split component that shifts upward in frequency as the stress is increased decreases in intensity. 

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IR absorption and Raman spectroscopy are also well suited to the application of uniaxial stress techniques. Stress-induced splittings of the vibrational bands give information about the symmetry of the defect. In favorable cases, it has been possible to determine the kinetics of the H motion between equivalent sites around an impurity from a study of the alignment of the H-related complexes that can be induced by stress. 

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