Stress-induced alignment experiments

Stress-induced alignment experiments [236,237], primarily on TD3, show that the defects can reorient with a barrier of 2.7$\pm$0.2eV, likely to be through interstitial oxygen motion. The time constant is however 5 times longer than that of isolated interstitial oxygen, suggesting that reorientation time is limited by $\sim$5 O_i hops. It was shown with IR that this time constant increases with higher order TDs [238].

Analysis of the NL8 alignment gives the average effective C_2v strain coupling tensors shown in Table 9.1. This means the defect must be compressive along $\langle$001$\rangle$ , tensile along $\langle$110$\rangle$ , and weakly tensile along $\langle$110$\rangle$ . IR excitation spectra were used to show that the B₃ coupling coefficient dropped off with increasing TD⁺ species [237].

 

3cAverage effective strain coupling tensor Anneal Time Primary Thermal Donor

B₁ B₂ B₃ (minutes)

$$\langle \rangle \langle \rangle \langle \rangle$$

1.9 10.3 -12.2 90 TD3

1.1 8.5 -9.6 360 TD3, TD4

1.1 6.6 -7.7 600 TD5