Sample | IR spectrum α-form (cm−1) | IR spectrum β-form (cm−1) | Direct transitions (eV) | Indirect transitions (eV) |
SMA (KBr pellets) | 720 | 735, 783 | - | - |
SMA (thin films) | 721 | 732, 785 | 3.1 | 2.0 |
SMB (KBr pellets) | 721 | 730 | - | - |
SMB (thin films) | - | - | 1.4 | 1.2 |
SMC (KBr pellets) | 720 | 735, 781 | - | - |
SMC (thin film) | 717 | 732, 780 | 2.5, 2.6 | 2.4, 2.6 |
SMD (KBr pellets) | 721 | 779 | - | - |
SMD (thin film) | - | - | 1.3, 1.7, 3.1 | 1.4, 1.5, 2.3 |