SrTiO3 crystals have a high refractive index in the visible range (2.407 at 589 nm) and are transparent in a wide range of visible to infrared regions, 400 nm to 6 μm. Non-doped SrTiO3 is an insulator, but can be made conductive by doping it with impurities such as Niobium (Nb) and Lanthanum (La). Conductive SrTiO3 crystals become black in color and lose their transmission properties as the impurity concentration increases. Conductive SrTiO3 is mainly used as a substrate for thin-film growth and is useful for evaluating the electrical properties of crystal thin-films grown on the substrate and for eliminating charge-up during electron beam analysis.
Refractive index of SrTiO3
Transmittance of SrTiO3
Nb doping concentration of SrTiO3 vs. resistivity and carrier density at room temperature
| SrTiO3 | Nb：SrTiO3 | ||
|---|---|---|---|
|
Nb concentration |
0 | 0.05 wt% (0.1 at%) | 0.5 wt% (1.0 at%) |
| Resistivity (Ω/cm) | > 107 | 7 – 10 × 10-2 | 3 – 7 × 10-3 |
| Carrier density (cm-3) | ― | 1 – 2 × 1019 | 1 – 2 × 1020 |
