Pr6O11-doped bismuth titanate (BixPryTi3O12, BPT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the structures and ferroelectric properties of the films were investigated. XRD studies indicate that all of BPT films consist of single phase of a bismuth-layered structure with well-developed rod-like grains. For samples with y=0.06 , 0.3, 1.2 and 1.5, I—E characteristics exhibit negative differential resistance behaviors and their ferroelectric hysteresis loops are characterized by large leakage current. Whereas for samples with y=0.6 and 0.9, I—E characteristics are of simple ohmic behaviors and their ferroelectric hysteresis loops are saturated and undistorted. The remanent polarization (Pr) and coercive field (Ec) of the BPT Film with y=0.9 are above 35 μC/cm2 and 80 kV/cm, respectively.
Two-dimensional (2D) closed-cavity single quantum well (SQW) and multiple quantum well (MQW) structures are proposed based on the traditional 2D open-cavity SQW structures of photonic crystals. The numerical calculation results show that the proposed structures can greatly improve the optical characteristics compared with the traditional structures. It is found that the barrier thickness has a great impact on the optical characteristics of the closed-cavity MQW structures: when the barrier thickness is narrower, each resonant peak which appears in the SQW would split, the number of split times is just equal to the number of wells, and each well in the MQW structures is a travelling-wave-well, similar to the well in the open-cavity SQW structures; when the barrier thickness is wider, there is no effect of spectral splitting, and each well in the MQW structures is a standing-wave-well, just like the well in the closed-cavity SQW. The physical origin of different field distributions and the effect of the spectral splitting are provided.
