Due to the interesting phase transition properties, Vanadium dioxide is a promising materials for smart windows. But phase transition temperature of 68° is high for this application. Doping is an useful method for transition temperature reducing in previous works. In this paper, different thickness VO<sub>2</sub> films were prepared by reactive pulsed magnetron sputtering, and a novel doping method was employed to reduce transition temperature. The results of XRD, Raman, transmittance spectra, and thermal hysteresis reveal that the transition temperature of un-doped samples is about 54~58°, and the increasing of phase transition amplitude and optical transmittance in visible decreasing with film thickness was observed. While for doped samples, all the transition temperatures reduced below 37°. For the thin thickness 12.5nm and 25nm, which phase transition performance deteriorated seriously. The thickness 25nm deposited for 1.5 h has the optimal performance of high optical transmittance and high IR adjustment ability.
A new doping approach of preparing VO<sub>2</sub> film was proposed to significantly tune the transition phase temperature. The heavy Ni-Cr-codoped VO<sub>2</sub> film ultra-thin layer was deposited on the pure VO<sub>2</sub> film by reactive pulsed magnetron sputtering on the Si substrate followed with annealing. The microstructure, optical and phase transition performance of VO<sub>2</sub> films were characterized via X-ray diffraction, UV/VIS/NIR spectrophotometer and thin film phase transition measurement system, respectively. The result indicates that the transition phase temperature of VO<sub>2</sub> film can be reduced from 53 ℃ to 30 ℃ by easily controlling different doping time.
Single quantum dot-cavity system with a deep confinement potential quantum dot is detailedly investigated, with both s- and p-exciton incoherent pump. Through gradually increasing pump rate (about 10<sup>-4</sup>=<i>ps </i>∼ 12=<i>ps</i>), the mean photon number shows a linear-dependence on pump power, the photon probability distribution, characterized by <i>g</i><sup>(2)</sup>(0), transforms from antibunching to bunching through Poisson, and the spectra go from the doublet to a singlet, the linewidth shows clear reduction in the lasing region. If we increase pump rate further, the mean photon number decreases monotonically to zero, g(2)(0) reaches its maximum value 2, and all the electrons stack at upper lasing level, indicating thermal light generation. The results show, the deep QD-cavity system under s- and p-exciton pump can generate laser although it is not an ideal coherent light, and with only p-exciton pump considered, in spite of the coherent light generated, this pump method is unreasonable to simulate the experimental conditions for the negligible energy spacing between s-exciton and p-exciton.