氧化锌纳米棒中自发辐射的回音壁模腔增强

Enhancement for Spontaneous Emission from ZnO Hexagonal Microrods Based on Whispering Gallery Mode Resonators

应用气相传输法制备了氧化锌纳米线和具有六方对称截面的纳米棒,利用电子扫瞄显微镜,X-射线衍射仪等进行形貌与结构表征。室温下,用355nm激光脉冲,以260 W/cm2相同光强激励条件,分别测量其光致发光(PL)谱,在棒状样品中发现393nm有发光峰,而线状样品是在382nm处。二者相比,棒状样品的紫光波段自发辐射光强增加、频谱展宽、中心波长红移和绿光波段辐射被显著抑制。基于半导体材料的能带理论、激子复合发光理论和费米黄金定则等,对样品PL谱差异原因进行理论分析,结果表明上述现象源于棒状样品中回音壁模谐振腔(WGMRs)的自发辐射增加。利用强激励条件下样品光致发光谱,验证了实验结果与理论分析结果较好吻合。

The samples of zinc oxide nano-wires and hexagonal micro-rods are fabricated by using vapor phase transport method under the almost same conditions. Their morphology and the same crystal structures are examined and characterized by scanning electron microscopy and X-ray diffraction. The photoluminescence （PL） spectra of hexagonal samples, excited by 355 nm laser pulse with excitation power density （260 W/cmZ）, is measured and compared with those from nano-wires with the same exciting condition at room temperature. There are a more intensive broaden violet emission peaking at 393 nm, frequency spectrum broatening, the red shift of center wavelength and an almost disappearing green band emission in the PL of hexagonal rods while an emission peaking at 382 nm, flat green emission for wires samples. The difference of PL spectra between the two kinds of samples may be attributed to the enhancement of spontaneous emission in whispering gallery modes resonators （WGMRs） by theoretical analysis based on the theory of energy bands for semiconductors, emission from excitons, and Fermi golden rules. PL spectrum measuring experiments with higher excitation power density for the same samples are arranged to verify the theoretical analysis results, which fit with experimental results well.