多孔氧化铝薄膜的光致发光起源:三种缺陷中心

在草酸溶液中用二次阳极氧化法制备了纳米多孔氧化铝薄膜,分析了制备过程中氧化铝薄膜中缺陷的形成机理.场发射电子显微镜给出了薄膜的表面形貌和结构.X射线色散能谱和傅里叶红外透射光谱测试表明,进入薄膜中的草酸杂质加热到500℃未全部分解.对多孔氧化铝薄膜的光致发光PL光谱做了高斯拟合,结合测试结果和薄膜中的缺陷分析指出:多孔氧化铝薄膜的发光由F+,F和草酸杂质相关缺陷引起,对应发光中心分别在402,433,475 nm处,并提出F中心起主导作用.对不同草酸浓度中制备的多孔氧化铝薄膜的PL光谱讨论指出:随草酸浓度增加,三种发光中心的峰位不会发生变化,但相对强度发生改变,F+中心和F中心减少,草酸杂质相关发光中心增加,PL峰红移.最后提出通过控制草酸浓度来控制多孔氧化铝薄膜中的草酸杂质.此研究将对多孔氧化铝薄膜发光起源和机理有更深入的理解,同时也为多孔氧化铝薄膜的制备提供一种全新的思路.

Origin of nanopore alumina film photoluminescence: three kinds of defect centers

Nanopore alumina films (PAF) are fabricated by two-step anodic oxidation of aluminum in oxalic acid. The field emission scanning electron microscope measurement reveals the surface microstructure of PAF, and the defect formation mechanism in PAF is analyzed. The energy dispersive X ray spectroscopy and the Fourier transform infrared spectroscopy results indicate that oxalic ions are incorporated into the PAF in the synthesis process and further heating up to 500 ℃ does not cause oxalic ions to completely decompose. The photoluminescence (PL) spectra of PAF can be divided into three bands by Gaussion fitting method. The measurement results and the defects in PAF show that the PL originate from optical transitions of two kinds of different oxygen-deficient defect centers (F and F⁺) and oxalic impurities related defect center, PL centered at 402, 433 and 475 nm, respectively. We put forward for the first time that F centers play a leading role. The PL characteristics of the PAF prepared in oxalic acids with different concentrations suggest that three kinds of the luminescent center positions do not change with the increase of the oxalic acid concentration, but their relative intensities change with the increase of the oxalic acid concentration, i.e., F and F⁺ decrease, oxalic impurities related defects increase, and these will cause the PL peak position to be red-shifted. Finally, we put forward that the oxalic impurities in PAF can be changed by controlling the concentration of oxalic acid. The present experiments and results will be beneficial to the understanding of light-emitting mechanism in PAF, meanwhile, in this paper we propose a new train of thought for PAF preparation application.
Keywords： pore alumina film luminescent center defect mechanism impurities control