不同退火条件对纳米多孔氧化铝薄膜光致发光的影响

以草酸为电解液，采用二次阳极氧化法制备出了纳米多孔氧化铝薄膜，经不同退火温度和退火气氛处理氧化铝薄膜后，通过分析其光致发光光谱得出：相同的退火气氛中, 退火温度T≤600 ℃ 时，T=500 ℃具有最大的光致发光强度;退火温度T≥700 ℃时，随着退火温度的升高，样品的发光强度增大。在不同的退火气氛中，多孔氧化铝薄膜随着退火温度的升高，发光峰位改变不同，即在空气中退火处理后，随着退火温度的升高，发光峰位蓝移，而在真空中退火处理后，发光峰位并不随退火温度的升高而变化;通过对1 100 ℃高温退火处理后的氧化铝薄膜的光致发光曲线的高斯拟合，可以看出，经退火处理后的多孔氧化铝，主要存在三个发光中心，发光曲线在350～600 nm范围内对应三个发射峰, 发射波长分别为387，410，439 nm。相同的退火温度下，空气中退火得到的氧化铝薄膜的光致发光强度大于真空中退火处理后的氧化铝薄膜。基于实验结果，结合X射线色散能谱(EDS)、红外反射光谱等表征手段，探讨了多孔氧化铝薄膜的发光机制，并对经过不同退火条件得到的多孔氧化铝薄膜的光致发光特性的改变做出了合理的解释。

Effects of Different Annealing Conditions on the Photoluminescence of Nanoporous Alumina Film

The nanoporous alumina films were prepared by two-step anodic oxidation in 0.5 mol·L-1 oxalic acid electrolyte at 40 V. Photoluminescence (PL) of nanoporous alumina films was investigated under different annealing atmosphere and different temperature. The authors got three results about the PL measurements. In the same annealing atmosphere, when the annealling temperature T≤600 ℃, the intensity of the PL peak increases with elevated annealing temperature and reaches a maximum value at 500 ℃, but the intensity decreases with a further increase in the annealing temperature, and the PL peak intensity of samples increases with the increase in the annealing temperature when the annealling temperature T≥800 ℃. In the different annealling atmosphere, the change in the photoluminescence peak position for nanoporous alumina films with the increase in the annealing temperature is different: With the increase in the annealling temperature, the PL peak position for the samples annealed in air atmosphere is blue shifted, while the PL peak position for the samples annealed in vacuum atmosphere will not change. The PL spectra of nanoporous alumina films annealed at 1 100 ℃ in air atmosphere can be de-convoluted by three Gaussian components at an excitation wavelength of 350 nm, with bands centered at 387，410 and 439 nm, respectively. These results suggest that there might be three luminescence centers for the PL of annealed alumina films. At the same annealling temperature, the PL peak intensity of samples annealed in air atmosphere is stronger than that annealed in the vacuum. Based on the experimental results and the X-ray dispersive energy spectrum (EDS) combined with infrared reflect spectra, the luminescence mechanisms of nanoporous alumina films are discussed. There are three luminescence centers in the annealed nanoporous alumina films, which originate from the F center, F+ center and the center associated with the oxalic impurities. The effects of different annealing conditions on the photoluminescence of nanoporous alumina film are reasonably explained.