OPTICAL CHARACTERIZATION OF ANODIC ALUMINUM-OXIDE FILMS CONTAINING ELECTROCHEMICALLY DEPOSITED METAL PARTICLES .1. GOLD IN PHOSPHORIC-ACID ANODIC ALUMINUM-OXIDE FILMS
OPTICAL CHARACTERIZATION OF ANODIC ALUMINUM-OXIDE FILMS CONTAINING ELECTROCHEMICALLY DEPOSITED METAL PARTICLES .1. GOLD IN PHOSPHORIC-ACID ANODIC ALUMINUM-OXIDE FILMS
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DOI：
10.1021/j100134a019
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发表时间：
1993-08-12
影响因子：
--
通讯作者：
MOSKOVITS, M
中科院分区：
文献类型：
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作者：
PRESTON, CK;MOSKOVITS, M
在之前的一篇论文中(Preston，C.K.；Moskovits，M.J.Phys.化学。1988，92,2957)，我们提出了一种基于反射光谱测量的表面等离子体吸收宽度的技术，用于确定电化学沉积在阳极氧化铝薄膜中的贵金属颗粒的平均尺寸。这种方法在这里被扩展，以考虑薄膜的光学各向异性和非均匀性，该光学各向异性和非均匀性是由粒子本身的非球形以及它们的分布引起的。建立了描述这类薄膜预期反射光谱的方程，假设该薄膜由氧化铝覆盖层、金属填充氧化层和铝衬底组成。实验测量了在磷酸中制备的含金阳极氧化铝薄膜的S和p偏振可见反射光谱，得到了膜的光学厚度、金金属颗粒的平均尺寸和形状以及沉积的金的当量质量厚度作为可调参数。颗粒大小由p偏振谱更可靠地确定，而氧化铝覆盖层的厚度由S偏振谱更准确地得到。采用交流电沉积的方法将金引入到阳极氧化膜的均匀孔道中。随着沉积时间的延长，金属沉积量、颗粒的平均尺寸和偏心率增加。然而，在50-500赫兹的范围内，这些参数没有随着交流沉积电压的频率而显著变化。用光学方法确定的几个参数得到了薄膜切片和分离的金金属颗粒的透射电子显微镜以及薄膜中总的金金属含量的原子吸收测量的证实。
In a previous paper (Preston, C. K.; Moskovits, M. J. Phys. Chem. 1988, 92, 2957) we presented a technique, based on the width of the surface plasmon absorption measured by reflectance spectroscopy, for determining the average size of noble metal particles electrochemically deposited in anodic aluminum oxide films. This method is expanded, here, to take into account the optical anisotropy and nonuniformity of the film which arises from nonspherical nature of the particles themselves as well as from their distribution. Equations describing the reflectance spectrum expected for such films, assumed to consist of an alumina overlayer, a metal-filled oxide layer, and an aluminum substrate, are developed. Experimentally measured s- and p-polarized visible reflectance spectra of gold-filled anodic alumina films prepared in phosphoric acid are found to fit these expressions very well, yielding, as adjustable parameters, the optical thickness of the film, the average size and shape of the gold metal particles, and the equivalent-mass thickness of deposited gold. Particle sizes are found to be more reliably determined from the p-polarized spectra, while the thickness of the alumina overlayer was more accurately derived from the s-polarized spectra. ac electrodeposition was used to introduce gold into the uniform pores of the anodic oxide films. The quantity of metal deposited and the average size of the particles and their eccentricity were found to increase with increasing deposition time. However, these parameters did not vary significantly with the frequency of the ac deposition voltage over the range 50-500 Hz. Several of the parameters determined by the optical method were corroborated by transmission electron microscopy of sections of the films and of isolated gold metal particles and by atomic absorption measurements of the total gold metal content in the films.