平滑处理和扫描范围对多孔膜原子力显微镜分析的影响

Influence of flattening and scan size on surface analysis of porous film using atomic force microscopy

原子力显微镜(AFM)能获得材料表面形貌、三维图、表面粗糙度等信息,是定量分析材料表面的主要工具之一.以自制的多孔膜为研究对象,通过对AFM图像的平滑处理以及改变扫描范围,系统研究了上述因素对多孔膜孔深和表面粗糙度参数测量的影响.结果表明,多孔膜的AFM图像经平滑处理后局部会发生扭曲,多孔部分与膜之间的界限变得模糊,使孔深测量偏差较大,不能完全反映膜的表面微观结构.当扫描范围较小时(≤2μm×2μm),孔深和表面粗糙度参数测量的相对误差较小,而不同扫描范围下得到的表面粗糙度参数的相对标准偏差有较大差异.最大高度和最大孔深的相对标准偏差达到了25%以上,平均粗糙度和均方根粗糙度相对标准偏差在15%左右,而平均最大孔深的相对标准偏差小于3.5%.

Atomic force microscopy（AFM） is one of the powerful instruments which can acquire information about surface morphology, three-dimensional（3D） image and surface roughness of materials. Taking homemade chitosan porous film as the research object, the influences of scan size and flattening of the AFM image on the measurement of morphology, pore depth and surface roughness parameters were systematically studied.The results show that AFM images, which are locally smooth, fluctuate overall at larger scan size. Besides,AFM images distort partially after they have been flatten, and the boundaries between the pore and the film become blurry, which enlarges the deviation of the measured pore depth and obscures the real surface microstructures. The relative errors of the pore depth decrease dramatically with the reduction of the scan size,and they are smaller at minor scan sizes of ≤2 μm×2 μm. Meanwhile, flattening the AFM images decreases the accuracy of the pore depth. With regard to various surface roughness parameters, their relative standard deviations show significant differences under variant scan sizes. The relative standard deviation of max high and max peak is over 25%, and that of mean roughness and root mean square roughness is about 15%. Nevertheless, the relative standard deviation of average max depth is less than 3.5%.