Zhang Ping, Urban Marek W
School of Polymers and High Performance Materials, Shelby F. Thames Polymer Science Research Center, The University of Southern Mississippi, Hattiesburg, Mississippi 39406-0076, USA.
Langmuir. 2004 Nov 23;20(24):10691-9. doi: 10.1021/la049434o.
It is well established that the photoacoustic effect based on absorption of electromagnetic radiation into thermal waves allows surface depth profiling. However, limited knowledge exists concerning its spatial resolution. The spiral-stepwise (SSW) approach combined with phase rotational analysis is utilized to determine surface depth profiling of homogeneous and nonhomogeneous multilayered polymeric surfaces in a step-scan photoacoustic FT-IR experiment. In this approach, the thermal wave propagating to the surface is represented as the integral of all heat wave vectors propagating across the sampling depth xn, and the spiral function K'beta(lambda)e(-beta)(lambda)xne(-x)n/mu(th)e(i)(omegat-(xn/mu(th))) represents the amplitude and phase of the heat wave vector propagating to the surface. The SSW approach can be applied to heterogeneous surfaces by representing thermal waves propagating to the surface as the sum of the thermal waves propagating through homogeneous layers that are integrals of all heat vectors from a given sampling depth. The proposed model is tested on multilayered polymeric surfaces and shows that the SSW approach allows semiquantitative surface imaging with the spatial resolution ranging from micrometer to 500 nm levels, and the spatial resolution is a function of the penetration depth.
基于电磁辐射吸收转化为热波的光声效应可实现表面深度剖析，这一点已得到充分证实。然而，关于其空间分辨率的知识却很有限。在步进扫描光声傅里叶变换红外实验中，采用螺旋逐步（SSW）方法结合相位旋转分析来确定均匀和非均匀多层聚合物表面的表面深度剖析。在这种方法中，传播到表面的热波表示为在采样深度xn上传播的所有热波矢量的积分，螺旋函数K'β(λ)e^(-β)(λ)xne^(-xn/μth)e^(i)(ωt-(xn/μth))表示传播到表面的热波矢量的幅度和相位。通过将传播到表面的热波表示为通过均匀层传播的热波之和，SSW方法可应用于异质表面，这些均匀层是来自给定采样深度的所有热矢量的积分。所提出的模型在多层聚合物表面上进行了测试，结果表明SSW方法允许进行半定量表面成像，其空间分辨率范围从微米到500纳米级别，并且空间分辨率是穿透深度的函数。
