摘要:
在前期研究(声学学报;1991;16(3):161—169)的基础上,建立了改进的热源分布模型。利用积分变换和特征函数展开法,求解了强度简谐调制的电子束源在各向同性试样中所激发的各种Lamb波模式,以及耦合在试样背面的压电片的电压输出,并分析了扫描电子声显微镜(SEAM)的信号激发机理。结果表明SEAM是一种高分辨率的近场成像技术,它的最佳横向空间分辨率为221/2倍的电子束焦斑半径。实验结果表明SEAM的空间分辨率可优于0.5μm,小于试样的热扩散长度,从实验上证实了理论预计的SEAM的近场成像特征。
Abstract:
Based on the research (Acta Acustica (In Chineses), 1991; 16(3):161-169), an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency fare obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2 (a is the radius of the focused electron beam). Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.
下载:
