扫描探针声显微镜轻敲模式中相位像的反差机理

Contrast mechanism of phase image in tapping mode of scanning probe acoustic microscope

根据扫描探针声显微镜(SPAM)轻敲工作模式中探针作周期振动的特点,以及在探针与试样相接触过程中激振力和悬臂探针自由振动的阻尼力很小的假设下,解析求解了探针与试样的碰撞运动方程,得到了最大压痕深度和碰撞时间与探针半径、等效杨氏模量以及界面吸附能等之间的关系式,较直观地说明了SPAM中轻敲模式的相位像反差机理:信号的相位与试样微区的性质、探针振幅、设置点以及试样形貌等有关。并定量预计了纳米金刚石像中的相位差值72.59°,与实验测量平均值73.2°±8.2°一致。同时,合理地解释了实验得到的光学薄膜试样相位像的反差。这些表明SPAM轻敲模式的相位成像是一种纳米分辨率测量材料表面物理性质的成像技术。

In tapping mode of Scanning Probe Acoustic Microscope （SPAM）, based on the characteristics of probe vibrated periodically as well as both driving and damping forces of free vibration are small in the contact time, the impact motion equation between probe and sample is solved. The maximum indentation depth and impact time can be found, and the relations between them and reduced Youth modulus, interface adhesion energy as well as probe radius are obtained. It is shown that the phase contrast in tapping mode is produced by local properties of the sample, probe amplitude and setpoint, as well as topography of the sample. And the contrast on the phase images of nanodiamond is predicted as 72.59°and it is in good agreement with the measured average result 73.2° ± 8.2°. The contrast on phase images of optical films is explained reasonably. It shows that Phase imaging in SPAM tapping mode can detect the surface properties of the sample with nanoscale resolution.