Development of Photon Atomic Force Microscope

1)在高真空条件下，采用调频（FM）检测方法的非接触式原子力显微镜，对倏逝场引起的力梯度进行检测。这种方法有两个优点。一个是作为力传感器的高灵敏度。二是可以在不受毛细力影响的情况下估算出棱镜表面的局部力梯度。用这种方法测量了倏逝场引起的力梯度距离曲线。我们测量了倏逝场引起的入射光束强度和偏置电压与力梯度的关系。结果证实了表面光电压（SPV）模型。此外，利用SPV模型，我们解释了力梯度的距离和极化依赖的结果。2)提出了一种基于调频检测的非接触原子力显微镜方法，以高分辨率同时检测表面上的范德华力梯度和光倏逝场引起的力梯度。施加偏置电压可以增强倏逝场引起的力梯度。观察到直径为100 nm的聚苯乙烯乳胶球，其空间分辨率优于50 nm （λ /14）。悬臂梁的最小可测频移为0.09 Hz，由此估计力梯度和力的最小可测值分别小于3.8x10^<-5> N/m和0.66 pN。

1) By using the noncontact mode atomic force microscope with frequency modulation (FM) detection method in a high vacuum, the force gradient induced by the evanescent field was detected. There are two advantages of this method. One is high sensitivity as a force sensor. The other is that the local force gradient can be estimated without influence of capillary force due to water film on the prism surface. Using this method, we measured the force gradient distance curve induced by the evanescent field. We measured the incident beam intensity and bias voltage dependence of the force gradient induced by the evanescent field. As a result, we confirmed the surface photo-voltage (SPV) model. Furthermore, using the SPV model, we explained the results of the distance and polarization dependence of the force gradient.2) We demonstrated a novel method to detect the van der Waals force gradient and the force gardient induced by the optical evanescent field on the surface simultaneously with high resolution, using the noncontact mode atomic force microscopy with frequency modulation detection method. The force gradient due to the evanescent field could be enhanced by applying the bias voltage. Polystirene latex spheres with 100 nm diameter were observed with spatial resolution better than 50 nm (lambda/14). Minimum detectable frequency shift of the cantilever was 0.09 Hz, by which the minimum detectable values of the force gradient and force due to the evanescent field were estimated to be under 3.8x10^<-5> N/m and 0.66 pN,respectively.