Development of SNOM/KFM probe microscope and investigation of optical properties of organic thin films with the microscope

我们已经成功地开发了一种探针显微镜与近场光刺激和开尔文探针力检测，这使我们能够测量薄膜的表面电位，并通过光照射通过光纤探针的孔径来刺激表面。本文对Alq 3薄膜表面电位的光致降低进行了深入的研究，通过对Alq 3薄膜表面电位的光致图形化以及光致表面电位随曝光时间和曝光强度的变化关系的研究，探讨了Alq 3薄膜表面电位光致降低的特点和机理。在n-Si（001）衬底上的300 nm Alq_3薄膜中，通过接触掩模曝光，可以在至少700 nm的空间尺度上形成14-17 V的均匀表面电位图形，并且图形在黑暗中保持一年以上。潜在还原对暴露时间和/或暴露强度的依赖性 ...更多信息 考虑Poole-Frankel电子迁移率公式，可以很好地拟合由于光激发载流子漂移引起的电势降低的计算。这些结果表明，Alq 3表面光致电位降低的机理是光激发载流子的漂移，基于光激发电子/空穴漂移降低表面电位的假设，通过拟合计算，很好地再现了光致电位降低与曝光强度的关系。二维（2D）传递函数的KFM探针讨论从KFM电位轮廓获得的表面电位的阶梯图案。通过光纤探针的孔径的近场光刺激被证明为扫描近场光学显微镜（SNOM）与KFM（SNOM-KFM）相结合。通过SNOM-KFM测量，可以将来自SNOM探针孔径的光发射图案可视化为Alq 3薄膜上的表面电势图案。少

We have succeeded to develop a probe microscope with near-field optical stimulation and Kelvin probe force detection, which allows us to measure the surface potential of the thin films and to stimulate the surface by photo irradiation through the aperture of optical fiber probes. Photoinduced reduction of surface potential of Alq3 thin films have been intensively investigated as follows.The characteristics and mechanisms of photoinduced reduction of surface potential on tris(8-hydroxyquinolinato)aluminum(III) (Alq3) thin films are investigated and discussed from the results of photo-patterning of the surface potential and the reduction dependence on exposure time/intensity. The uniform surface potentials of 14-17 V in 300-nm Alq3 thin films on n-Si (001) substrates can be patterned by contact-mask exposure with spatial scales down to 700 nm at least, and the patterns remain more than one year in the dark. The dependence of potential reduction on exposure time and/or exposure intensity … More can be fitted well with the calculation of potential reduction due to the drift of photoexcited carriers with taking into account Poole-Frankel formula for the electron mobility. These observations indicate that the mechanism of photoinduced reduction of surface potential of Alq3 should be the drift of photoexcited carriers.The dependence of photo-induced reduction of surface potential on photo-exposure intensity is reproduced well by fitting calculation based on the assumption that the drift of photo-excited electrons/holes decreases the surface potential. Two-dimensional (2D) transfer functions of KFM probes are discussed from KFM potential-profiles obtained for a step pattern of surface potential. Near-field optical stimulation through an aperture of an optical-fiber probe is demonstrated as scanning near-field optical microscope (SNOM) combined with KFM (SNOM-KFM). A photoemission pattern from an aperture of SNOM probes can be visualized as a surface-potential pattern on Alq3 thin films by means of SNOM-KFM measurements. Less