Department of Applied Physics, Osaka University, Suita, Osaka, Japan.
Rev Sci Instrum. 2023 Mar 1;94(3):033702. doi: 10.1063/5.0132166.
In this paper, we develop optical and electronic systems for photoinduced force microscopy (PiFM) that can measure photoinduced forces under low temperature and ultrahigh vacuum (LT-UHV) without artifacts. For our LT-UHV PiFM, light is irradiated from the side on the tip-sample junction, which can be adjusted through the combination of an objective lens inside the vacuum chamber and a 90° mirror outside the vacuum chamber. We measured photoinduced forces due to the electric field enhancement between the tip and the Ag surface, and confirmed that photoinduced force mapping and measurement of photoinduced force curves were possible using the PiFM that we developed. The Ag surface was used to measure the photoinduced force with high sensitivity, and it is effective in enhancing the electric field using the plasmon gap mode between the metal tip and the metal surface. Additionally, we confirmed the necessity of Kelvin feedback during the measurement of photoinduced forces, to avoid artifacts due to electrostatic forces, by measuring photoinduced forces on organic thin films. The PiFM, operating under low temperature and ultrahigh vacuum developed here, is a promising tool to investigate the optical properties of various materials with very high spatial resolution.
在本文中，我们开发了用于光诱导力显微镜（PiFM）的光学和电子系统，可在低温和超高真空（LT-UHV）条件下测量无伪影的光致力。对于我们的低温超高真空 PiFM，光从侧面照射在针尖-样品结上，通过组合真空室内的物镜和真空室外的 90°反射镜，可以对其进行调整。我们测量了由于针尖和 Ag 表面之间的电场增强引起的光致力，并确认我们开发的 PiFM 可以进行光致力映射和光致力曲线的测量。Ag 表面被用于以高灵敏度测量光致力，并且使用金属尖端和金属表面之间的等离子体间隙模式有效地增强了电场。此外，我们通过测量有机薄膜上的光致力，证实了在测量光致力时需要开尔文反馈，以避免由于静电力引起的伪影。在这里开发的低温超高真空下工作的 PiFM 是一种很有前途的工具，可以非常高的空间分辨率研究各种材料的光学性质。
