Stroboscopic Scanning Probe Microscopy and Time-Resolved Molecular-Scale Imaging of Photoexcited Carriers

光激发载流子的频闪扫描探针显微镜和时间分辨分子尺度成像

• 批准号: 16310074
• 负责人: MATSUMOTO Takuya
• 金额: $ 9.73万
• 依托单位: Osaka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16310074/
• 关键词: Stroboscopic probe; Photo-excited charge transfer; Time-resolved measurement; Electrostatic field calculation; Kelvin force microscopy; Electrostatic force microscopy; ストロボスコピック・プローブ顕微鏡

In this year, we demonstrated time-resolved force detection by using scanning force microscopy. In the dynamic-mode operation, the tip interacts with the surface only at the moment when the tip closes to the sample surface. The interactive duration can be estimated or less. Taking advantage of this short duration, submicrosecond-class time-resolved force detection has been achieved by the coincidence between photo-irradiation and cantilever motion.Since the frequency of cantilever oscillation is modulated by the tip-sample force change during the scan, it is necessary that the timing of each laser pulse should be synchronized by each stroke of cantilever motion. We examined that the relationship between oscillation amplitude and the laser-pulse delay with various sample bias voltage. The sample was a Si(111) flushed in UHV condition. In usual, oscillation amplitude does not changed by bias voltage in non-contact region. Actually, in case of no laser irradiation, there is no bias effect. However, under the pulsed laser irradiation, the oscillation amplitude is dramatically changed as a function of both delay time and bias voltage. Furthermore, we found dead zone in delay time. These results indicate that the transient charge generated by pulsed laser irradiation can be detected with μs-class resolution.

今年，我们使用扫描力显微镜演示了时间分辨力检测。在动态模式操作中，尖端仅在尖端接近样品表面的时刻与表面相互作用。利用光照射与悬臂梁运动的同步性，实现了亚微秒级的时间分辨力检测，由于扫描过程中悬臂梁的振动频率受针尖-样品力变化的调制，因此，每个激光脉冲的定时必须与悬臂梁的每次运动同步。研究了不同样品偏置电压下振荡幅度与激光脉冲延迟的关系。样品是在UHV条件下冲洗的Si（111）。通常情况下，在非接触区，偏置电压不改变振荡幅度。实际上，在没有激光照射的情况下，不存在偏置效应。然而，在脉冲激光照射下，振荡幅度作为延迟时间和偏置电压的函数而显著改变。此外，我们还发现了延迟时间的死区。这些结果表明，脉冲激光辐照产生的瞬态电荷可以检测到μ s级的分辨率。