Ritz Christian, Wagner Tino, Stemmer Andreas
Nanotechnology Group, ETH Zürich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland.
present address: Zurich Instruments AG, Technoparkstrasse 1, 8005 Zürich, Switzerland.
Beilstein J Nanotechnol. 2020 Jun 15;11:911-921. doi: 10.3762/bjnano.11.76. eCollection 2020.
Kelvin probe force microscopy is a scanning probe technique used to quantify the local electrostatic potential of a surface. In common implementations, the bias voltage between the tip and the sample is modulated. The resulting electrostatic force or force gradient is detected via lock-in techniques and canceled by adjusting the dc component of the tip-sample bias. This allows for an electrostatic characterization and simultaneously minimizes the electrostatic influence onto the topography measurement. However, a static contribution due to the bias modulation itself remains uncompensated, which can induce topographic height errors. Here, we demonstrate an alternative approach to find the surface potential without lock-in detection. Our method operates directly on the frequency-shift signal measured in frequency-modulated atomic force microscopy and continuously estimates the electrostatic influence due to the applied voltage modulation. This results in a continuous measurement of the local surface potential, the capacitance gradient, and the frequency shift induced by surface topography. In contrast to conventional techniques, the detection of the topography-induced frequency shift enables the compensation of all electrostatic influences, including the component arising from the bias modulation. This constitutes an important improvement over conventional techniques and paves the way for more reliable and accurate measurements of electrostatics and topography.
开尔文探针力显微镜是一种扫描探针技术，用于量化表面的局部静电势。在常见的实现方式中，会调制针尖与样品之间的偏置电压。通过锁相技术检测由此产生的静电力或力梯度，并通过调整针尖 - 样品偏置的直流分量将其消除。这使得能够进行静电表征，同时将静电对形貌测量的影响降至最低。然而，由于偏置调制本身产生的静态贡献仍未得到补偿，这可能会导致形貌高度误差。在此，我们展示了一种无需锁相检测即可找到表面电势的替代方法。我们的方法直接对调频原子力显微镜中测量的频移信号进行操作，并持续估计由于施加的电压调制而产生的静电影响。这导致对局部表面电势、电容梯度以及由表面形貌引起的频移进行连续测量。与传统技术相比，对形貌引起的频移的检测能够补偿所有静电影响，包括由偏置调制产生的分量。这是对传统技术的一项重要改进，为更可靠、准确地测量静电和形貌铺平了道路。
