Quantifying Surface Charge Density by Using an Electric Force Microscope with a Referential Structure

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• 作者：Guicun Qi ; Yanlian Yang ; Hao Yan ; Li Guan ; Yibao Li ; Xiaohui Qiu ; Chen Wang
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：January 8, 2009
• 年：2009
• 卷：113
• 期：1
• 页码：204-207
• 全文大小：172K
• 年卷期：v.113,no.1(January 8, 2009)
• ISSN：1932-7455

文摘

A comparative method was proposed to quantitatively measure the charge density on sample surfaces at the nanometer scale by using an electric force microscope (EFM). By introducing a millimeter-sized conductive sphere as a charge reference, whose surface charge density was proportional to the applied voltage, the electrostatic interaction between an EFM probe and the sphere could be calibrated as a function of charge density. Because the Coulombic force acting on the probe is proportional to the linear term of the phase shift (Δθ) versus tip voltage (V_t) characteristics, the charge density of an unknown sample could be derived by comparing the slopes of the characteristic curves measured on the studied sample with that obtained on the reference sphere whose absolute charge density had been known. The approach was applied to determine the charge density of a freshly cleaved mica surface. The comparative scheme avoids the complex influence from the irregular shape of EFM tips, providing a facile approach for quantitative analysis of the charge density on sample surfaces at the nanometer scale.