Force modulation for improved conductive-mode atomic force microscopy

We present an improved conductive-mode atomic force microscopy (C-AFM) method by modulating the applied loading force on the tip. Unreliable electrical contact and tip wear are the primary challenges for electrical characterization at the nanometer scale. The experiments show that force modulation reduces tip wear by a factor of three and enhances electrical contact between tip and sample, which allows operation at lower loading force and further reduction of tip and sample wear. Long-term wear experiments with platinum silicide tips on phase change media (Ge8Sb2Te11) show a nine and two times higher conductance for loading forces of 10 and 20 nN, respectively. The proposed technique could be of significant importance in applications such as probe storage and metrology, as long-term, reliable conduction in C-AFM remains a challenge.