We report scanning tunneling microscopy (STM) and spectroscopy (STS) measurements on single layer Ti0.87O2 nanosheets deposited on Pt(200 nm)/Si substrates. These nanosheets have a band gap of 3.8 eV and are virtually invisible in conventional STM images. However, an impressive contrast is observed in the di/dz map, which allows for a clear identification of the nanosheets. The di/dz signal is obtained by adding a high frequency, small amplitude modulation to the z-piezo using a lock-in amplifier.
Kumar, A., Chinnasamy Palanisamy, S. K., Boter, J. M., Hellenthal, C., ten Elshof, J. E., & Zandvliet, H. J. W. (2013). Imaging of Ti0.87O2 nanosheets using Scanning Tunneling Spectroscopy. Applied surface science, 265, 201-204. https://doi.org/10.1016/j.apsusc.2012.10.169