Joseph F. Keithley Award For Advances in Measurement Science Talk: Development of Scanning Probe Instruments and Application to the Graphene 2D Electron System

The invention of the scanning tunneling microscope ushered in the nanoscience revolution with the ability to “see atoms” in imaging surfaces. With the spread of the first initial ultra-high vacuum instruments in the first few years, the STM as an electronic structure tool quickly followed by tunneling spectroscopy measurements demonstrating that the observed atomic corrugation represents electronic wavefunctions maps, and that the tunneling spectrum would measure the energy resolved local density of states [1,2]. The quest for higher energy resolution in electronic spectra measurements drove the development of cryogenic scanning probe systems, starting at liquid He temperatures of 4 K, and then following a path to lower and lower temperatures, with a decade of development for almost each major advance. Today, scanning probe instruments can operate routinely at mK temperatures [3]. In this presentation, I will review some of these developments, including our recent efforts to combine STM together with atomic force and transport measurements at mK temperatures. Applications of tunneling spectroscopy to the graphene 2D electron system, ranging from fractional Landau levels [4] to graphene quantum dots [5] will be used as illustrations.

[1]. J. A. Stroscio, R. M. Feenstra, and A. P. Fein, Phys. Rev. Lett. 57, 2579 (1986).
[2]. R. M. Feenstra, J. A. Stroscio, J. Tersoff, and A. P. Fein, Phys. Rev. Lett. 58, 1192 (1987).
[3]. Y. J. Song, A. F. Otte, V. Shvarts, Z. Zhao, Y. Kuk, S. R. Blankenship, A. Band, F. M. Hess, and J. A. Stroscio, Rev. of Sci. Instr. 81, 121101 (2011).
[4]. Y. J. Song, A. F. Otte, Y. Kuk, Y. Hu, D. B. Torrance, P. N. First, W. A. de Heer, H. Min, S. Adam, M. D. Stiles, A. H. MacDonald, and J. A. Stroscio, Nature 467, 185 (2010).
[5]. F. Ghahari, D. Walkup, C. Gutierrez, J. F. Rodriguez-Nieva, Y. Zhao, J. Wyrick, F. D. Natterer, W. G. Cullen, K. Watanabe, T. Taniguchi, L. S. Levitov, N. B. Zhitenev, and J. A. Stroscio, Science 356, 845 (2017).