Title: Pair Correlation Function of a 2D Molecular Gas Directly Visualized by Scanning Tunneling Microscopy.
When: Wednesday, November 15, (2017), 12:00.
Place: Department of Condensed Matter Physics, Faculty of Science, Module 3, Seminar Room (5th Floor).
Speaker: Ivan Ošťádal, Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, Prague Czech Republic.
The state of matter in fluid phases, determined by the interactions between particles, can be characterized by a pair correlation function (PCF). At the nanoscale, the PCF has been so far obtained experimentally only by means of reciprocal-space techniques. We use scanning tunneling microscopy (STM) at room temperature in combination with lattice-gas kinetic Monte Carlo (KMC) simulations to study a two-dimensional gas of highly mobile molecules of fluorinated copper phthalocyanine on a Si(111)/Tl-(1×1) surface. A relatively slow mechanism of STM image acquisition results in time-averaging of molecular occurrence under the STM tip. We prove by the KMC simulations that in the proximity of fixed molecules STM images represent the PCF. We demonstrate that STM is capable of visualizing directly the pair correlation function in real space.