Computational insight into the origin of unexpected contrast in chiral markers as revealed by STM. Issue 4 (21st December 2017)

• Record Type: Journal Article
• Authors: Sanz-Matías, Ana; Ivasenko, Oleksandr; Fang, Yuan; De Feyter, Steven; Tahara, Kazukuni; Tobe, Yoshito; Harvey, Jeremy N.
• Is Part Of: Nanoscale. Volume 10:Issue 4(2018)
• Page Start: 1680
• Page End: 1694
• Publication Date: 2017-12-21
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c7nr07395j
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : Chiral substituents in self-assembled molecular layers show differences in bias dependence in STM image contrast. Abstract : Internal substituents can serve the double purpose of generating stereogenic centers and (potentially) being identifiable with Scanning Tunneling Microscopy (STM) in 2D self-assembled molecular layers. We investigate computationally the origin of stark contrast variations in STM images of chirally substituted self-assembled organic films. STM images of alkyl derivatives with secondary –CH3 and –OH groups have been simulated. Density functional theory calculations reveal bias-dependent contrast reversals in the substituent regions: a lack of local density of states in the relevant energy regime results in 'dark spots' in the simulated STM images, which turn bright upon increasing the bias voltage.