Direct Imaging of Intermolecular Bonds in Scanning Tunneling Microscopy

Abstract

Local, noncovalent intermolecular interactions in organic monolayers have been directly imaged using scanning tunneling hydrogen microscopy (STHM). Unprecedented spatial resolution directly reveals the relation between the intermolecular interactions, the molecular chemical structure, and the ordering in the film.

Temperature-dependent self-assembly of NC–Ph5–CN molecules on Cu(111)

“…High resolution measurements were carried out by functionalizing the STM tip with a CO molecule. [35][36][37] The molecular coverage (monolayer (ML)) is defined in terms of the densest structure we have observed, i.e., the compact structure formed at room temperature reported in Sec. III E. The evaporation flux and the deposition time, and therefore the molecular exposure, are identical for each preparation.…”

“…4(b), the chemical bonds between the CN groups and the Cu coordination atoms are visible. 36 The CN-Cu bonds are imaged as bright connections between the endgroup and the coordination atom in a darker circular halo, slightly distorted in the case of the rotated node, surrounding the Cu atoms.…”

Orbital resolution of molecules covalently attached to a clean semiconductor surface

“…Such a good resolution heavily depends on the tip condition, as we obtained conventional resolution if we scanned the sample after dosing. STM tips were reported to offer better resolution when the tip apexes are modified by CO or organic molecules 14,17,18,20 . In our experiments, the onset of better resolution is related to a molecule dropping and reattaching process by tracing the tip state ( Supplementary Fig.…”

“…It has been demonstrated on other surfaces that once molecular orbitals are resolved by STM, many chemical reaction mechanisms and inherent electronic properties of single molecules can be directly and reliably elucidated [9][10][11][12][13] . However, orbital resolution is rather difficult to achieve because of the need of delicate STM tip modification [14][15][16][17][18][19][20] and substrate preparation 12,15,21,22 . In addition, most molecules undergo addition or dissociation on semiconductor surfaces, resulting in blurred profiles during STM scanning, thus losing insightful electronic details such as orbitals 23 .…”

Visualization of nucleation and growth of supramolecular networks on Cu(001) and Au(111)

“…To clarify the picture we obtained here by studying mostly the ordering on the mesoscopic scale with LEEM, further research with other techniques is required. For example by imaging directly the intermolecular bonds with high resolution STM [125,126] or by unambiguously assigning a deprotonation reaction with spectroscopic methods [106].…”