title: Nanoscale Chemical Imaging of a Dynamic Molecular Phase Boundary with Ultrahigh Vacuum Tip-Enhanced Raman Spectroscopy.
abstract: Nanoscale chemical imaging of a dynamic molecular phase boundary has broad implications for a range of problems in catalysis, surface science, and molecular electronics. While scanning probe microscopy (SPM) is commonly used to study molecular phase boundaries, its information content can be severely compromised by surface diffusion, irregular packing, or three-dimensional adsorbate geometry. Here, we demonstrate the simultaneous chemical and structural analysis of N-N'-bis(2,6-diisopropylphenyl)-1,7-(4'-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) molecules by UHV tip-enhanced Raman spectroscopy. Both condensed and diffusing domains of PPDI coexist on Ag(100) at room temperature. Through comparison with time-dependent density functional theory simulations, we unravel the orientation of PPDI molecules at the dynamic molecular domain boundary with unprecedented ∼4 nm spatial resolution.
authors.affiliation: Department of Chemistry, University of Illinois at Chicago , Chicago, Illinois 60607, United States.
authors.forename: Nan
authors.initials: N
authors.lastname: Jiang
authors.forename: Naihao
authors.initials: N
authors.lastname: Chiang
authors.forename: Lindsey R
authors.initials: LR
authors.lastname: Madison
authors.forename: Eric A
authors.initials: EA
authors.lastname: Pozzi
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.forename: Tamar
authors.initials: T
authors.lastname: Seideman
authors.forename: Mark A
authors.initials: MA
authors.lastname: Ratner
authors.forename: Mark C
authors.initials: MC
authors.lastname: Hersam
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.forename: Richard P
authors.initials: RP
authors.lastname: Van Duyne
keywords: Tip-enhanced Raman spectroscopy (TERS); dynamic molecular phase boundary; time-dependent density functional theory (TDDFT); ultrahigh vacuum scanning tunneling microscopy (UHV-STM)