Multiscale Insights into Molecular Interfaces: STM Imaging and Ultrafast Laser-Induced Dynamics

This thesis explores the multiscale characterization of molecular self-assembly and ultrafast dynamics at interfaces by integrating high-resolution scanning tunneling microscopy (STM) with advanced spectroscopic and ultrafast laser techniques. Focusing on cyclopentadienyltricarbonylmolybdenum dimer (CPTCMD) as a model metallocene, the study demonstrates how a customized liquid-phase STM cell enables direct imaging of self-assembled structures at the liquid-solid interface, overcoming the challenges posed by ambient STM conditions. Two distinct molecular packing motifs were resolved, with lattice parameters determined through Fourier analysis of STM data. Resonance Raman spectroscopy and density functional theory (DFT) calculations provided further insight into the dominant molecular conformer, confirming that the C2 cis structure is favored in both crystal and surface-bound states. To extend structural observations to dynamic processes, a home-built optical pump-probe STM (OPP-STM) platform utilizing femtosecond lasers was developed and validated. Systematic time-zero calibration and pump-probe experiments, including studies on coproporphyrin I dihydrochloride (CID), confirm the system’s temporal resolution and ability to resolve ultrafast events. The OPP-STM platform is positioned to enable future investigations of photoinduced processes and spin-orbit interactions in complex molecular systems, including single-molecule magnets. Overall, the work highlights the power of combining scanning probe microscopy, vibrational spectroscopy, and ultrafast laser methods for comprehensive understanding of functional molecular assemblies and light-matter interactions at the nanoscale.

Name thesis:degree_name

Master of Science

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Houston

Year dc:date.issued

2025

Author dc:creator

• Chen, Yen-Chen

Advisor dc:contributor.advisor

• Chiang, Naihao

Committee members dc:contributor.committeemember

• Baldelli, Steve
• He, Xing
• Xu, Shoujun
• Cai, Chengzhi

• Chemistry

Language dc:language.iso

English

Handle dc:identifier.uri

https://hdl.handle.net/10657/20711

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/20711