Manipulating the orientation of an organic adsorbate on silicon: a NEXAFS study of acetophenone on Si(001)

TL;DR

This study uses NEXAFS and DFT to analyze how acetophenone molecules adsorb and reorient on silicon surfaces, revealing temperature-dependent structural changes relevant for surface chemistry applications.

Contribution

It provides detailed insights into the adsorption configurations and thermal reorientation mechanisms of acetophenone on Si(001) surfaces using combined spectroscopic and computational methods.

Findings

Acetophenone adsorbs flat on Si(001) at room temperature.

Thermal annealing causes Si-C bond breaking.

Reorientation of adsorbate from flat to upright occurs upon heating.

Abstract

We investigate the chemical and structural configuration of acetophenone on Si(001) using synchrotron radiation core-level spectroscopy techniques and density functional theory calculations. Samples were prepared by vapour phase dosing of clean Si(001) surfaces with acetophenone in ultrahigh vacuum. Near edge X-ray adsorption fine structure spectroscopy and photoelectron spectroscopy measurements were made at room temperature as a function of coverage density and post-deposition anneal temperature. We show that the dominant room temperature adsorption structure lies flat on the substrate, while moderate thermal annealing induces the breaking of Si-C bonds between the phenyl ring and the surface resulting in the reorientation of the adsorbate into an upright configuration.