Quantitative evaluation of covalently bound molecules on GaP (100) surfaces

Rosangelly Flores-Perez, Purdue University - Main Campus
Dmitry Zemlyanov, Birck Nanotechnology Center, Purdue University
Albena Ivanisevic, Purdue University - Main Campus

Date of this Version


This document has been peer-reviewed.



The study utilizes surface sensitive techniques in order to quantitatively characterize the nature of organization and bonding of alkanethiol adsorbates on GaP (100) surfaces. The evaluation was performed using water contact angle, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The hydrophobicity and consistency of surface roughness were studied via water contact angle and AFM. The FT-IR experimental protocol permitted the identification of characteristic functional groups on the surface and enabled insight into the organization within the adlayers on the GaP surface. XPS data showed evidence for the formation of a covalent bond between the sulfur and the surface and was used to calculate the adlayer thicknesses, tilt angles, and molecular coverages for different adsorbates. The thickness and tilt angles values were comparable to other modified semiconductor materials. High coverages were observed for all alkanethiols on GaP (100). The quantitative XPS protocol reported can be applied to the evaluation of other adsorbates on semiconductor materials.


Nanoscience and Nanotechnology