Structural modifications of gold thin films produced by thiol-derivatized single-stranded DNA immobilization

摘要

Recent experiments have reported an opposite sign of the differential surface stress produced on goldcoated cantilevers by a thiolderivatized singlestranded DNA (SHDNA) immobilization process. The sign of the surface stress depends on the method used to evaporate the gold thin film, being compressive (negative) or tensile (positive) for ebeam or resistively deposited gold, respectively. This study investigates the origin of this effect by means of a combination of xray diffraction and xray photoelectron spectroscopy. Both ebeam and resistively grown gold thin films are characterized to find the subtle differences responsible for this intriguing stress behaviour. Somewhat remarkably, these studies show a tight relation between the surface structure of the gold overlayer and the SHDNA immobilization efficiency. The average grain size variation seems to correlate well with the differential surface stress triggered by the SHDNA immobilization previously reported. These results suggest that the relation of the probe molecules with the surface structure must be considered to understand surface stress changes.