Thermal stability of size-selected arrays of gold nanoparticles on ( 1 1 2 ¯ 0 ) sapphire – A thermal desorption spectroscopy study

• Published in: Surface science 2008-12, Vol.602 (24), p.3714-3720
• Main Authors: Weigl, F., Koslowski, B., Ziemann, P.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Gold nanoparticles; Heat of sublimation; Micelle; Physics; Thermal desorption spectroscopy; Thermal stability
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2008.10.015

Exploiting the self-organization of spherical gold salt loaded inverse micelles formed from diblock copolymer poly(styrene)- block-poly(2-vinylpyridine) (PS- b-P2VP) in toluene, arrays of Au nanoparticles were prepared exhibiting narrow size as well as interparticle distance distributions. Starting with such Au nanoparticles (average particle diameters ranging between 1 nm and 5 nm) deposited on top of ( 1 1 2 ¯ 0 )-oriented sapphire substrates, thermal desorption spectroscopy (TDS) experiments were performed up to a maximum temperature of 1473 K at a standard rate of 5 K/s in order to test for size dependent vapor pressures as expected from Kelvin’s equation. Opposite to the expected increase of the vapor pressure for decreasing particle diameters, a split desorption behavior is observed with two peaks. Analyzing the data according to the Polanyi–Wigner equation, from the peak at lower temperature a desorption energy and attempt frequency close to bulk Au is extracted while the peak at higher temperature delivers significantly larger values for both properties. The latter observation is attributed to a substrate–nanoparticle interaction, which becomes dominant for decreasing particle diameters.