TY - JOUR
T1 - A comparative STM study of Ru nanoparticles deposited on HOPG by mass-selected gas aggregation versus thermal evaporation
AU - Nielsen, Rasmus Munksgård
AU - Murphy, Shane
AU - Strebel, Christian Ejersbo
AU - Johansson, Martin
AU - Nielsen, Jane Hvolbæk
AU - Chorkendorff, Ib
PY - 2009
Y1 - 2009
N2 - Scanning tunneling microscopy was used to compare the morphologies of Ru nanoparticles deposited onto highly-oriented graphite surfaces using two different physical vapour deposition methods; (1) pre-formed mass-selected Ru nanoparticles with diameters between 2 nm and 15 nm were soft-landed onto HOPG surfaces using a gas-aggregation source and (2) nanoparticles were formed by e-beam evaporation of Ru films onto HOPG. The particles generated by the gas-aggregation source are round in shape with evidence of facets resolved on the larger particles. Annealing these nanoparticles when they are supported on unsputtered HOPG resulted in the sintering of smaller nanoparticles, while larger particles remained immobile. Nanoparticles deposited onto sputtered HOPG surfaces were found to be stable against sintering when annealed. The size and shape of nanoparticles deposited by e-beam evaporation depend to a large extent on the state of the graphite support and the temperature. Ru deposition onto unsputtered HOPG is characterised by bimodal growth with large flat particles formed on the substrate terraces and smaller diameter particles aligned along the substrate steps. Evaporation onto sputtered HOPG results in the formation of 2 nm round particles with a narrow size distribution. Finally, thermal deposition onto both sputtered and unsputtered HOPG at 660 degrees C results in larger particles showing a flat Ru(0 0 0 1) top facet. (C) 2009 Elsevier B.V. All rights reserved.
AB - Scanning tunneling microscopy was used to compare the morphologies of Ru nanoparticles deposited onto highly-oriented graphite surfaces using two different physical vapour deposition methods; (1) pre-formed mass-selected Ru nanoparticles with diameters between 2 nm and 15 nm were soft-landed onto HOPG surfaces using a gas-aggregation source and (2) nanoparticles were formed by e-beam evaporation of Ru films onto HOPG. The particles generated by the gas-aggregation source are round in shape with evidence of facets resolved on the larger particles. Annealing these nanoparticles when they are supported on unsputtered HOPG resulted in the sintering of smaller nanoparticles, while larger particles remained immobile. Nanoparticles deposited onto sputtered HOPG surfaces were found to be stable against sintering when annealed. The size and shape of nanoparticles deposited by e-beam evaporation depend to a large extent on the state of the graphite support and the temperature. Ru deposition onto unsputtered HOPG is characterised by bimodal growth with large flat particles formed on the substrate terraces and smaller diameter particles aligned along the substrate steps. Evaporation onto sputtered HOPG results in the formation of 2 nm round particles with a narrow size distribution. Finally, thermal deposition onto both sputtered and unsputtered HOPG at 660 degrees C results in larger particles showing a flat Ru(0 0 0 1) top facet. (C) 2009 Elsevier B.V. All rights reserved.
U2 - 10.1016/j.susc.2009.10.005
DO - 10.1016/j.susc.2009.10.005
M3 - Journal article
SN - 0039-6028
VL - 603
SP - 3420
EP - 3430
JO - Surface Science
JF - Surface Science
IS - 24
ER -