Three dimensional accurate morphology measurements of polystyrene standard particles on silicon substrate by electron tomography.
Polystyrene latex (PSL) nanoparticle (NP) sample is one of the most widely used standard materials. It is used for calibration of particle counters and particle size measurement tools. It has been reported that the measured NP sizes by various methods, such as Differential Mobility Analysis, dynamic light scattering (DLS), optical microscopy (OM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), differ from each other. Deformation of PSL NPs on mica substrate has been reported in AFM measurements: the lateral width of PSL NPs is smaller than their vertical height. To provide a reliable calibration standard, the deformation must be measured by a method that can reliably visualize the entire three dimensional (3D) shape of the PSL NPs. Here we present a method for detailed measurement of PSL NP 3D shape by means of electron tomography in a transmission electron microscope. The observed shape of the PSL NPs with 100 nm and 50 nm diameter were not spherical, but squished in direction perpendicular to the support substrate by about 7.4% and 12.1%, respectively. The high difference in surface energy of the PSL NPs and that of substrate together with their low Young modulus appear to explain the squishing of the NPs without presence of water film.
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan; National Institute for Nanotechnology (NINT), 11421 Saskatchewan Drive, Edmonton T6G 2M9, Canada. Electronic address: misa.hayashida@ualberta.ca.
Misa
M
Hayashida
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan.
Kazuhiro
K
Kumagai
National Institute for Nanotechnology (NINT), 11421 Saskatchewan Drive, Edmonton T6G 2M9, Canada; Department of Physics, University of Alberta, Edmonton T6G 2E1, Canada.
Marek
M
Malac
(Scanning) Transmission electron microscopy ((S)TEM); Accurate shape measurement; Calibration sample; Electron tomography; Metrology; Nanoparticle deformation; Polystyrene latex spheres; Quantitative electron tomography; Surface energy