Graphene-Supported High Resolution TEM and STEM Imaging of ...
Graphene-Supported High Resolution TEM and STEM Imaging of Silicon Nanocrystals and their Capping Ligands Matthew G. Panthani,a Colin M. Hessel,a Dariya Reid,a Gilberto Casillas, b Miguel JoséYacamán,b and Brian A. Korgela,* a
Department of Chemical Engineering, Texas Materials Institute, and Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712 b Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249 *Corresponding author: (T) +1-512-471-5633; (F) +1-512-471-7060; [email protected] Supporting Information Figure 1 shows bright-field and HAADF STEM images of Si nanocrystals on graphene. The graphene has a tendency to wrinkle and curl, but extended regions of graphene exist. These areas have the lowest image contrast and yield the clearest nanocrystal images. Figure 2 compares TEM images of alkene-passivated Si nanocrystals on few-layer graphene and amorphous carbon obtained using a JEOL 2010F TEM operated at 200 kV. Single-layer graphene can degrade rapidly under an electron beam at voltages greater than 100 kV.1,2 We found that few-layer graphene provided a stable support for imaging Si nanocrystals at higher accelerating voltage (i.e., 200 kV) with still quite good imaging resolution. However, imaging with single layer graphene at lower accelerating voltage (80-120 kV) provided better contrast.
Figure 1. STEM images of Si nanocrystals on graphene. (a,c) HAADF and (b,d) bright field images were obtained simultaneously with HAADF) and in-line detectors on a JEOL JEM S-1
ARM200F microscope with spherical aberration (Cs) correction operated at 120 kV accelerating voltage.
Figure 2. TEM images of alkene-passivated Si nanocrystals acquired with a JEOL 2010F microscope operated at 200 kV on (a) few-layer graphene and a (b) standard amorphous carbon film. Both nanocrystals are imaged with similar crystallographic orientation down the Si [110] zone axis. (Insets) Fast Fourier transforms (FFTs) of the TEM images.
References
(1) Girit, Ç. Ö.; Meyer, J. C.; Erni, R.; Rossell, M. D.; Kisielowski, C.; Yang, L.; Park, C.-H.; Crommie, M. F.; Cohen, M. L.; Louie, S. G.; Zettl, A. Science 2009, 323, 1705. (2) Meyer, J. C.; Girit, C. O.; Crommie, M. F.; Zettl, A. Nature 2008, 454, 319.
S-2
Department of Chemical Engineering, Texas Materials Institute, and Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712 b Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249 *Corresponding author: (T) +1-512-471-5633; (F) +1-512-471-7060; [email protected] Supporting Information Figure 1 shows bright-field and HAADF STEM images of Si nanocrystals on graphene. The graphene has a tendency to wrinkle and curl, but extended regions of graphene exist. These areas have the lowest image contrast and yield the clearest nanocrystal images. Figure 2 compares TEM images of alkene-passivated Si nanocrystals on few-layer graphene and amorphous carbon obtained using a JEOL 2010F TEM operated at 200 kV. Single-layer graphene can degrade rapidly under an electron beam at voltages greater than 100 kV.1,2 We found that few-layer graphene provided a stable support for imaging Si nanocrystals at higher accelerating voltage (i.e., 200 kV) with still quite good imaging resolution. However, imaging with single layer graphene at lower accelerating voltage (80-120 kV) provided better contrast.
Figure 1. STEM images of Si nanocrystals on graphene. (a,c) HAADF and (b,d) bright field images were obtained simultaneously with HAADF) and in-line detectors on a JEOL JEM S-1
ARM200F microscope with spherical aberration (Cs) correction operated at 120 kV accelerating voltage.
Figure 2. TEM images of alkene-passivated Si nanocrystals acquired with a JEOL 2010F microscope operated at 200 kV on (a) few-layer graphene and a (b) standard amorphous carbon film. Both nanocrystals are imaged with similar crystallographic orientation down the Si [110] zone axis. (Insets) Fast Fourier transforms (FFTs) of the TEM images.
References
(1) Girit, Ç. Ö.; Meyer, J. C.; Erni, R.; Rossell, M. D.; Kisielowski, C.; Yang, L.; Park, C.-H.; Crommie, M. F.; Cohen, M. L.; Louie, S. G.; Zettl, A. Science 2009, 323, 1705. (2) Meyer, J. C.; Girit, C. O.; Crommie, M. F.; Zettl, A. Nature 2008, 454, 319.
S-2
