Microscopy and Microanalysis

Materials Applications

A Method for Directly Correlating Site-Specific Cross-Sectional and Plan-View Transmission Electron Microscopy of Individual Nanostructures

Daniel K. Schreibera1a2 c1 p1, Praneet Adusumillia1, Eric R. Hemesatha1, David N. Seidmana1a3, Amanda K. Petford-Longa1a2a4 and Lincoln J. Lauhona1

a1 Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108, USA

a2 Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA

a3 Northwestern University Center for Atom-Probe Tomography, 2220 Campus Drive, Evanston, IL 60208-3108, USA

a4 Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439, USA

Abstract

A sample preparation method is described for enabling direct correlation of site-specific plan-view and cross-sectional transmission electron microscopy (TEM) analysis of individual nanostructures by employing a dual-beam focused-ion beam (FIB) microscope. This technique is demonstrated using Si nanowires dispersed on a TEM sample support (lacey carbon or Si-nitride). Individual nanowires are first imaged in the plan-view orientation to identify a region of interest; in this case, impurity atoms distributed at crystalline defects that require further investigation in the cross-sectional orientation. Subsequently, the region of interest is capped with a series of ex situ and in situ deposited layers to protect the nanowire and facilitate site-specific lift-out and cross-sectioning using a dual-beam FIB microscope. The lift-out specimen is thinned to electron transparency with site-specific positioning to within ∼200 nm of a target position along the length of the nanowire. Using the described technique, it is possible to produce correlated plan-view and cross-sectional view lattice-resolved TEM images that enable a quasi-3D analysis of crystalline defect structures in a specific nanowire. While the current study is focused on nanowires, the procedure described herein is general for any electron-transparent sample and is broadly applicable for many nanostructures, such as nanowires, nanoparticles, patterned thin films, and devices.

(Received March 19 2012)

(Accepted June 16 2012)

Key words

  • transmission electron microscopy;
  • focused ion beam;
  • sample preparation;
  • nanowires

Correspondence:

c1 Corresponding author. E-mail: daniel.schreiber@pnnl.gov

p1 Current address: Pacific Northwest National Laboratory, Richland, WA 99352, USA