Paul Anzalone

Site-Specific Manipulation of CNTs to EXpressLO™ Grids for TEM Analysis

Carbon nanotubes (CNTs) may be prepared for transmission electron microscopy (TEM) by processing them in a liquid solution and then dispersing them onto holey carbon coated TEM grids [1]. However, residual solution products remaining on the CNTs may alter their surface structure. In addition, the carbon thin film may inhibit analysis of the CNTs, and it is difficult to prevent agglomeration and force individual CNTs to bridge across open holes in the film so they can be viewed directly through vacuum (e.g., without viewing through a support film). In addition, methods of isolating 2D graphene from graphite via micromechanical cleaving with adhesive tape [2] may damage multi-walled CNTs surfaces or CNT ends. The authors have vast experience in focused ion beam (FIB) specimen preparation methods but prefer avoiding possible damage to the CNTs by ion implantation or recoil displacement.

Focused Ion and Electron Beam Techniques

This chapter gives a brief detail on the focused ion and electron beam techniques. A DualBeam is a focused ion beam (FIB) column and a scanning electron microscope (SEM) on the same platform. Commercial FIB columns generally use Ga ions and are available with energy ranges from 500 eV to 30 keV. Commercial SEM columns are available with energy ranges from 200 eV to 30 keV, with beam currents up to 200 nA, with an ultimate resolution of 0.9 nm. The FIB or SEM can be directly used for fabrication of MEMS/ NEMS structures. The electron or ion beam energy and spot size may be varied to yield different milling or deposition characteristics. DualBeam techniques may be utilized to either directly fabricate MEMS/NEMS devices or to site specifically section and image MEMS/NEMS devices. FIB milling can be used to site specifically remove material to create MEMS/NEMS devices. The FIB can also be used to site specifically deposit structures either in the plane or out of the plane of the substrate. The deposit height varies where different bitmap grayscale values define unique dwell times of the beam. The SEM can also be used for electron beam lithography applications using metallization and lift-off techniques. The microscopic optical semiconductor mirror device that is the backbone of the Texas Instruments DLP projection systems is a well-known commercially available MEMS structure. DualBeam can be used to directly prototype or manufacture MEMS devices, as well as characterize the devices made by the DualBeam or by some other process.