In April 2013, a local electrode atom probe (LEAP 4000HR) instrument from CAMECA Instruments was installed at the Electron Microscopy Facility at Deakin University, Geelong Waurn Ponds Campus. The new atom probe provides state-of-the-art atomic-scale analysis capabilities to support metallurgical research of materials design and performance at Deakin.
The microscope, courtesy of funding from the Australian Research Council's Linkage Infrastructure, Equipment and Facilities scheme is the 50th LEAP to be installed around the world. It offers unparalleled insight into the microstructure of materials allowing atomic resolution chemical and spatial analysis in three dimensions. The LEAP 4000HR utilises a large-angle reflectron lens to provide high mass resolution in voltage mode operation with a large field of view; enabling differentiation between all elements and their isotopes. The local electrode design allows analysis of microtip specimens as well as conventional needle-shaped samples.
In atom probe tomography (APT), atoms are progressively removed from the surface of a sharp tip specimen by the process of field evaporation. By the application of a high DC voltage (~2-11 kV), a very intense electrostatic field is produced at the apex of the specimen tip, having a radius of curvature of a few tens of nanometres. In a controlled manner, using voltage pulsing in the LEAP 4000HR instrument, the atoms are subsequently field ionised and then evaporated layer by layer towards a position-sensitive detector, where their chemical identity is determined by time-of-flight mass spectrometry. The evaporated volume is then reconstructed in three dimensions, using an inverse projection reconstruction algorithm and the sequence of detected events. The result is a tomographic data set, typically spanning some hundreds of nanometres in depth and containing the spatial coordinates and elemental identities of tens to hundreds of millions of atoms with near atomic resolution.
Typical capabilities of the LEAP 4000HR instrument include:
- acquisition rates of 1 to 10 million ions per hour
- millions to tens of millions of atoms per specimen
- tomographic analysis volume in the range of 50 x 50 x 200 nm
- spatial resolution: ~ 0.1 - 0.5 nm
- mass resolution: ~ 1000 (FWHM)
- chemical sensitivity: ~ 10 ppm
The LEAP 4000HR instrument will allow researchers to investigate the distribution of the different types of atoms within an alloy’s microstructure. The materials to be studied with this instrument include light alloys for weight and fuel reduction in transport vehicles, biomaterials for implants and drug delivery, nano-structured materials, and characterization of alloys produced via new energy efficient processing routes. The information can then be used to design engineering alloys with improved strength, biocompatibility and reduced environmental footprints. It can also be used to characterize alloys produced by new green technologies.
For further details contact Dr Ross Marceau (email: firstname.lastname@example.org).