Shared Facilities

FUNCTION:
Understanding the properties and performance of materials requires knowledge of their characteristic structures and local compositions, often at an atomic scale and in three dimensions. NUCAPT is a laboratory where such measurements can be performed with atom-probe tomography. The microstructural features studied might typically be of the following types: Composition of second-phase precipitates or inclusions (down to 1nm diameter) or small clusters, compositional variation in modulated structures, layer-by-layer analysis of ordered phases or multi-layer thin-film structures, dopant profiles of semiconductor structures (transistors), and observation of interfaces (e.g. chemistry of grain boundaries).

EQUIPMENT:
1. LEAP 3000X manufactured by Imago Scientific Instruments: This instrument, a local electrode atom-probe (LEAP) tomograph, has an ultrafast detector capable of collecting up to 72 million atoms per hour. Atoms are evaporated from the sample surface either by voltage or laser pulses and a computer reconstructs a three-dimensional image with both the chemical identity and positions of individual atoms, with a depth resolution of a single atomic plane of 0.1 - 0.3 nm. A microelectrode allows the analysis of microtips, prepared by FIB (ion-milling and/or lift-out technique to target specific features), or wire tips prepared by conventional electropolishing. A forthcoming upgrade will feature increased data collection rates, digital field-ion microscopy and a larger field-of-view.

2. Three-dimensional Atom Probe (3DAP) for wire specimens, with voltage-pulsed field-evaporation, energy compensating reflectron lens for high mass resolution, and phosphor-screen based field-ion microscopy.

3. A specimen preparation laboratory for preparing needle-shaped specimens for atom-probe tomography. Our lab features a high-speed precision saw to cut specimen blanks, an electropolishing station with a high-resolution stereo-microscope, and a Simplex Electropointer automated electropolisher.