Atom probe

Oxford nanoScience has announced a breakthrough in 3-Dimensional Atom Probe (3DAP) technology. By using a femtosecond laser to evaporate atoms from samples, high resistivity materials such as undoped silicon can now be analysed.

Conventional 3DAP systems require a high voltage pulse to be applied to the tip of the specimen to evaporate the atoms, which has in the past restricted the application to conducting samples only. However, laser evaporation allows examination of both conducting samples and those with high resistance.

Oxford nanoScience Managing Director, Richard Davies, said: "This is one of the most significant developments to date for the 3DAP technique. The semiconductor industry has been aware for many years of the capabilities of 3DAP for metals and alloys. Now, for the first time, we have the technology to allow the evaporation, counting, identification and spatial location of individual atoms in a semiconductor sample to produce a 3-dimensional visualisation of the atomic arrangement within that sample."

"What is more", he continued, "not only have we opened up a completely new area of materials that can be analysed by the technique, but there are also a number of other major benefits in terms of speed of analysis, mass resolution and stability of the samples."

A host of materials have been evaluated using the laser system, including single element metals, metal alloys, silicon samples of different conductivities and metal multilayer structures, including metal oxide layers, grown on a silicon substrate.

Dr. Peter Clifton, Head of Process Development and Applications at Oxford nanoScience, commented: "The laser system provides very rapid analysis, taking just 10 minutes to run a complete data set. For some delicate samples, repeated voltage pulsing can result in the sample disintegrating. This is not the case with the laser system."

Another benefit offered by the laser system is the mass resolution (M/DM). The Oxford nanoScience instrument uses a high mass resolution reflectron lens which already gives excellent M/DM figures of 300 at FWTM and 100 at FW0.1%M for high voltage evaporation, but these figures soar to around 1000 for FWTM and 500 for FW0.1%M for the laser system.

Specifying resolution figures at FW0.1%M, which is closer to the spectral baseline is a measure of the instrument’s ability to identify small peaks adjacent to major peaks that are several orders of magnitude higher.