Space Sciences Lab has a Tescan Vega XM3 Scanning Electron Microscope with integrated EDS microanalysis system. The instrument uses a tungsten filament and has a large chamber and range of motion that allows samples up to 20 cm x 20 cm to be analyzed. The instrument has low vacuum capability, allowing for imaging and microanalysis of non-conductive samples without applying surface coatings. Resolution varies by sample type but features <100 nm can be resolved for most samples.
The X-ray microanalysis system is an Oxford Instruments x-max 80 EDS detector. The instrument also has numerous automated scanning features, allowing for imaging and data collection over large areas, and automatic feature detection and. It uses the current AZtec software suite, with Particle automation package. This allows automated X-ray mapping of large areas, which can be combined to provide gigapixel elemental maps. This feature automatically identifies up to 100,000 particles per run according to preset parameters for particles of interest, based on average Z, size and/or shape using the BSE images it collects. The chemical compositions of these particles can then be analyzed with EDS, at a significant time savings compared to traditional analysis methods. Automated image collection and montaging allows sub-micron imaging over large areas, up to 100 cm 2 during an overnight run. Below are a few examples of samples studied with our SEM, but it can be used for a wide range of geologic, aerospace or material science samples:
The instrument was used to examine Molybdenum (Mo) on Platinum (Pt) foils from the Genesis mission. Foils were badly contaminated in the unexpected hard landing in the Utah desert in 2004. More than 6,000 cm2 of the foil has been examined by SEM and the contamination, which includes a mixture of terrestrial dirt as well as spacecraft materials (Al, Si, stainless steel, Ge, paint, etc.) has been identified and quantified. In addition, examination of the Genesis Pt/Mo foil by SEM indicated that the collector material was undergoing delamination of the Mo layer.
Two applications of SEM for Genesis Mo-Pt foils. Left: montage image of 5 cm x 5 cm area, showing different types of contamination (in pink, red and green) identified by AZtec Particle analysis. Right: BSE image of 2 mm x 2 mm of Genesis foil showing the Mo layer in grey and the underlying Pt substrate (where Mo delaminated) in white.
This Titanium bolt was examined on the SEM at high resolution, showing no indications of stress cracking.
A ~5 pm cross section of a multilayer thin film coating was examined by SEM to determine the thickness of Ni (bleu) and Au (green) layers on an Al (red) substrate. Composition and thickness were easily confirmed for the 3.0 pm Ni and 1.3 pm Au layers.
On the left, an EDS analysis of a thin-section of a micrometeorite, revealing the identification of 9 distinct mineral phases. On the right – a BSE image of a potential iron meteorite (a heavy, metallic looking, magnetic rock). The EDS analysis showed that the grey matrix is almost pure Fe2O3, while the tiny dark inclusions are dominated by Al-oxide. The composition (including lack of Ni, Co) identifies the rock as terrestrial.
We have a Thermo Fisher iCAP 6300 Duo ICP-OES instrument for analyzing up to 70 elements in aqueous solutions (dilute nitric or hydrochloric acid) at concentrations of parts per million (ppm) to parts per billion (ppm). It is routinely used for analyzing major/minor elements (Na through Ni) in extraterrestrial samples, but other elements can be easily added, or new methods can be set up for specific mixtures of elements. We generally use a quartz torch and quartz sample introduction system but have a Teflon spray chamber and a ceramic injection tube available for dilute HF solutions (up to 5%).
We also use an Agilent 8800 Triple Quad ICP-MS instrument for analyzing major and trace elements in aqueous solutions at concentrations of parts per million (ppm) to parts per trillion (ppt). The instrument is equipped with a multipole-based collision/reaction cell (CRC), which eliminates spectral interferences to a significant extent, for instance, by using a non-reactive collision gas such as helium to slow down polyatomic interfering ions such that they can be selectively discriminated against on the basis of their lower kinetic energy. Unlike the ICP-OES, this instrument is able to do isotopic measurements at a few permille precision.
