Glow Discharge Optical Emission Coded Aperture Spectral Imaging Elemental Mapping (GOCAEM) for Ultrahigh Throughput 3D Surface Analysis of Nanoscale Materials

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Gerardo Gamez at Texas Tech University is studying and developing Glow Discharge Optical Emission Coded Aperture Spectral Imaging Elemental Mapping (GOCAEM), which is a novel method for analyzing and measuring chemical elements on surfaces. A variety of fields, including materials, geological, and biological sciences, use elemental mapping to gain an improved understanding of naturally occurring systems or improve performance of manufactured systems.

However, current elemental mapping techniques suffer from lengthy sample analysis times or accessibility restrictions, which limits their use to a small group of systems. GOCAEM leverages the ability of glow-discharge spectroscopy to overcome such limitations (>1000x faster vs typical EM techniques) and incorporates compressed sensing spectral imaging strategies to offer greatly improved abilities, offering advantages that allow analysis of challenging systems, such as nanoscale materials.

Thus, fast, routine diagnostic three-dimensional elemental mapping of many nano-structured surface systems is a real possibility with this approach. Outcomes from the project will have an impact on many fields, especially those relying on ultra-thin films and nanoparticle materials, which is in alignment with serving the needs and vision of the National Nanotechnology Initiative.

The project will take place at a designated Hispanic Serving Institution, which provides an uncommon opportunity to reach underrepresented minorities in science, technology, engineering, and mathematics (STEM). Multidisciplinary training opportunities for graduate and undergraduate researchers include those with instrument development, plasma spectroscopy, imaging, nanomaterials characterization, and surface analysis.

The goal of this project is to enable elemental mapping (EM) of nanomaterials via glow discharge optical emission spectroscopy (GDOES). GDOES has been initially developed as an alternative elemental mapping technique that offers significant (several orders of magnitude) improvement in analysis time compared to typical techniques. GDOES also gives access to significantly faster three-dimensional elemental mapping protocols through sputter sampling and its high-throughput two-dimensional elemental mapping.

Nevertheless, the depth resolution is still limited by the two-dimensional elemental mapping time; thus, significant gains must still be achieved to reach the highest depth resolution (~nm) and limits of detection offered by GDOES. We will develop Glow Discharge Optical Emission Coded Aperture Spectral Imaging Elemental Mapping (GOECAEM), where hyperspectral imaging enabled by compressed sensing (CS) strategies will achieve the required gains in depth resolution and limits of detection.

CS is a recently developed measurement strategy that represents a paradigm shift in sampling. It allows employment of compression protocols (typically reserved for software data processing) during the data acquisition step: this results in significantly improved data collection efficiency and measurement time required. Coded aperture compressed sensing hyperspectral imaging will be developed and implemented using spatial light modulators and array detectors.

As such, high throughput three-dimensional elemental mapping of nano-structured materials will be sought here with the development of methods for two different types of materials. The three main objectives of the proposed research are 1) design and construction of GOECAEM instrumentation; 2) development of 3-dimensional GOECAEM enabled methods for ultra-thin film materials characterization at the nanoscale; and 3) development of GOECAEM-enabled methods for nanoparticle characterization.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.