Large-Area Photoemission Tool
This page provides details on the large-area photoemission tool in the Stand-Alone Measurements and Characterization bays of the Process Development and Integration Laboratory. This tool is a stand-alone imaging photoemission tool manufactured by Kratos Analytical, who modified it to achieve full 157-mm x 157-mm sample access and allow it to mate to an ultra-high-vacuum transfer station. This capability should be operational within 2009.
Techniques available with this tool are X-ray photoelectron spectroscopy (XPS), angle-resolved XPS, depth profiling, and ultraviolet photoelectron spectroscopy (UPS). The transfer station allows platens to be introduced via either a transport pod or an atmospheric load lock; if necessary, they can be flipped to the correct orientation for analysis. These modifications do not hinder the tool from performing angle-resolved XPS measurements.
Unlike small-spot XPS tools that use a micro-focused X-ray beam, this tool uses a large-area X-ray flood source, combined with selectable apertures, to create a virtual X-ray probe. Small-area spectra can be acquired in spectroscopy mode from regions as small as 10 µm using an electrostatic deflection system to position the virtual probe anywhere on the sample. In parallel imaging mode, a direct chemical image or map of the surface with spatial resolution as small as 3 µm can be obtained without rastering the X-ray beam. Parallel images can thus be acquired more rapidly than traditional approaches to mapping, thereby reducing the potential for damage to samples sensitive to X-rays. A hemispherical analyzer and spherical mirror analyzer facilitate spectroscopy mode and parallel-imaging mode, respectively. A dual-anode Al and Ag X-ray source allows a wide range of core levels to be probed. An integrated sputter ion gun allows depth profile analysis.
- Analyzing surface composition qualitatively (Li through U) and quantitatively (about 0.1 at.%)
- Identifying chemical state and chemical environment
- Producing depth profiles to reveal bulk composition; non-destructive depth profiling uses angle-resolved XPS
- Generating chemical maps with fast XPS parallel imaging without X-ray beam rastering, with spatial resolution as small as 3 µm using a spherical mirror analyzer
- Creating combinatorial maps of select areas of a sample
- Determining band positions, alignments, Fermi edge, and work function
- System is a Kratos Axis Nova modified to accept 7"x7" platens and analyze full 157-mm x 157-mm platen area
- Chamber base pressure is <5x10-10 torr
- Virtual X-ray probe uses large-area X-ray flood source in combination with analyzer apertures
- Variable analysis areas in spectroscopy mode use select apertures as small as 10 µm
- Parallel imaging (chemical maps) from predefined fields of view that range from 950 µm x 950 µm (low magnification) down to 220 µm x 220 µm (high magnification). Larger maps can be done through image stitching.
- Al Kα and Ag La monochromatic radiation for XPS. Ag La source allows for increased information depth and probes deeper core levels.
- High-flux floating ion gun improves interfacial resolution and effective sputtering even at low ion-beam energies
- Self-regulating charge-compensation system facilitates analysis of insulators
- He-discharge lamp produces He (I) or He (II) radiation for UPS
- Standard load lock can be used for small sample entry, thereby bypassing pod and flipping station
- Two in-situ optical microscopes assist sample navigation and identification
- Angle-resolved XPS (ARXPS) uses separate small-sample platen
- Compucentric rotation (Zalar) is possible during depth profiles with separate small-sample platen
- Delay line detector (DLD) with 128 channels allows photoelectron detection in spectroscopy and imaging modes. "Snapshot" spectroscopy (without scanning the analyzer) is useful for dynamic surface characterizations.
- The system is highly automated, allowing the operator to define a sequence of analyses for multiple analysis areas using a variety of collection conditions.
- Bake-out shrouds are permanently fitted.
Contact Sally Asher for more details.