Electron Spectrometer: Auger/Scanning Auger
Quick Specs
- Analyzer energy resolution: Resolution 0.5%
- 20-kV beam size: 13 nm
- 5-kV beam size: 33 nm
- Copper data (10 kV, 10 nA): Signal-to-noise: 650 Sensitivity: 500,000 counts per second
- X-ray detector: X-ray detection: 150-eV to 25-keV range Resolution: 130 eV
- Ion-sputtering rate: Approximately 1 nm/s
EMSL's model 680 Auger electron spectroscopy (AES)/scanning auger microprobe (SAM) is based upon a field-emission electron source and a cylindrical mirror analyzer. This instrument provides information about elemental composition of the outer surface of samples at very high magnifications (beam size down to 13 nm). It has the highest spatial resolution of any standard surface science instrument. Nano-scale structures, particles, and areas can be analyzed for composition. Additionally, this instrument can provide elemental maps of surfaces at very high magnification.
The electron beam size can be focused as small as 13 nm at 20 kV, although somewhat larger beams are typically used to collect AES data. Instrument features and capabilities include beam rastering, secondary electron map imaging, mapping, a sputter gun for specimen cleaning, depth profiling, and sample rotation to allow "Zalar" rotation during sputtering. The system is configured with an X-ray detector for near-surface analysis in combination with AES surface analysis. Given the surface sensitivity of the method, AES/SAM provides the smallest analysis volume of any standard analysis method; therefore, this technique is excellent for locating compositions of particulates, interfaces, and second phases.
System Configuration and Operational Overview
Sample Preparation and Handling
This instrument is equipped to handle both the standard Physical Electronics, Inc. (PHI) platen for the AES/SAM and EMSL specimen platens. The standard PHI holder is a disk that can accommodate samples up to 2 cm in diameter and up to 1.3 cm in height. A large PHI sample holder can accommodate samples up to 5 cm in diameter. Almost any vacuum-compatible specimen that fits within the x-y dimensions of the holder and is less than 1.3-cm thick can be analyzed. Insulating or beam-sensitive specimens require special consideration because of the electron-simulated technique. The instrument is equipped with an impact specimen fracture unit that can be used to open fresh surfaces in specimens (approximately 2.5-cm long and approximately 1/8-inch diameter or square). Ideally, the fracture sample should be notched 1.1 cm from one of its ends. For detailed specifications, please contact the equipment custodian.
The EMSL sample platen can hold specimens up to 2.5 cm in diameter, although small specimens (∼1 cm2) are preferred. This holder allows interconnection with other parts of the EMSL Sample Transfer System, which allows samples to be prepared and altered in several unique ways, including electrochemical or liquid exposure, plasma treatment, coating deposition, and processing by heating or cooling.
Specimen handling for surface analysis and vacuum work involves several considerations. Users not familiar with specific needs and requirements should contact EMSL staff or ASTM E-1078, Standard Guide for Sample Handling in Auger Electron Spectroscopy, X-ray Photoelectron Spectroscopy, and Secondary Ion Mass Spectrometry.
Samples must be vacuum compatible and no larger than the dimensions given in the preceding guidelines. In general, the samples should at least be semi-conducting; however, the system has been upgraded with a low-energy ion gun that allows for some charge neutralization on insulating samples. Fracture samples must be of the correct dimensions: 1/8 inch in diameter or in cross-section and 0.85 inch in length.
The laboratory is equipped with a variety of methods to cut and clean specimens prior to analysis or experiment. All laboratory and AES/SAM work must be performed in compliance with EMSL practices and permits.
Field Emission Gun
The field emission gun uses a Shottky Field Emitter to produce a finely focused, high intensity, stable electron source.
Analyzer
The energy analyzer consists of a cylindrical mirror analyzer and a multichannel detector. The multichannel detector provides enhanced sensitivity over a single channel cylindrical mirror analyzer by allowing the collection of several energy channels in parallel and has an overall gain of 106 to 107.
Imaging
The PHI 680 is equipped with a secondary electron detector to obtain scanning electron micrographs. Back-scattered electrons also can be used for sample imaging. Minimum beam size is 33 nm for 5-kV electrons and 13 nm for 20-kV electrons.
Ion Gun
The instrument is equipped with a PHI Model 06-350E argon ion source for sputter cleaning of the sample and for depth-profiling of layered materials. Sputtering rates of 1 nm/sec are typical but adjustable. Independent horizontal and vertical rastering may be used to cover an area of up to 1 cm2. This ion gun features a floating column design that generates high-current densities at low-beam energies and has the capacity for low-energy ion neutralization of charging materials.
X-Ray Detector
An energy dispersive X-ray detector (Noran 958A-ISES) with an energy resolution of 130 eV is mounted to the chamber to provide bulk atomic sample analysis. X-rays in the energy reange 150eV to keV are detectable.
Data Collection
A PC computer, interfaced to the AES/SAM, controls the instrument, collects data, and provides data analysis. A Sun SPARCstation collects energy-dispersive X-ray data, provides data analysis, and maintains control of the X-ray detector.
Fracture Stage
The AES/SAM is equipped with a fracture stage to provide in vaccuo fracture analysis of samples. A liquid nitrogen dewar attachment is available, allowing for cold temperature sample fracture.
EMSL Transfer Capability
The PHI 680 has an optional EMSL transfer arm that can accommodate EMSL platens. When attached, this transfer arm can manipulate samples to a number of other systems under controlled atmospheric conditions, e.g., ultrahigh vacuum or inert gas, via the EMSL Transfer System.
Research Applications
Recognized and established research applications include the following:
- Nanodots, quantum dots, and nanodevices
- Thin-film analysis (semiconductors, magnetic storage, and spintronics)
- Metal grain boundary analysis and corrosion analysis
- Atmospheric particles.
This equipment is available to external users after extensive training. However, it is recommended that users collaborate with the equipment custodian for best results.
All Related Publications Related Publications
- Characterization Challenges for Nanomaterials.
- Tilted domain growth of metalorganic chemical vapor (MOCVD)-grown ZnO(0001)on a-Al2O3(0001).
- A New Mechanism for Ozonolysis of Unsaturated Organics on Solids: Phosphocholines on NaCl as A Model for Sea Salt particles.
- Shared and closed-shell O-O interactions in silicates.
- Rapid synthesis and size control of CuInS2 semi-conductor nanoparticles using microwave irradiation.
