Surface Analysis

• Faculty Advisor: C. Sung, Department of Chemistry
• Supervisor: D.Oblas
• Graduate Students : Arvind Viswanathan, Frank Yang, Shaobao Shui

X-Ray Photoelectron Spectrometry - XPS

Surface chemistry of metals, semiconductors, insulators, powders and vacuum and x-ray stable polymers by a nondestructive technique. Compositional information is obtained from the first 20 Angstroms of the surface with detection limits in the range of .5%

Instrument: Fisons Instruments, ESCALAB II
Features: The instrument utilizes a high resolution, hemispherical,electron energy analyzer with easily interchangeable Al & Mg X-ray anodes. Analyzer energy resolution is approximately 0.8 eV. Analytical information is collected from a sample area of about 3 mm in diameter, adjustable down to ~ 200 µm. Detection is accomplished with a 5 channel electron detector for improved sensitivity. The sample can be heated in introduction chamber (to ~ 800 degrees C) or cooled (to ~ -195 degrees C) and a Ar ion sputter gun is used for cleaning sample surfaces in-situ, prior to analysis. Overlapping spectral lines can be resolved using a deconvolution algorithm which allows for easier data interpretation. A CCD video camera with a magnification of 250x is available for viewing the sample and locating the region of interest.

Applications:

• Characterization of polymer films and components
• Effects of treatment on surface of metals, polymers, semiconductors, ceramics
• Oxidation state of metal and semiconductor films
• Surface composition of thin films

Secondary Ion Mass Spectrometry - SIMS

Surface composition of metals, semiconductors, insulators and vacuum stable polymers with detection sensitivity all in the parts per million range. All elements are detectable and spatial resolution is about 2 microns

Instrument: Fisons Instruments, SIMSLAB I (Upgraded)
Features: The SIMS LAB is a quadrupole based instrument with a mass range of 1-800 amu. Any one of three ion sources is available as the primary ion beam:Ga liquid metal ion source for imaging, a Cs ion source for electronegatives and an O2 duoplasmatron ion source for a wide range of sample problems covering metals, semiconductors. SIMS experiments can be carried out in several different modes: depth profiling, survey scanning , line scanning, and 3-dimensional imaging.

The instrument is retrofitted with the latest in transfer optics, the HTO 2000, for optimizing collection and transmission of the secondary (positive or negative) ions. There is also capability for doing secondary neutral mass spectrometry (SNMS). This mode of operation, in principle, allows for obtaining semiquantitative results by circumventing the effects due to the wide range in sensitivity factors of the secondary ion yields among the elements. A scanning electron flood gun allows the analysis of nonconducting samples, such as silica glass. A stylus profilometer is used for measuring crater depths after depth profiling in order to establish sputtering rates and also for determining film thickness, as well.

Applications:

• Depth profiles of ion implanted semiconductors, metals and ceramics
• Depth profiles of multi-layer, optical coatings on glass
• Spatial and in depth distributions of elements by imaging
• Depth profile of ternary/quaternary quantum well structures on GaAs
• Relative hydrogen content in CVD grown diamond thin films
• Cross sectional distribution of elements by line scanning
• Surface composition of processed materials: metals, semi- conductors, ceramics, polymers