X-Ray Photoelectron Spectroscopy (XPS), also known as Electron Spectroscopy for Chemical Analysis (ESCA), is a surface analysis technique used for obtaining chemical information about the surfaces of solid materials. Insulators and conductors can easily be analyzed from areas a few microns and larger. The method utilizes an x-ray beam to excite a solid sample resulting in the emission of photoelectrons. An energy analysis of these photoelectrons provides both elemental and chemical bonding information about the material comprising the sample surface. All elements, except hydrogen and helium can be detected.

In XPS analysis, the sample is placed in an ultrahigh vacuum environment and exposed to a low-energy, monochromatic X-ray source, x-ray excitation causes the emission of photoelectrons from the atomic shells of the elements present on the surface. The energy of these electrons is characteristic of the element from which they are emitted. By counting the number of electrons as a function of energy, a spectrum representative of the surface composition is obtained. The area under peaks in the spectrum is a measure of the relative amount of each element present, and the shape and position of the peaks reflect the chemical state for each element.

XPS is a surface sensitive technique because only those photoelectrons generated near the surface can escape and become available for detection. Due to collisions within the sample's atomic structure, those photoelectrons originating much more than about 20 to 100 Å below the surface are unable to escape from the surface with sufficient energy to be detected.

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Survey scan - Identifies the elemental composition of the uppermost 20 to 100 Å of analyzed surface.

High resolution multiplex scan - Measures the atomic concentrations of the elements identified in the survey scan. Detection limits are approximately 0.1 atom percent for most elements. This technique also measures the chemical environment of each element through its binding energies. Precise determination of binding energies are made through the use of curve-fitting routines. A NIST database is available for identifying binding energies with actual compounds.

Depth profile - Measures the distribution of elements as a function of depth into the sample. Depth resolution is dependent upon sample and sputtering parameters (< 100 Å resolution is possible).

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• Analysis of thin contamination films
• Measurement of elemental composition of insulating materials (e.g. polymers, glasses)
• Identification of the chemical state of elements (e.g. metal or oxide)
• Quantitative profiling of thin insulator layers

MODEL: PHI5400

Sample size cannot exceed 1 in. (25 mm) in any lateral direction. Height should not exceed 1/2 in. (12 mm). Must be compatible with high vacuum environment (<1x10 -9 Torr).

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