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X-ray investigation of a near surface layer of metal samples

: Gilev, O.N.; Asadchikov, V.E.; Duparre, A.

Al-Jumaily, G.A.; Duparre, A.; Singh, B. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical Metrology Roadmap for the Semiconductor, Optical, and Data Storage Industries
Bellingham/Wash.: SPIE, 2000 (SPIE Proceedings Series 4099)
ISBN: 0-8194-3744-1
Conference "Optical Metrology Roadmap for the Semiconductor, Optical, and Data Storage Industries" <2000, San Diego/Calif.>
Fraunhofer IOF ()
x-ray scattering; roughness; near surface layer

It is demonstrated that the simplest model of a surface, assuming step-like variation of the dielectric permeability at a vacuum-matter interface, does not permit the quantitative description of all the features of x-rays reflection and scattering observed in experiment, even though the effects of the surface roughness are taken into consideration accurately. These features are much more pronounced for metals having a large number of the conductivity electrons which are bound slightly with individual atoms. Evidently, the wavefunction of the electron gas of a metal cannot abrupt sharply at a surface but decreases gradually into vacuum at a distance of several angstroms. To validate or disprove the hypothesis for the presence of a near surface transition layer of the electron density in metals, a set of experiments is performed. Reflection and scattering of hard and soft x-rays, and cold neutrons (which are sensitive to nuclear density distribut ion and insensitive to the electron one) from metal samples are measured. The independent measurements of the surface microtopography are performed with the use of atomic force microscopy. The results obtained demonstrate the presence of a near surface layer, which is caused by gradual change of electron density, with a thickness of several angstroms.