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X Ray Diffraction for Identifying Epitaxy Single Crystal Thin Film

IP.com Disclosure Number: IPCOM000076163D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Tu, KN: AUTHOR

Abstract

A procedure has been devised for testing the crystalline structure of a thin film, using the Seeman-Bohlin X-ray diffraction system, in order to determine whether that crystalline structure is a single crystal, without the need to separate the film from its substrate.

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X Ray Diffraction for Identifying Epitaxy Single Crystal Thin Film

A procedure has been devised for testing the crystalline structure of a thin film, using the Seeman-Bohlin X-ray diffraction system, in order to determine whether that crystalline structure is a single crystal, without the need to separate the film from its substrate.

It is known that the Seeman-Bohlin diffractometer is suitable for polycrystalline thin film studies. This diffractometer uses monochromatic CuK alpha radiation (lambda=1.542 angstroms) which is emitted at a low incident angle alpha=6.4 degrees onto the thin film under study. Although such diffractometer was not built originally for studying single-crystal films, nevertheless it can be set to detect them provided their crystalline structure is given. The prerequisite of the setting of the diffractometer is a programmed calculation based on the wavelength lambda of the radiation, the incident angle alpha, and the crystalline orientation of the substrate.

In order to identify an epitaxial single-crystal film, the following steps are followed: 1) Determine the orientation of the substrate by its Laue picture.

2) Assuming that a single-crystal film has the same orientation as its substrate, the epitaxially grown film has a crystal plane (HKL) determined by the orientation of its substrate. In general, crystal plane (HKL) is a low index of minimum surface free energy.

3) Since the structure of the crystalline film and the wavelength lambda of the x-ray radiation are known, all the positions theta(hkl) of its reflections can be calculated. The values of theta(hkl-) gamma, where gamma is the incident radiation equal to 6.4 degrees and lambda=1.542 angstroms. These calculated values are listed in Table I.

4) Since theta(hkl)-gamma equals the angle between the deposited thin film surface and its (hkl) plane, then one can match any one of the values of theta(hkl)-gamma within a range of +/-3 degrees with the corresponding angles between (HKL) and (hkl)...