Browse Prior Art Database

Electron Diffraction System for Growth Rate Measurement during Molecular Beam Epitaxy

IP.com Disclosure Number: IPCOM000109073D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Jackson, T: AUTHOR [+3]

Abstract

Disclosed is a method for using a simple, low-energy electron diffraction (LEED) system to make growth rate measurements during molecular beam epitaxy. Measurements can be made during substrate rotation and coupled to the flux sources for growth of lattice-matched alloys.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Electron Diffraction System for Growth Rate Measurement during Molecular Beam Epitaxy

       Disclosed is a method for using a simple, low-energy
electron diffraction (LEED) system to make growth rate measurements
during molecular beam epitaxy.  Measurements can be made during
substrate rotation and coupled to the flux sources for growth of
lattice-matched alloys.

      A commonly used technique for measurement of growth rate in
molecular beam epitaxy is by recording the oscillations in the
reflection electron diffraction (RED) pattern.  The oscillation
period corresponds to the deposition of one monolayer.  Both the
growth and diffraction conditions must be carefully controlled to
obtain strong oscillations.  In particular, the strength of the
oscillations is strongly dependent upon the incident angle of the
electron beam.  The best signal is obtained at low incident angles of
2-4 degrees, and with  the incident angle maintained within 0.1
degree of an angle which corresponds to an "off-Bragg" condition.
The oscillation signal also depends upon the azimuthal angle of the
electron beam in a complex way, depending upon the step direction and
reconstruction of the surface.  Data are taken from a single azimuth,
and the growth rate which is measured is an average along the stripe
on the surface which is intersected by the beam.  Typically, only a
limited number of oscillation periods are measured because they damp
out.  The damping is due to natural growth processes taking place on
the surface, nonuniform growth rate, and electron beam wandering
during the measurement.  Because the incident beam is at glancing
angle to the substrate surface, it would be extremely difficult to
perform oscillation measurements during substrate rotation.  Aside
from the complications in deconvolving the data, only a slight amount
of wobble in the substrate rotation would wash out the diffraction
conditions for strong oscillations.

      Described here is an alternate approach which circumvents a
number of these difficulties, and which provides a simple method for
feedback control of fluxes. The system consist of a low-...