REAL-TIME CHARACTERIZATION OF EPITAXIAL GROWTH USING GLANCING-ANGLE IONS

Scott A. Barnett, Paul DeLuca, and Kurt Ruthe

Department of Materials Science and Engineering, Northwestern University,

Evanston, IL 60208

A new technique for characterizing surfaces and epitaxial growth is described. The technique involves measuring the specularly scattered component of a glancing-incidence-angle ion beam. Since specular ion reflection requires a locally-flat surface, changes in the specularly scattered ion current provides a quantitative measure of time-dependent surface defect populations. A glancing-incidence beam is needed to obtain a strong specular reflection, and it also minimizes sputtering and damage caused by the beam. In the examples to be discussed, GaAs and InGaAs(001) surfaces were characterized in a molecular beam epitaxy chamber using 2-4 keV He or Ar ions, typically impinging at 1-3 from the surface plane. A few applications of the technique will be discussed. First, ion-current oscillations are observed that provide accurate growth rate information as well as quantitative information about growth processes. Second, measurements during step-flow growth on vicinal surfaces provide information on surface diffusion coefficients. Third, nucleation and subsequent coarsening of two-dimensional islands can be quantified in real time. Fourth, ion-enhanced diffusion can be induced and measured directly for sufficiently high ion currents.