Abstract

Monochromatic soft x-rays can be utilized as a nondestructive probe of microscopic structure in heterojunctions by measurement of the angular dependence of their reflectivity, total electron yield (TEY), and fluorescence yield (FY). Interference between the x-rays incident and reflected from the buried interface creates modulation in the radiant energy distribution, which results in the characteristic oscillation pattern in the angular profile of the scattered radiation. The angular dependence of TEY and FY maps the integrated electromagnetic field depth distribution weighted by the soft x-ray photon attenuation length (for FY) or the secondary electron mean free path (for TEY) in the investigated material. The interaction of the soft x-rays with the stratified media is described by the optical electromagnetic wave solution to the Fresnel equations on each interface.¹ Heterojunctions grown by molecular beam epitaxy were investigated by means of reflectivity and TEY at the U15 beamline of the National Synchrotron Light Source at Brookhaven National Laboratory. By fitting the experimental data to the model, the layer thickness, surface and interfacial rms roughness parameter, and refractive index were obtained. This demonstrates the use of the optical model of x-ray interaction with heterojunctions, and the value of reflectivity and total electron yield as a tool for the study of layered systems.

© 1989 Optical Society of America