Looking 100 Å deep into spatially inhomogeneous dilute systems with hard X-ray photoemission

We present hard x-ray photoemission measurements from GaAs samples with a 10-Å-thick layer of AlAs buried at different depths. The intensity trend versus kinetic energy of the Al 1s signal allows extraction of the x-ray attenuation length, which we find to reach ,100 Å at a kinetic energy of 6 keV. On one sample exposed to air for several days we obtain qualitative information on the oxidation at different depth scales by exploiting the energy dependence of the attenuation length. This suggests the strong potential of hard x-ray photoemission in the nondestructive characterization of diluted materials on a depth scale interesting to modern nanotechnologies.