Free-standing wire arrays prepared by holographic exposure and wet chemical deep etching on a vertically arrangedGaAs/GaInAs/GaAs[001]single quantum well structure were characterized by x-ray grazing incidence diffraction using synchrotron radiation. Using a grazing angle of&agr;i≈0.05°the diffracted intensity stems primarily from the surface grating. It’s periodicity(D≈480 nm)was determined close to the(−220)and(220)Bragg reflection being parallel and perpendicular to the orientation of wires, respectively. The average wire width [(21.6±1.5) nmand(96.6±1.5) nm, respectively] and the coherence length of the grating(&xgr;≈2 &mgr;m)were obtained via Fourier transformation of the(220)shape function. ©1997 American Institute of Physics.