We have used coaxial impact-collision ion scattering spectroscopy (CAICISS) and time-of-flight elastic recoil detection analysis (TOF-ERDA) to investigate the adsorption of atomic hydrogen on the 6H-SiC(0 0 0 1)root3 x root3 surface. It has been found that the saturation coverage of hydrogen on the 6H-SiC(0 0 0 1)root3 x root3 surface is about 1.7 ML. Upon saturated adsorption of atomic hydrogen, the root3 x root3 surface structure changes to the 1 x 1 structure. The data of the CAICISS measurements have indicated that as a result of the hydrogen adsorption, Si adatoms on the root3 x root3 surface move from T-4 to on-top sites. O 2001 Elsevier Science B.V. All rights reserved.