Various amounts of H-termination on a Ge surface were prepared by dipping a Ge wafer in differentially diluted hydrofluoric acid solutions for different periods of time. Formation of Ge-H-x in hydrofluoric acid and its disappearance in hydrochloric acid (HCl) were directly measured by using multiple internal reflection Fourier transform infrared spectroscopy (MIR FT-IR). Peak intensity of Ge-H, vibration mode was increased with diluted hydrofluoric acid (DHF) treatment time and the concentration of HF solution. Therefore, it is suggested that microroughness of a Ge surface changes depending on the concentration of HE Peak intensity of Ge-H-x vibration mode was reduced when the Ge-H-x surface was treated in HCl solution. With an increase in HCl treatment time, peak intensity of Ge-H-x vibration mode was reduced. Ge surfaces treated in a more diluted HF solution were barely modified, because it was thought to have fewer kink sites, dihydrides and trihydrides. (C) 2007 Elsevier B.V. All rights reserved.