Atomic force microscopy on bare and thiol monolayer covered gallium arsenide

In this work, we study the functionalized gallium arsenide (GaAs) surface w ith self-assembled monolayer (SAM) by means of atomic force microscopy (AFM ). First, we study the flatness of the dummy GaAs surface through AFM in el ectrolyte. Second, with the same technique, we study the effect of SAMs of octadecanethiol (C18H37SH) and alcohol-thiol (HOCH2(CH2)(10)SH) on GaAs sur face. Finally, for GaAs treated with octadecanethiol monolayer, we observe a hysteresis-demonstrating that the surface is hydrophobic and that the Van der Waals interaction between the tip and the sample is very high. GaAs tr eated with alcohol-thiol shows hysteresis, which shows that the surface is hydrophilic and uncharged. (C) 2001 Elsevier Science B.V. All rights reserv ed.