The photochemical grafting of methyl groups onto an n-type Si(1 1 1) substrate was successfully achieved using a Grignard reagent. The preparation involved illuminating a hydrogen-terminated Si(1 1 1) that was immersed in a CH3MgBr-THF solution. The success was attributed to the ability of the n-type hydrogenated substrate to produce holes on its surface when illuminated. The rate of grafting methyl groups onto the silicon surface was higher when a larger illumination intensity or when a substrate with lower dopant concentration was used. In addition, the methylated layer has an atomically flat structure, has a hydrophobic surface, and has electron affinity that was lower than the bulk Si. (C) 2013 Elsevier Inc. All rights reserved.