A new class of materials, organic semiconductors, has been developed for novel applications, such as large-area lighting and flexible displays, plastic solar cells or modern low cost devices. The device performance significantly depends on the properties of the interface layer between the organic semiconductor and the inorganic electric components. The focus in this contribution is put on the surface investigations of three different organic surface layers. Organosilane self-assembled oligolayers, i.e. thin layers of (Heptadecafluoro-1, 1, 2, 2-tetrahydrodecyl) trichlorosilane (PFDTS) and 2-(4-Chlorosulfonylphenyl) ethyltrichlorosilane (CSTS), are investigated. These are typically applied in Organic Thin Film Transistors (OTFTs) as interfacial layers and strongly influence the device performance. Using Atomic Force Microscopy (AFM), surface roughness parameters have been determined. Comparing the surface properties of layers formed by different methods, the preparation method in a glove box turns out to be the best method. Contact Angle measurements were used to follow the chemical modification of the surface. In addition, photosensitive organosilane surface layers - thin layers of (4-thiocyanatomethyl) phenyltrimethoxysilane (Si-SCN) - which can be easily photoisomerized by UV light and subsequently modified to form functionalized patterned surfaces, are investigated using Friction Force Microscopy (FFM). The applicability of FFM for the examination of chemically patterned surfaces is demonstrated and the friction contrast between modified and unmodified stripes of the patterned surface is revealed. The hierarchy of the friction coefficient of at least three different surface terminations could be identified. Through a Photo-Fries rearrangement, an acetic acid 4-(2-trichlorosilanyl-ethyl)-phenyl ester layer can form a patterned functionalized surface using lithographic techniques and post modification. FFM measurements have been utilized to detect chemical contrast on these patterned surfaces, too.