Corrales, Tomas P.Tomas P.CorralesBai, MengjunMengjunBaiDel Campo, ValeriaValeriaDel CampoHomm, PiaPiaHommFerrari, PieroPieroFerrariDiama, ArmandArmandDiamaWagner, ChristianChristianWagnerTaub, HaskellHaskellTaubKnorr, KlausKlausKnorrDeutsch, MosheMosheDeutschRetamal, Maria JoseMaria JoseRetamalVolkmann, Ulrich G.Ulrich G.VolkmannHuber, PatrickPatrickHuber2021-07-152021-07-152014ACS Nano 8 (10): 9954-9963 (2014)http://hdl.handle.net/11420/9911We present an experimental study of the micro- and mesoscopic structure of thin films of medium length n-alkane molecules on the native oxide layer of a silicon surface, prepared by dip-coating in a n-C32H66/n-heptane solution. Electron micrographs reveal two distinct adsorption morphologies depending on the substrate withdrawal speed v. For small v, dragonfly-shaped molecular islands are observed. For a large v, stripes parallel to the withdrawal direction are observed. These have lengths of a few hundred micrometers and a few micrometer lateral separation. For a constant v, the stripes quality and separation increase with the solution concentration. Grazing incidence X-ray diffraction and atomic force microscopy show that both patterns are 4.2 nm thick monolayers of fully extended, surface-normal-aligned alkane molecules. With increasing v, the surface coverage first decreases then increases for v > vcr ∼ 0.15 mm/s. The critical vcr marks a transition between the evaporation regime, where the solvents meniscus remains at the bulks surface, and the entrainment (Landau-Levich-Deryaguin) regime, where the solution is partially dragged by the substrate, covering the withdrawn substrate by a homogeneous film. The dragonflies are single crystals with habits determined by dendritic growth in prominent 2D crystalline directions of randomly seeded nuclei assumed to be quasi-hexagonal. The stripes strong crystalline texture and the well-defined separation are due to an anisotropic 2D crystallization in narrow liquid fingers, which result from a Marangoni flow driven hydrodynamic instability in the evaporating dip-coated films, akin to the tears of wine phenomenology.en1936-086X20141099549963American Chemical Society2D crystallizationatomic force microscopyMarangoni flowsn -alkanescanning electron microscopysiliconX-ray diffractionChemieJournal Article10.1021/nn5014534Other