dc.contributor.author | Volkmann, Ulrich G. | eng |
dc.contributor.author | Pino, M. | eng |
dc.contributor.author | Altamirano, L. A. | eng |
dc.contributor.author | Taub, Haskell | eng |
dc.contributor.author | Hansen, Flemming Y. | eng |
dc.date.issued | 2002 | eng |
dc.description | doi:10.1063/1.1429645 | eng |
dc.description.abstract | Using high-resolution ellipsometry and stray light intensity measurements, we have investigated during successive heating-cooling cycles the optical thickness and surface roughness of thin dotriacontane (n-C32H66) films adsorbed from a heptane (n-C7H16) solution onto SiO2-coated Si(100) single-crystal substrates. Our results suggest a model of a solid dotriacontane film that has a phase closest to the SiO2 surface in which the long-axis of the molecules is oriented parallel to the interface. Above this "parallel film" phase, a solid monolayer adsorbs in which the molecules are oriented perpendicular to the interface. At still higher coverages and at temperatures below the bulk melting point at Tb = 341 K, solid bulk particles coexist on top of the "perpendicular film." For higher temperatures in the range Tb<T<Ts where Ts = 345 K is the wetting temperature of the bulk phase, the coexisting bulk particles melt into droplets; and for T>Ts, a uniformly thick fluid film wets to the parallel film phase. This structure of the alkane/SiO2 interfacial region differs qualitatively from that which occurs in the surface freezing effect at the bulk alkane fluid/vapor interface. In that case, there is again a perpendicular film phase adjacent to the air interface but no parallel film phase intervenes between it and the bulk alkane fluid. Similarities and differences between our model of the alkane/SiO2 interface and one proposed recently will be discussed. Our ellipsometric measurements also show evidence of a crystalline-to-plastic transition in the perpendicular film phase similar to that occurring in the solid bulk particles present at higher coverages. In addition, we have performed high-resolution ellipsometry and stray-light measurements on dotriacontane films deposited from solution onto highly oriented pyrolytic graphite substrates. After film deposition, these substrates proved to be less stable in air than SiO2. | eng |
dc.description.sponsorship | This work was supported by the Chilean government under CONICYT Grant No. 018/AT/005NSF and FONDECYT Grant No. 1980586 and by the U.S. National Science Foundation under Grant Nos. INT-9605227, DMR-9802476, and DMR-0109057. | eng |
dc.identifier.citation | J. Chem. Phys. 116, 2107 (2002) | eng |
dc.identifier.issn | 0021-9606 | eng |
dc.identifier.uri | http://hdl.handle.net/10355/8763 | eng |
dc.language | English | eng |
dc.publisher | American Institute of Physics | eng |
dc.relation.ispartof | Missouri Research Reactor publications (MU) | eng |
dc.relation.ispartofcommunity | University of Missouri--Columbia. University of Missouri Research Reactor Center | eng |
dc.subject.lcsh | Silicon compounds | eng |
dc.subject.lcsh | Organic compounds | eng |
dc.subject.lcsh | Thin films | eng |
dc.subject.lcsh | Ellipsometry | eng |
dc.title | High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface | eng |
dc.type | Article | eng |