Ellipsometric Study of Multilayer Growth and Wetting of C2Cl2F4 Physisorbed on Graphite

Volkmann, U.G.; Mannebach, H.; Knorr, K.

doi:10.1021/la971049u

Cited by 7 publications

(10 citation statements)

References 22 publications

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“…9 Briefly, it employs the PCSA configuration ͑polarizer, Soleil-Babinet compensator, sample, analyzer͒. After passing through a polarizer and compensator, light from a He-Ne laser ͑wavelength ϭ6328 Å͒ is incident on the sample at an angle of 60°to the surface normal and illuminates an area of ϳ1 mm 2 .…”

Section: Methodsmentioning

confidence: 99%

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Volkmann

Pino

Altamirano

et al. 2002

The Journal of Chemical Physics

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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-C 32 H 66 ) films adsorbed from a heptane (n-C 7 H 16 ) solution onto SiO 2 -coated Si͑100͒ single-crystal substrates. Our results suggest a model of a solid dotriacontane film that has a phase closest to the SiO 2 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 T b ϭ341 K, solid bulk particles coexist on top of the ''perpendicular film.'' For higher temperatures in the range T b ϽTϽT s where T s ϭ345 K is the wetting temperature of the bulk phase, the coexisting bulk particles melt into droplets; and for TϾT s , a uniformly thick fluid film wets to the parallel film phase. This structure of the alkane/SiO 2 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/SiO 2 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 SiO 2 .

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Section: Methodsmentioning

confidence: 99%

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Volkmann

Pino

Altamirano

et al. 2002

The Journal of Chemical Physics

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“…These angles are valid for a null-ellipsometer setup with the incident angle and wavelength given in Table I. 22 We used two different methods to grow the films: ͑a͒ slow dip coating ͑SDC͒ at room temperature in a C32/ heptane solution and ͑b͒ physical vapor deposition ͑PVD͒. The SDC method is described elsewhere.…”

Section: A Materialsmentioning

confidence: 99%

“…The ellipsometer setup has been described previously. 16,22 Briefly, we use a null-PCSA configuration 25 with a fixed wavelength 0 and fixed angle of incidence , whose values are given in Table I. The resolution of the apparatus is of the order of 10 −3 deg in the polarizer angle, which is achieved by using a Faraday glass placed between the polarizer and the compensator and controlled by an electronic feedback loop.…”

Section: B Ellipsometrymentioning

confidence: 99%

Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces

Cisternas

Corrales

Campo

et al. 2009

The Journal of Chemical Physics

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Crystalline-to-rotator phase transitions have been widely studied in bulk hydrocarbons, in particular in normal alkanes. But few studies of these transitions deal with molecularly thin films of pure n-alkanes on solid substrates. In this work, we were able to grow dotriacontane ͑n-C 32 H 66 ͒ films without coexisting bulk particles, which allows us to isolate the contribution to the ellipsometric signal from a monolayer of molecules oriented with their long axis perpendicular to the SiO 2 surface. For these submonolayer films, we found a step in the ellipsometer signal at ϳ331 K, which we identify with a solid-solid phase transition. At higher coverages, we observed additional steps in the ellipsometric signal that we identify with a solid-solid phase transition in multilayer islands ͑ϳ333 K͒ and with the transition to the rotator phase in bulk crystallites ͑ϳ337 K͒, respectively. After considering three alternative explanations, we propose that the step upward in the ellipsometric signal observed at ϳ331 K on heating the submonolayer film is the signature of a transition from a perpendicular monolayer phase to a denser phase in which the alkane chains contain on average one to two gauche defects per molecule.

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“…(62) Optical techniques are useful over a wide range of ambient conditions, can be extremely sensitive and offer real-time detection. (63)(64)(65) A number of different optical techniques have been developed to study surfaces. For example, infrared (IR) spectroscopy is widely applied to investigate adsorbates on both metal and semiconductor surfaces.…”

Section: Optical Surface Probesmentioning

confidence: 99%

“…Optical differential reflectance (ODR) is an optical technique that has been applied to investigate adsorption and desorption on surfaces, resulting in estimation of coverage from optically determined film thickness. (65,71) This technique uses the small change induced in the reflectivity when a molecule adsorbs onto the surface. (72,73) ODR has been used to investigate adsorption and desorption kinetics of a chemisorbed species, CO, on a metal surface, Cu(100), at visible wavelengths (632 nm) under ultra high (71) , and NO on Cu(111).…”

Section: Optical Surface Probesmentioning

confidence: 99%

Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of Vapor-Phase Mercury Uptake by Carbonacoues Surfaces

Vidić¹

2002

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Ellipsometric Study of Multilayer Growth and Wetting of C₂Cl₂F₄ Physisorbed on Graphite

Cited by 7 publications

References 22 publications

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

High-resolution ellipsometric study of an n-alkane film, dotriacontane, adsorbed on a SiO2 surface

Crystalline-to-plastic phase transitions in molecularly thin n-dotriacontane films adsorbed on solid surfaces

Combined Theoretical and Experimental Investigation of Mechanisms and Kinetics of Vapor-Phase Mercury Uptake by Carbonacoues Surfaces

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