Explanation and correction of false step heights in amplitude modulation atomic force microscopy measurements on alkane films

Bai, Mengjun; Trogisch, S.; Magonov, Sergei; Taub, H.

doi:10.1016/j.ultramic.2008.03.009

Cited by 21 publications

(23 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The SDC method is described elsewhere. 23 With this simple technique, we obtained submonolayer films having morphology very similar to those obtained by spin coating but without coexisting bulk particles. 8,24 To determine the ellipsometric thickness of each SDC film, we measured the absolute P angle and compared it with the absolute P 0 angle for the clean substrate as described in the next section.…”

Section: A Materialsmentioning

confidence: 79%

“…Because of the small increase in thickness required to explain the step up with the "untilt" hypothesis it could be argued that the complementary techniques of x-ray reflectivity and AFM measurements do not have sufficient precision to observe such a small tilting effect and the related 0.74 Å thickness increase in the perpendicular monolayer. 4,14,15,23 Going one step further, we have to assume that the supposed tilted monolayer is stabilized for T Ͻ 331 K by some mechanism. An obvious argument for stabilization considers the molecules as snapped-in to their zig-zag conformation.…”

Section: Figmentioning

confidence: 99%

See 1 more Smart Citation

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

View full text Add to dashboard Cite

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.

show abstract

Section: A Materialsmentioning

confidence: 79%

Section: Figmentioning

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

View full text Add to dashboard Cite

show abstract

“…The image shows an island of adsorbed C32 having a "dragonfly" shape. Topographic cross-sections indicate the height of this feature to be ∼ 4.2 nm after calibration using the AFM contact mode [12,13] and X-ray specular reflectivity measurements [11]. Because this height is approximately equal to the all-trans length of the C32 molecule, we interpret the dragonfly feature as consisting of a single layer of molecules oriented with their long axis perpendicular to the surface.…”

Section: -P1mentioning

confidence: 92%

Nanoscale observation of delayering in alkane films

et al. 2007

View full text Add to dashboard Cite

-Tapping-mode Atomic Force Microscopy and synchrotron X-ray scattering measurements on dotriacontane (n-C32H66 or C32) films adsorbed on SiO2-coated Si(100) wafers reveal a narrow temperature range near the bulk C32 melting point T b in which a monolayer phase of C32 molecules oriented perpendicular to surface is stable. This monolayer phase undergoes a delayering transition to a three-dimensional (3D) fluid phase on heating to just above T b and to a solid 3D phase on cooling below T b . An equilibrium phase diagram provides a useful framework for interpreting the unusual spreading and receding of the monolayer observed in transitions to and from the respective 3D phases.

show abstract

“…At the microscopic viewpoint of surface science, the growth mechanism of n-alkane layers on SiO 2 surface has attracted increasing interest. [27][28][29][45][46][47] Both of theoretical simulation 47 and experimental measurements 48,49 confirmed such a structural model: one or two layers of C 32 H 66 are immediately adsorbed on the SiO 2 surface with the long axis of the molecule parallel to the interface; and then additional layers of molecules are standing upright with the molecules' long axis oriented perpendicularly and all-trans length. As we mentioned before, these two phases, representing two cases of monolayer formation, need thorough analysis.…”

Section: B Effect Of Bombardment On Thin Film Height and Molecular Dmentioning

confidence: 76%

Study of a hydrogen-bombardment process for molecular cross-linking within thin films

Liu¹,

Yang²,

Nie³

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

A low-energy hydrogen bombardment method, without using any chemical additives, has been designed for fine tuning both physical and chemical properties of molecular thin films through selectively cleaving C-H bonds and keeping other bonds intact. In the hydrogen bombardment process, carbon radicals are generated during collisions between C-H bonds and hydrogen molecules carrying ∼10 eV kinetic energy. These carbon radicals induce cross-linking of neighboring molecular chains. In this work, we focus on the effect of hydrogen bombardment on dotriacontane (C(32)H(66)) thin films as growing on native SiO(2) surfaces. After the hydrogen bombardment, XPS results indirectly explain that cross-linking has occurred among C(32)H(66) molecules, where the major chemical elements have been preserved even though the bombarded thin film is washed by organic solution such as hexane. AFM results show the height of the perpendicular phase in the thin film decreases due to the bombardment. Intriguingly, Young's modulus of the bombarded thin films can be increased up to ∼6.5 GPa, about five times of elasticity of the virgin films. The surface roughness of the thin films can be kept as smooth as the virgin film surface after thorough bombardment. Therefore, the hydrogen bombardment method shows a great potential in the modification of morphological, mechanical, and tribological properties of organic thin films for a broad range of applications, especially in an aggressive environment.

show abstract

Explanation and correction of false step heights in amplitude modulation atomic force microscopy measurements on alkane films

Cited by 21 publications

References 18 publications

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

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

Nanoscale observation of delayering in alkane films

Study of a hydrogen-bombardment process for molecular cross-linking within thin films

Contact Info

Product

Resources

About