A comparative study of the frictional properties of alkanethiols and alkylsilanes as a function of chain length is presented. The monolayers were produced by self-assembly on Au(111) and mica, respectively. The same tip was used for all the experiments, and freshly cleaved mica was used as a reference. For both types of films, the frictional forces depend strongly on the number of carbon atoms in the alkane chain (CH3−(CH2) n - 1−R). Thiols and silanes give rise to similar frictional force for the same n when n > 11, while for n < 11 the behavior is markedly different; the silanes exhibit higher friction, larger than that for the thiols by a factor of ∼3 for n = 6. The increase in friction is attributed to the increased disorder that occurs when going from a thiol to a silane anchor or when decreasing n. It is proposed that disorder favors the increase of the number and type of low-energy modes (kinks, bending, distortions) that are available for excitation and energy dissipation.

The structure of water films on mica was locally modified by contact with the tip of an atomic force microscope (AFM) in a humid environment. The subsequent evolution of the film was studied by noncontact scanning polarization force microscopy. At high relative humidity (>20%), capillary condensation caused water to form droplets and two-dimensional islands around the contact point. The droplets evaporated in a short period of time, but the islands remained for much longer periods (hours). At low relative humidity (<20%), the tip contact produced a circular depression in the local polarizability. None of these structures could be observed in contact AFM images which revealed only the usual atomically flat mica surface.

Biological matrices can direct the absolute alignment of inorganic crystals such as calcite. Cooperative effects at an organic-inorganic interface resulted in similar co-alignment of calcite at polymeric Langmuir-Schaefer films of 10,12-pentacosadiynoic acid (p-PDA). The films nucleated calcite at the (012) face, and the crystals were co-aligned with respect to the polymer's conjugated backbone. At the same time, the p-PDA alkyl side chains reorganized to optimize the stereochemical fit to the calcite structure, as visualized by changes in the optical spectrum of the polymer. These results indicate the kinds of interactions that may occur in biological systems where large arrays of crystals are co-aligned.

Polymerized thin films based on polydiacetylenes (PDAs) undergo distinct color transitions that lend themselves to applications in biosensing, surface modification, nonlinear optics, and molecular electronics. The mechanism of the thermochromic blue to red color transition of PDA thin films was investigated at the molecular level using atomic force microscopy and at the macroscopic level with visible absorption and Fourier transform infrared spectroscopy. The thermochromic transition temperature is found to be between 70 and 90°C. At the molecular level, the ordering of the film increases at the thermochromic transition and remains ordered up to temperatures well above the transition (e.g., 130°C). No evidence for previously suggested entanglement or disordering of the alkyl side chains is observed. The pendant side chains rearrange from a partially disordered configuration characteristic of the blue film, to a well-ordered closepacked hexagonal arrangement in the red form. The rearrangment of the pendant side chains is linked to the formation of the red phase PDA.

Atomic force microscopy (AFM) has been used to study the effect of pressure on the structural and frictional properties of self-assembled monolayers of n-octadecanethiol on Au(111). Sharp microfabricated silicon nitride tips (tip radii 100-300 Å) were used. At low load, the periodicity of the thiol layer is imaged. At higher load, the layer is observed to become disordered. At a critical contact pressure of ∼2.3 GPa, a transition from the thiol overlayer to the Au(111) substrate periodicity is observed in the lattice resolution images. This transition is gradual and reversible. During the transition, frictional forces first increase and then decrease as the tip-sample separation decreases by a distance approximately equivalent to the thickness of the thiol layer.

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Imaging of organic molecular films using a scanning near-field optical microscope combined with an atomic force microscope J.Despite decades of study, the exact mechanism for chromatic transitions in polydiacetylene materials remains somewhat elusive. The mechanism of the blue to red color transition for overcompressed mixed lipid thin films of 10,12 pentacosadiynoic acid has been investigated by atomic force microscopy. Blue layers were prepared by the horizontal Langmuir-Schaefer deposition method. The red form was attained by thermal annealing of blue films ͑thermochromism͒. The blue films reveal micro-sized domains. Each domain shows a stripelike morphology on top of a nearly complete layer. The polymer backbone direction shows a high degree of order. A partial disorder is shown to exist along the interbackbone direction. Our study of the red form films indicates that changes occur in the micron-scale morphology of the films. Interestingly the alkyl side chains rearrange into a completely ordered structure and remain ordered well beyond the transition temperature ͑70°CϽTϽ90°C͒. Our results strongly suggest that the reorganization of the side chains is the origin of the thermochromic effect for these films.

The need to print smaller features and tighter pitches drives the development of new photolithography technologies. Extreme Ultraviolet Lithography (EUVL) at 13.5 nm wavelength is expected to provide considerable resolution gain over the current technology based on 193 nm wavelength. In this paper we assess the current status of EUV photoresists and their readiness for EUVL insertion into High Volume Manufacturing (HVM). In addition, we discuss the requirements that EUV photoresists will need to satisfy in the near and long term future.