The alignment mechanism of liquid crystals on polymeric surfaces that were patterned using an atomic force microscope ͑AFM͒ tip was studied by polarizing optical microscopy. Depending on the thickness of the polymer, polymer chain alignment or grooves appear to be responsible for the liquid crystal alignment. In thick polymer films ͑above 100 nm͒ the polymer chains will align in the direction of the scan due to the large lateral force exerted by the tip. In thin polymer films ͑5-20 nm͒ the polymer chains are strongly fixed to the surface and will not realign by the tip; instead grooves will be formed. The azimuthal surface anchoring the energy of thick polymer films does not depend on the scan line separation and scan force, is of the same order of magnitude as for conventionally rubbed polyimide surfaces, but increases by the number of scans. AFM patterned pixels do not show a pretilt angle.

Surface optical second-harmonic generation measurements were used to determine the change in the surface density and the surface orientational order parameter of the trans-cinnamoyl side groups of unidirectionally photopolymerized poly͑vinyl cinnamate͒ ͑PVCN͒ films. The observed surface features were compared to the bulk properties of the films, which were probed by their UV absorption spectra and birefringence measurements. We found that the surface and the bulk photoreaction kinetics of the trans cinnamoyl side groups of the PVCN are very similar. The two photoreaction processes ͑trans-cis photoisomerization and photo-induced cross linking͒ appear to affect the linear and nonlinear optical properties of the polymer differently. This may explain the discrepancy between the birefringence and the azimuthal anchoring force of the unidirectionally photopolymerized PVCN. ͓S1063-651X͑99͒06909-3͔

We have prepared a grooved indium tin oxide ͑ITO͒ surface with groove widths of ϳ40-90 nm and a variable groove separation up to 36 m using atomic force microscopy nanolithography. Twisted nematic pixels with 4-n-pentyl-4-cyanobiphenly ͑5CB͒ liquid crystal were prepared using a rubbed polyimide counter plate. The 5CB molecules align along the direction of the grooves, but no pretilt angle was observed on the ITO surface. The surface anchoring energy appeared not to depend on the groove separation nor on the scan force. The lateral correlation length of 5CB on ITO was measured to be 2.2 m. If a grooved surface is scanned in another direction, liquid crystal molecules follow the direction of the last scan.In liquid crystal displays ͑LCDs͒ liquid crystal molecules should be aligned in order to have a collective response to an electric field over a large area. Presently, the most common method of alignment is accomplished by the rubbing of a thin polymer film that is coated on a thin conductive electrode on a glass substrate. The detailed structure of the polymer alignment layer determines the anchoring strength and the pretilt angle of the liquid crystals. 1,2 The question with large practical implications is: would it be possible to merge two separate layers that are used for alignment and electrode into one conductive alignment layer? To achieve this, one might consider alignment on conductive polymer films or using conductive oxides. In this letter we will discuss the second approach.Indium tin oxide ͑ITO͒ is the most popular electrode for liquid crystal displays due to its high optical transparency and relatively good electrical conductivity. Depending on the method of preparation, ITO films can have different surface structures, conductivity and transparency. If ITO is prepared by rf sputtering, the resulting film usually will have a granular structure. The ITO surface is much harder than the polymer surface. Therefore, conventional methods that are used for rubbing polymer films can hardly deform the surface of ITO. Attempts to align liquid crystal molecules on rubbed ITO films lead to a very weak alignment. 3 Following our former approach to study the alignment of LC molecules on nanopatterned polymer surfaces, 4 we have performed a series of experiments to study the alignment of LC molecules on nano patterned ITO surfaces using the tip of an atomic-force microscope ͑AFM͒. We have found that a good alignment of LC molecules on submicron patterned ITO surfaces can be obtained, with an azimuthal anchoring energy that is comparable to that of rubbed polymer films like polyimide ͑PI͒. However, in contrast to rubbing no pretilt angle is found by the AFM technique.Indium tin oxide coated glass was purchased from Applied Film Corporation 5 and consisted out of 19 nm ITO coated by rf sputtering over a polycrystalline SiO 2 ͑20 nm͒ layer on a 1.1 mm sodalime glass substrate. The ITO layer had a granular structure with grain size of the order of 5-10 nm and was polished by the manufacturer to obtain optical quality for...

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