Fluorescent Trimeric Liquid Crystals: Modular Design of Emissive Mesogens
✍ Scribed by A. C. Sentman; D. L. Gin
- Publisher
- John Wiley and Sons
- Year
- 2001
- Tongue
- English
- Weight
- 188 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0935-9648
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✦ Synopsis
The substrates were small pieces cut from different, polished, p-doped silicon wafers (specific resistivity 0.1± 150 X cm; the different doping levels had no influence on the charge storage behavior). The pieces were cleaned for 2 min in an air plasma before coating. The plasma was generated by a 2 kV pp alternating current (AC) signal at frequency 10 kHz and pressure 5 10 ±2 hPa. The thickness of the fluorocarbon layer was controlled by the duration of the process (here between 1 min and 1 h) which resulted in layers of a few to several hundreds of nanometers. The so produced material is a polymerized network of fluorocarbon monomers as determined by X-ray photoelectron spectroscopy (XPS) measurement data [16]. The physical properties of this layer are similar to PTFE. The solvent for the silica beads was Fluorinert FC-77 (3M Company, St. Paul, MN, USA), an inert, organic, not water-miscible liquid consisting of a mixture of fully fluorinated alkanes with very high specific electrical resistivity of about 1.9 10 15 X cm (average molecular mass 415, boiling point 97 C, viscosity 1.28 cP, and static dielectric constant e m = 1.86). Silica beads (static dielectric constant e p = 3.7, density 1.96 g/cm 3 ) of 290 nm (Bangs Laboratories, Inc., Fishers, IN, USA) and 50 nm (Polysciences, Inc., Warrington, PA, USA) diameter were provided in aqueous suspension with 10 wt.-% and 5.34 wt.-%, respectively. Light microscopy images were taken with a Nikon Eclipse E800 with 40/0.75 NA objective using reflection contrast. The SEM images were taken in an Hitachi S-900 in-lens field emission SEM at 30 kV acceleration voltage. The samples were previously coated with 5 nm Pt.