Organic sample preparation for femtosecond electron diffraction: Tetra-n-butylammonium triiodide and 1,2-di(2-dimethyl-5-phenylthiophen-3-yl) perfluorocyclopentene

Femtosecond electron diffraction is a technique developed over the last decade that can be used to study transient states of chemical species proceeding along a reaction pathway. The use of an ultrafast electron packet as a probing element imposes stringent requirements upon the sample being studied. Essentially, all samples must be nanometer thin films with a surface area comparable to the radius of the electron beam (>150 mum).;Four different types of sample preparation methods are investigated for the potential to be used on one of two photoreactive organic systems-namely tetra-n-butylammonium triiodode (TBAT) and the diarylethene 1,2-Di(2-dimethyl-5-phenylthiophen-3-yl) perfluorocyclopentene (DMP). The techniques include microtoming, nano-etching with an atomic force microscope, nanosecond excimer laser ablation, and high pressure/slow crystallization from a melt.;Using the high pressure/slow crystallization technique it was possible to grow 200 nm TBAT films containing highly oriented crystalline domains. The area of the films was ∼1 cm2.