Use of Matrix Assisted Pulsed Laser Evaporation (Maple) for the Growth of Organic Thin Films

A novel variation of conventional pulsed laser deposition, called matrix assisted pulsed laser evaporation, or MAPLE, has been utilized for growing organic thin films. The MAPLE technique is carried out in a vacuum chamber and involves directing a pulsed laser beam) onto a frozen target consisting of an organic compound dissolved in a solvent matrix. The laser beam evaporates the surface layers of the target with both solvent and organic molecules being released into the chamber. The volatile solvent is pumped away, whereas the organic molecules coat the surface of a substrate. Very thin and uniform films (50 to 100 nm) of various organic materials, such as carbohydrates, have been deposited on Si(111) and NaCl substrates. The films prepared using this method have been examined by optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and electrospray mass spectrometry. Careful control of the processing conditions allowed carbohydrates such as sucrose and glucose, in addition to high molecular weight polymers such as dextran, to be transferred to the substrate as uniform films, without significant chemical decomposition. The use of MAPLE films for chemical and biological sensor applications is being investigated and the potential of this technique for producing high quality thin films of other organic compounds will be discussed.