Papers by Keyword: Organic Molecules

Abstract: We investigated Si surfaces modified by wet-chemical and electrochemical treatments using pulsed photoluminescence (PL) and infrared spectroscopic ellipsometry during and after processing, both also in surface mapping techniques. Etching of oxidized Si surfaces by HF containing solutions lead to an enhancement in PL due to hydrogenation of the surface what improves the surface passivation and reduces the recombination loss of charge carriers via surface/interface states. PL measurements show that the H-terminated surface is attacked soon by HF or H2O species increasing again the recombination loss. Hence, a narrow time window for this type of processing exists. Nitrogen purging or exchanging the etching solution by a non-etching solution under negative bias decelerated the defect formation in HF solutions. Grafting of organic molecules (exchanging the H-Si by a C-Si bond) induces only small amounts of defects at the interface but stabilizes PL on a high level (i.e. surface recombination is low) for much longer times than for H-terminated Si surfaces.

Abstract: Intensive research is currently underway to exploit the highly interesting properties of nano-sized particles and organic molecules for optical, electronic and other applications. Recently, it has been shown that nano-sized particles and small organic molecules embedded in polymer matrices can be used to realise memory devices. Such memory devices are simple to fabricate via the spin-on technique. This work presents an attempt to use sea salt, embedded in polyvinyl acetate, in the making of the memory devices. A polymer blend of polyvinyl acetate and sodium chloride (NaCl) was prepared in methanol and spin coated onto a glass substrate marked with thin Al tracks and a top contact was evaporated onto the blend after drying - this resulted in a metal-organic-metal (MOM) structure. The current-voltage (I-V) behaviour of MOM devices shows that the devices can be switched from a high conductivity state to a low conductivity state, by applying an external electric field - this property can be exploited to store data bits. The possible charging mechanism, based on the electric dipole formation, is presented in this work. Polymer blends of polyvinyl acetate with nano-particles of BaTiO3 are also investigated to further our understanding of charging mechanism(s).