Vladimir Burtman

Organic Quantum‐Confined Structures through Molecular Layer Epitaxy

A new approach, molecular layer epitaxy (MLE), is introduced for the vapor-phase assembly of organic multilayers integrated in molecular electronic devices. The MLE approach uses carrier gas assisted epitaxial deposition, covalent bonding, and horizontal π stacking in a pulsed mode for layer-by-layer growth of 1,8:4,5-naphthalenetetracarbodiimide with a hexamethylene spacer (shown schematically).

Quinolinium derived acentric single crystals

Abstract Derivatives of quinolinium-iodide exhibit a second-order nonlinear optical (NLO) response in their crystalline form. Here we present single crystal growth of three quinolinium-derivatives by the hanging drop method and their characterization by X-ray diffraction (XRD). These latter provided a rationale for the NLO response of these materials, allowing an application of general theoretical approaches, connecting second harmonic generation (SHG) response with structural parameters.

Raman and infrared spectroscopy and transport properties of aged organometallic precursors used for the deposition of high-Tc superconducting films

Abstract Raman and infrared (IR) spectra of Ba, Sr and Ca 2,2,6,6-tetramethyl-3,5-heptanedionates (THD), volatile precursors used for organometallic chemical vapor deposition (OMCVD) of high- T c superconducting (HTCS) thin films, have been studied for freshly supplied commercial materials or those prepared in our laboratory and aged for several months in vacuum and in air. Some of the spectral lines present in freshly prepared material disappeared in precursors aged in air but were unchanged if aged in vacuum. Only freshly prepared or vacuum-stored Ba(THD) 2 could be 100% transported by sublimating at 210°C. Air aged material transported only 60% under the same conditions of evaporation. Mixing 20% aged Ba(THD) 2 with 80% naphthalene achieved 100% transport of Ba(THD) 2 .

Kinetics of evaporation of barium THD precursors used for organometallic chemical vapor deposition (OMCVD) thin films

Abstract Various methods have been used to synthesize Ba(THD)2 and its molecular structure has been studied using nuclear magnetic resonance. Compared with Raman and infrared spectroscopy it was found that NMR is very useful to determine quantitatively the decomposition through aging of Ba(THD)2. The transport kinetics of Ba(THD)2 has been studied under experimental conditions of a OMCVD reactor. It has been found that the freshly prepared Ba(THD)2 by the reaction of Ba metal with THD ligand in anhydrous conditions with subsequent crystallization from methanol transported quantitatively without decomposition. A simple model shows that the transport kinetics corresponds to a diffusion controlled process.