Dennis P. Strommen

GeS2 and GeSe2 PECVD from GeCl4 and Various Chalcogenide Precursors

The plasma enhanced chemical vapor depositions of germanium chalcogenide thin films from germanium tetrachloride, hydrogen sulfide and alkyl chalcogenides were studied to determine the viability of these reagents for thin film deposition. Hydrogen sulfide is a commonly used reagent for this technique and was used to determine optimal reaction conditions for thin film deposition. Germanium tetrachloride, alkylsulfides and alkylselenides were also employed because of their lower potential toxicities and higher availabilities compared to their more typical congeners: germane, hydrogen sulfide and hydrogen selenide in the formation of germanium chalcogenides. Alkylsulfides were found to be unsuitable for the deposition of germanium sulfides, however alkylselenide precursors were used successfully for the deposition of germanium selenides. The relative mass flow rates, reactor pressure, substrate temperature and plasma power density were studied for their effects on germanium chalcogenide deposition. These parameters affected the composition, deposition rate, film quality, and spectroscopic properties of the deposited films.

Theoretical and spectroscopic characterization of 1,4-bis-ethoxymethylene-(2,3)-butadione: a molecule with an extraordinary low frequency “CO” stretching mode

During a recent investigation of the photophysical properties of Ru(II) complexes containing the ligand 4,4 0 -bipyridine we had occasion to prepare an intermediate, 1,4-bisethoxymethylene-2,3-butadione, abbreviated as EMB. We were surprised to find a strong band at ca. 1590 cm ˇ1 (IR spectra) which had all the characteristics of a carbonyl stretch but saw no comparable bands in the region where one would normally expect the CO resonance. This frequency is the lowest among all known organic carbonyl compounds. We performed theoretical calculations on isolated EMB molecule by using Gaussian 94 package (RHF and DFT methods with the 6-311G and 6-311aG(d,p) basis sets). Within the DFT methods the functionals SVWN and B3LYP have been tested. Calculated IR, Raman, 1 H NMR and 13 C NMR spectra appeared to be in good agreement with experimental data. We also calculated potential energy distribution (PED) for presented in the paper vibrational bands. # 2001 Elsevier Science B.V. All rights reserved.

The acid catalyzed conversion of 1,3,5-trimethyl-2,4,6-tris(2-pyridyl)hexahydro-s-triazine into the asymmetric monomer, N-methylpyridine-2-carboxaldimine

Abstract This paper discusses the nature of the products formed from the reaction of 2-pyridinecarboxaldehyde and methylamine. The synthesized products manifest themselves in two distinct forms, one an oil and the other crystalline, which have identical chemical properties but differ dramatically in their spectroscopic parameters. A novel trimeric structure, the hexahydro- s -triazine, is suggested for the crystalline form, while the oil appears to be the monomeric N -methyl pyridine-2-carboxaldimine. IR, UV–vis, Raman and NMR spectroscopies are used to validate the proposed structures. The conversion of the trimeric crystalline form to the monomeric oil form, is acid-catalyzed and occurs rapidly.