Complementary techniques for the characterization of thin film Ti/Nb multilayers

An aberration corrector on the probe-forming lens of a scanning TEM (STEM) equipped with an electron energy-loss spectrometer (EELS) and X-ray energy-dispersive spectrometer (XEDS) has been employed to investigate the compositional variations as a function of length scale in nanoscale Ti/Nb metallic multilayers. The composition profiles of EELS and XEDS were compared with the profiles obtained from the complementary technique of 3D atom probe tomography. At large layer widths (h≥7 nm, where h is the layer width) of Ti and Nb, XEDS composition profiles of Ti/Nb metallic multilayers are in good agreement with the EELS results. However, at reduced layer widths (h≈2 nm), profiles of EELS and atom probe exhibited similar compositional variations, whereas XEDS results have shown a marked difference. This difference in the composition profiling of the layers has been addressed with reference to the effects of beam broadening and the origin of the signals collected in these techniques. The advantage of using EELS over XEDS for these nanoscaled multilayered materials is demonstrated.     

Mössbauer spectroscopy study on the corrosion inhibition of carbon steel in hydrochloric acid solution

The effect of ammonium polymolybdate (APM) on the corrosion of carbon steel in a solution of 1 M HCl was studied by weight loss and Mössbauer spectrometry. Inhibition efficiencies (P) have been obtained from weight measurement. The inhibition efficiencies increased with increase APM concentration. Mössbauer spectrometry shows that a superficial compound is formed on the electrode surface as a result of corrosion.     

Influence of technological conditions on electronic transitions in chemical vapor deposited poly(azomethine) thin films

Thin films of poly(1,4-phenylenemethilidynenitrilo-1,4-phenylenenitrilomethilidyne) (PPI) have been prepared by chemical vapor deposition in the horizontal geometry using gaseous argon as a transport agent. PPI thin films have been grown by polycondensation of para-phenylene diamine (PPDA) and terephtal aldehyde (TPA). Fourier Transform Infrared spectra confirm formation of PPI layers without end groups. The strongest absorption band with discernible vibronic progression has been found to be due to superposition of 2.64, 2.82 and 3.03 eV bands corresponding to interband transitions connecting electronic ground state and vibrational levels of electronic excited state. A feature seen at about 2.6 eV in the spectra of PPI films prepared at higher temperatures of PPDA and TPA sources are attributed to excitons connected with the π-π? gap. Shoulder at 3.31 eV is attributed to interband transitions between delocalized states, while a peak at 4.2 eV is attributed to excitons formed by localized holes and delocalized electrons and vice versa and interband transitions connecting delocalized and localized bands, with the binding energy of about 0.8 eV. Thin films prepared at low temperatures of monomers consist of randomly distributed PPI chains weakly bound together.     

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