Effect of ethanol concentration on the porosity of spray pyrolyzed TiO2 films and their utility as humidity sensor

Titanium oxide films were prepared on ITO coated glass substrates at 350 degrees C using titanium (IV) isopropoxide, acetylacetonate and absolute ethanol as precursors by spray pyrolysis technique. The prepared films were characterized by X-ray diffraction, Scanning electron microscope, Fourier transform infrared spectroscopy and Energy dispersive analysis of X-rays. Estimated optical and electrical parameters such as refractive index, porosity, dielectric constant, energy band gap, carrier concentration, mobility by UV-Vis spectrophotometer, Hall effect and Van der pauw techniques were found to vary with ethanol volumetric concentration of 22.5-23. The observed increase in porosity from 45-59% facilitates the adsorption of water molecules inside films. The capacitance and resistance of metal-insulator-semiconductor structure were found to vary between 1.08-3.48 nF and 436-15 k Omega with increase in relative humidity. The fabricated humidity sensor found to posses 4s criterion such as sensitivity, stability and response-recovery times as 180%, +/- 10% and 58-106 s, respectively

Coexistence of para and ferromagnetic phases of Fe3+ in undoped CdZnTe (Zn similar to 4%) crystals

The signatures of the coexistence of para and ferromagnetic phases for the Fe3+ charge state of iron have been identified in the low temperature electron spin resonance (ESR) spectra in undoped CdZnTe (Zn similar to 4%) crystals and independently verified by superconducting quantum interference device (SQUID) and AC susceptibility measurements. In the paramagnetic phase the inverse of AC susceptibility follows the Curie-Weiss law. In the ferromagnetic phase the thermal evolution of magnetization follows the well-known Bloch T-3/2 law. This is further supported by the appearance of hysteresis in the SQUID measurements at 2 K below T-c which is expected to lie in between 2 and 2.5 K. (C) 2010 Elsevier Ltd. All rights reserved