Showing papers by "Somnath C. Roy published in 2005"
TL;DR: In this paper, the ammonia-sensing behavior of barium strontium titanate (BST) thin films have been reported for the first time, and the sensitivity variation was from 20 to 60%, with lowest detection limit of about 160ppm.
Abstract: In this paper, ammonia-sensing behavior of barium strontium titanate (BST) thin films have been reported for the first time. Thin films of BST deposited by sol–gel spin coating technique have been found to show an increase in resistance when exposed to ammonia gas. The sensitivity variation was from 20 to 60%, with lowest detection limit of about 160 ppm. The films were prepared with different pre-sintering temperatures and thickness and effect of these parameters on the ammonia-sensing have been studied. The optimum temperature for operation was found to be close to 270 °C. The ammonia-sensing studies were also performed for other gases like ethanol, NO 2 and CO; but the sensitivity in these cases was negligibly smaller than that in case of ammonia.
33 citations
TL;DR: In this paper, the pyroelectric coefficient at room temperature was found to be 10−8 C/cm 2 K. The ferroelectric phase has been confirmed from the C-V and P-E studies.
Abstract: (Ba,Sr)TiO 3 (BST) thin films have received considerable interest in recent years due to their many attractive properties like high dielectric constant, high dielectric breakdown strength and high pyroelectric coefficent. These films have been identified as promising material for several applications such as ferroelectric non-volatile memories and uncooled infrared focal plane arrays [UFPAs]. Barium strontium titanate (Ba 0.75 Sr 0.25 TiO 3 ) thin films of thickness 0.5 μm have been deposited on Pt/TiO 2 /SiO 2 /Si substrate by sol-gel spin coating method. The glancing angle X-ray diffraction of these films sintered at 700°C in air shows polycrystalline nature. Dielectric constant (ϵ r ) and dielectric loss (tanδ) of the film measured at 1 KHz are found to be 400 and 0.02 respectively. The ferroelectric phase has been confirmed from the C-V and P-E studies. After poling the sample by corona charging technique, the pyroelectric coefficient at room temperature was found to be order of 10−8 C/cm 2 K.
10 citations
TL;DR: In this article, room temperature photoluminescence (PL) spectroscopy was done to investigate luminescent trap states in sol-gel deposited (Ba,Sr)TiO3 thin films.
Abstract: Room temperature photoluminescence (PL) spectroscopy was done to investigate luminescent trap states in sol–gel deposited (Ba,Sr)TiO3 thin films. The pre-sintered films showed three distinct PL peaks. Increase in the peak intensity was observed with increase in pre-sintering temperature. These PL peaks were assigned to (a) singly charged oxygen vacancies (b) TiO2 networks and (c) the contribution from the substrate. In contrast, the sintered samples showed only a band-edge luminescence with an intense peak near the band-gap energy. Identification of such observed trap states are important in understanding the results of dielectric measurements because they contribute to the leakage currents and loss mechanisms.
5 citations