Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

Low k thin films based on rf plasma-polymerized aniline

Abstract: Thermally stable materials with low dielectric constant (k<3.9) are being hotly pursued. They are essential as interlayer dielectrics/intermetal dielectrics in integrated circuit technology, which reduces parasitic capacitance and decreases the RC time constant. Most of the currently employed materials are based on silicon. Low k films based on organic polymers are supposed to be a viable alternative as they are easily processable and can be synthesized with simpler techniques. It is known that the employment of ac/rf plasma polymerization yields good quality organic thin films, which are homogenous, pinhole free and thermally stable. These polymer thin films are potential candidates for fabricating Schottky devices, storage batteries, LEDs, sensors, super capacitors and for EMI shielding. Recently, great efforts have been made in finding alternative methods to prepare low dielectric constant thin films in place of silicon-based materials. Polyaniline thin films were prepared by employing an rf plasma polymerization technique. Capacitance, dielectric loss, dielectric constant and ac conductivity were evaluated in the frequency range 100 Hz–1 MHz. Capacitance and dielectric loss decrease with increase of frequency and increase with increase of temperature. This type of behaviour was found to be in good agreement with an existing model. The ac conductivity was calculated from the observed dielectric constant and is explained based on the Austin–Mott model for hopping conduction. These films exhibit low dielectric constant values, which are stable over a wide range of frequencies and are probable candidates for low k applications.

Gadanki radar observations of F region field‐aligned irregularities during June solstice of solar minimum: First results and preliminary analysis

Abstract: [1] In this paper we present the first results of F region field-aligned irregularities (FAI) made during the summer of low solar condition using the Gadanki mesosphere-stratosphere-troposphere radar. FAI echoes were observed on all 20 nights of radar observations and were mostly confined to the postmidnight hours. Echo morphology is found to be very different from the equinoctial postsunset features reported earlier from Gadanki. Echo SNRs are lower by 25 dB than their equinoctial postsunset counterparts but are quite comparable to those of the equinoctial decaying FAI during the postmidnight hours. The Doppler velocities, which lie in the range of ±100 m s−1, are predominantly upward-northward during 0000–0300 LT and downward-southward afterward, in contrast to those observed as predominantly downward-southward associated with the decaying equinoctial postmidnight F region FAI. Spectral widths of the summer echoes, which are well below 50 m s−1 and are very similar to those of the decaying equinoctial irregularities, represent the presence of weak plasma turbulence. Simultaneous observations made using a collocated ionosonde show no ionogram trace during 2200–0530 LT except for a few cases of weak spread F events. Concurrent ionosonde observations made from magnetic equatorial location Trivandrum also show very similar results. The observations are discussed in the light of current understanding on the postmidnight occurrence of F region irregularities in the summer of low solar condition.