S B Krupanidhi
Articles written in Bulletin of Materials Science
Volume 28 Issue 4 July 2005 pp 303-303
Volume 29 Issue 6 November 2006 pp 547-547
Volume 31 Issue 3 June 2008 pp 199-199
Volume 32 Issue 3 June 2009 pp 215-215
Volume 32 Issue 3 June 2009 pp 259-262
The electrocaloric effect is calculated for PMN–PT relaxor ferroelectric thin film near morphotropic phase boundary composition. Thin film of thickness, ∼ 240 nm, has been deposited using pulsed laser deposition technique on a highly (111) oriented platinized silicon substrate at 700°C and at 100 mtorr oxygen partial pressure. Prior to the deposition of PMN–PT, a template layer of LSCO of thickness, ∼ 60 nm, is deposited on the platinized silicon substrate to hinder the pyrochlore phase formation. The temperature dependent P–E loops were measured at 200 Hz triangular wave operating at the virtual ground mode. Maximum reversible adiabatic temperature change, 𝛥 𝑇 = 31 K, was calculated at 140°C for an external applied voltage of 18 V.
Volume 33 Issue 3 June 2010 pp 191-196 Thin Films and Nanomatter
The present paper deals with the study of the effects of electron (8 MeV) irradiation on the dielectric and ferroelectric properties of PbZrO3 thin films grown by sol–gel technique. The films were (0.62 𝜇m thick) subjected to electron irradiation using Microtron accelerator (delivered dose 80, 100, 120 kGy). The films were well crystallized prior to and after electron irradiation. However, local amorphization was observed after irradiation. There is an appreciable change in the dielectric constant after irradiation with different delivered doses. The dielectric loss showed significant frequency dispersion for both unirradiated and electron irradiated films. 𝑇c was found to shift towards higher temperature with increasing delivered dose. The effect of radiation induced increase of 𝜀′(𝑇) is related to an internal bias field, which is caused by radiation induced charges trapped at grain boundaries. The double butterfly loop is retained even after electron irradiation to the different delivered doses. The broader hysteresis loop seems to be related to radiation induced charges causing an enhanced space charge polarization. Radiation-induced oxygen vacancies do not change the general shape of the AFE hysteresis loop but they increase 𝑃s of the hysteresis at the electric field forced AFE to FE phase transition. We attribute the changes in the dielectric properties to the structural defects such as oxygen vacancies and radiation induced charges. The shift in 𝑇c, increase in dielectric constant, broader hysteresis loop, and increase in 𝑃r can be related to radiation induced charges causing space charge polarization. Double butterfly and hysteresis loops were retained indicative of AFE nature of the films.
Volume 33 Issue 3 June 2010 pp 221-226 Thin Films and Nanomatter
Nanosized hexagonal InN flower-like structures were fabricated by droplet epitaxy on GaN/Si(111) and GaN flower-like nanostructure fabricated directly on Si(111) substrate using radio frequency plasma-assisted molecular beam epitaxy. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the crystallinity and morphology of the nanostructures. Moreover, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to investigate the chemical compositions and optical properties of nano-flowers, respectively. Activation energy of free exciton transitions in GaN nano-flowers was derived to be ∼ 28.5 meV from the temperature dependent PL studies. The formation process of nanoflowers is investigated and a qualitative mechanism is proposed.
Volume 42 | Issue 6
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