Deceptive lattice spacings in HRTEM Imaging of nanocrystals
Abstract
In nano particle, length of the atomic column varies from centerof the grain to the edge which resulted in curved lattice planes (off zoneaxis tilting) and delocalization (can be solved using Cs correctedmicroscope). Overlap of the top atomic column with bottom of an adjacentcolumn give rise to fringe pattern having deceptive lattice spacing. Inthis talk, we will discuss the various reasons for the deceptive latticespacing in HRTEM imaging and its rectification.This technique will help usin analyzing the strain and composition of bimetallic nanoparticles withmore accuracy. In addition to this, we will discuss about the Precessionelectron Diffraction technique(PED) which is an advanced TEM technique foranalyzing the strain in bulk and thin film samples.
23/08/2013 at 4:00 pm
Prof. A.M. Srivastava, IOP, Bhubaneswar
General Seminar
Lecture Hall Block A, Institute of Physics
Document Date:
Learning Science, Doing Research, Three Idiots’ Way
Tailoring of the two-dimensional electron gas conductivity in LaAlO3/SrTiO3 interfaces
Abstract
The two-dimensional electron gas (2DEG) formed at the interface betweentwo band insulators LaAlO3 (LAO) and SrTiO3 (STO) is one of the mostfascinating systems in the field of oxide research. Tuning of theconductivity of this interface 2DEG and to create a spatially selectiveinsulating state is one of the key challenges in oxide electronics. Wefound that low Z ion irradiation can be utilized to manipulate theconductivity at the LAO/STO interface by carrier localization arising fromthe defects created by the ion beam exposure, and eventually producing aninsulating ground state. The results of electrical transport, Ramanspectroscopy and spectroscopic ellipsometry will be discussed. This processof ion induced defect creation results in structural changes in SrTiO3 asrevealed by the appearance of symmetry forbidden first-order TO2, andTO4 vibrationalmodes in the Raman spectra of the irradiated samples. In spectroscopicellipsometry measurements, the optical conductivity features of theirradiated interface were found to be broadened due to the localizationeffects along with a decrease of spectral weight from 4.2-5.4 eV. Theseresults indicate that the interface ground state (metallic/insulating) atthe LAO/STO can be controlled by engineering the SrTiO3 with ionirradiation. The consequences of the irradiation effects and possibleorigin of the reduction in conductivity will be discussed.
12/08/2013 at 4:00 pm
Professor K. Sridhar, Tata Institute of Fundamental Research, Mumbai
Colloquium
Lecture Hall Block A, Institute of Physics
Document Date:
NRQCD — How effective a theory of charmonium is it?
NRQCD — How effective a theory of charmonium is it?
Abstract
I will present a review and status update of Non-Relativistic QCD (NRQCD)and its application to charmonium systems. In particular, I will bediscussing the production of charmonia at colliders and critically examinehow well NRQCD fares in describing the available data. To do this, I willbegin by presenting a historical account of the theoretical models thatwere developed to understand charmonium production and how these led to thedevelopment of the effective theory approach that we call NRQCD.
