Next Generation of Transparent Electrode Materials for Flexible Devices
Abstract
Transparent conductors play an important role in modern electronics.Commercially, this area is dominated by doped metal oxides, most commonlyindium tin oxide (ITO). However, the future of ITO as the main material inthis area may be limited for economic and technical reasons. In short, anew material is required that must be compatible with low temperature,large area deposition and must be flexible. This is in addition todisplaying high transparency, T, and low sheet resistance, Rs. It has beenknown for the past few years that flexibility and low temperatureprocessing can be achieved by the deposition of nanostructured thin films,often from the liquid phase. These are known to be stable under flexingand can be deposit on flexible substrate. Like carbon nanotubes, graphenecan be dispersed in common solvents as well as surfactants and can bedeposited as thin film. The most significant materials studied till noware carbon nanotube (CNT), graphene, metal gratings, and random networksof metallic nanowires. CNT and Metal nanowires network have propertiesthat are promising. CNT-PEDOT composites and Graphene-CNT hybrid films arebetter than CNT only. For most nanostructured films thin enough to displayT > 90% (industrial requirement), the conduction can be described bypercolation theory. This means DC conductivities are lower than in bulk,giving correspondingly higher sheet resistances, Rs. To improve ourunderstanding of the consequences of this, we develop a model whichrelates T to Rs in the percolation regime.
18/04/2011 at 4:00 pm
Prof. Kalobaran Maiti, Department of Condensed Matter Physics and Materials Science, TIFR, Mumbai
Colloquium
Lecture Hall Block A, Institute of Physics
Document Date:
Novel non-magnetic phase in magnetic materials – universality of Kondo effect
Novel non-magnetic phase in magnetic materials – universality of Kondo effect
Abstract
Antiparallel coupling of the impurity states with the conduction electronicstates leads to interesting phenomena in solid – the magnetic moments arecompletely compensated leading to a non-magnetic Fermi liquid phase in amagnetic material – this is known as Kondo effect. Such coupled electronicstates appear as a sharp feature at the chemical potential, called Kondoresonance feature. Employing high resolution photoemission spectroscopy, westudied the evolution of Kondo resonance feature in RB6 (R = La, Ce, Pr, Nd)and Ce2(RhCo)Si3 as a function of temperature that helps to probe thiseffect as a function of 4f binding energy and 4f-conduction electronhybridization strength. Experimental spectra of Kondo systems reveal thegrowth of multiple Kondo resonance features with decreasing temperaturerelative to the uncompensated local moment contributions that experimentallydemonstrates the Kondo effect. Ironically, the features near Fermi level inthe valence band spectra of PrB6, NdB6, Ce2RhSi3 etc also exhibit similartemperature dependence signalling the presence of Kondo compensation effectalthough their bulk physical properties do not exhibit Kondo effect.
