Tunable Dielectric Function in Electric‐Responsive Glass with Tree‐Like Percolating Pathways of Chargeable Conductive Nanoparticles

Abstract

The design of nanostructured materials with specifi c physical properties is generally pursued by tuning nanoparticle size, concentration, or surface passivation. An important step forward is to realize "active" systems where nanoparticles are vehicles for controlling, in situ, some specifi c, tuneable features of a responsive functional material. In this perspective, this work focuses on the rational design of a nanostructured glass with electrically tuneable dielectric function obtained by injection and accumulation of charge on embedded conductive nanocrystals. This enables electrically controlled switching of semiconducting nanophases to charged polarisable states to be achieved, which could lead to smart, fi eld-enhancement applications in nanophotonics and plasmonics. Here, it is shown that such response switching can be obtained if a percolating charge-transport mechanism is activated through a disordered tree-like network, as is demonstrated to be possible in SiO 2 fi lms where suitable dispersions of SnO 2 nanocrystals, with conductive interfaces, are obtained as a result of a new synthesis strategy.

Copper-Doped Inverted Core/Shell Nanocrystals with “Permanent” Optically Active Holes

“…In the case of colloidal nanostructures, such doping with electrically active charges would facilitate charge transport (Figure b, right) and could help to resolve the problem of extremely low intrinsic conductivity of NC assemblies. It will also benefit practical applications of NCs in electronic and optoelectronic devices by allowing for a facile engineering of built-in electric fields via controlled placement of p–n junctions …”

“…It will also benefit practical applications of NCs in electronic and optoelectronic devices by allowing for a facile engineering of built-in electric fields via controlled placement of pÀn junctions. 7 So far, most successful NC doping efforts have focused on magnetically active Mn ions. 8À13 Temporary introduction of active charge carriers using strongly reducing chemical agents has also been demonstrated previously.…”

Responsive charge transport in wide-band-gap oxide films of nanostructured amorphous alkali-gallium-germanosilicate

“…Charge percolation across the system can cause voltage-dependent charge transport to dead-end lines of the conductive network, which possess an entry path but no exit path in the field direction to further transfer the charge to the electrode. 8 The nonlinear response of the system can then be used to switch off the entry path too, by lowering the bias. As a result, the system can undergo a change of its charge state thanks to the disorder-induced occurrence of switchable dead-end steps in the conduction network.…”

“…Electrically driven functions in oxide-in-oxide structures were indeed demonstrated in silica-based nanostructured films where SnO2/SnO nanoparticles enabled both electric and capacitance responses, as well as electroluminescence. 8,9 In the present work, we have faced the task of investigating whether systems consisting of Ga-oxide containing silicate glasses could give rise to nanosized layered systems providing us with new strategies for obtaining electrically driven responsive materials. The idea is to take advantage of the propensity of Ga-containing silicates to generate segregated nanophases and of the concomitant potential of Ga oxide as a carrier of functional properties in the field of conductive oxides.…”