Rebecca Cortez

Investigation of the drain current shift in ZnO thin film transistors

The combinational properties of ZnO of hardness to visible light, transparency, low temperature deposition, high mobility, and the ability to crystallize on almost any substrate enables ZnO Thin Film Transistors (TFTs) to be promising low-cost optoelectronic devices for the next generation of invisible and flexible electronics, such as switches for addressing active matrices based on organic light-emitting diodes. Using high-K dielectrics in ZnO TFTs substantially increases its transconductance, gm [1]. Using Barium Strontium Titanate (BST) may result in the increase of gm by more than 200 times it value if SiO2 is used.

Local transport properties, morphology and microstructure of ZnO decorated SiO2 nanoparticles

We report on a novel, surfactant free method for achieving nanocrystalline ZnO decoration of an SiO(2) nanoparticle at ambient temperature. The size distributions of the naked and decorated SiO(2) nanoparticles are measured by means of dynamic light scattering, and a monodisperse distribution is observed for each. The morphology and microstructure of the nanoparticles are explored using atomic force microscopy and high resolution transmission electron microscopy. Investigation of the optical properties of the ZnO decorated SiO(2) nanoparticles shows absorption at 350 nm. This blue shift in absorption as compared to bulk ZnO is shown to be consistent with quantum confinement effects due to the small size of the ZnO nanocrystals. Finally, the local electronic transport properties of the nanoparticles are explored by scanning conductance atomic force microscopy. A memristive hysteresis in the transport properties of the individual ZnO decorated SiO(2) nanoparticles is observed. Optical absorption measurements suggest the presence of oxygen vacancies, whose migration and annihilation appear to contribute to the dynamic conduction properties of the ZnO decorated nanoparticles. We believe this to be the first demonstration of a ZnO decorated SiO(2) nanoparticle, and this represents a simple yet powerful way of achieving the optical and electrical properties of ZnO in combination with the simplicity of SiO(2) synthesis.

Electrical conductivity of cationized ferritin decorated gold nanoshells

We report on a novel method of controlling the resistance of nanodimensional, gold-coated SiO2 nanoparticles by utilizing biomolecules chemisorbed to the nanoshell surface. Local electronic transport properties of gold-coated nanoshells were measured using scanning conductance microscopy. These results were compared to transport properties of identical gold nanoshells biofunctionalized with cationized ferritin protein both with and without an iron oxide core (apoferritin). Measured resistances were on the order of mega-ohms. White light irradiation effects on transport properties were also explored. The results suggest that the light energy influences the nanoshells’ conductivity. A mechanism for assembly of gold nanoshells with cationized ferritin or cationized apoferritin is proposed to explain the resistivity dependence on irradiation.