Isidro Cruz-Cruz

Interfacial insertion of a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) layer between the poly(3-hexyl thiophene) semiconductor and cross-linked poly(vinyl alcohol) insulator layer in organic field-effect transistors

The role of a thin layer of conductive poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT?:?PSS), inserted between the gate dielectric and the active layer in poly(3-hexylthiophene)-based transistors was investigated. The devices were fabricated in the bottom-gate top-contact geometry by using cross-linked poly(vinyl alcohol) as the dielectric, whereas the PEDOT?:?PSS layer was prepared by using an aged aqueous dispersion with addition of different amounts of dimethyl sulfoxide (DMSO) as a secondary dopant. Under these conditions, both a significant reduction in the number of electrically active traps at the interface with the semiconductor and an improvement in the field-effect mobility were obtained, whereas the low power consumption was preserved. The threshold voltage was also displaced by approximately ?1?V.

Carbon nanostructures in organic WORM memory devices

We briefly review recent developments concerning the use of carbon nanostructures in polymer composite thin films for write-once-read-many-times memory devices. We also show that carbon sphere/poly(vinylphenol) composites prepared with the addition of hexadecyltrimethylammonium bromide as a surfactant show better carbon sphere dispersion, allowing in principle a memory device size reduction. Devices constructed with surfactant added carbon-sphere/poly(vinylphenol) composites allow writing the ON state in ∼200 ns and the write operation consumes 5 × 10−5 J cm−2 when a pulse with an amplitude of 5 V and a length of 1 μs is used.

Study of poly(3-hexylthiophene)/cross-linked poly(vinyl alcohol) as semiconductor/insulator for application in low voltage organic field effect transistors

In this work we study the cross-linked poly(vinyl alcohol)/poly(3-hexylthiophene) interfacial properties of an organic field effect transistor. We use cross-linked poly(vinyl alcohol) prepared with different ammonium dichromate:poly(vinyl alcohol) proportions, ranging from 0% to 35%, as insulator. Using admittance spectroscopy, we show that the interfacial properties change when the ammonium dichromate concentration is altered. The interfacial properties and the better insulation are responsible for the improvement of the device performance in these organic field effect transistors, achieving best performance in the blend with ammonium dichromate:poly(vinyl alcohol) proportion of 0.25:1.

Gate dielectric surface treatments for performance improvement of poly(3-hexylthiophene-2,5-diyl) based organic field-effect transistors

We report on enhanced performance in poly(3-hexylthiophene-2,5-diyl) (P3HT) based organic field effect transistors (OFETs) achieved by improvement in hole transport along the channel near the insulator/semiconductor (I/S) interface. The improvement in hole transport is demonstrated to occur very close to the I/S interface, after treatment of the insulator layer with sodium dodecyl sulfate (SDS). SDS is an anionic surfactant, with negatively charged heads, known for formation of micelles above critical micelle concentration (CMC), which contribute to the passivation of positively charged traps. Investigation of field-effect mobility (μFET) as a function of channel bottleneck thickness in OFETs reveals the favorable gate voltage regime where mobility is the highest. In addition, it shows that the gate dielectric surface treatment not only leads to an increase in mobility in that regime, but also displaces charge transport closer to the interface, hence pointing toward passivation of the charge traps at I/S interface. OFETs with SDS treatment were compared with untreated and vitamin C or hexadecyltrimethylammonium bromide (CTAB) treated OFETs. All the treatments resulted in significant improvements in specific dielectric capacitance, μFET, on/off current ratio and transconductance.