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We fabricated pentacene-based memory field-effect transistors (FETs) in which a monolayer of semiconductor colloidal nano-dots (NDs) is embedded as a floating gate. After a sufficiently large writing voltage was applied on the control gate, the fabricated FETs showed a large positive threshold voltage (V th) shift that was attributed to electrons trapped in embedded NDs. The V th shift was measured as a function of the writing voltage, and it was shown that the minimum writing voltage for memory FETs with small NDs is significantly larger than that for FETs with large ones. This result supports the proposed model of the memory effect in which electrons that tunneled from nearby pentacene molecules are trapped in embedded NDs because the electron energy level in small NDs is higher than that in large ones.

We fabricated organic memory field-effect transistors (FETs) using PbS colloidal nano-dots (NDs) dispersed in thin poly(methyl methacrylate) (PMMA) layers inserted between gate insulators (SiO2) and pentacene active layers as floating gates. The colloidal NDs were dispersed in chloroform solution with PMMA, and spin-coated on SiO2 surfaces. The fabricated memory FETs showed significantly large threshold voltage shifts of 64.5 V at maximum after a writing voltage of 100 V was applied to their control gates, and a maximum carrier mobility of 0.36 cm2 V-1 s-1, which was comparable to that of reference pentacene FETs without colloidal NDs, was obtained because of the improved crystallinity of the pentacene films.

We have investigated contact and channel resistances of organic field-effect transistors (FETs) based on benzodithiophene (BDT)-dimer films deposited on thin pentacene layers used as crystallinity control layers (CCLs). The contact resistance of source/drain electrodes made of conductive organic films instead of Au films has been reduced for pentacene-CCL/BDT-dimer FETs; the carrier mobility has been improved to 1.2 cm2 V−1 s−1 at maximum. Because the channel resistance of the pentacene-CCL/BDT-dimer FETs is found to be lower than that of reference pentacene FETs, the carrier transport in the BDT-dimer layers is more important than that in the pentacene CCLs for the high mobility.

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