Low-Voltage Organic Field-Effect Transistors For Complementary Circuit And Memory Applications

With the increasing demand for wearable products,electronic products are developing towards flexible,light-weight,and designable devices,which becomes an important research topic in the area of information technology.Comparing with traditional inorganic field-effect transistors,organic field-effect transistor(OFET)possesses the advantages of low-cost,light-weight,ultrathin,and large-area flexible fabrication,which can meet the dual requirements of device functionality and flexibility,and has been applied in flexible logic circuits,memories,sensors,etc.However,the operation voltage of the present OFET is too high,resulting in high power consumption,low integration,and unapplicable in wearable products.Meanwhile,the diffusion of nano metal floating-gate will lower the program/erase reliability and the fabrication cost of metal is always high.In this thesis,in order to solve the above problems,the low-cost carbon based nanomaterials by simple fabrication process is introduced to construct the novel nano carbon/polymer hybrid dielectric layer and polymer/nano carbon/polymer hybrid floating gate,based on which a low-voltage OFET,complementary inverter and OFET nano floating-gate memory with high performance and reliability are achieved.Firstly,a simple and low-cost method is introduced to fabricate a novel hybrid dielectric layer and realize low-voltage OFETs.To replace silicon dioxide with low-k polymer dielectric layer modified with sputtered carbon nanoparticles(NPs),carbon NPs/polymer hybrid dielectric layer is obtained with high capacitance and low leakage,lowering the operation voltage effectively.Based on such hybrid dielectric and pentacene channel,low-voltage p-type OFET device is obtained with high performances:operation voltage<2 V,mobility>0.4 cm2/Vs,ON/OFF ratio>106,threshold voltage<1 V and good bias-stress-stability over 60000 seconds.The possibility of other carbon materials such as graphene oxide employed in such hybrid dielectric layer is explored,demonstrating the role of carbon nano-materials in hybrid dielectric layer.The underlying mechanism for hybrid dielectric layer in high performance low-voltage OFET is revealed,providing theoretical guidance for exploring other strategies to realize low-voltage OFETs.Secondly,low-voltage n-type OFETs based on the carbon NPs/polymer hybrid dielectric layer with the semiconducting n-type PTCDI-C13H27 channel are obtained,and thus high performance complementary inverters are achieved by integration with p-type OFETs:operation voltage<3 V,voltage gain>600,low steady power consumption and good cycle stability.Moreover,based on such dielectric layer,flexible complementary inverters are also fabricated with high performances:operation voltage<3 V,voltage gain>300 and good cycle stability.Thirdly,to overcome the metal nano-floating-gate diffusion and high cost issues,the carbon nanoparticles with graphene domain and oxygen functional groups are introduced to replace traditional metal NPs as the nano-floating-gate for non-volatile memories.The fabricated carbon-based nano-floating-gate OFET memory exhibits high memory performances:memory window>40 V,mobility>0.4 cm2/Vs,ON/OFF ratio>105,good retention over 10000 seconds and endurance properties over 1000 progran/reading/erase times.Moreover,low-voltage OFET nano-floating-gate memory with high memory performances is also fabricated with polymer dielectric as control insulating layer and sputtered carbon NPs as nano-floating-gate,respectively.