Printed and flexible Printed and flexible electronics have drawn tremendous interest as a new paradigm for the fabrication of wearable devices, internet of things (IoTs), artificial synapse, et al. For low-power operation of those electronic applications, high-k dielectrics must be used in the organic field-effect transistors (OFETs) and circuits.
PVDF-based fluoropolymer is used in various application fields and is applied to non-volatile memory due to its ferroelectric characteristics. In addition, it has a higher dielectric constant than other polymer dielectrics and is characterized by being able to control ferroelectric properties according to temperature.
In this report, we studied the dielectric characteristics of PVDF-based fluoropolymer; DPVDF (Double bond-contain-PVDF) as a gate insulator in staggered OFETs. DPVDF is modified PVDF-CTFE with vinyl group through dechlorination, which is expected to have a lot of advantages such as high capacitance, reconfigurable dielectric properties, and chemical & heat resistance. Herein, 16%, 52%, and 96% of DPVDF were used according to the double bond ratio of the dechlorinated PVDF-CTFE polymer chain.
Firstly, fundamental dielectric properties, such as leakage current and dielectric constant, were measured based on metal-Insulator-metal (MIM) structure, and their film thickness was carefully controlled by changing the concentration of the solution. The low-voltage and ferroelectric characteristics of the DPVDF insulators were confirmed by fabrication of OFETs based on various organic semiconductors. The electrical characteristics of the OFETs showed high charge carrier mobilities more than 3 cm2/Vs under the low bias conditions below 5 V.
We also secured temperature-specific electrical properties by taking advantage of the fact that we can regulate the ferroelectric properties by annealing temperature conditions of gate dielectrics. What's interesting here is that a material can be applied to two applications, transistors, and memory, by controlling annealing temperature conditions.
In addition, it is expected to be applied to complex integrated circuits as well as memory and low voltage driving transistors. Furthermore, it seems that it can be applied to synaptic transistors through these ferroelectric characteristics.
Since it is a fluorine-based ferroelectric polymer including a double bond, crosslinking properties can be seen because bonding with other polymer chains is induced at the double bond site of the polymer chain. To understand the conditions, the crosslinking characteristics through UV/thermal treatment were identified, and the possibility of an insulator capable of patterning was studied by adding a crosslinker.