Research On The Nonvolatile Organic Thin Film Transistor Memory Based On Metal Nanoparticle Float Gate

As an important part of the information industry, information storage has become a pillar industry of national economic development. In recent years, floating gate transistor nonvolatile memory continues to develop, promoting the development of a variety of consumer electronics products and the advancement of electronics information to some extent, it indicates the development of this technology has broad market prospect and far-reaching research significance. non-volatile floating-gate organic thin film transistor memory(FG-OTFT-NVM) gets wide attention because of single transistor realization, nondestructive read-out, light weight, low cost, simple process, a large area of low-temperature processing, and complementary integrated circuit architectural compatibility, etc. but realizing practical application there is a big gap in the device performance. the floating gate layer and the tunneling layer have a significant impact on storage, retention characteristics of nonvolatile floating-gate organic thin film transistor. in this paper we researched on optimizing floating gate layer and the tunneling layer, we have used gold, silver, copper, aluminum four metals as a floating gate layer, and then focus on gold and aluminum as a floating gate, selected the appropriate tunneling layer to fabricate device, and studied its storage, retention performance in detail.First we researched what influence different composite electrode MoO3/Cu,MoO3/Ag, MoO3/Al made on the charge injection of Pentacene-based organic thin film transistor. The data simulation analysis demonstrated that MoO3 modification layer can significantly enhance the injection ability of holes independent of source and drain electrodes. Then based on the above experiments,we fabricated floating-gate organic thin film transistor memory inserting gold nanoparticles as a floating gate layer and depositing MoO3, m-MTDATA or TTC as tunneling layer, but only TTC showed good field-effect and storage effect, so an ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory was made, with discrete distributed gold nanoparticles, TTC with different thicknesses, pentacene as the floating-gate layer, tunneling layer, and active layer, respectively. The electron traps at the TTC/pentacene interface were significantly suppressed, which resulted in an bipolar operation in present memory. as both electrons and holes were supplied in the channel and trapped in the floating-gate by programming/erasing operations, respectively, i.e. one type of charge carriers was used to overwrite the other, trapped, one, a large memory window, extending on both sides of the initial threshold voltage, was realized. Further thickness and surface topography of tunneling layer is very important for the storage devices memory and retention performance. Based on an optimized thickness of 30 nm for the TTC layer, a memory window of 18.1 V and a retention time of 7.5 h were obtained for our bipolar FG-OTFT-NVM.Then we study charge trapping in floating-gate organic thin-film transistor nonvolatile memories(FG-OTFT-NVMs) fabricated by a simple method. The inner discrete distribution aluminum nanoparticles(Al-Nps) and the continuous compact thin alumina film were formed to act as the floating-gate and the tunneling dielectric layer, respectively by thermally evaporated Al at a slow rate and then heat annealed in dry air. The devices exhibited remarkable photoresponse and memory effect. Compared with the unidirectional threshold voltage(VT) shifts of memories by programming/erasing(P/E) in dark, larger bidirectional VT shifts were obtained by light-assisted programming, and therefore the memory performances were enhanced. A multilevel memory behavior was observed in our memories, which depended on programming conditions. The results indicate that optimal memory performance requires charge carriers of both polarities, because it is a very efficient method to enlarge the memory window and to lower the P/E voltage by overwriting trapped charges by injected charges of opposite polarity. the obvious difference of reading state suggested that our memory has a potential application as multilevel nonvolatile memory depended on the P conditions.