Enhancing the retention properties of ZnO memory transistor by modifying the channel/ferroelectric polymer interface

Abstract

We report on the fabrication of ZnO nonvolatile memory thin-film transistors (NVM-TFTs) with thin poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] ferroelectric layer. Our NVM-TFT operates on glass substrates under low voltage write-erase (WR-ER) pulse of ±20 V with a maximum field effect mobility of ∼1 cm2/V s, maximum memory window of ∼20 V, and WR-ER current ratio of 4×102. When the NVM-TFT has a modified channel/ferroelectric interface with an inserted thin Al2O3 buffer layer, our device shows long retention time of more than 104 s, which is much enhanced compared to that of the other device without the buffer. The dynamic response of our devices with or without the buffer was clear enough to distinguish the WR and ER states as performed with 300 ms pulse.

The flexible non-volatile memory devices using oxide semiconductors and ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene)

“…Recently, ZnO-channel Fe-TFTs were reported, which exhibit better performance of higher fieldeffect mobility than organic-semiconductor-channel FeTFTs. [6][7][8][9] However, the ZnO films are polycrystalline and have grain boundaries that may deteriorate the TFT performance, stability, and uniformity. Amorphous indium gallium zinc oxide (a-IGZO) can be deposited using low thermalbudget processes and exhibits higher mobility than organic semiconductors.…”

Ferroelectric Copolymer-Based Plastic Memory Transistors

“…The first one is that the memory device reliabilities, especially data retention, were not so satisfying at this stage. The typical retention times of the previously reported memory TFT employing the polymeric ferroelectric GI and oxide channel are still in the range of several hours even when they were fabricated on the glass substrate (Lee K. H. et al, 2009a;Noh S. H. et al, 2007;Park C. H. et al, 2009). Three significant factors that critically affect the retention behaviors are intrinsic depolarization field, gate leakage components, and interface quality.…”

Transparent photostable ZnO nonvolatile memory transistor with ferroelectric polymer and sputter-deposited oxide gate

“…6,9,10 Our previous work reported on ZnO-based ferroelectric NVM-TFTs with a nanometer thin Al 2 O 3 layer inserted between the ferroelectric P͑VDF/ TrFE͒ and ZnO channel, exhibiting relatively a good memory window and improved retention properties as well. 11 In the present work, we attempted to fabricate a transparent ZnO NVM-TFT with transparent gate and source/ drain ͑S/D͒ electrodes, driven by such a motivation that transparent oxide TFTs are to be used as functional devices in the coming ubiquitous technology era 12 as well as a practical transparent pixel driver in the present. [13][14][15] Transparent NVM and logic devices are very necessary if we aim at various transparent device applications.…”

“…The nominal channel length ͑L͒ was 90 m and the width ͑W͒ was 500 m. As a thin buffer layer with a high dielectric constant, 5 nm thin Al 2 O 3 layers were deposited by atomic layer deposition at a temperature of 200°C. 11 Then 200 nm thick films of P͑VDF/TrFE͒ 75/25 mol % copolymer were coated by spin casting 6 wt % cyclohexanone solutions. The P͑VDF/TrFE͒ polymer films were cured at 160°C for 2 h in a vacuum oven and then subsequently quenched to the RT by blowing N 2 gas ͑99.9% purity͒.…”