Properties of Au/Pb(Zr 0.52 Ti 0.48 )O 3 / Bi 4 Ti 3 O 12 /p-Si Ferroelectric Memory Diodes
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Properties of Au/Pb(Zr0.52Ti0.48)O3/ Bi4Ti3O12/p-Si Ferroelectric Memory Diodes Jun Yu1
Hua Wang1,2 Xiaomin Dong1
Wenli Zhou1
Yunbo Wang1
Lili Zhu1
1 Department of Electronic Science & Technology, Huazhong University of Science & Technology, Wuhan, 430074, China 2 Department of Electron & Information, Guilin institute of Electronic Technology, Guilin, 541004, China
Abstract A ferroelectric memory diodes that consists of Au/Pb(Zr0.52Ti0.48)O3/Bi4Ti3O12/p-Si multilayer configuration was fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the electrical characteristics of the ferroelectric film system were investigated. The polarization-voltage curve of Pb(Zr0.52Ti0.48)O3/Bi4Ti3O12 thin films system had an asymmetry hysteresis loop with Pr=20µC/cm2 and Ec=48 kV/cm, and the decay in remnant polarization was only 10% after 109 switching cycles. The C-V curve and the I-V curve showed memory effects derived from the ferroelectric polarization of PZT/BIT films. The current density was 6.7È10-8A/cm2 at a voltage of +4V, and the conductivity behavior is discussed. The results suggested that the growth of the BIT ferroelectric layer is helpful to good ferroelectric properties, fatigue and capacitance retention characteristics.
Key words: Ferroelctric diodes, Pb(Zr0.52Ti0.48)O3, Bi4Ti3O12, buffer layer, pulsed laser deposition In recent years, ferroelectric memories have attracted much attention due to the promise of high speed, high density, low operation-voltage, radiation hardness and low power consumption
[1, 2]
.
Pb(Zr,Ti)O3 (PZT) has been widely studied for ferroelectric random-access memories (FRAMs), metal-ferroelectric-semiconductor field-effect transistors (MFS-FETs) and ferroelectric memory diode (FMD)[2-4] due to its higher permitivity(εr), higher remanent polarization(Pr) and lower coercive field (Ec). FMD is a kind of ferroelectric memory with a metal-ferroelectric-semiconductor (MFS) structure like an MFS-FETs, but it allows a lower voltage operation than an MFS-FETs and provides nonvolatile memory without a data storage capacitor or floating gate. However, the synthesis of PZT thin films on a Si substrate, which is important for practical applications, is rather difficult and the serious interaction and interdiffusion between PZT ferroelectric films and Si substrate lead to low retention and large leakage current, which are the fundamental properties of ferroelectric memory. To obtain a good interface and highly oriented ferroelectric films on silicon substrate, CeO2, SiO2 and CaF2 have been widely introduced as buffer layers between the ferroelectric films and the Si substrate [4-6]
. But these buffer layers are not ferroelectric materials themselves and their permitivity(εr) are much lower than PZT’s, which will increase the operation voltage and impair the ferroelectric properties of ferroelectric memory. To solve the interface problem, we introduced Bi4Ti3O12 (BIT) as
the buffer layer between PZT and Si substrate. The BIT is a kind of ferroelectric material its
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