A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Summary

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Abstract

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

Introduction

The successful fabrication of flexible nonvolatile memory elements (NVME) plays a key role in exploiting the full potential of flexible electronics. NVME shall feature light weight, low cost, low-power consumption, fast speed and high storage density capabilities besides data storage, information processing and communication. Perovskite Pb (Zr,Ti)O₃ (PZT) acts as a popular system for such applications considering its large polarization, fast polarization switching, high Curie temperature, low coercive field and high piezoelectric coefficient. In ferroelectric nonvolatile memories, an external voltage pulse can switch the two remnant polarizations between tw....

Protocol

1. Fabricating Flexible PZT Thin Films

1. Cut a 1 cm x 1 cm mica substrate from a mica sheet with scissors.
2. Fix this 1 cm x 1 cm mica substrate on a desk using double-sided tape.
3. Use tweezers to peel-off the mica layer-by-layer until the desired thickness (50 µm), measured with a micrometer.
4. Paste this freshly cleaved mica substrate on a 5'' substrate holder using a thin layer of silver paint and cure it at 120 °C on a hot plate for 10 minutes to affix mica on substrate firmly.
5. Put the PLD (Pulsed Laser Deposition) substrate holder into the PLD chamber.
6. Select the repetition rate (e.g.

Results

The epitaxial PZT/SRO/CFO/mica thin films were deposited with the pulsed laser deposition technique as outlined in Step 1. Figure 1 shows the growth scheme and Figure 2 shows an actual flexible NVM element based on the PZT.

Mechanical stability is a crucial aspect of flexible device application. The macroscopic ferroelectric performance of the heterostructure ag.......

Discussion

The key step in the fabrication of ferroelectric elements lies in the use of a clean and even/flat substrate surface. Though freshly cleaved mica surface is atomically smooth, it is necessary to pay attention to preventing surfaces from suffering visible splintering, split layers, cracks, inclusions, etc. After deposition of the PZT layer, the sample was cooled under a high oxygen pressure (200-500 Torr) to reduce the oxygen vacancies. Ex situ top platinum electrodes were deposited via a predefined mesh.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Equipment
hot plate	Polish	P-20
PLD system	PVD products	PLD 5000
Ferroelectric test system	Radiant Technologies Precisions workstations	RT66A
Semiconductor device analyzer	Agilent	B1500A
Bending molds	home-made		Machined teflon material
Bending stage	home-built		Labview interfaced setup which provides a prescise displacemnt as small as 1 micrometer
Sputtering system	Beijing Elaborate	ETD-3000
Materials
mica(001) sheets	Nilaco corporation	990066
conductive silver paint	Ted Pella, INC	No.16033
CoFe2O4 target	Kurt J.Lesker
SrRuO3 target	Kurt J.Lesker
PbZr0.2Ti0.8O3 target	Kurt J.Lesker
Pt target	Hefei Ke jing