Multi-states nonvolatile opto-ferroelectric memory material and process for preparing the same thereof

Patent metadata

Field	Value
Publication number	US-10115456-B2
Application number	US-201715406236-A
Country	US
Kind code	B2
Filing date	Jan 13, 2017
Priority date	Jan 14, 2016
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

The invention deals with multi-states nonvolatile opto-ferroelectric memory element and method of preparing the same thereof. This invention describes multi-states nonvolatile opto-ferroelectric memory element consisting of opto-ferroelectric memory material comprised of Pb 1-x (Bi 0.5 Li 0.5 ) x (Ti 1-y Zr y )O 3 , wherein x=0.2 to 0.8 and y=0.2 to 0.6, said memory material (PBLZT) photovoltaic ferroelectric material is characterized by a single-phase opto-ferroelectric materials, photovoltaic and multi-states ferroelectric memory material. The invention relates to process of preparing multi-states nonvolatile opto-ferroelectric memory material by solid route, solution-gel process and pulsed laser process. It describes development of multi-states nonvolatile opto-ferroelectric memory material at room temperature. Invention describes a ferroelectric material whose polarization is switched by white light and low power LASER (10-50 mW) with wavelength (405 nm).

First claim

The invention claimed is:

1. Multi-states nonvolatile opto-ferroelectric memory element comprising:
an opto-ferroelectric memory material comprised of:
Pb 1-x (Bi 0.5 Li 0.5 ) x (Ti 1-y Zr y )O 3

wherein
x=0.2 to 0.8
y=0.2 to 0.6

said memory material (PBLZT) photovoltaic ferroelectric material includes a single-phase opto-ferroelectric materials, photovoltaic and multi-states ferroelectric memory material.

2. The opto-ferroelectric memory element as claimed in claim 1 , wherein spontaneous polarization is in the range of 4-30 μC/cm 2 with and without using illumination of light from near UV to visible region frequencies by said opto-ferroelectric memory element and said probed frequencies are ranging from 0.1 Hz to 10 Hz.

3. The opto-ferroelectric memory element as claimed in claim 2 , wherein illumination used is white light tungsten filament at 20-100 mW/cm 2 or white light xenon lamp at 20-100 mW/cm 2 and monochromatic light source is 405 nm at 30-50 mW.

4. The opto-ferroelectric memory element as claimed in claim 1 , wherein fatigue ranges from 10-25% under high stress electric field (80 KV/cm) in the absence of light, and fatigue is improved under high stress electric field (80 KV/cm) under illuminated light ranging less than 10-100 mW/cm 2 .

5. The opto-ferroelectric memory element as claimed in claim 1 , wherein ON and OFF photocurrent is ranging from 4:1 to 6:1 depending on 405 nm (10-50 mW) laser and white light source.

6. The opto-ferroelectric memory element as claimed in claim 1 , wherein white and monochromatic light are used to switch the polarization states, and concerned logic states for multi-states memory elements.

7. The opto-ferroelectric memory element as claimed in claim 1 , wherein white light and 405 nm wavelength laser source is used, and wherein the laser source is selected from complete range of near UV and visible light for realizing the multi nonvolatile logic states.

8. The opto-ferroelectric memory element as claimed in claim 1 , wherein dielectric constant is ranging below 1000 and low tangent loss is ranging below 0.05 (<0.05) over temperature ranging below 400° C. and frequency ranging from 50 Hz to 1 MHz.

9. The opto-ferroelectric memory element as claimed in claim 1 , wherein switching of polarization is ranging from 100-500% first time under 405 nm laser light depending on probe frequency and electrical stress.

10. The opto-ferroelectric memory element as claimed in claim 1 , wherein switching is fast and repeatability of polarization is ranging from greater than two minutes and less than 30 minutes by using 405 nm laser light, and wherein the polarization is in the range of 20-50% depending on probe frequency and electrical stress.

11. The opto-ferroelectric memory element as claimed in claim 1 , further comprising multi-states memory with an electrically WRITE operation and optically READ operation and vice-versa, and/or combination of these two, and/or separately by electric field and different wavelength of monochromatic laser light in near UV and visible regions.

12. The opto-ferroelectric memory element as claimed in claim 1 , wherein transformer oil or silicon oil or combination thereof is used as electrical stress medium.

13. Opto-ferroelectric nonvolatile multistate memory cells, visible or weak UV detector, perovskite based photovoltaic and miniaturized microelectronic memory devices prepared by multi-states nonvolatile opto-ferroelectric memory element as claimed in claim 1 .

14. A process for preparation of opto-ferroelectric material,
Pb 1-x (Bi 0.5 Li 0.5 ) x (Ti 1-y Zr y )O 3
wherein x=0.2 to 0.8 and y=0.2 to 0.6,

said process comprising steps of:
i) physical mixing of ingredient oxides of PbO (99.5%), ZrO 2 (99.86%), TiO 2 (99.96%), Bi 2 O 3 (99.99%) and Li 2 CO 3 (97%) in a ratio of x=0.2 to 0.8, and y=0.2 to 0.6 and further mechanical mixing in liquid alcoholic (Isopropyl alcohol—IPA) media in the range of 5 to 10 ml with 99.9% purity, and mol fraction of Pb 1-x (Bi 0.5 Li 0.5 ) x (Ti 1-y Zr y )O 3 (x=0.4 & 0.5, and y=0.2) (PBLZT) electro-ceramics;
ii) calcining composites of step (i) at a temperature in the range of 800-850° C. for a period of 11-13 hours to get the desired phase followed by X-ray diffraction (XRD) study to verify the phase purity and crystallinity;
iii) sintering composites of step (ii) at a temperature in the range of 1100-1200° C., to obtain desired opto-ferroelectric material; and
iv) sintering composites of step (iii) were further processed for mechanical grinding and polishing to get the desired thickness in the range of 400 to 600 microns of opto-ferroelectric material.

Assignees

• Council Scient Ind Res

Inventors

• Kumar Ashok
• Borkar Hitesh
• Rao Vaibhav
• TOMAR Monika
• Gupta Vinay

Classifications

• B05D5/12

  to obtain a coating with specific electrical properties · CPC title

• G11C11/42 Primary

  using opto-electronic devices, i.e. light-emitting and photoelectric devices electrically- or optically- coupled {or feedback-coupled} · CPC title

• H01L28/55

  Electricity · mapped topic

• G11C11/2275

  Writing or programming circuits or methods · CPC title

• G11C11/2273

  Reading or sensing circuits or methods · CPC title