slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
11/13 PowerPoint Presentation
Download Presentation
11/13

Loading in 2 Seconds...

play fullscreen
1 / 19

11/13 - PowerPoint PPT Presentation


  • 139 Views
  • Uploaded on

11/13. Development of ferrite-based electronic-phase-change devices. Tanaka lab. Tatsuya Hori. What is Mott insulator ?. Hubbard model. As U increases. U : Coulomb repulsion t : Transfer integral . Localization ( U ) vs Delocalization ( t )

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '11/13' - amil


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

11/13

Development of ferrite-based

electronic-phase-change devices

Tanaka lab.Tatsuya Hori

slide2

What is Mott insulator ?

Hubbard model

As U increases

U : Coulomb repulsion

t : Transfer integral

Localization (U) vs Delocalization (t)

U > t insulator with immobile electrons

slide3

Electronic phase change

External stimuli

(T, H, E, n)

H2O :

Electrons : Insulator

Metal

New promising principles to create devices

slide4

Electronic-phase-change devices

Pr0.7Ca0.3MnO3

Fe3O4

However, device operations have so far been limited

at low temperature (<<RT) !

Fe3O4: S. Lee et al., Nature Mater.,7, 130 (2008). PCMO: A. Asamitsuet al., Nature,388, 50 (1997).

slide5

A candidate material : layered ferrite

RE = Y, Dy…Yb, Lu

Fe2.5+ (Fe3+:Fe2+=1:1)

+or

RE

?

O

Fe

RE/O

layer

+

Interaction

Fe/O

bilayer

~320 K

~500 K

Charge-ordered (immobilized) state

at room temperature

N. Kimizuka et al., Solid State Commun., 15, 1321 (1974).

吉井et al.,日本結晶学会誌,51, 162 (2009).

slide6

Electric-field-induced current switching

Bulk crystal

Electronic phase change Current switching

L. J. Zeng et al., EPL84, 57011 (2008).

slide7

Charge-ordered LuFe2O4 films

Grown by pulsed-laser deposition

Out-of-plane 2q/q scan

Thermaly activated

conduction

LuFe2O4

c-axis oriented growth

*

(003)

(006)

(009)

slide8

Current switching in the thin-film structure

LuFe2O4

310K

300K

3D

2D

Vsample

A significant step to device applications

K. Fujiwara, T. Hori, H. Tanaka, J. Phys. D: Appl.Phys., 46, 155108 (2013).

slide9

Summary : current switching function

・Fabricated charge-ordered LuFe2O4 and YbFe2O4thin films.

・Induced the current switching effect in the thin film structure.

slide10

Current work

What’s my next target ?

Another way to control the electronic phases by electric fields.

E

It’s electrostatic carrier doping.

slide11

What is electrostatic doping ?

VG

Gate

Metal

Insulator

Gate insulator

Source

Drain

Mott insulator

Substrate

External control of the number of charge carriers

and resulting electronic states (order vs disorder)

slide12

Collapse of CO by chemical carrier doping

LuFe2O4

Lu(Fe1.85Mg0.15)O4

Fe+2.5 (Fe+2 : Fe+3 = 1 : 1)

Fe+2.5-dMg+2

Superlattice reflections

Very sensitive to external carrier doping !

Y. B. Qin et al., J. Phys. Condens. Mater. 21, 015401 (2009).

slide13

Key component : gate insulator

Gate

Gate insulator

Source

Drain

Substrate

Q = CV

C = ere0S/d

n2D = Q/S = ere0V/d

slide14

Mott-transition needs large n2D

at 0 K

C. H. Ahnet al., Nature424, 1018 (2003).

slide15

Ionic liquid – giant carrier accumulation capability

VO2

Suitable for

Mott-insulator systems

・High n2D ~ 1013~15 /cm2

・No structural mismatching

M. Nakano et al., Nature487, 459 (2012).

slide16

Toward purely electronic Mott-transistors

Structural phase transition

NdNiO3 : MITcontrol

(Charge-Disproportionation)

Structural

phase

transition

MIT

S. Asanuma et al., APL97, 142110 (2010).

Pursue and investigateMIT in

the system without struct. phase trans.

slide17

Device structure

VG

VD

ID

IG

Ionic liquid*

Separator

SiO2

D

S

G

REFe2O4

Cation

YSZ(111) Substrate

Anion

A

A

*N,N-Diethyl-N-methyl-N-(2-methoxyethyl)ammonium

bis(trifluoromethanesulfonyl)imide

slide18

Fabrication processes

Thin film fabrication

Masking process

Milling process

Masking process

Electrode attaching

Separator

SiO2

Masking process

Ionic liquid*

REFe2O4

D

S

G

Separator attaching

YSZ(111) Substrate

Dropping ionic liquid

slide19

Summary

Through fabricating and evaluating

Mott-transistors with REFe2O4

・Reveal the nature of the field effect in

Mott insulator systems.