ISIR Tanaka lab.Tatsuya Hori

層状鉄酸化物を用いた電子相変化デバイスの応用に向けた研究

Differences between semiconductor device andElectronic phase transition device (EPT device).

・ Semiconductor device　 Current control is main feature.

・ EPT device　 Transition induce drastic changing of physical property. Unprecedented almost all new device.　 (Not only current control)

Semiconductor EPT devices

・ Scaling merit

( 電子相変化デバイス )

What are EPT devices?

Stimulation(T, H, E, N)

H2O: Ice

Electrons: Insulator

Water

Metal

Applying the transition of stable electronic phase for electronics

Necessity for invention of EPT device

Considerable expectations…But only few device works in RT has invented

Conceivable applications

・ Optical switch・ Photochromic devices・ Magnetic modulators・ ESD protection devices・ etc…

Candidate material for EPT device

　 240 320 350 500KCharge order 3D charge-ordering 2D charge-ordering 　Dielectricity anti-ferroelectric paraelectric 　Magnetic property

ferrimagnetic paramagnetic 　

Fe/O double layerFe3+:Fe2+=1:1

Re/O

?

+ −Interaction

+or

c ab

ReFe2O4

(Re = Dy, Ho, Er, Tm, Yb, Lu, Y)

We can get the charge-ordering in room temperature. (= the state electrons are frozen)

Electronic field induced resistive switching in RT

L. J. Zeng et al., EPL 84, 57011 (2008).

Electronic phase transition Resistive switching

Motivations

・ Fabricating the ReFe2O4 thin films, 　 then observing the resistive switching phenomenon.

・ For the electronics applying, investigate the 　 switching phenomenon

What is PLD method?

Substrate

Target

Heater

Plasma plume

Gases

Feature・ Suitable for high-melting-point materials.・ Easy to control thickness.・ In situ RHEED observation.・ etc…

Lase

rRecipeLaser medium: ArF (l = 193nm)Tsub = 950˚C, pO2 = 1×10−4 PaPost-annealing: 800˚C, in vacuum (b.p. ~ 1×10−5 Pa)

I could fabricate LuFe2O4 and YbFe2O4 thin films.

1/2Re2O3+2Fe+5/2O2 ReFe2O4

10 20 30 40

HoFe2O4 ErFe2O4 YbFe2O4 LuFe2O4

Inte

nsity

(ar

b. u

nit)

2 (deg.)

10-7

10-6

10-5

10-4

10-3

log(

PO

2/(P

a))

Ho Er Tm Yb LuY

Out-of-plane 2q/q scan

Achievable in our chamber

** ***

* *

(003

)

(006

)

(009

)

I succeeded in fabrication of LuFe2O4 and YbFe2O4 thin film.The orientation is ReFe2O4[001]//YSZ[111]

T = 1470 K

*

*

*

Revelation of charge-ordering

2.5 3 3.5 4 4.5 51

10

102

103

104

105

1000/Temperature (K-1)

Res

istiv

ity (

cm)

2.5 3 3.5 4 4.5 5

100

101

102

103

104

Res

istiv

ity (

cm

)

1000/Temperature (K-1)

Electron transport properties are same as that of bulks’. Existence of charge-ordering confirmed.

LuFe2O4 YbFe2O4

Resistive switching phenomenon was observed

Vsample

-50 -40 -30 -20 -10 0 10 20 30 40 50-1

-0.5

0

0.5

1

Voltage (V)

Cur

rent

(m

A)

-50 -40 -30 -20 -10 0 10 20 30 40 50-1

-0.5

0

0.5

1

Voltage (V)

Cur

rent

(m

A)

At 285 K 1st

-50 -40 -30 -20 -10 0 10 20 30 40 50-1

-0.5

0

0.5

1

Voltage (V)

Cur

rent

(m

A)

At 285 K 1st 2nd

-50 -40 -30 -20 -10 0 10 20 30 40 50-1

-0.5

0

0.5

1

Voltage (V)

Cur

rent

(m

A)

At 285 K 1st 2nd 3rd

Interrelation between charge-ordering and switching

250 300 350 400

104

T (K)

Eth

(V

/cm

)3D 2D

250 300 350 400104

105

T (K)

Eth

(V

/cm

)

3D 2D

40

0.4

0 V (V)I (

mA

)

310K

40

0.4

0V (V)

I (m

A)

300K

LuFe2O4YbFe2O4

Resistive switching phenomenon is observed under 3D charge-ordering region

Conclusion

・ I successfully fabricated ReFe2O4 thin films and　 observed resistive switching phenomenon in two systems.

・ I got the data which imply switching phenomenon　 is observable under 3D charge-ordering region.

From the above, I revealed this kind of switching phenomenon is common property of these charge-ordering systems.

Fe/O double layer in ReFe2O4