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 and Electronic 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) SemiconductorEPT devices ・ Scaling merit ( 電子相変化デバイス )

What are EPT devices? Stimulation (T, H, E, N) H 2 O: 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 K Charge order3D charge-ordering2D charge-ordering Dielectricityanti-ferroelectricparaelectric Magnetic propertyferrimagneticparamagnetic Fe/O double layer Fe 3+ :Fe 2+ =1:1 Re/O ? + Interaction c a b ReFe 2 O 4 (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, (2008). Electronic phase transition Resistive switching

Motivations ・ Fabricating the ReFe 2 O 4 thin films, then observing the resistive switching phenomenon. then observing the resistive switching phenomenon. ・ For the electronics applying, investigate the switching phenomenon 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… Laser Recipe Laser medium: ArF ( = 193nm) T sub = 950˚C, p O2 = 1×10 −4 Pa Post-annealing: 800˚C, in vacuum (b.p. ~ 1×10 −5 Pa)

I could fabricate LuFe 2 O 4 and YbFe 2 O 4 thin films. 1/2Re 2 O 3 +2Fe+5/2O 2 ReFe 2 O 4 HoEr Tm YbLu Y Out-of-plane 2  /  scan Achievable in our chamber * * * * * * * (003) (006) (009) I succeeded in fabrication of LuFe 2 O 4 and YbFe 2 O 4 thin film. The orientation is ReFe 2 O 4 [001]//YSZ[111] T = 1470 K * * *

Revelation of charge-ordering E A = (eV) Electron transport properties are same as that of bulks’. Existence of charge-ordering confirmed. LuFe 2 O 4 YbFe 2 O 4

Resistive switching phenomenon was observed V sample

Interrelation between charge-ordering and switching 3D 2D 3D 2D 310K 300K LuFe 2 O 4 YbFe 2 O 4 Resistive switching phenomenon is observed under 3D charge-ordering region

Conclusion ・ I successfully fabricated ReFe 2 O 4 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 ReFe 2 O 4