New functionalities in abundant element oxides: ubiquitous element - - PowerPoint PPT Presentation

Hideo HOSONO

Tokyo Institute of Technology, Yokohama, Japan

Japan-EU Workshop “Substitution of Critical Raw Materials” @ EU Japan Office(Nov.21)

nm-sized structure μm-scale m-sized structure

New functionalities in abundant element oxides: ubiquitous element strategy

Function Element Structure

interface defect nanostructure

Unconventional Valence state

measurement theoretical

Research on C12A7 led to a Science & Technology Policy

Ti 10 H 9 Mg 8 K 7 Na 6 Ca 5 Fe 4 Al 3 Si 2 O 1 Ti 10 H 9 Mg 8 K 7 Na 6 Ca 5 Fe 4 Al 3 Si 2 O 1 Ti 10 H 9 Mg 8 K 7 Na 6 Ca 5 Fe 4 Al 3 Si 2 O 1 Ti 10 H 9 Mg 8 K 7 Na 6 Ca 5 Fe 4 Al 3 Si 2 O 1 Element Order

Clark Number

“Element Strategy for Sustainable society” National Policy (Started from 2008)

Ubiquitous Element Strategy

size charge

• rbital

spin

Fe As La

e-

La-O layer Fe-As layer O F Fe As La

e-

La-O layer Fe-As layer O F

Proposal of Transparent Amorphous Oxide Semicoductors (1995) Fabrication of transparent flexible transistor(2004, Nature) 70-inches , UD, 240Hz LCD driven by TAOS-TFT Arrays (Samsung@ FPD Int ’10)

Focusing on Built‐in nanostructure In 12CaO・7Al2O3(1998)

Conversion toTransparet metal. (2004,Science) Breaking a common sense that Iron is the last element for superconductivity

Highest Tc except Cuprates, “2 nd fever”

（2008,JACS & Nature)

Electro-active materials made from 3 Structural Materials

High Performance Transistor Transparent metal from Cements

Discovery of a new high Tc

• Supercond. since 1986

molten metallic electride (2011, Science)

Transparent p-type semiconductor

high precision, high quality ultra low power assumption 2010 2011 2012

tablet computer terminal smart phone

Introduction of IGZO-TFT to Kameyama-2 factory

Production expansion

• f mobile LCD

SHARP has announced adoption of a-IGZO-TFTs for mobile LCDs (June 3, 2011)

• Pres. Katamaya

a-IGZO TFTs are going to apply to iPad3 with high resolution.

JST issued parent license ( non-exclusive) of I GZO-TFT

• Sam sung EL

• A constituent of alumina cements
• Large band gap ~7 eV
• Cubic (a = 1.199 nm, I43d)
• Unit cell: Ca24Al28O66 = [Ca24Al28O64]+4+ 2O2–

Unit cell 1.199 nm

12CaO∙7Al2O3 (C12A7)

Densely Packed Sub-nano-sized Cages

12 Cages 6×1021 cm–3

Free Oxygen Ions

1×1021 cm–3 Ca Al O

• Mp. 1415 ºC

Fast Oxygen I on Conductor single crystal powder

Electronic Structure of C12A7

• 4
• 2

2 4 6 Γ Ξ Ρ Ζ Γ Α Μ

Energy (eV)

Ζ

Conduction Band (Framework) Valence Band (Framework) Cage Conduction Band Wave functions confined in cages O2p (Free Oxygen)

PRL(2003), PRB(2005), Nanolett(2007), Adv.Mat (2007)

k

tunneling Evac WF=2.4eV

Adv.Mater. (2007)

Cage Conduction Band

Cage conduction band

Fermi edge

Hard XPS

Electron-doping to C12A7

e–

TiOX Ti

Out-diffusion of free O2-

[Ca24Al28O64]4+ (2O2–) + Ti → [Ca24Al28O64]4+ (4e–) + TiOX

cage Free O2-

(insulating) (metallic) (Max 2.3x102 1cm -3)

Science(2003), Nanolett(2007)

Metal – Insulator Transition

Hopping Conduction Band Conduction electron concentration In cages Nc = ~1 × 1021 cm–3 Metal – Insulator Transition

Metal composed of typical insulators, lime and alumina !

Polaron : electron localized by lattice distortion

Nano Nano Lett

• Lett. 2007

. 2007

1.5x103Scm -1@RT

3x1019cm -3 2x1021cm -3

σ = ∼10-10Scm -1

Metal-Superconducting Transition in C1 2 A7 :e - single crystals

JACS.(２００７)

100% 100%

First s-metal superconductor at P= 1atm FZ-grown single crystal

Work function of C12A7:e-

~ 2.4 eV

Ca Mg Ba Sr Na Li K Rb Cs Al Eu Sm LaB6

Alkaline earth

C12A7:e-

1 2 3 4

Alkaline Rare earth

Work function (eV)

2.7 2.3 2.2 2.1 2.9

O-LED E-gun

Unique Properties of C12A7:e- metal:

small workfunction and chemical inertness

2.4eV

WF=

WF

Li(2.9),Na(2.7),K(2.4), Mg(3.7),Ca(2.9) Adv.Mater(2007) (cage conduction band)

① ② ③ ④ ⑤ ⑥ ① ② ③ ④ ⑤ ⑥

1,2-diol O C Ar H O H H Ar Ar HO OH Al

Encaged electron

Ca

in water

• 4
• 2

2 4 6 Γ Ξ Ρ Ζ Γ Α Μ

Energy (eV)

Ζ

H -

C12A7:O-

Strong

• xidation power

C12A7:H-

UV(e-beam)-induced Insulator-conductor conversion

C12A7:e-

Field e-emitter Cathode for OLED

3x1019cm -3 2x1021cm -3 3x1019cm -3 2x1021cm -3

MI& MS transition

ReRAM

reagents for organic reaction

C12A7:O2

• Unique band structure

single cryst. thin film

Low work function but stable

マスク 絶縁性 C12A7:H-

C12A7 world

Surface Melt&Glass

Is it possible?

Low work function ~2.4 eV High density of electron trapped cages ~1013/cm2

Activation of Inert chemical species at C12A7 electride surface

Low work function electron

Activation by electron transfer

STM Observation on C12A7:e- surfaces

Ex Situ I-V characteristics

Enlarged View

(110) (111) (100) 3x3 nm, +2.5 V, 0.05 nA

0.2 ~ 0.3 nm ~ 4 nm ~ 0.2 nm 2 ~ 7 ° atomistic order

1 nm 1 nm 1 nm

Surface model for (100)

Cage conserved Bulk truncated

Atom density Thermal stability Open mouths : Not observed by experiments Conductivity

Cage conserved

STM Images vs. Cage conserved model

(110) (111) (100)

X: Ca

White: Defect Black: Adatom

ACS Nano (2011)

Can we obtain solvated electron in high temperature oxide melt /glass?

Solvated cation

Solvated electron

Liquid ammonia

M‐I transition

Molten state of C12A7 electride : metallic conduction

C12A7:O2− Melt C12A7:e− Melt Transparent Strongly Colored

The photo was taken through a color filter

Metallic conducting Ionic conducting Concentration of Solvated electrons ~1021cm-3 Science, 333, 71 (2011)