MEXT Elements Strategy Initiative: To Form Core Research Centers
Electronic Materials

Tokodai Institute for Element Strategy (TIES)ESIAC2019 Activity Report

Hideo Hosono
Director/Representative Researcher
December 13, 2019

ESIAC2019 TIESOutline
1. Background
2. Goals and Approaches
3. Organization
4. Roadmap
5. Technical Topic
6. Achievement
7. Summary

ESIAC2019 TIES

1. Background
Characteristics of Electronic Materials

Style of TIESl Contributions of electronics industry to GDP is as large
as those of automotive and chemical ones.

l Persistently based onacademia.

l Almost all elements are used in electronic materials
composed of wide variety of matters: dielectrics,semiconductors, superconductors, etc.

l Different perspective fromthose of previous nationalprojects.
l Focus on variety of mattersand utilization of abundantelements.

l There has so far been a large number of big national
projects in Japan.

Problems in previous materials researches
matters

Similarity of crystalstructure

Similarity of chemicalbonding

Semiconductors Diamond-like structure

Covalent bonding

TCOs

Heavy-metal cation oxides

Ionic bonding

Ferroelectrics

Perovskite structures2 electron configuration
Heavy metalsApproaches aredeadlocked!
We needexploring studies
based on novel
viewpoints.
3

ESIAC2019 TIES

2. Goals & Approaches
1. Breaking the spells over old-fashioned materials designconcepts base on past experiences of successes,
2. Exploring electronic material frontiers by nonconventional combination and arrangements of elements,
3. Establishing new design concepts and guidelines forfurther advancement of materials technologies,
4. Creating and utilizing dreamlike electronic materials
composed of abundant and non-toxic elements.
Technical issues

Reason why unresolved

Approaches

Stagnant development ofsemiconductor materials

Impact of previous
successes in existing
specific materials

Ubiquitous elements

Stagnant developmentof ferroelectric materials

Novel anions, H–,
electrides, metalides

Concentration upon
specific elements
and crystal structures

Unique nanostructures

Immature
guiding principles

Unique electronic states
Dirac electron systems

Demand for better TCO
Stagnant increase of
superconductor TC

Novel materials
High mobility/highly stable/flexible semiconductors
Highly efficient inorganic
light-emmiting materials
Heavy metal-free
flexible TCOs
Heavy & toxic elements-free ferroelectricsToxic elements-freehigh TC superconductors

4

ESIAC2019 TIES

3. Organization: strong collaborations among institutes

MCES

5

ESIAC2019 TIES

3. Organization: young P.I.s for 10-years project
Most of the P.I.s are forties at the beginning of the project.
Materials Creation Group

Hosono GL
Ohtomo SGL
semiconductor
superconductor

Funakubo
ferro/dielectrics

Hiramatsu
epitaxial films

Kanemitsu *Kondo

Ohashi2D nanosheetssemiconductor
dielectrics

Yamada *Shimamuratunabledielectrics

single crystal
growthoptical property
emissive material

Wakabayashi *SR X-rayinformatics-based

Murakami

Electronic Theory Group
Kamiya GL

Murakami

semiconductor

DIrac electrons

ObaSaito

semiconductor

2D materials

Analysis & Evaluation Group
Majima GL

PF X-rayneutronKumigashira

KimotoHRTEM

PF X-ray
ARPES

YamauraSakataKadonoPF X-rayneutronSPring-8
X-ray

J-PARCmuon

sub-nanodevices

NIMS
members

KEKmembers* New attendees in 20196

ESIAC2019 TIES

4. Roadmap

Phase 1
Phase 2comprehensive
materials selection
materials exploration

Phase 3collaboration with industry

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ESIAC2019 TIES

4. Focus areas after Phase 2
Semiconductorsl Lacked areas in mainstream ofJapanl High mobility/Bipolar/Ultra-wide Egl Novel doping methodsl P-type amorphous semiconductors
l Nitrides, Sulfides、Hydridesl Dirac electron systems

Roles & Functionalities ofHydrogenl Ever-ignored hydrogens in oxides
l Quantification & state analyses
l Correlation between hydrogens
and electronic statesl Hydrogens as functional elementsl Novel hydride materials

High-kdielectrics/ferroelectrics
l For power electronics at high T
l Stable oxygen deficiencies
l Abundant & nontoxic elementsl Non/low-dimensional perovskytesl Non-oxide/(oxy)nitridesl Hydrides

Collaboration of theory &synthesis
Rapid screeningl Calculation methods with defects
l Theoretical prediction of synthesis
routesl Materials Informatics
8ESIAC2019 TIES

5．Technical Topics
Dielectrics

Sci. Reps. 6, 32931 (2018)

ion
borat
Colla dustry
nw i th iDielectrics

Phys. Rev. Mater. 2, 045603 (2017)

ion
borat yalloC
trndusw i th i

Fluorite Ferroelectrics
with high TC & PS: HfO2:Y

Stable High-k Silicate
Dielectrics: (BiXLa1-X)2SiO5l Ferroelectric epitaxial thin films of Y-doped HfO2
was successfully grown and high TC and PS weredemonstrated.

l The materials creation group discovered silicate
ferroelectrics of Bi2SiO5 (BSO).

l In addition to power electronics application, the thinfilm exhibits highly-stable ferroelectric memory
switching with retention cycle over 1011.

Positioning map of TC-PS correlationl DFT calculations elucidated the origin offerroelectricity, implying the BSO can beparaelectric by substitutional La doping into Bi sites.
l (BiXLa1-X)2SiO5 shows stable high-k for wide
temperature range which satisfies an industrial
standard for condensers on automobiles.

Crystal structure

Temperature dependenceof dielectric constant and loss

9ESIAC2019 TIES

5．Technical Topics
Cryst. Growth Des. 16,2151 (2016)

Dielectrics

noratio
ball
Co
try
ndus
i
hti
w

Semiconductor

JACS 139, 17175 (2017)

ionborat yal
loC
trndusw i th i

Piezoelectrics for Automobiles : Transparent Bipolar Oxysulfide
CTAS (Ca3TaAl3Si2O14)
Semiconductor: ZrOSl The materials creation group succeeded in growover two-inches wide single crystals of Langasite
piezoelectric CTAS (Ca3TaAl3Si2O14).
l CTAS satisfies a demand of high-temperatureleakage (>1010 Ω cm at 400 ℃) for extreme leanburn conditions in automobile combustion engines.
l Pressure sensor manufacturer fabricatedprototype module showing 150% larger sensitivity.

n P-type doping is difficult in late/post-transition
metal oxides due to oxygen vacancies.
l New design concept was established based onearly transition metals with high valence andcoordination numbers suppressing anion vacancies.
l Tetragonal ZrOS was theoretically predicted andexperimentally demonstrated with wide band gapof 2.5 eV and bipolar dopability.

Resistivity (Ωcm)

Temperature (℃)
1000 800
6004001010

CTAS N2air108
LTGA2-inch single crystal

106
0.8

1.0

1.2
1.4
1000/T (K-1)

Temperature dependenceof resistivity

Band structure
Sensor module

Bipolar doping behavior

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ESIAC2019 TIES

5．Technical Topics
Semiconductor

Adv. Mater. 30, 1706573 (2018)ion
borat yalloC
trndusw i th i

Semiconductor

Adv. Mater. 30,1804547 (2018)ion
borat yalloC
trndusw i th iP-type Amorphous
Semiconductor: a-Cu-Sn-I

Blue-Light Emitting Lead-Free
Inorganic Perovskite: Cu3Sn2I5

n Among previous amorphous semiconductors, only
n-type oxides show high carrier mobility.

n Halide perovskite semiconductors for inorganic
light emitters always contain a toxic element, lead.

l We notice that 5p orbitals of iodine are similar to s
orbitals of heavy metals and could have a large
spherical spread around an iodine atom.

l We focused on Cu halides with small binding
energy, and found lead-free Cu3Sn2I5 having zerodimensional optically-active sites in the electronicstructure.

l P-type transparent (Eg~3 eV) amorphoussemiconductor with 9 cm2V–1s–1 was demonstrated
by 140 ℃ solution-processed a-Cu-Sn-I thin films
to be applied to PV/light-emitting devices or TFTs.

Crystal & band structure

Hall mobilityl Bright blue-light emission with PLQY>90% andLED were demonstrated.

PL & PLE spectra

I-V / L-V characteristics of LED

11ESIAC2019 TIES

5．Technical Topics
Semiconductor

PNAS 114, 233 (2017)

ion
borat yalloCtrndusw i th iAppl. Phys. Rev. 6, 031402 (2019)

ionborat
Colla dustry
nw i th i

Universally Ohmic with Low Work Function & High Mobility ZSO
Application to OLED
Application to PeLEDn Electron transport layers (ETL) of current OLED
are made of organics with very low mobility (~10–3cm2V–1s–1) which limits yield and efficiency.
l We discovered amorphous Zn-Si-O (ZSO) exhibit
high mobility (~1 cm2V–1s–1) and low work function(3.5 eV), and can form excellent ohmic contact.
l OLED devices with ETL of ZSO show better
performance than ordinary devices with organicETL even in the inverted device structure.

n Inorganic halide perovskite LED (PeLED) is also
suffered from ETL issues to be solved by ZSO.
l Green PeLED exhibit ultimate performance of VTH(2.9 V), efficiency (33 lm·W–1) and brightness(~5×105 cd·m–2), and spectrum (FWHM~15 nm)
which solve the green-gap in GaN-based LEDs.
l Red and blue PeLEDs are also demonstrated andsatisfy wide color gamut for BT2020.

L-V
I-V

I-V characteristics

Layer structures

P-L
L/I-V

Colorgamut
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ESIAC2019 TIES

5．Technical Topics (6)Semiconductor

Appl. Phys. Rev. 6,031402 (2019)

ionborat
Colla dustrynw i th i

Ultra Bright Flexible PeLEDl Green PeLED exhibit ultimate performance of VTH(2.9 V), efficiency (33 lm·W–1) and brightness(~5×105 cd·m–2), and spectrum (FWHM~15 nm)
which solve the green-gap in GaN-based LEDs.
l Red and blue PeLEDs are also demonstrated andsatisfy wide color gamut for BT2020.
l Readily applicable to flexible devices on plastic
substrates due to room-temperature sputter
deposition of ZSO and low-temperature printable
solution process of halide perovskite!

13ESIAC2019 TIES

5．Technical Topics
HydrogenRev. Sci. Instrum. 88,
053103 (2017)

ion
borat yallo
C
trndusw i th i

HydrogenAppl. Phys. Lett. 110,232105 (2017)

ion
borat yallo
C
trndusw i th i

High-Sensitivity Thermal
Desorption Spectroscopy

Hydride Anions (H–) ina-IGZO and the TFT Instabilityn Ordinary mass spectroscopy like SIMS cannot
measure low hydrogen density <~1018 cm–3.

n Oxide semiconductors like a-IGZO usually containhigh-density hydrogen (~1020 cm–3), but their states,roles, and functionalities have not been elucidated.

l For low hydrogen density limit, we developed anoriginal method and apparatus based on TDS
thoroughly suppressing residual hydrogen.
l High sensitivity (~1016 cm–3) measurement wasdemonstrated in a-IGZO thin films.
l The apparatus will be commercialized by somecompanies soon.

l We precisely analyzed the bonding states of H ina-IGZO thin films by FTIR, and identified hydrogenrelated peaks in the IR spectra by DFT calculations.
l It is found that 1/3 of H in the film are H– at oxygen
vacancy sites, which form deep sub-gap states andorigin of the TFT instability under illumination.

VOSchematic of system

H2 desorption spectrum
from a-IGZO thin films

H IR spectra

Local and band structure

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ESIAC2019 TIES

6. Achievement: Development of Core Research Center
New building exclusive to MCES
with dedicated collaboration floor (2015-)

Discussion at monthly meetingsof all researchers

Employment of full-time professors Head-hunt of Prof. F. Oba Participation utilizing
by MCES (2013-)
from Kyoto Univ. (2015-)
Tokyo Tech MSL
Collaborative Research ProjectT. Tada S. Matsuishi
Assoc. Prof. Assoc. Prof. M. Kitano↓
Assoc. Prof.
J. KimProf.
Assist. Prof.
Kyushu Univ.

Prof. F. Oba（Frontier Lab. &MCES）

Prof. S. Wada
(Yamanashi
Univ. 2013–)

Prof. H. Taniguchi(Nagoya Univ.
2014–）
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ESIAC2019 TIES

6. Achievement: Development of Core Research Center
Camp meeting to summarize the 2nd phaseand discuss the final goal & beyond (2017/10/28-29)

Reinforcement of research portfolio
by incorporation of young researchers
completing JST Element Strategy projectProf. T. Kondo(Tsukuba Univ. 2016-)

Tokyo Tech declared “New Element Strategy”
as the top priority research areas
upon selection
as Designated National University (2018-)

International expansion
using JSPS Core-to-Core Program
to form international research institute (2018-)
Defects Modeling Institute Surface Analysis Institute

New Element Strategy

Focus Areas

Prof. A. Yamamoto(TUAT 2016–)

Univ. College
London (UK)Prof. A. Shluger

toward sustainable society
efficiently utilizing limited resources

MacGill
Univ.(Canada)Prof. P. Grutter

Comprehensive Energy Science
toward rich society
based on sustainable energies
Device & System in Digital Society
toward infrastructures of future society
merging hardwares & softwares

Organized as Focus Research Centers
Basic Structure of Focus Areas

TIES (Tokyo Tech)
MCES
Prof. H. Hosono

Materials Creation Institute16

ESIAC2019 TIES

7. Summary: Final Goal & Beyond

Development of Electronic Materials
Institute in all Tokyo Tech from MCES
Transfer of technical achievements to industryl Semiconductor Materials for Flat-Panel Displaysl High-k Dielectrics for Power Electronics
Successive Evolution ofChallenging Materials
Research based on novel
ideas
Publication of Summaries ofTIES’s Concept, Approaches,
Design Principles, andAchievements

Technology Transfer ofPromising Achievements toIndustry
Evolutional Development toPost Element Strategy (NewElement Strategy)