発表用意 20171117 公開用...
TRANSCRIPT
![Page 1: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/1.jpg)
放射光を用いた強誘電体薄膜の解析
東工大1、名大2、JASRI/SPring-83、NIMS/SPring-84
舟窪浩1、清水荘雄1、山田智明1, 2、
今井康彦3、木村滋3、坂田修身3,4
第5回次世代デバイス研究会/第19回SPring8先端利用技術ワークショップ日時:2017年11月2日(木)13:00-19:00 会場:AP品川
転載不可
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目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望
![Page 3: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/3.jpg)
目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望
![Page 4: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/4.jpg)
Pola
riza
tion
Electric Field
Palaelectricity Ferroelectricity
Antiferroelectricity Ferrielectricity
Polarization vs Electric Field
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Ferroelectricity
O
OA
A
A
A
BOO
A
A
Perovskite StructureP - E Hysteresis
O
OA
A
A
A
BOO
A
A
・Stable Two states Without Electric Field・Remanent Polarization・ Hysteresis Loops
''0''
''1''
AD
0 EcE
P
PrPs
-Ec
B C
B'C'
D'-Pr-Ps
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圧電体とは?
stress-induced electricity
+ + + +
- - - -
1880 P. Curie & J. Curie
electric field-induced displacement
1881 Lippman
正圧電効果(direct piezoelectric effect)
逆圧電効果(inverse piezoelectric effect)
誘電体
圧電体
焦電体
強誘電体
強誘電体は誘電性、圧電性、焦電性を併せ持つ。
自発分極をもつ
外場により自発分極が反転可能
結晶構造が対称中心を持たず、イオンが変位して分極を生じる。
![Page 7: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/7.jpg)
メモリデバイスの分類および動作原理
* 日経エレクトロニクス (2001年2月12日号)
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メモリデバイスの性能比較
※ 日本セラミックス協会 第19回電子材料部会セミナー斎藤好昭 「磁気抵抗効果メモリと磁気抵抗効果材料」2000年11月22日
記録情報の不揮発性
セルサイズ(相対値)
書き込み速度
読み出し速度
書き換え回数の限界
消費電力
製造コスト(相対値)
DRAM FLASH FeRAM MRAM PSRAM
× ○ ○ ○
~ 1 ~ 0.5 ~ 1 ~ 1
50 ns > 20,000ns 80~130 ns 5~50 ns
50 ns 20~110 ns 80~130 ns 5~50 ns
1012 105 1012 1015
400 mW 100 mW 2 mW 10~400 mW
1 1~2 1 1~3
○
PSRAM
PSRAM
PSRAM
PSRAM
PSRAM
PSRAM
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9
圧電体
stress-induced electricity
+ + + +
- - - -
1880 P. Curie & J. Curie
electric field-induced displacement
1881 Lippman
正圧電効果(direct piezoelectric effect)
逆圧電効果(inverse piezoelectric effect)
誘電体
圧電体
焦電体
強誘電体
強誘電体は誘電性、圧電性、焦電性を併せ持つ。
自発分極をもつ
外場により自発分極が反転可能
結晶構造が対称中心を持たず、イオンが変位して分極を生じる。
![Page 10: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/10.jpg)
脳(コンピュータ)
神経(ネットワーク網)
手、筋肉(アクチュエータ):さらなる微細化、高機能化が必要
高度情報社会の実現に向け順調に発達
電気エネルギー 機械エネルギー
圧電素子(アクチュエータの心臓部品)
エネルギー変換素子
電気ー機械エネルギーの変換圧電素子
「マイクロマシン(MEMS)技術」
高性能化がマイクロマシンの高性能化に不可欠
動力部分である「圧電アクチュエータ」
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⑤
印加電界+ 印加電界-
① ② ③ ④ ⑥
bipolar測定bipolar測定
分極の向き
unipolar測定unipolar測定
S
P
E
E
①
②
③
④
⑥
①
②
③⑥
⑤
④
⑤
S
P
E
E
①
①
②
②
元の大きさ
①②
Electric field ( kV/cm)
Stra
in(%
)
Electric field ( kV/cm)
Stra
in(%
)
実用の用途
bipolar測定とunipolar測定
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Electrical Field
Polarization
non-volatile memories
ctric State:rie Point)
Application of Piezoelectric PropertySensor Ink Jet Printer
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新規分野新規分野
圧電発電圧電発電
医療応用医療応用
ロボットロボット
家電家電
現応用現応用
圧電体の応用
自律移動ロボット
3次元
超音波診断機
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目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望
![Page 15: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/15.jpg)
HfO2薄膜の強誘電性
15
HfO2は強誘電体デバイス作製に有望な材料
[1] K. Mistry et al., IEDM Tech. Dig., 247 (2007).[2] T. S. Boscke et al., Appl. Phys. Lett. 99, 102903 (2011).
Siプロセスとの親和性
Metal
Si
SiGe SiGeHfO2
[1]
ゲート絶縁体 強誘電性の発見
既存の強誘電体材料にない特長
[2]
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16
強誘電性の起源
“斜方晶相”
Switchable spontaneous polarizationE
Metastable and noncentrosymmetricorthorhombic phase
AlloyingHeat treatment
Stable Monoclinic phaseJ. Müller, et al., nano. Lett. 12 4318 (2012).
Johannes Müller, et al., Appl. Phys. Lett. 99 102903 (2011).
Orthorhombic a = 5.24 Åb = 5.05 Åc = 5.01 Å
FERROELECTRIC
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Y2O3-HfO2 のパフォーマンス
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強誘電体トンネルジャンクション
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強誘電体トンネルジャンクション
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集積強誘電体トンネルジャンクション
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強誘電体トンネルジャンクション
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メモリスター
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25
圧電体
stress-induced electricity
+ + + +
- - - -
1880 P. Curie & J. Curie
electric field-induced displacement
1881 Lippman
逆圧電効果(inverse piezoelectric effect)
誘電体
圧電体
焦電体
強誘電体
強誘電体は誘電性、圧電性、焦電性を併せ持つ。
自発分極をもつ
外場により自発分極が反転可能
結晶構造が対称中心を持たず、イオンが変位して分極を生じる。
![Page 26: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/26.jpg)
トランジスタ応用 ⇒Piezoelectronic transistor (PET)
S
G
D
G
SD S
D
G
ピエゾレジスティブ効果 (応力印加による金属-絶縁体転移)
ピエゾトランジスタ(PET)
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目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望
![Page 29: 発表用意 20171117 公開用 [互換モード]support.spring8.or.jp/Doc_workshop/iuss/2017/otft-5/...1880 P. Curie & J. Curie electric field-induced displacement 1881 Lippman 正圧電効果(direct](https://reader030.vdocuments.pub/reader030/viewer/2022011913/5fb076ff59f6fa50bb4898f1/html5/thumbnails/29.jpg)
HfO2基強誘電体の特徴
極薄膜でも安定して強誘電性が発現
[1] T. S. Boscke et al., Appl. Phys. Lett. 99, 102903 (2011).
従来の強誘電体にない特徴
極薄膜強誘電体デバイスへの期待
2011年に初めて報告された新規の強誘電体
Hf
O
[1]
HfO2基強誘電体とは
29
HfO2基強誘電体
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強誘電体の温度安定性
デバイス応用の観点から高いキュリー点を有することは重要
強誘電体とキュリー点
30
キュリー点の膜厚依存性と配向依存性
強誘電体のキュリー点には膜厚依存性および配向依存性が存在
HfO2基強誘電体においてもキュリー点の膜厚依存性および配向依存性を調査
P
Tetragonal CubicTc
1 10 100 1000200
400
600
800
Tc
[°C]
Thickness [nm]
PT on (100)STO
PT on (100)KTO
BNT-BKT on STO(111)(100)(110)
[3] P. Li et al., J EUR CERAM SOC.36 3139–3145 (2016)
[3]
[2]
[2] S. K. Streiffer et al., Phys. Rev. Lett. 89, 067601 (2002)
P
E
P
E
PT on (100)SRO
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HfO2基強誘電体の研究
31
従来の研究 我々の研究
結晶構造解析 困難 容易
結晶相の膜厚依存性
大 小
配向制御 不可能 可能
Substrateelectrode
エピタキシャル成長した7%YO1.5-HfO2 基強誘電体を用いてキュリー点の膜厚依存性、配向依存性を調査
SubstrateITO
多結晶膜
ParaelectricFerroelectric
7%YO1.5-HfO2エピタキシャル成長膜
Ferroelectric
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本研究の目的
32
HfO2基強誘電体における温度安定性の調査
エピタキシャル成長した7%YO1.5-HfO2 基強誘電体を用いてキュリー点の膜厚依存性および配向依存性を調査
③ (111)Pt/(100)Si
無配向多結晶膜
(100)Si
(111)PtHfO2
(111)YSZ(111)HfO2
① (111)YSZ
(111)配向エピタキシャル膜
下記の3つの基板上で調査
② (100)YSZ
(100)配向エピタキシャル膜
(100)YSZ(100)HfO2
膜厚依存性を調査
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実験方法
33
基板 基板 基板
成膜後HfO2膜
熱処理後HfO2膜室温成膜 熱処理
(111)YSZ(100)YSZPt/Si
製膜法 :PLD法製膜温度:室温ターゲット:7%YO1.5-93%HfO2 (YHO7)
熱処理温度:1000℃保持時間:10s 雰囲気:N2
高温XRD測定により結晶構造変化を観察キュリー点を調査
極薄膜サンプルおよび多結晶膜などX線回折強度が弱いものはSpring-8 BL15で測定
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結論
34
・YHO7膜のキュリー点には配向依存性と膜厚依存性が存在
・(111)配向膜では膜厚の低下に伴いキュリー点が低下
・極薄膜の4.6 nm でも350℃
YHO7強誘電体は膜厚の薄いところまで温度安定性が高く極薄膜デバイスの応用に適応可能
(111)配向膜 58 ~ 140 nm:550℃4.6 ~ 14 nm : 350 ~450℃ (膜厚依存性が存在)
(100)配向膜 14 ~ 86 nm : 550℃多結晶膜 10 nm : 550℃
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目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望
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圧電性の起源
2. 格子の変形以外の要因弾性ドメインの変化電圧誘起相転移粒界すべり
1. 結晶格子の変形
c domain a domain
90°switching
c domain c domain
電界印加後
電界印加後
P P + Pc c’
a a’
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時間分解測定の必要性強誘電体メモリ
• 結晶構造変化 ⇒ メモリの動作そのもの
ドメイン反転のダイナミックス
⇒ 高速動作の限界チェック
信頼性の確保
⇒ 劣化機構の解明
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⑤
印加電界+ 印加電界-
① ② ③ ④ ⑥
bipolar測定bipolar測定
分極の向き
unipolar測定unipolar測定
S
P
E
E
①
②
③
④
⑥
①
②
③⑥
⑤
④
⑤
S
P
E
E
①
①
②
②
元の大きさ
①②
Electric field ( kV/cm)
Stra
in(%
)
Electric field ( kV/cm)
Stra
in(%
)
実用の用途
bipolar測定とunipolar測定
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内容
1.測定の動機
2.測定方法の構築
3.測定の実際
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Electric Field E
Polarization, PStrain ∆x
∆x = Qij (P2 ー P2r)
P = ε E + Pr ∆x = dij E
Intrinsic value New information
piezoelectric constant dij
electrostrictive coefficient Qij
The Combination of Δx and Polarization Allow us to Determine Electrostrictive Coefficient, Q, of Piezoelectric Films
Measure Bragg position under an applied electric field. ⇒ Lattice strain.
Ferroelectric tester
Q : a conversion factor of electrical energy to mechanical energy
200ns pulse
電気測定と回折の同時測定
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Images of in-situ measurements
Microscope
Diffractometer@Exp. hutch 1
Sample & stage equipped w/ Prober (Tungsten, R10 m)
Voltage applied between two top electrodes
Sample (7x 5 mm)
Φ3 mm
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圧電性の評価方法について
分極(⊿P)電界(E)
通常の電気測定
エネルギー変換効率
synchrotron-XRDを用いた電界印加時の格子歪観察
格子歪(⊿x) (格子の変形)
• 格子の変形を直接測定できる• 極薄膜でも測定できる• エネルギ変換係数を直接出せる (唯一の方法)• 絶縁性の悪いサンプルでも測定できる
高速パルス
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内容
1.測定の動機
2.測定方法の構築
3.測定の実際
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100 150 200
In
tens
ity (a
rb. u
nits
)
Raman shift (cm-1)
Pb(Zr0.35Ti0.65)O3 (3m)//SrRuO3//LaNiO3//(100)CaF2
Selected-area electron diffraction patterns (SADP)
Growth of Perfectly Polar-axis-oriented PZT Films From
Bottom to Top Parts
XRD measurementa // = 0.398 nm
c ⊥ = 0.415 nm
a // 0.401 nm
a // 0.401 nm
a // 0.401 nm
c ⊥ 0.416 nm
c ⊥ 0.416 nm
c ⊥ 0.416 nm
CaF2
LaNiO3
SrRuO3
PZT
Diffraction Pattern only from Polar-axis Oriented Domain
Bottom part
Upper part
Middle part
Raman Spectroscopy
Obvious Peak Shift was not Observed
Growth of Almost Uniform Strain Film Along Film Thickness
A1(1TO)
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nm-sec Time-resolved synchrotron XRDPolarization Response by 200 nsec Pulse
-150 -100 -50 0 50 100 150-100
-75
-50
-25
0
25
50
75
100
Electric field (kV/cm)
Pola
riza
tion
(C
/cm
2 )
PmaxPr
-150 -100 -50 0 50 100 150-100
-75
-50
-25
0
25
50
75
100
Electric field (kV/cm)
Pola
riza
tion
(C
/cm
2 )
-150 -100 -50 0 50 100 150-100
-75
-50
-25
0
25
50
75
100
Electric field (kV/cm)
Pola
riza
tion
(C
/cm
2 )
PmaxPr
EE=0 =0 EE==EEaa
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Result 2-1Lattice Parameter Change with Applied Electric Field
57.4 57.5 57.6 57.7 57.8 57.9 58.00
1x105
2x105
3x105
4x105
5x105
Inte
nsity
(cou
nt)
2 (deg)
(c)
30V20V
10V0V
57.4 57.5 57.6 57.7 57.8 57.9 58.00
1x105
2x105
3x105
4x105
5x105
Inte
nsity
(cou
nt)
2 (deg)
(c)
30V20V
10V0V
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0 50 100 150 200 2500.00
0.05
0.10
0.15
0.20
Lat
tice
stra
in (%
)
Electric field (KV/cm)
Piezoelectric Property Estimation - PbZr0.35Ti0.65O3
d33,(obs)
= 60-70pm/Vd33,(obs)
= 65 pm/V
Two Measurement Results Showed Similar Values
Direct Observation of Lattice Change
SPring8 PFM
Piezoelectric Response of This Film Mainly Originated From Lattice Distortion
d33,(obs)
= 60-70pm/V
PFM
EE=0 =0 EE==EEaaEE=0 =0 EE==EEaa
Lattice Strain
EE=0 =0 EE==EEaaEE=0 =0 EE==EEaa EE=0 =0 EE==EEaaEE=0 =0 EE==EEaaEE=0 =0 EE==EEaaEE=0 =0 EE==EEaa EE=0 =0 EE==EEbbEE=0 =0 EE==EEbbEE=0 =0 EE==EEaaEE=0 =0 EE==EEaa
Extrinsic
EE=0 =0 EE==EEaaEE=0 =0 EE==EEaa
Domain Swiching etc.
EE=0 =0 EE==EEbbEE=0 =0 EE==EEbb
+
Lattice Strain
Intrinsic
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Schematic of displacement measurement by SPM
probe was contacted onPt top electrode(100 m in diameter)
SubstrateBottom electrode
PZT film
Pulse generator
LaserDetector
Conductivecantilever
A/D Converter
Piezoelectric and ferroelectric properties
Q/V Converter
Displacement meter
PC
Pt top electrode(100m)
・contact AFM mode・field-induced displacement and ferroelectric
property were measured simultaneously
Field-induced displacement of the films was measured usingSPM connected with a Ferroelectric Test System.
Scanner
Ag paste
Feed back signal
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定量性の評価
PZT
フリースタンディング⇒ 材料定数 d33、Q11
基板からのクランピング⇒ d33,obs、Q11,obs
Substrate
PZTクランプ
分極軸配向薄膜測定⇒放射光時分割測定⇒PFM測定
単結晶理論計算単結晶測定
クランピングモデルとの比較
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Lattice Distortion):Up to Pico sec(THz)~Sub Nano Sec
(MHz)
Elastic Deformation, Non-180o Domain Switching :Up to micro sec (kHz)
Reports of Simultaneous Observation of These Two Types of Deformation in Piezoelectric Films are Limited→Direct Observation of These Deformation by In-situ Time-resolved XRD Analysis Under Applied Electric Filed.
Crystal Structure Change Under Appling Electric Filed in Ferroelectric Tetragonal Pb(Zr, Ti)O3 Films
Applicable up to High Frequency Applicable such as Sensors
Impossible to Apply High Frequency applications
Applicable such as Actuators
Intrinsic Effect + Extrinsic Effect(Non180o Domain)
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52
a-domain(100)
orientation
c-domain(001)
orientation
60.0
60.5
61.0
61.5
62.0
62.5
2 (d
eg.)
-4.0 -2.0 0.0 2.0 4.056.5
57.0
57.5
58.0
58.5
59.0
(deg.)
2 (d
eg.)
SrRuO3 004c
a DomainPZT 400
KTaO3 004
c-domainPZT 004
(a)
(b)
Model Structure
scan II
scan V
scan I
scan IIIscan IV
Sample Characterization
Typical Structure of 200nm-thic (100)/(001) Tetragonal Pb(Zr, Ti)O3 Films
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1. Lattice Distortion: Expected Change under E
53
Lattice Deformation of (001) Domain
Related Change of (100) Domain
2. Out of Plane Lattice of (100) Domain Shrink Response to Shrinkage of In-plane Lattice of (001) Domain
1. Out-of-Plane Lattice of (100) Domain Elongate Followed by Elongation of (001) Out-of Lattice.
+
Electric Filed
Electric Filed
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1. Lattice Distortion: Experimental Results
△ 0V● 10V
57.6 58.0
Int.
(arb
. uni
ts)
2 (deg)60.5 60.6 60.7 60.8 60.9 61.0 61.1
Int.
(arb
. uni
ts)
2 (deg)
△ 0V● 10V
(100) Domain:Positive Transverse Piezoelectric Constant(100) Domain:Negative Transverse Piezoelectric Constant
+d-d
Out of Plane Lattice(001) Domain:Elongation(100) Domain:Shrinkage
400004
(001) Domain (100) Domain
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2. Elastic Deformation Under E2-1. Domain Wall Motion
(400)(004)(001) Domain:Intensity Increased(100) Domain:Intensity Decreased
(001) Domain(100) Domain
(100) Domain (001) Domain
Domain Switching by Electric Filed
V001: Volume Fraction of (001) OrientationFrom 40% to 60%.
□ 0V● 10V
57.6 58.0
Int.
(arb
. uni
ts)
2 (deg)60.5 60.6 60.7 60.8 60.9 61.0 61.1
Int.
(arb
. uni
ts)
2 (deg)
△ 0V● 10V
(001) Domain(100) Domain
Electric Filed
Electric Filed
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Time Response
Obvious Delay is Not Detected for Electric Charge, Lattice Elongation, Tilting Angle and Elastic Deformation
Thin Films Change Very First by Electric Filed
Volu
me
Frac
tion
Charge
Strain
Tilting Angle
Volume Fraction
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SummaryChange of Crystal Structure Under Applied Electric Filed was Investigated In-situ for (100)/(001)-Oriented Tetragonal Pb(Zr, Ti)O3Films
Crystal Structure Change Under Electric Filed is Successfully Observed.
+d-d
1. Lattice Deformation(001) Domain:Out of Plane lattice Elongation(100) Domain:Out of Plane lattice Shrinkage
2. Elastic Deformation• Domain Switching from (100) to (001) Domain: Increase of V00• Increase and Decrease of Tilting Angle of (001) and (100) Domains :
Increase and Decrease of and Angles, Respectively.
EE
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目次
1.背景
強誘電体とは
次世代先端デバイス
2.HfO2極薄膜の測定
3.圧電MEMS応用に向けた測定
4.今後の展望