IMPACT‐2012

PRECISE DEFECTS CONTROL IN TRANSITION METAL OXIDES

Gennady Logvenov

Max Planck Institute for Solid State Research Scientific Service Group Technology

10nd September 20121

Outline

• Introduction

• ALE MBE defects control

• PLD defects controlPLD defects control 

• Conclusions

Defect

1. a shortcoming, fault, or imperfection: a defect in an argument; a defect in a machinedefect in a machine. 2. lack or want, especially of something essential to perfection or completeness; deficiency: a defect in hearing. 3. Also called crystal defect, lattice defect. Crystallography . a discontinuity in the lattice of a crystal caused by missing or extra t i b di l tiatoms or ions, or by dislocations. 

Relevant QuestionsRelevant Questions verb (used without object) 4. to desert a cause, country, etc., especially in order to adopt another (often followed by from  or to ): He defected from the U.S.S.R to the West. 

3http://dictionary.reference.com/browse/defect

Real crystals are never perfect

A 2D perfect single crystal Poly-crystal with many defects

GB

Crystals are like people, it is the defects in them which tend to make them interesting

4

Colin Humphreys

Complexity of Metal oxides (strong correlations)

5

Source Drain

EDoping without introducing disorder

GdVGVE

tBD

)(0

01

Cf. The talks D. Pavuna, J.‐M. Triscone,

6

Cf. The talks D. Pavuna, J. M. Triscone, A. Goldman, A. Bhattacharya

Bulk RNiO3 Properties

R+3

Ni+3

O-2

Simple distortion modifies physical properties

O

Distortions in La2NiO4+Lattice distortion create interstitial sites

V. Faucheux et. al., J f S l St t Ch 177 4616 (2004)

H.L.Zhang, et. al., Phys.Rev. B 71, 064422 (2005)

J. of Sol. Stat. Chem. 177, 4616 (2004)

Schematic model of the 1D interstitial oxygen 

( ) A i f h h bi L NiO

ordering in La2NiO4+

↔ mechanism formation stripes (a) Atomic structure of the orthorombic  La2NiO4+(b) Oxygen vacancy surrounded by oxygen atom 

La2‐xSrxCuO4 vs. La2CuO4+yQuenched disorder of Sr2+ Annealed disorder of O2‐Q

Lattice distortion create interstitialLattice distortion create interstitial sites

B.O. Wells, et.al., Science 277,1067 (1997)

Our Deposition methods

High level control of deposition process on an atomic level;

Oxide PLD MPIp ;

• Pulsed Laser Deposition 

• Molecular Beam Epitaxy

Oxide MBE BNL,USAOxide MBE BNL,USA

Th k d i hi h li f hi filThe key word is high quality of thin films

Big Brother of BNL MBE system

Dual Oxide MBE system with cluster tool in Max-Planck Institute

The key word is new metastable compounds (high quality of thin films)

Sketch of the growth chamber

12

Cf. I. Bozovic, A. Bhattacharya

Creating new materials (artificial stacking) 

• Stacking molecular layers up to one unit cell (PLD and MBE)

– Multilayers/superlatticesMultilayers/superlattices

St ki t i l (MBE)• Stacking atomic layers (MBE)

– growing oxide based on single atomic layers sequence (example; metastable poly‐types, deleting atomic layers, adding atomic layers and synthesize new artificial compounds: 2234,…2278, 1234,   (MnLa2‐xSrxCuO6)

• Engineering inside atomic monolayers (MBE)

doping selected atomic monolayers– doping selected atomic monolayers

– modulation doping/delta doping

Creating new cuprate based materials

in heterostructures the CuO2 planes at interfaces i diff t t ll d i tare in a different, controlled environment

heterostructures may provide the possibility to dope without introducing disorderdope without introducing disorder

Outline

• Introduction

• ALE MBE defects control

• PLD defects controlPLD defects control 

• Conclusions

High Tc Interface superconductivity

UnderdopedInterface?

Overdoped layerInterface?

Stacking Atomic layersg y

It was found superconductivity in bilayer consisting of an insulator (La2CuO4) and a metal (La1.55Sr0.45CuO4 neither of which is superconducting individually. In the bilayer Tc is either 15 K or 30 K depending on layer sequence. This highly robust phenomenon is confined at the interface

Nature 455, 782 (2008)

Push number of exciting experiments!

Isovalent substitution Cu↔Zn

145

K)

0.5 / R

(4

Zn‐LSCO LCO*

R(T

)

Zn‐LCO* LSCO

010 20 30 40

T (K)

3 %3 % Zn causes pair breaking and reduces Tc

Engineering inside one atomic layer

35LSCO-LCO

Logvenov, Gozar, Bozovic Science 326, 699 (2009)

30

25

T c (K

)

20

T

CO interfa

ce

Zn-LCO*

Doping inside Atomic layers

LSCO

‐L

Zn LCO

-6 -5 -4 -3 -2 -1 1 2 3 4 5 6

N6 5 4 3 2 1 1 2 3 4 5 6

By atomic-layer-by-layer synthesis it is possible to dope selectively at specific atomic sites, e.g. within a single CuO2 plane

Superfluid density

drive coilIdrive = I0*sin(t)j

The most superfluid density is confined ina single CuO2 layer

SC filmjs

pick-up coil

2

dD:

0

2

0

sinh)( M

dM

dTM

)2()](Im[

12 Dnd

TM s

CInsert one atomic layer – delta doping

CuO2

CuO2LaO

LaOLaO

CuO2LaO

LaOLaO

CuO2LaO

LaOSrO

CuO2LaO

LaO

LaOCuO2LaOLaOLaO

CInsert one atomic layer – delta doping

500

400

300

Ohm

] Tc=25K

200

R[O

100

0 50 100 150 200 250 3000

T[K]

Construct a new material 

CuO2

SrO

CuO2LaO

LaOLaO

CuO2LaO

LaOLaO

CuO2LaO

LaOSrO

CuO2LaO

LaO

LaOCuO2

SrOL OLaO

CInsert one atomic layer – delta doping

drive coil

8

SC film

drive coilIdrive = I0*sin(t)js

6

d R

e

pick-up coil

4

m a

nd #39

2

Im

0

0 10 20 30 40 50

T [K ]T [K]LLong route to search new functional metastable layered compounds 

Outline

• Introduction

• ALE MBE defects control

• PLD defects controlPLD defects control 

• Conclusions

Bulk RNiO3 Properties

R+3

Ni+3

O-2

Simple distortion modifies physical properties

O

Epitaxial srain effect

k

PrNiO3 single film grown on different substrates: DSO, STO, LSAT and LSAOG. Cristiani, N.U.Nwanko MPI

Surface roughness effect

La2/3Ca1/3MnO3 thin film on STO substrateAll films are 100 nm thick 

RMS:3.824nm

RMS: 0.389

RMS: 0.325nm

K. Kawashima MPI

RHEED images vs. Laser fluency 

2J/cm2 1.8J/cm2 1 67J/cm2 0 7J/cm20 82J/cm2 0 75J/cm22J/cm 1.8J/cm 1.67J/cm 0.7J/cm0.82J/cm 0.75J/cm

All films 55 nm–thick LaNiO3/SrTiO3(100)

Ch i i f L NiO fil i h i l flChanging properties of LaNiO3 films with varying laser fluency

D. Kukuruznyak MPI

RHEED images vs. Laser fluency 

-5.8

-5.6

-5.4

-7em

u) H// 100 Oe

5

6

7

-7em

u)

-6.4

-6.2

-6.0

5.8

M(1

0-2

3

4

5

M(1

0-

0.82J/cm21.67J/cm20 50 100 150 200 250 300

Temp.(K)

7 00

-6.80

-6.60

H//1000 Oe-5em

u)0 50 100 150 200 250 3002

Temp.(K)

1 5

2

2.5

-6em

u)

7 60

-7.40

-7.20

-7.00 H// 1000 Oe

M(1

0-

0

0.5

1

1.5

M(1

0-

0 50 100 150 200 250 300-7.60Temp.(K)

1

1.5

emu) 5k

0 50 100 150 200 250 300Temp.(K)

6

emu)

2

4

-1

-0.5

0

0.5

M(1

0-5 e

-4

M(1

0-6 e

6

0

-2

-2000 -1000 0 1000 2000-1.5H (Oe)

-2000 -1000 0 1000 2000H (Oe)

-6

LaNiO3‐LaAlO3 SL with NiO precipitates on STO interface 

STO is non‐polar substrate

(a) HAADF image of LaNiO3‐LaAlO3 SL with NiO precipitates(a) HAADF image of LaNiO3 LaAlO3 SL with NiO precipitates(b) EELS showing Ni enrichment within the precipitate (Ni is colored red, Al‐blue, (c) La‐yellow

R ddlesden Poper t pe fa lts on LSAOLSAO is polar s bstrate

LaNiO3‐LaAlO3 SL on LSAO 

Ruddlesden‐Poper‐type faults on LSAOLSAO is polar substrate

HRTEM image of RP faults 

(a) HAADF image of a planar RP fault:

J. App. Phys. 112, 013509 (2012)

La‐blue, Ni‐yellow, O‐grey, (La,Sr)‐green, Al‐red(a) and (c) Elemental EELS maps (2.56x2.56 nm2)

Ruddlesden‐Poper‐type faults on LSAO

(a) HAADF image showing several blocks(a) HAADF image showing several blocks(b) Enlarged image (solid rectangle)(c) 3D atomic model (La‐blue, Ni‐yellow, Al‐ red

LaNiO SrTiO 2x10 superlattice LaNiO SrTiO 3 5x3 5 superlattice

SLs with complete and incomplete unit cell layers

LaNiO3-SrTiO3 2x10 superlattice LaNiO3-SrTiO3 3.5x3.5 superlattice

110

106 90

120

102-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

106

H (Tesla) at T=2K-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

60

Hp (Tesla) at T=2KR(

)Hp (Tesla) at T=2K Hp (Tesla) at T 2KR

Hext

Is

Influence of incomplete layers on magnetoresistance

Conclusions and Outlook

• Variety of physical properties are related to defect structure of complex oxides.

• Oxide MBE and PLD deposition enable the precise control of thin films growth

• The only way to new phenomena new physics and new functionalities in complex materials is via precise defectsfunctionalities in complex materials is via precise defects control

High quality of oxides thin films and heterostructures ↔High level of defects controlHigh level of defects control 

Aknowledgments

Prof. B. Keimer

D H U H b i Dr. H.U. Habermeier

Dr. D. Kukuruznyak

G. Cristiani

F. Baiutti

S. Soltan, 

K. Kawashima, 

Dr. I. Bozovic

Dr. A. Gozar

B. Stuhlhofer Dr. A. Bollinger

Dr. V. Butko

36

Interface – topological defectCharge reconstruction at the interface

interface bulk new properties LaTiO3 / SrTiO3 (Pascal PLD system)Abrupt layers of LaTiO3 embeded in SrTiO3

Charge reconstruction at the interface

Abrupt layers of LaTiO3 embeded in SrTiO3Ohtomo et.al. Nature 2002Quasi-2D electron gas in LaAlO3/SrTiO3, Ohtomo et.al. Nature 2004Interface supercondutivityInterface supercondutivityReyren et.al, Science 2007 (Tc0.2K)

Ri h h i d h i t ll t it f l t i

QHE in ZnO-Mg1-xZnxO bilayerTzukazaki et.al. Science 2007

Tunable quasi-2D electron gas Thiel et.al.Science 2006

Rich physics and chemistry as well an opportunity for electronics