Amorphous Transparent Cond

Oxides (TCOs) Deposited at T 1

John Perkins, Maikel van Hest, Charles Teplin

Jeff Alleman, Matthew Dabney, Lynn GedvilasBrian Keyes, Bobby To, David GinleyNational Renewable Energy Lab., Golden CO Matthew Taylor, Dennis ReadeyColorado School of Mines, Golden CO 80401

NREL/PR-520-39868Presented at the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4) held May 
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This work has been authored by Midwest Research Institute (MRI) under Contract No. DE-AC36-99GO10Department of Energy (the “DOE”). The United States Government (the “Government”) retains and the pthe work for publication, acknowledges that the Government retains a non-exclusive, paid-up, irrevocablepublish or reproduce the published form of this work, or allow others to do so, for Government purposes.Neither MRI, the DOE, the Government, nor any other agency thereof, nor any of their employees, makes or implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulness of any product, or process disclosed, or represents that its use would not infringe any privately owned rights. Respecific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise dimply its endorsement, recommendation, or favoring by the Government or any agency thereof. The viewauthors and/or presenters expressed herein do not necessarily state or reflect those of MRI, the DOE, the agency thereof. 
In-Zn-O (IZO), 

an Amorphous Mixed Metal 

Transparent Conducto

• Low Temperature Deposition (TS ≤ 100 °C

• Smooth (RRMS < 0.5 nm)

• Thermally Resilient• Good Conductivity (σ ≈ 3000 Ω-1- cm-1)

• High Mobility for Amorphous material (μ ≈ 
Combinatorial Approac

IZO: 5 - 95 %In with 4 depos

CompositionallyGraded Films

Optical

Chemical
Metal Oxide

Co-sputtering 

– 5cm x 5cm 

glass substrates

– 25°C - 550°C

Film Deposition

ZnO, MoO2, TiO2 In2O3

3.02.52.01.51.00.50.0

0 2 4 

 16 

 12 

 14 

 10 

 8 

030828_02, 30/0/75, 100

increasing In co

2 inch

Binary In-Zn-O 

EPMA Ana
XRD for IZO Deposited at T

S 

• Amorpho

55 - 85 

• Crystallin

Textured

ZnOIn

2

O

3
As-dep IZO: Conductivity, Str

Roughness & Refractive In

a-

σ = 3

RR

Conductivity maximum occurs in smooth amorp
As-deposited IZO Optical Pr

σ

= 

λ p

• Typical TC• Fringes g•

λ

p change

• Conductiv
Annealing of IZO Librar

• Libraries annealed for 1 hour at target • Electrical, optical and structural proper• Process repeated

• 1 set of libraries annealed in air

• 1 set of libraries annealed in argon
IZO Annealed in Air

• Amorphous IZO generally does not recrystallize for up • Conductivity drop for air-annealed a- IZO 80/20 much 

crystalline material.

As-dep

ZnO In

2

O

3
Conductivity Drops Less for Argon 

Air Anneal

Final Anneal:σmax~ 200 (

Ω·cm)-1 

σmin~ 0.04 (

Ω·cm)-1

Final Anneal:σmax~ 1,350 (

Ω·cm)-1 1

σmin~ 6 (

Ω·cm)-1

Argon Anneal

As Dep

ZnO 
IZO 70/30: Center of Amorphous 

2” Single Composition Target

• Pressed at 25,000psi

• Sintered in air 800°C, 24hrs

• Two Phases: ZnO, In

2

O

3
RT Sputtered IZO 70/30 

Amorphous and Smoo

XRD, TEM
O2 in Sputter Gas Reduc

Conductivity

• N stro• μ near• μ ≈ 30 
Effect of O2 Scales with Sput
Summary

•Amorphous InZnO (a-IZO) is a very versa

– Low process temperatures (~ 100 °C)– Easy to make by sputtering– Excellent optical and electronic properties– Very smooth etchable films– Remarkable thermal processing stability
In-Zn-O (IZO): as-dep @ T

S = 
IZO: H2 in Sputter Gas

10 -310 -210 -1

10 010 110 210 310 4

0 1 2 3 4 5 6

%H2 in Ar

100

50

0

% T

4 6

1

2 4

λ (μm)

σ ( Ω·cm) -1

μ (cm 2/V·s)

 N (x10 19 /cm 3) 2.4%

σ, μ ,N % H2

1.1%

4.0%

• Overa• No inc

conce

• Samp