Motivation•Thin-film polycrystalline silicon solar cells exhibit higher efficiency when the grain boundaries are low-angle

•Heteroepitaxy on biaxially aligned cerium oxide may improve efficiency

Goal: Sputter biaxially textured CeO2 on glass as a model template layer

Motivation•Thin-film polycrystalline silicon solar cells exhibit higher efficiency when the grain boundaries are low-angle

•Heteroepitaxy on biaxially aligned cerium oxide may improve efficiency

Goal: Sputter biaxially textured CeO2 on glass as a model template layer

2D X-Ray Detector Images Explained

Horizontal direction is standard 2θ axisVertical direction is χ, similar to ω in rocking curvesχ-plots shown for (111) peak

Example powder diffraction images (CeO2 target):

Localization in χ means texturingA negative shift in χ means grains are tilted towards gunA shift in θ indicates lattice strain (oxygen vacancies)

2D X-Ray Detector Images Explained

Horizontal direction is standard 2θ axisVertical direction is χ, similar to ω in rocking curvesχ-plots shown for (111) peak

Example powder diffraction images (CeO2 target):

Localization in χ means texturingA negative shift in χ means grains are tilted towards gunA shift in θ indicates lattice strain (oxygen vacancies)

Texture Control in Cerium Oxide FilmsTexture Control in Cerium Oxide FilmsMaikel F.A.M. van Hest1, Andrew J. Leenheer2, Charles W. Teplin1,

John D. Perkins1, and David S. Ginley1

1National Renewable Energy Laboratory; 2Colorado School of Mines 

Maikel F.A.M. van Hest1, Andrew J. Leenheer2, Charles W. Teplin1,

John D. Perkins1, and David S. Ginley1

1National Renewable Energy Laboratory; 2Colorado School of Mines 

25°25°

φφ

Substrate:Substrate:

Sputtering gun:

Sputtering gun:

φφ~5 in.~5 in.

Chi

2 Theta

25

20

15

10

5

0

Chi

2 Theta

30

20

10

0

Chi

2 Theta

60

40

20

0

Chi

2 Theta

50

40

30

20

10

0

Chi

2 Theta

25

20

15

10

5

0

Chi

2 Theta

15

10

5

0

Chi

2 Theta

30

25

20

15

10

5

0

80

70

60

50

40

30Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

80

70

60

50

40

30Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

100

80

60

40Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

160

120

80

40Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

120

100

80

60

40Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

80

70

60

50

40

30Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

60

50

40

30Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

500

400

300

200

100

Inte

nsity

-120 -100 -80 -60

Chi

500

400

300

200

100

Inte

nsity

-120 -100 -80 -60

Chi

Chi

2 Theta

25

20

15

10

5

0

90807060504030In

ten

sity

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

600

500

400

300

200

100

Inte

nsity

-120 -100 -80 -60

Chi

600

500

400

300

200

100

Inte

nsity

-120 -100 -80 -60

Chi

800

600

400

200Inte

nsity

-120 -100 -80 -60

Chi

800

600

400

200Inte

nsity

-120 -100 -80 -60

Chi

500

400

300

200

100

Inte

nsity

-120 -100 -80 -60

Chi

300

250

200

150

100

Inte

nsity

-120 -100 -80 -60

Chi

Chi

2 Theta

60

50

40

30

20

10

0

200

150

100

50

0

Inte

nsi

ty

6055504540353025

2 Theta

120

100

80

60

40

20

0

1 1 

1

2 0 

0

2 2 

0

3 1 

1

2 2 

2

1 1 

1

2 0 

0

2 2 

0

3 1 

1

 CeO2 on (100) YSZT  CeO2T  ZrO2Y2O3

600

500

400

300

200

100

Inte

nsity

-105 -100 -95 -90 -85 -80 -75Chi

Width = 3.19

Chi

2 Theta

140

120

100

80

60

40

20

0

30

25

20

15

10

5

0

Inte

nsi

ty

504540353025

2 Theta

1 1 

1

2 0 

0

2 2 

0

400

300

200

100

0

Inte

nsity

-120 -110 -100 -90 -80 -70 -60Chi

(111)(111) (200)(200) (220)(220) (311)(311)

Tilted (111) biaxial texturing evident in pole figuresTilted (111) biaxial texturing evident in pole figures

Conclusions

•Texture control is possible in cerium oxide by epitaxial growth or adjusting the substrate angle

•Biaxial (111) texture emerges with inclined angle depositions on glass

•Biaxial (200) texture emerges by epitaxial growth on YSZThe information contained in this poster is subject to a government license; NREL/PO-520-39889; World Conference on Photovoltaic Energy Conversion; Waikoloa, Hawaii; May 7-12th 2006

Conclusions

•Texture control is possible in cerium oxide by epitaxial growth or adjusting the substrate angle

•Biaxial (111) texture emerges with inclined angle depositions on glass

•Biaxial (200) texture emerges by epitaxial growth on YSZThe information contained in this poster is subject to a government license; NREL/PO-520-39889; World Conference on Photovoltaic Energy Conversion; Waikoloa, Hawaii; May 7-12th 2006

Observations

Texture initially tends towards uniaxial [111] direction at normal incidence (wire texture)

χ-plots indicate grains angle towards gun at low angles

Another [-111] normal direction exists at φ= 70°;biaxial (111) texturing emerges when {111} points towards both the gun and substrate normal

Observations

Texture initially tends towards uniaxial [111] direction at normal incidence (wire texture)

χ-plots indicate grains angle towards gun at low angles

Another [-111] normal direction exists at φ= 70°;biaxial (111) texturing emerges when {111} points towards both the gun and substrate normal

Texture Control: Room Temperature Epitaxy on YSZTexture Control: Room Temperature Epitaxy on YSZCeO2 sputtered on single-crystal substrates of yttria-stabilized zirconiaCeO2 sputtered on single-crystal substrates of yttria-stabilized zirconia

•Sputtered cerium oxide grows epitaxially on (100) YSZ at T=25 °C•Biaxial (200) CeO2 exhibits epitaxial columnar growth•(200) texturing evident even when inclining the substrate

•Sputtered cerium oxide grows epitaxially on (100) YSZ at T=25 °C•Biaxial (200) CeO2 exhibits epitaxial columnar growth•(200) texturing evident even when inclining the substrate

Experimental details:•Blocks of various angles placed under glass substrates during sputtering•Room temperature depositions•300 nm maximum film thickness

Experimental details:•Blocks of various angles placed under glass substrates during sputtering•Room temperature depositions•300 nm maximum film thickness

Pole Figures at φ = 55°Pole Figures at φ = 55°

Texture Control: Inclined Substrate DepositionsTexture Control: Inclined Substrate Depositions

φ =0°φ =0° 15°15°

35°35°

45°45°

55°55°

65°65°

75°75°[111][111]

Grains tend to orient with [111] direction 

leaning towards gun:

Grains tend to orient with [111] direction 

leaning towards gun:

Solar celltemplate concept: 

may work well with lattice-matched 

(200) CeO2

Solar celltemplate concept: 

may work well with lattice-matched 

(200) CeO2

Experimental Approach•Deposit CeO2

• RF magnetron sputtering

• Ceramic ceria target

• Room temperature

• Inclined Substrate Deposition

•Examine orientation using X-Ray diffraction

•Sputtered cerium oxide tends to orient (111) towards the gun and parallel to the surface; can we change the orientation?

Experimental Approach•Deposit CeO2

• RF magnetron sputtering

• Ceramic ceria target

• Room temperature

• Inclined Substrate Deposition

•Examine orientation using X-Ray diffraction

•Sputtered cerium oxide tends to orient (111) towards the gun and parallel to the surface; can we change the orientation?

C.W. Teplin et. al., J. of Non-crystalline Solids, In 

press.