Ming H. Cheng, Yu Liu, Allie Margarella

John C. Hemminger group

March 15, 2011

1

Outline

• Pyrite thin films on the glass, ITO, Mo-glass, AF-32 (Alkali-free glass) How Na plays the role in growing pyrite thin film on the glass.

• Band gap determination for Pyrite thin films on Si Valence band spectrum

Valence band spectrum + X-ray absorption spectrum (XAS)

2

Pyrite thin films on the glass without annealing in elemental sulfur condition

700 710 720 730 740

20000

25000

30000

35000

40000

Iron

oxide

Fe2p1/2

Fe2p3/2

Fe2p

Binding Energy (eV)

Iron

oxide

Inte

ns

ity

155 160 165 170 1754000

6000

8000

10000

12000

14000

16000

18000

20000

Inte

ns

ity

Binding Energy (eV)

S2p

Sulfate (SO-2

4)

Sulfide (FeS2)

1060 1064 1068 1072 1076 1080

60000

65000

70000

75000

Inte

ns

ity

Na1s

Binding Energy (eV)

• The pyrite has been oxidized.

• Na exists on the surface of the pyrite thin film.

3

4

700 710 720 730 740 750

B.E. (eV)

Fe 2p

Fresh Pyrite thin films on the glass

155 160 165 170 175 180 185

B.E. (eV)

S 2p

1065 1070 1075 1080 1085 1090

40000

41000

42000

43000

44000

45000

46000

Na 1s

B.E. (eV)

• No oxidation occurs on the surface of fresh pyrite.

• Na really exists on the surface.

SEM and XRD of pyrite on the glass

5

Na 1s spectrum for the blank annealed glass

6

1060 1065 1070 1075 1080 1085

25000

30000

35000

40000

Binding Energy (eV)

Na 1s

Inte

ns

ity

Where did Na come from ??

Na comes from the glass substrate and leaches into the pyrite thin films.

Na 1s Mo-glass V.S Annealed ITO

7

1060 1064 1068 1072 1076 1080

Na1s

B.E. (eV)

Annealed Mo glass

1060 1064 1068 1072 1076 1080

Na 1s

B.E. (eV)

Annealed ITO glass

8

155 160 165 170 175 180 185

B.E. (eV)

S 2p

Fresh Pyrite thin films on the ITO glass

700 710 720 730 740 750

B.E. (eV)

Fe 2p

1060 1065 1070 1075 1080 1085 1090

B.E. (eV)

Na 1s

It appears to be a little amount of Na still on the surface.

AcAc/TBDS Growth on ITO

15 20 25 30 35 40 45 50 55 60 65 70

400

600

800

1000

1200

1400

Inte

nsi

ty

2 Theta

2010-12-6_E_ITO

ito_blank

Marcasite

pyrite

AcAc/TBDS Growth on ITO

11

690 700 710 720 730 740

B.E. (eV)

Fe 2p

Fresh Pyrite thin films on the AF-32 glass (alkali free glass)

150 155 160 165 170 175 180 185

B.E. (eV)

S2p

1055 1060 1065 1070 1075 1080 1085

B.E. (eV)

Na 1s

It appears to be no Na leaches into the pyrite thin film.

AcAc/TBDS Growth on AF32

20 40 60

600

800

1000

1200

Inte

nsi

ty

A

2010-12-6_D_AF32

Marcasite

pyrite

AcAc/TBDS Growth on AF32

14

1060 1065 1070 1075 1080 1085 109018000

18500

19000

19500

20000

20500

21000

Na 1s

B.E. (eV)

Na 1s spectrum for the blank annealed AF-32 glass

Alkali-free is NOT really alkali-freeFrom commercial AF-32 glasses.

Na concentration V.S. degree of crystalline pyrite

15

Glass slide AF-32 Glass0.0

0.1

0.2

0.3

0.4

0.5

0.6

Na

/Si

rati

o

20 40 60

600

800

1000

1200

Inte

nsi

ty

A

2010-12-6_D_AF32

Marcasite

pyrite

Take-home messages

16

• The source of Na in pyrite thin films comes from glass substrates.

• AF-32 glass is NOT a alkali-free glass.

• The glass substrate with well-controlled Na concentration is needed to further clarify how Na plays the role in growing of pyrite thin films on the glass.