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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.