Transcript Nessun titolo diapositiva

Synchrotron radiation XAFS studies
of transition metal oxide thin films prepared
by reactive magnetron sputtering
Juris Purāns
Institute of Solid State Physics University of Latvia
Internet: http://www.cfi.lu.lv/exafs/
E-mail: [email protected]
http://www1.cfi.lu.lv/teor/ERAF/
RSD2011 J.Purans – ISSP,LU
Transparent Conductive Oxides
RSD2011 J.Purans – ISSP,LU
Transparent Conductive Oxides (TCO)
From 1980 =>n-type TCOs,
with good optical and
electrical properties
http://www.iesl.forth.gr/conferences/tco2006/index.aspx
RSD2011 J.Purans – ISSP,LU
Transparent Conductive Oxides
T. Minami, Semicond. Sci. Technol. 20(2005) S35-S44.
RSD2011 J.Purans – ISSP,LU
Time variable (”chromogenic”) window coatings
Photochromic
Thermochromic
Electrochromic
Gasochromic
UV irradiation
Temperature
Electric voltage or charge
Reducing/oxidizing gas
RSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LU
Operating the Electrochromic Element
The ECE can be colored by applying negative potential (-2.4 < U < 0 V)
to the working electrode (WE) for a time t < 5 sec.
W6+O3 +e- + H+ => HW5+O3
The ECE can be bleached by applying positive potential (0 < U < +1.5 V)
to the working electrode (WE) for a time t < 5 sec.
W6+O3 +e- + H+ <= HW5+O3
RSD2011 J.Purans – ISSP,LU
Why zinc oxide ?
• Resource availability
• Low cost material
• Non-toxicity
• High thermal/chemical stability
• Electrical resistivity tailored [1010-10-4Ωcm]
• High transmittance in the VIS-IR
• Lithography compatible ZnO
RSD2011 J.Purans – ISSP,LU
Why Ga as dopant?
RSD2011 J.Purans – ISSP,LU
Presently HF magnetron sputtering is the background of the technology,
but it is underproductive and quite expensive in comparison with DC
and MF magnetron sputtering
RSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LU
341HT
338
346HT_30s
Intensity (cps)
(201)
(103)
(112)
(004)
Intensity (cps)
(200)
(102)
c-ZnO
(110)
(002)
(100)
341HT2
(from met-Zn)
(101)
RT, Cu anode
XRD Results
TEC1/Si
TEC2/Si
TEC5/Si
347HT_30s
Zn
7%Cd 480HT2_30s
Si
30
40
50
60
2 (degree)
70
30
40
50
60
2 (degree)
70
RSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LU
ZnO samples prepared in ISSP (EXAFS Lab.)
morphology
1.0µm
ZnO/Si produced
by magnetron sputtering in argon
followed by oxidation in air at 800ºC
1.0µm
ZnO/Si produced
by magnetron sputtering in Ar-O2
APCVD ZnO/Si sample
(image size: 890  660 µm)
RSD2011 J.Purans – ISSP,LU
DC magnetron deposition of Zn-based TCO-s:
process control by plasma optical emission spectroscopy
R.Kalendarev, K.Vilnis, A.Ecis, M.Zubkins, A.Azens, J.Purans
Institute of Solid State Physics, University of Latvia, Riga, Latvia
O (777.19, 777.41, 777.53 nm)
The scope: the usefulness of plasma Optical Emission Spectroscopy (OES)
for the sputtering process tuning has been investigated with the aim
to ensure the process stability and reproducibility, and the quality of ZnO:Al films
in terms of [minimized] electrical resistivity and [maximized] optical transmittance
5000
0
400
Intensity (counts)
Ar (763.51nm)
10000
1500
1000
500
0
760
Zn (481.05nm)
Intensity (counts)
2000
500
770
780
790
Wavelength (nm)
600
700
800
900
1000
Wavelength (nm)
Optical emission spectrum upon sputtering of a ZnAl target
RSD2011 J.Purans – ISSP,LU
in an atmosphere of Argon and Oxygen
12000
conditioning
deposition
10000
Intensity (counts)
Zn (481.05nm)
8000
6000
Ar (763.51nm)
4000
2000
O (777.19, 777.41, 777.53nm)
0
0
5
10
15
20
25
30
Time (min)
Selected Zinc, Argon and Oxygen optical emission line intensities
during the process conditioning and film deposition
RSD2011 J.Purans – ISSP,LU
Resistivity for ZnO:Al films deposited at different Zinc and Oxygen
optical emission line intensity ratios.
0,010
Resistivity, ohm*cm
0,008
0,006
0,004
0,002
0,000
8
10
12
14
16
OES Intensity ratio, I(Zn)/I(O)
Although the film resistivity data is not completely free from scattering [yet],
the correlation between the values of the OES line intensities
upon film deposition and the film properties confirms the usefulness
of OES for the deposition process control of ZnO:Al films
RSD2011 J.Purans – ISSP,LU
Ar + O2
60
Ar + O2 + H2 (5%)
Ar + O2 + H2 (25%)
50
30
-3
*10 , ohm*cm
40
20
10
0
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1,0
IZn/IZn(max)
Film resistivity as a function of Zinc optical emission line IZn/IZnmax ratio.
The IZn/IZnmax ratio range corresponds to the oxygen flow range after
the maximum in Zinc line intensity
RSD2011 J.Purans – ISSP,LU
Acknowledgements
We are grateful to the
Eiropas Reģionālās attīstības fonda
2.1.1.1.aktivitātes „Atbalsts zinātnei un pētniecībai”
2010/0272/2DP/2.1.1.1.0/10/APIA/VIAA/088
http://www1.cfi.lu.lv/teor/ERAF/
RSD2011 J.Purans – ISSP,LU