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Synchrotron radiation XAFS studies of transition metal oxide thin films prepared
by reactive magnetron sputtering
Juris PurānsInstitute 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,LURSD2011 J.Purans – ISSP,LU
Transparent Conductive Oxides
RSD2011 J.Purans – ISSP,LURSD2011 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,LURSD2011 J.Purans – ISSP,LU
T. Minami, Semicond. Sci. Technol. 20(2005) S35-S44.
Transparent Conductive Oxides
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
Time variable (”chromogenic”) window coatings
PhotochromicThermochromicElectrochromicGasochromicUV irradiationTemperatureElectric voltage or chargeReducing/oxidizing gas
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LURSD2011 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+O3RSD2011 J.Purans – ISSP,LURSD2011 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,LURSD2011 J.Purans – ISSP,LU
Why Ga as dopant?
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
Presently HF magnetron sputtering is the background of the technology, but it is underproductive and quite expensive in comparison with DCand MF magnetron sputtering
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
XRD Results RT, Cu anode
30 40 50 60 70
Si
Zn
TEC5/Si
(004
)(2
01)
(112
)(2
00)
(103
)(110
)
(102
)
(101
)
(002
)(1
00)
TEC2/Si
TEC1/Si
c-ZnO
Inte
nsi
ty (
cps)
2 (degree)
30 40 50 60 70
338
7%Cd 480HT2_30s
347HT_30s
346HT_30s
341HT
341HT2(from met-Zn)
Inte
nsi
ty (
cps)
2 (degree)RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
ZnO samples prepared in ISSP (EXAFS Lab.) ZnO samples prepared in ISSP (EXAFS Lab.) morphologymorphology
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,LURSD2011 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.PuransInstitute of Solid State Physics, University of Latvia, Riga, Latvia
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
400 500 600 700 800 900 10000
5000
10000
760 770 780 7900
500
1000
1500
2000
Ar
(763
.51n
m)
Zn
(481
.05n
m)
Inte
nsity
(co
unts
)
Inte
nsity
(co
unts
)
Wavelength (nm)
Wavelength (nm)
O (
777.
19,
777.
41,
777.
53 n
m)
Optical emission spectrum upon sputtering of a ZnAl target in an atmosphere of Argon and Oxygen RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
Selected Zinc, Argon and Oxygen optical emission line intensities during the process conditioning and film deposition
0 5 10 15 20 25 300
2000
4000
6000
8000
10000
12000
O (777.19, 777.41, 777.53nm)
Ar (763.51nm)
Inte
nsi
ty (
cou
nts
)
Time (min)
conditioning deposition
Zn (481.05nm)
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
8 10 12 14 160,000
0,002
0,004
0,006
0,008
0,010
Re
sist
ivity
, oh
m*c
m
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
Resistivity for ZnO:Al films deposited at different Zinc and Oxygen optical emission line intensity ratios.
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU
0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,00
10
20
30
40
50
60 Ar + O2
Ar + O2 + H
2 (5%)
Ar + O2 + H
2 (25%)
*10
-3, o
hm*c
m
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,LURSD2011 J.Purans – ISSP,LU
AcknowledgemenAcknowledgementsts
We are grateful to the
Eiropas Reģionālās attīstības fonda Eiropas Reģionālās attīstības fonda 2.1.1.1.aktivitātes „Atbalsts zinātnei un pētniecībai” 2.1.1.1.aktivitātes „Atbalsts zinātnei un pētniecībai”
2010/0272/2DP/2.1.1.1.0/10/APIA/VIAA/0882010/0272/2DP/2.1.1.1.0/10/APIA/VIAA/088http://www1.cfi.lu.lv/teor/ERAF/http://www1.cfi.lu.lv/teor/ERAF/
RSD2011 J.Purans – ISSP,LURSD2011 J.Purans – ISSP,LU