G.Zvereva S.I.Vavilov State Optical Institute, St-Petersburg, Russia Application of vacuum ultraviolet (VUV) emission of excimer lamps in ecology and biology
G.Zvereva
S.I.Vavilov State Optical Institute,
St-Petersburg, Russia
Application of vacuum
ultraviolet (VUV) emission of
excimer lamps in ecology and
biology
VUV excimer lamps (excilamps)
working media: Ar, Kr, Xe
р ~ 1 atm
U=1-10 kV f= 10-100 kHz
efficiency η < 60 %
wavelengths:
λ= 126 nm (Ar2*)
λ= 146 nm (Kr2*)
λ= 172 nm (Xe2*)
advantages: environmentally safe, high photon energy (high photochemical
possibilities), cheap, wide range of constructions, long time of work
history:
~1980 – one of the 1st patent in our institute (I.Podmoshenskii, G.Volkova et al)
~1990-2005- R&D U. Kogelshatz (ABB, Switzerland)
- our days : R&D (Russia, Australia)
R&D, commercial production – USIO (Japan), OSRAM
115 120 125 130 135 140 145 150 155 160 165 170 175 180 185
0
20
40
60
80
100
Xe 172
Kr 146
Ar 126
Инте
нси
вно
сть
изл
., о
тн.е
д.
Длина волны, нм
I(a.u.)
λ(nm)
Influence of VUV emission on surface
Edis,eV λ,nm
by direct irradiation by reactive products of
(chemical bonds breaking) VUV photolysis of
near-surface media
O2, H2O
Name of oxidant Oxidation potential (eV)
Hydroxyl radical •OH 2.7
Ozone O3 2.1
Hydrogen peroxide H2O2 1.8
D
D
Hg
F ///////
HO-O
VUV photolysis of water
k(cm-1) absorption coefficient σ(cm2) absorption cross section
λ(Ǻ) λ(nm)
liquid water vapor water
H2O+hv = •OH + H• H2O+hv = •OH + H•
H2O+hv = •OH + H+ + eaq
Water absorption of VUV emission (172nm)
0
0,0001
0,0002
0,0003
0,0004
0,0005
0,0006
0,0007
0,0008
0,0009
0,001
0 0,0005 0,001 0,0015 0,002
Толщина слоя d, см
Ин
те
нси
вн
ость и
зл
уче
ни
я I, В
т
liquid vapor
I(W) I(mW)
d(cm) d(cm)
d ~ 10-3 cm d ~ 10-2 - 1 cm
VUV photolysis of O2
O2+hv = O + O(1D) d~ 1-5mm
σ(cm2)
Рис. 7. Сечение поглощения О2 в области 100-250 нм.
1,00E-25
1,00E-24
1,00E-23
1,00E-22
1,00E-21
1,00E-20
1,00E-19
1,00E-18
1,00E-17
1,00E-16
100 120 140 160 180 200 220 240
Длина волны, нм
Сеч
ен
ие
по
гло
ще
ни
я,
см
.кв
.
O2 absorption cross section λ(nm)
VUV excilamps applications in surface technologies
already used in industries: at the R&D stage:
Removal of polymers: – abrasive-free polishing
– Removal of organic residue method
– Cleaning of photo masks – VUV/OH cleaning process
– Etching (e. g. Teflon®) – VUV/OH decontamination
Surface treatment:
– Activation of surface bonds
– Adjustment of wetting angle
– VUV/ozone cleaning process
for semiconductor and flat panel
display production
Commercial VUV technologies (OSRAM)
Vacuum process chamber
for side treatment(OSRAM)
Increasing of wettability by VUV irradiation
Contact angle vs irradiation time for glass
Irradiation of glass substrate for impoving wettability
Commercial VUV technologies (USHIO)
Removal of organic residue from surface
- in flat panel display production industry
- in semiconductor industry
Xe*2 excilamp λ=172 nm
USIO JAPAN
VUV surface technologies at R&D stage
Abrasive-free polishing O.Kirino and T.Enomoto (Japan), ”Development of Abrasive-Free Polishing
Method for Cu Utilizing Vacuum Ultraviolet Light”, J. of Environment and
Engineering, v.4, N3,(2009)
Mechanism of Cu polishing with VUV light irradiation
VUV surface technologies at R&D stage
Use of VUV water photolysis products for cleaning
liquid water water vapor pollution surface to be cleaned
VUV VUV
OH H2O2 OH O(1D) O3
VUV + H2O reactive species (OH, H2O2, O(1D), O3 )
reactive species + pollution CO2, H2, O2, H2O
Numerical model (liquid water)
Water decomposition products (λ=172 nm,I=10 mW/cm2):
·H, ·OH, eaq, H2, OH-, ·O-, H+, H2O2, O2·-, HO2·, HO2
-, O3-
i=1,12
Ni-concentration of i-th product
Fij(cm-3/s)-velocity of Ni formation in reaction j
Fik(cm-3/s)-velocity of Ni loss in reaction k
Conditions: Δt < τ =10-2(s) Δd =1 µm
distilled water with O2 (1017 cm-3)
j k
ikiji FF
dt
dN
Degradation of polychlorinated biphenyls by ·OH radicals
PCB+·OH products k= 1.5 10-11 cm3/s
C12H10-nCln n=1-10
Excilamps biological application
DNA destruction by photolysis products
DNA+·OH products k=1.3 10-12 cm3 s-1
DNA+H· products k=1.2 10-13 cm3 s-1
DNA+eaq products k=2.2 10-13 cm3 s-1
dH2O=1 μm
Numerical model (water vapor)
Water decomposition products (λ=172 nm, I=10 mW/cm2):
·Н, ·ОН, H2O2, O, HO2, O(1D), H2, O2, O3
i=1,12
Ni-concentration of i-th product
Fij(cm-3/s)-velocity of Ni formation in reaction j
Fik(cm-3/s)-velocity of Ni loss in reaction k
Conditions: Δt < τ =10-2(s) Δd =0.1 cm
saturated vapor at T=24 ºC
j k
ikiji FF
dt
dN
Radical ·OH formation at different temperatures of saturated water vapor
0
2E+13
4E+13
6E+13
8E+13
1E+14
1,2E+14
0 0,002 0,004 0,006 0,008 0,01
90оС
60oC
24oC
7oC
NOH(cm-3)
t(s)
Degradation of polychlorinated biphenyls by ·OH radicals
lg Ni(cm-3)
t(s)
PCB
PCB + ·OH products k= 1 10-11 cm3/s
Conclusions
1)VUV excilamps are environmentally safe light
sources with strong photochemical opportunities
2)VUV photolysis of O2 and H2O produce high
reactive environmentally safe radicals important for
surfaces cleaning
3)Irradiation of water containing layers by VUV
emission leads:
- halogenated aromatic compounds transformation by
water photolysis products
- DNA transformation by water photolysis products