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)

Laboratory sample of excilamp Different constructions of

in working regime excilamps

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

Concentrations of liquid water VUV photolysis products

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)

Concentrations of vapor water VUV decomposition products

lg Ni(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