The design o an elec os a ic a iable ene gy posi on beam o
s udies o de ec s in ce amic coa ings and polyme ilms
E. Abadjie a
*
, H. Schu , A. Alba Ga cı
´a, R. Escoba Galindo,
A. an Veen, S.M. Pimblo
1
In e acul y Reac o Ins i u e, Del Uni e si y o Technology, Mekelweg 15, NL-2629 JB Del , The Ne he lands
Abs ac
An elec os a ic a iable ene gy posi on beam o s udying de ec s in ce amic coa ings, polyme ilms and MOS-de ices is
de eloped o ope a ion in Dopple -b oadening (DB) and posi on annihila ion li e ime (PAL) modes. In DB mode he
implan a ion ene gy can be a ied be ween 3 and 30 keV wi h a beam diame e on he a ge anging om 0.4 o 0.5 mm FWHM.
In PAL mode he s a -signal is gi en by seconda y elec on emission om a 25 nm hin ca bon oil placed in on o he a ge .
A e passing he oil he posi on beam is ocused on he a ge wi h a spo size o 2 mm FWHM a 1 keV down o 0.6 mm
FWHM a 30 keV. The a ge chambe is equipped wi h an in si u ou -poin bending de ice o s udying de ec s in oduced by
ensile and comp essi e s esses. #2002 Published by Else ie Science B.V.
Keywo ds: Elec os a ic posi on beam; Dopple -b oadening; Posi on li e ime
1. In oduc ion
The posi on annihila ion Dopple -b oadening (DB)
and posi on annihila ion li e ime (PAL) echniques
a e known as sensi i e me hods o he cha ac e iza-
ion o de ec s in a wide a ie y o solids. Combined
wi h a beam o a iable ene gy posi ons hey o e he
possibili y o cha ac e ize no only he bulk, bu also o
s udy he p ope ies o su aces, in e ace egions and
hin ilms. An o e iew o he acili ies and echniques
employed is gi en by, e.g. Coleman [1] and Schul z
and Lynn [2]. In o de o s udy ce amic and polyme
coa ings, and MOS-de ices we designed a a iable
ene gy posi on beam acili y, which ope a es in bo h
DB and PAL modes. Bo h echniques can be pe -
o med subsequen ly using he same beam-line. The
posi ion o he a ge emains ixed and he op ical
sys em, based on a se o elec os a ic lenses, can be
uned acco ding o he espec i e expe imen .
2. Desc ip ion o he acili y
2.1. Dopple -b oadening mode
The op ical design o he acili y is shown in Fig. 1.
Posi ons om a 22Na sou ce a e mode a ed in a
3.5 mm hick annealed polyc ys alline ungs en oil.
A modi ied Soa gun and Einzel-lens, and addi ional
de lec ion pla es o ine alignmen , ocus he beam
a he en ance o a cylind ical mi o , which bends
he beam o e 908[3]. In DB mode he beam is
Applied Su ace Science 194 (2002) 47–51
*
Co esponding au ho . Tel.: þ31-152781961;
ax: þ31-152786422.
E-mail add ess: [email p o ec ed] (E. Abadjie a).
1
Pe manen add ess: Radia ion Labo a o y, Uni e si y o No e
Dame, No e Dam, IN 6556-0579, USA.
0169-4332/02/$ – see on ma e #2002 Published by Else ie Science B.V.
PII: S 0169-4332(02)00087-9
anspo ed and ocused on a a ge , which is kep
a g ound po en ial. The anspo a ion and ocusing
a e achie ed by ou symme ic Einzel-lenses (lenses
1, 2, 3 and 6). Lenses 4, 5 and 7 a e a g ound po en ial.
The implan a ion ene gy is se by changing he po en-
ial di e ence be ween he sou ce and he a ge
and can be a ied be ween 3 and 30 keV. Lenses
1 and 2 ope a e a a ixed ol age a io. Thei diame e
(D) is 26 mm, he a io g/D¼0:15, whe e gis he
gap be ween he elec odes, and he a io A/D¼1,
whe e Ais he sum o he middle elec ode leng h
plus he gap dis ance g. Lenses 3 and 6 ha e a i-
able po en ial a ios. Thei diame e s a e 38 and
44 mm, espec i ely. They ha e a ios o : g/D¼
0:1, espec i ely 0.06 and A/D¼0:73, espec i ely
1.8. Behind he a ge , which is 35 mm away om he
las lens, a Ge-de ec o is placed ou side he acuum
chambe .
2.2. Posi on li e ime mode
In o de o pe o m posi on li e ime measu emen s
a 25 nm hin ca bon oil can be in oduced which
in e cep s he beam 60 mm behind he lens 3 (Fig. 1).
The oil is moun ed on a mo able holde and is il ed
o e 458wi h espec o he beam axis. The backwa ds
emi ed seconda y elec ons gene a ed by he inciden
posi ons a e collec ed by a mic o-channelpla e
(MCP) wi h anode assembly posi ioned no mal o
he oil su ace, on he side whe e he posi ons en e
he oil. The ou pu pulses o he MCP a e ed in o a
ime- o-ampli ude con e e (TAC) gi ing he s a -
signal o he li e ime measu emen . The elec os a ic
lens sys em (lenses 4–7) ocuses he ansmi ed beam
on he a ge . The e he annihila ion ga e de ec ed by a
BaF scin illa ion de ec o p o iding he s op-signal o
he TAC.
Mon e Ca lo simula ions we e pe o med o a se
o selec ed ene gies o he incoming beam o calcula e
he ac ion, ene gy and angula dis ibu ions o he
ansmi ed posi ons esul ing om he inelas ic and
elas ic posi on sca e ing p ocesses in he oil. The
used me hodology is desc ibed in [4].Fig. 2 shows he
calcula ed angula and ene gy dis ibu ions o posi-
ons wi h an ini ial ene gy o 7 keV, a which he
beam ansmission p o ile is in op imum. A his
ene gy 90% o he beam is ansmi ed wi hin a solid
angle o 158. The a e age ene gy loss is calcula ed o
be 3% o he ini ial alue. These da a de e mine he
op ical design, shown in Sec ion 3.2.
In addi ion, he beam p ope ies can be moni o ed
by a channel on a he posi ion o he ca bon oil o
he a ge . The acili y is equipped wi h a PC and
so wa e o au oma ed se ings and con ol o he
lens po en ials and da a accumula ion in bo h DB and
PAL mode. A ou -poin bending de ice can be
ins alled in he sample chambe o s udying he
de ec gene a ion and adhesion p ope ies o polyme
and ce amic coa ings unde comp essi e and ensile
s ess condi ions.
Fig. 1. Op ical design o an elec os a ic a iable ene gy posi on beam.
48 E. Abadjie a e al. / Applied Su ace Science 194 (2002) 47–51
3. T ajec o y calcula ions
3.1. Dopple -b oadening mode
The elec ic ield dis ibu ions along he beam-line
and ay- acing a e pe o med using he simula ion
p og am Simion 7 [5]. The emission angles o he
mode a ed posi ons om he ungs en oil su ace a e
assumed o ha e a Gaussian dis ibu ion wi h an
angula HWHM o 58[2]. The wo k- unc ion is
2.9 eV. The emi ing a ea o he mode a o oil
has a adius o 3 mm. We ha e simula ed he ajec-
o ies o posi ons wi h 3 eV ini ial ene gy and assum-
ing a uni o m angula dis ibu ion wi hin 108
Fig. 2. Calcula ed angula and ene gy dis ibu ions o posi ons wi h an ini ial ene gy o 7 keV ansmi ed h ough a 25 nm hin ca bon oil.
Fig. 3. Lens po en ial diag am in DB mode o 25 keV posi ons and in PAL mode o 3 and 25 keV posi ons, espec i ely.
E. Abadjie a e al. / Applied Su ace Science 194 (2002) 47–51 49
emission angles, he eby aking in o accoun he pos-
sible oughness o he mode a o su ace. Posi ons a e
gene a ed andomly om a uni o m spa ial dis ibu-
ion om su ace wi h adius 3 mm. The lens po en ial
diag am o achie ing a beam o 25 keV posi ons is
p esen ed in Fig. 3. The esul ing beam diame e a he
a ge is 0.4 mm FWHM. F om 3 o 30 keV he beam
diame e changes be ween 0.4 and 0.5 mm FWHM. In
his ene gy ange he longi udinal ene gy sp ead is
calcula ed o be less han 0.1 keV.
3.2. Posi on li e ime mode
In PAL mode he sou ce is kep ixed a 5 keV.
Lenses 1, 2 and 3 a e se a 3.3, 2.8, and 3.8 kV,
espec i ely. The posi on beam is hus ocused o a
beam diame e less han 1 mm on he ca bon oil,
which is kep a 2 kV. A 2D cu o he op ical sys em
be ween he ca bon oil and he a ge is shown in
Fig. 4. Lenses 4 and 5 se e o minimize he beam
di e gence. Lenses 6 and 7 a e used in combina ion o
ocus he beam on o he a ge . The inal implan a ion
ene gy can be a ied be ween 1 and 30 keV by chan-
ging he po en ial on he a ge .
In he simula ions he ini ial coo dina es o he 8000
posi ons a e gene a ed andom om a spo o 1 mm
diame e , angles and ene gies co esponding o he
dis ibu ions shown in Fig. 2. The beam diame e a
he a ge a ies om 2 mm FWHM a 1 keV o 0.6 mm
FWHM a 30 keV. Fo he ene gy ange be ween 1
and 5 keV he op ical sys em wo ks in decele a ing
mode and om 5 o 30 keV in accele a ing mode.
Examples o de i ed op imum lens po en ials o bo h
cases a e gi en in Fig. 3. The implan a ion ene gy
sp ead coming om educ ion o he longi udinal elo-
ci y is calcula ed o be 50 eV a 1 keV and 0.5 keV a
15 keV. This only causes small shi s in he li e ime
dep h-p o iling da a.
Examples o he ime-o - ligh dis ibu ions o he
elec ons (gi ing he s a -signal) and he posi ons o
h ee implan a ion ene gies 1, 5, and 15 keVa e shown
in Fig. 5. F om his da a we es ima e ha he op ical
design con ibu ion o he ime esolu ion is, app oxi-
ma ely 300 ps. The elec onics con ibu ion is in o de
o 250 ps.
Fig. 4. Two-dimensional cu o he op ical sys em be ween he ca bon oil and he a ge .
Fig. 5. Calcula ed ime-o - ligh dis ibu ions o elec ons and
posi ons a elling om he ca bon oil su ace o he MCP and o
he a ge , espec i ely.
50 E. Abadjie a e al. / Applied Su ace Science 194 (2002) 47–51
4. Conclusion
An elec os a ic a iable ene gy posi on beam is
designed o ope a e in wo modes. In DB mode he
beam ene gy can be a ied om 3 o 30 keV wi h an
ene gy sp ead o less han 0.1 keV and beam diame e
o 0.4–0.5 mm FWHM. In PAL mode he beam ene gy
can be a ied be ween 1 and 30 keV. The beam
diame e a ies om 2 o 0.6 mm FWHM. The posi-
on implan a ion ene gy sp ead is less han 5%. The
o al ime esolu ion o he acili y is de e mined by
he ime-sp ead due o he op ical design (300 ps) and
he con ibu ion o he elec onics (250 ps).
Re e ences
[1] P. Coleman, Posi on Beams and hei Applica ions, Wo ld
Science Publ. Co. P e. L d., Singapo e, 2000.
[2] P. Schul z, K.G. Lynn, In e ac ion o posi on beams wi h
su aces, hin ilms, in e aces, Re . Mode n Phys. 60 (1988)
701.
[3] L.V. Jo gensen, A. an Veen, H. Schu , A. Winkelman, P. K ui ,
Nucl. Ins . Me h. A427 (1999) 131.
[4] S.M. Pimblo , J.A. LaVe ne, A. Alba Ga cı
´a, L.D.A.
Siebbeles, J. Phys. Chem. B 104 (2000) 9607.
[5] D.A. Dahl, Simion 3D, Ve sion 7, Use s Manual, Idaho Na .
Eng. and En . Lab., Idaho Falls, 2000.
E. Abadjie a e al. / Applied Su ace Science 194 (2002) 47–51 51