Grzegorz P. Karwasz Istituto Nazionale per la Fisica della Materia, Università di Trento, Povo...
-
Upload
jenifer-manley -
Category
Documents
-
view
216 -
download
3
Transcript of Grzegorz P. Karwasz Istituto Nazionale per la Fisica della Materia, Università di Trento, Povo...
Grzegorz P. Karwasz
Istituto Nazionale per la Fisica della Materia, Università di Trento, Povo (TN), Italia and Instytut Fizyki, Pomorska Akademia Pedagogiczna, 76200 Slupsk, Polska
Roberto S. Brusa
Dipartimento di Fisica, Università Degli Studi di Trento, 38050 Povo (TN) Italia
Warszawa, 16.09.2003Warszawa, 16.09.2003
Techniques: - Doppler broadening (depth profile)- lifetime (in bulk)- coincidence (in bulk)
Samples: - Czochralski-grown silicon- He-implanted silicon
- low-k materials
- SiO2 and GeO2 conducting glasses
Positron identity
e+ is antiparticle of e- :
- mass 511.003 keV/c2
- spin ½ - opposite Q- opposite μ- stable in vacuum (>2x1021y)
Ps is light H :
- Energy E= ½ Ry- p-Ps: τ=125 ns, 2γ- o-Ps: τ=142 ns, 3γ
Positron history
History of “slow” positrons 1930 – e+ postulated by Dirac1932 – discovered in cosmic raysby Anderson“out of 1300 photographs of cosmic tracks, 15 were od positive particles which could nothave a mass greater as that of the proton”
1950 – Madanski-Rasetti try to moderate1951 – evidence of Ps atom (Deutsch) 1958 – moderated e+ , ε=3x10-8 (Cherry)1979 – single crystal moderator (Mills)
1980 – brightness enhancement (Mills)
Positron slowing down
Positron sources
Radioactive nuclides Moderators
W (100): ε= 4x10-4
Solid Ne: ε=1% ?
Positrons in Solid State Physics
Trento Positron Annihilation Set-up
E=100 eV – 25 keVspot < 1 mm
Trento Positron Annihilation Set-up
Trento-München Positron Microscope
E=500 eV – 25 keVspot = 2 μm
Positron walking
Positron in a crystal
Positron lifetime technique
τdefect > τbulk
Doppler broadening technique
ΔE = cpz / 2ptot=pe+pp
S=(E0±0.85keV)/(E0±4.25keV)
506 507 508 509 510 511 512 513 514 515 5160
20000
40000
60000
80000
100000
A+EA+B+C+D+E
A+B+C+D+E
C
W=
S=
E
B
A
D
C
Ilość
zlic
zeń
Energia [keV]
Doppler-broadening: normalization
0 2 4 6 8 10 12 14 16 18 200.90
0.92
0.94
0.96
0.98
1.00
1.02
1.04
250020001000500200100
mean positron implantation depth [nm]
reference sample
as impl. fluence 5x1015
sample 450°C annealing
S-p
ara
mete
r
positron implantation energy [keV]
He bubbles in Si
He – implantation
n=0.5x1016cm2 NO! n=2x1016cm2 YES!
0.1 1 10 100 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
2x1016
He cm-2
as impl. 150°C 200°C 250°C
S
mean positron implantation depth [nm]
0.1 1 10 100 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
2x1016
He cm-2
250°C 300°C 350°C 400°C 450°C
S
mean positron implantation depth [nm]
He bubbles in Si
He bubbles in Si
0.1 1 10 100 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
2x1016
He cm-2
500°C 550°C 600°C 700°C
S
mean positron implantation depth [nm]
0.1 1 10 100 10000.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
2x1016
He cm-2
700°C 750°C 800°C 850°C 900°C
S
mean positron implantation depth [nm]
He bubbles in Siquantization of S - values
0 100 200 300 400 500 600 700 800 900 10001,00
1,01
1,02
1,03
1,04
1,05
1,06
1,07
1,08
1,09
1,10
1,11
1,12
1,13
1,14
V5
V4
V3
V2
V1
próbki implantowane He o dozie
5x1015
cm-2
2x1016
cm-2
Sd
Temperatura wygrzewania (o
C)
Doppler-coincidence technique
505 510 515 520 525 530 535 540
101
102
103
104
105 low-momentum electrons
(conduction and valence bands)
high-momentum electrons(core electrons)
background in asingle-detector system
background ina coincidence system
Si coincidence Si non-coincidence
Cou
nts
Energy [keV]
0 10 20 30 40 50 60 70p
L [10
-3 m
0c]
0 10 20 30 40 501
10
100
1000
10000
100000
rys1wr2
Ni Al Ti Nb Ag Au Si
Coun
ts
pL (10
-3 m
0c)
Doppler-coincidence spectra
0 10 20 30 40 500.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
rys5wr2
Ti d2
V d3
Cr d5
Mn d5
Fe d6
Co d7
Ni d8
Cu d10
Zn d10
Rat
io t
o S
i (an
neal
ed s
ampl
es)
PL ( 10
-3 m
0c )
D-C - chemical sensitivity
0 10 20 30 40 500.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Hf d2
W d3
Pt d9
Au d10
Pb d10
Rat
io t
o S
i (an
neal
ed s
ampl
es)
PL ( 10
-3 m
0c )
D-C - chemical sensitivity
Si – Czochralski grown
cO≈ 1018 cm-3
cB≈ 1016 cm-3
Oxygen in Cz-grown silicon
“as grown”: annealed at 450°C
thermal donors
precipitates
new donors
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
as grown
Ra
tio to
Si
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
450°C
Ra
tio to
Si
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
450°C+650°CR
atio
to S
i
PL ( 10
-3 m
0c )
Oxygen in Cz-grown silicon
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
as grown
Ra
tio to
Si
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
450°C
Ra
tio to
Si
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
450°C+650°CR
atio
to S
i
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
-- + 900°CR
atio
to S
i
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
-- + 1050°C
Ra
tio to
Si
PL ( 10
-3 m
0c )
Oxygen in Cz-grown silicon
975oC/5h/100bar
975oC/5h/100bar
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
as grown
Ra
tio to
Si
PL ( 10
-3 m
0c )
0 5 10 15
0.9
1.0
1.1
1.2
Oxygen peak
450°C
Ra
tio to
Si
PL ( 10
-3 m
0c )
Oxygen in Cz-grown silicon
AFM picture of Si-Pb glass; a) freshly broken;
b) Annealed at 580ºC for 21h
a)
b)
Conducting glasses (SiO2+Bi2O3)
-100 0 100 200 300 400 500 600-0,3
-0,2
-0,1
0,0
0,1
0,2
0,3
270.6oC
231.5oC179oC
(485.2oC)0.3Bi2O30.7SiO2
CB
A
as obtained
reduced at 300oC
reduced at 300oC
and annealed at 400oC
DS
C [m
W/m
g]
T [oC]
Conducting glasses (SiO2+Bi2O3)
0 2 4 6 8 10 12 14 16 18 20 220.48
0.49
0.50
0.51
0.52
0.53
0.54
0.55
IIIIII
250 500 100050Mean positron implantation depth [nm]
91h25h3h20minas-grown
S-p
ara
met
er
Positron implantation energy [keV]
Conducting glasses (SiO2+Bi2O3)
Conducting glasses (SiO2+PbO2)
Conducting glasses (GeO2+Bi2O3)
0.1 1 10
0.47
0.48
0.49
0.50
0.51
0.52
0.53
Mean positron implantation depth (nm)
G0 G1 G2 G3
Pa
ram
ete
r S
Positron Energy (keV)
0.1 1 10 100 1000
Conducting glasses (SiO2+Bi2O3)
0.1 1 100.47
0.48
0.49
0.50
0.51
0.52
0.53
0.54
B0 B1 B2 B3 B4
Par
amet
er S
Energy (keV)
0.1 1 10 100 1000Mean implantation depth (nm)
Silica based, low ε materials - structure
From K.Maex et al. J. Appl. Phys. 11, 93, 8793
low ε materials - annealing
0.1 1 10 100 10000.90
0.92
0.94
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
1.12
Sn21ad Sn21a(400°C) Sn21b(450°C) Sn21c(500°C) Sn21d(600°C) Sn21e(700°C) Sn21f(800°C) Sn21g(900°C)
Sn
(ann
ihila
tion
with
low
mom
ent
ele
ctro
ns)
depth[nm]
low ε materials - annealing
0.1 1 10 100 10000.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28 PVmad21 PVm21a(400°C) PVm21b(450°C) PVm21c(500°C) PVm21d(600°C) PVm21e(700°C) PVm21f(800°C) PVm21g(900°C)
PV
(3
/2 r
atio
: O
Ps
form
atio
n)
depth[nm]
511 keV
Energia [keV]
obszar anihilacji 3Powierzchnia całkowita
Ilo
ść z
licze
ń
low ε materials - ageing
0.1 1 100.90
0.92
0.94
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
1.12
Sn
Energy[keV]
0.1 1 100.90
0.92
0.94
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
1.12
Sn
Energy[keV]
0.1 1 100.90
0.92
0.94
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
1.12
Sn
Energy[keV]
0.1 1 10
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
PV
(3
/2 r
atio
: o-P
s fo
rma
tion
)
Energy[keV]
0.1 1 10
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
PV
(3
/2 r
atio
: o-P
s fo
rma
tion
)
Energy[keV]
0.1 1 10
0.14
0.16
0.18
0.20
0.22
0.24
0.26
0.28
PV
(3
/2 r
atio
: o-P
s fo
rma
tion
)
Energy[keV]
Intense beams !
Auger Spectroscopy
Low-energy Positron Diffraction
Acknowledgements:
UniTN: Marco BettonteMonica SpagollaSebastiano Mariazzi
PAP: Tomasz WróblewskiEryk RajchDamian Pliszka
PG: Bogusław KuszMaria GazdaKonrad Trzebiatowski