Aplicaciones: Defectos en semiconductores

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Aplicaciones Defectos en semiconductores
Sustitución catiónica en polvos nanocristalinos
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t(ns)
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Aplicaciones Volúmenes libres en polímeros
Polivinilsiloxanos (PVS)
POSITRONFIT
CONTIN
Alessandrini, SLAP 2004, Spain
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Aplicaciones Volúmenes libres en polímeros
Polímeros de Poli(Acrilato de Etilo)
Se determinó el tamaño de los huecos R2.5 Å
M.A.Hernández-Fenollosa, APHYS 2003, Spain
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Aplicaciones Volúmenes libres en polímeros
Estructuras CBn
to-Ps en función del tamaño del hueco en las CBn
Variación de tave con el llenado de las
cavidades para CB7
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Application of positron annihilation techniques
for semiconductor studies
Techniques
- Doppler broadening (depth profile)
- lifetime (in bulk)
- coincidence (in bulk)
- He-implanted silicon
Samples
- Czochralski-grown silicon

• low-k materials

- SiO2 and GeO2 conducting glasses
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Positron identity
e is antiparticle of e-

• mass 511.003 keV/c2
• spin ½
• opposite Q
• opposite µ
• stable in vacuum (gt2x1021y)

Ps is light H

• Energy E ½ Ry
• p-Ps t125 ns, 2?
• o-Ps t142 ns, 3?

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Positron history
History of slow positrons   1930 e
postulated by Dirac 1932 discovered in cosmic
rays by Anderson out of 1300 photographs of
cosmic tracks, 15 were od positive particles
which could not have a mass greater as that of
the proton
1950 Madanski-Rasetti try to moderate 1951
evidence of Ps atom (Deutsch) 1958 moderated
e , e3x10-8 (Cherry) 1979 single crystal
moderator (Mills) 1980 brightness enhancement
(Mills)
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Positron slowing down
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Positron sources
Moderators
Radioactive nuclides
W (100) e 4x10-4 Solid Ne e1 ?
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Positrons in Solid State Physics
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Trento Positron Annihilation Set-up
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Trento-München Positron Microscope
E500 eV 25 keV spot 2 µm
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Positron walking
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 Positron in a crystal
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Espectroscopía de aniquilaciónde positrones
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Positron lifetime technique
tdefect gt tbulk
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Doppler broadening technique
?E cpz / 2
ptotpepp
S(E00.85keV)/(E04.25keV)
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Doppler-broadening normalization
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He bubbles in Si
He implantation
n0.5x1016cm2 NO!
n2x1016cm2 YES!
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He bubbles in Si
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He bubbles in Si
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He bubbles in Siquantization of S - values
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Doppler-coincidence technique
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Doppler-coincidence spectra
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D-C - chemical sensitivity
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D-C - chemical sensitivity
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Si Czochralski grown
cO 1018 cm-3
cB 1016 cm-3
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Oxygen in Cz-grown silicon
thermal donors
precipitates
new donors
as grown annealed at 450C
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Oxygen in Cz-grown silicon
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Oxygen in Cz-grown silicon
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Oxygen in Cz-grown silicon
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Conducting glasses (SiO2Bi2O3)
a)
b)
AFM picture of Si-Pb glass a) freshly broken
b) Annealed at 580ºC for 21h
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Conducting glasses (SiO2Bi2O3)
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Conducting glasses (SiO2Bi2O3)

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Conducting glasses (SiO2PbO2)
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Conducting glasses (GeO2Bi2O3)

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Conducting glasses (SiO2Bi2O3)

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Silica based, low e materials - structure
From K.Maex et al. J. Appl. Phys. 11, 93, 8793
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low e materials - annealing
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low e materials - annealing
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low e materials - ageing
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Positron Spectroscopy in Solid State Physics
Intense beams !
Future ?
Auger Spectroscopy
Low-energy Positron Diffraction
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Positron Spectroscopy in Solid State Physics
Intense beams !
Future ?
Auger Spectroscopy
Low-energy Positron Diffraction