Ryan Weed
Centre for Antimatter-Matter Studies
VACANCY CLUSTERS IN SELF-ION IMPLANTED GERMANIUM STUDIED
WITH PALS
BEAMLINE OVERVIEW
BEAMLINE OVERVIEW
Transport coils Trap SourceSample station
detector
PALS ANALYSIS
PALS ANALYSIS
MOTIVATION
Germanium is a good candidate to replace Silicon in CMOS devices
3-4 times higher mobility (determines device speed)
MOTIVATION
Implantation induced defects effect electrical activation
Dopant-defect relationship not well understood in Ge
Diffusion mechanisms dissimilar to Si
Positrons well suited to study evolution of vacancy type defects under thermal treatment
ION IMPLANTATION
800 keV Ge+ implantation
Fluence between 3x1012 and 3x1014 cm -2
Vacancy and interstitials damage distribution simulated in SRIM
RBS RESULTS
RBS RESULTS
As-implanted Annealed
High fluence sample ‘amorphized’ by ion implantation
No damage detected in low fluence sampleSPEG of amorphous region complete at 400 C anneal
PALS RESULTS
Vacancy clusters formed in both samples
Cluster size expected in magic numbers (N=6,10,14)
Clusters dissolve at 500 C in both samples
VARIABLE ENERGY PALS
2,10,18keV positron energies performed on 400 C annealed samples
Similar lifetime distribution for amorphous and sub-amorphous implants
Intensity distributions differ
Mobility differences or SPEG effect
THANKS
CAMS – James Sullivan, Steve Buckman, Michael Went, Jason Roberts
EME – Simon Ruffell Technical Staff - Steve Battison, Ross
Tranter, Colin Dedman, Graeme Cornish
PPC10 organizers for help in financing my attendance