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Presentacion final HZBTRANSCRIPT
Growth of chalcopyrite nanostructures and their characterization
Diana Perez Afanador, Katrin SedlmeierDep SE2
Sebastian Lehmann, Sascha Sadewasser
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Why nanostructures in photovoltaics?
-power supply for nanoscale devices
-novel devices with higher efficiency
Why chalcopyrites (I-III-VI)?
-high α
-low cost
How?Si <111> substrate
flat surface prestructured surface
MBE (molecular beam epitaxy)
nanocrystals, nanowires
Xiang et al.,Nano Lett.,2007,7,323-328
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flat surface – 2 approaches
Goal
deposition of CuGaSe2 crystallites
MBE (Molecular Beam Epitaxy)
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flat surface – 2 approaches
random distribution (as wanted)
no complete growth of some crystal
Parameters
• substrate temperature
• deposition rates
SEM
Goal
deposition of CuGaSe2 crystallites 1 APPROACH
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Gallium droplets
Random distribution of Ga droplets
flat surface – 2 approaches
parameters
• deposition rates
• substrate temperature
• deposition time SEM
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Gallium droplets
200nm
flat surface – 2 approaches
parameters
• deposition rates
• substrate temperature
• deposition time
Growth of nanocrystals
parameters
• deposition rates
• deposition Time
400nm
growth of nanocrystals random distributed over the surface
Size: 5 ... 300 nm
SEM
AFM
AFM
random distribution of Ga droplets
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Gallium droplets
Nice distribution over the substrate
flat surface – 2 approaches
parameters
• deposition rates
• substrate temperature
• deposition time
Growth of nanocrystals
parameters
• deposition rates
• deposition Time
Growth of nanocrystals nicely distributed over the surface
Size: 5 ... 300 nm
SEM
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prestructuring
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prestructuring
monolayers of hydrophobic polysterene micro-/ nanospheres on hydrophilic substrates
spin coating
ultrasonic bath
2µm spheres 200nm spheres
~ ¼ of sample covered by monolayers
optical microscope SEM1 µm50 µm
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prestructuring
deposition of metal precursor material (for example: gold)
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prestructuring
array of gold deposits
nanocrystals nanowires
suitable precursor substrate for growth of
1µm SEM
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