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ERDA, for measurement of hydrogen in PV applications -- DERF 06/08 -- Presented by: Andrew Thomson Supervisor: Dr Keith McIntosh. Introduction. Specialised form of ion beam analysis. Understand the role of H in passivation.
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ERDA, for measurement of hydrogen in PV applications -- DERF 06/08 -- Presented by: Andrew Thomson Supervisor: Dr Keith McIntosh
Introduction • Specialised form of ion beam analysis. • Understand the role of H in passivation. • Measuring SC dielectric coatings and silicon—dielectric interfaces, after various treatments. • Overview:
Really what is ERD – fancy RBS • Measurement of backscattered particle energy. • Gives energy count and yield. • Knowing “R cross-sections” give quantative measurement.
Generalised ERD setup • Forward scatter measured. • Incident ion suppressed. • Experimental cross-sections. • RBS and ERD combined. • Generally energy only is measured.
Resolution limits • Detection limits: • For an optimised sample 20 ppm, up to 1000nm depth. • Comparative techniques: • SIMS, similar resolution, better depth resolution. • FTIR, measures bonds, unsure of resolution.
The physics of ERD – descriptively • Single atomic layer • Multiple layers add spread • Increased variance. • Straggle lowers energy. • Measured spectrum convolution of input spectrum with straggling function.
The physics of ERD – descriptively • Example of an ideal RBS spectrum: • Generalised two part dielectric on a substrate. • Example of an actual silicon substrate.
Setup at ANSTO – Lucas Heights • 3 MeV tandem accelerator with a He ion source • So far we have used an incident power of 1.8 MeV. • Mylar foil • RBS: • Θ = 170 °, β = 60 °, α = 70 °. • ERD: • Θ = 30 °, β = 80 °, α = 70 °.
RBS and ERD measurements • RB Spectra of a TiO2 dielectric layer on. • ERD specra • Shows surface absorption of H
Modelling Spectrums • Guess work: • Layers. • Energy per channel. • Incident flux. • Substrate. • Experience needed:
PECVD vs. TiO2 • PECVD • Optimised TiO2
Plans for PV applications of ERDA • Hydrogen characterisation: • Basic PV processing steps. • PV dielectrics. • Hydrogenated TiO2 • Degradation processes. • Other applications: • Boron, and phos profiles. • Densification of TiO2.