ERDA for measurement of hydrogen in PV applications

ERDA, for measurement of hydrogen in PV applications -- DERF 06/08 -Presented by: Andrew Thomson Supervisor: Dr Keith Mc. Intosh

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 crosssections” give quantative measurement.

Generalised ERD setup § Forward scatter measured. § Incident ion suppressed. § Experimental crosssections. § RBS and ERD combined. § Generally energy only is measured.

Resolution limits § Detection limits: • For an optimised sample 20 ppm, up to 1000 nm 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

Setup at ANSTO – Lucas Heights § 3 Me. V tandem accelerator with a He ion source § So far we have used an incident power of 1. 8 Me. V. § Mylar foil § RBS: • Θ = 170 °, β = 60 °, α = 70 °. § ERD: • Θ = 30 °, β = 80 °, α = 70 °.

RBS and ERD measurements § RB Spectra of a Ti. O 2 dielectric layer on. § ERD specra § Shows surface absorption of H

Modelling Spectrums § Guess work: • • Layers. Energy per channel. Incident flux. Substrate. § Experience needed:

Modelling Spectrums – RBS Ti. O 2

Modelling Spectrums – ERD Ti. O 2

PECVD vs. Ti. O 2 § PECVD § Optimised Ti. O 2

Plans for PV applications of ERDA § Hydrogen characterisation: • • Basic PV processing steps. PV dielectrics. Hydrogenated Ti. O 2 Degradation processes. § Other applications: • Boron, and phos profiles. • Densification of Ti. O 2.