ERDA, for measurement of hydrogen in PV applications

1

• ERDA, for measurement of hydrogen in PV
  applications
• -- DERF 06/08 --
• Presented by Andrew Thomson
• Supervisor Dr Keith McIntosh

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Introduction

• Specialised form of ion beam analysis.
• Understand the role of H in passivation.
• Measuring SC dielectric coatings and
  silicondielectric interfaces, after various
  treatments.
• Overview

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Really what is ERD fancy RBS

• Measurement of backscattered particle energy.
• Gives energy count and yield.
• Knowing R cross-sections give quantative
  measurement.

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Generalised ERD setup

• Forward scatter measured.
• Incident ion suppressed.
• Experimental cross-sections.
• RBS and ERD combined.
• Generally energy only is measured.

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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.

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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.

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The physics of ERD descriptively

• Example of an ideal RBS spectrum
• Generalised two part dielectric on a substrate.
• Example of an actual silicon substrate.

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Setup at ANSTO Lucas Heights

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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
• T 170 , ß 60 , a 70 .
• ERD
• T 30 , ß 80 , a 70 .

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RBS and ERD measurements

• RB Spectra of a TiO2 dielectric layer on.

• ERD specra
• Shows surface absorption of H

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Modelling Spectrums

• Guess work
• Layers.
• Energy per channel.
• Incident flux.
• Substrate.
• Experience needed

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Modelling Spectrums RBS TiO2
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Modelling Spectrums ERD TiO2
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PECVD vs. TiO2

• PECVD

• Optimised TiO2

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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.