Evaporated aluminum on polypropylene: oxide layer thicknesses as a function of oxygen plasma treatment level Donald J. McClure, Acuity Consulting and Training and 3M Corporate Research Laboratory Carolin Struller, Technische Universität München, Fraunhofer AIMCAL October 24, 2011
Evaporated aluminum on polyester: optical and electrical properties as a function of thickness Donald J. McClure, Acuity Consulting and Training Nick Copeland, General Vacuum Equipment AIMCAL October 18, 2010
PET paper results aluminum oxide layers formed on both sides of the aluminum metal film the oxide layers were consistently 3.0-3.3 nm thick, independent of metal thickness the optical properties of the films matched values calculated based on bulk optical constants when the aluminum thickness used was the aluminum metal thickness the electrical conductivity was consistently lower than predicted from bulk properties with the error worse for thinner films the aluminum had a 111 preferred orientation
Evaporated aluminum on polypropylene: oxide layer thicknesses as a function of oxygen plasma treatment level Donald J. McClure, Acuity Consulting and Training and 3M Corporate Research Laboratory Carolin Struller, Technische Universität München, Fraunhofer AIMCAL October 24, 2011
CENTER OF LIFE AND FOOD SCIENCES WEIHENSTEPHAN TECHNISCHE UNIVERSITÄT MÜNCHEN FRAUNHOFER INSTITUTE FOR PROCESS ENGINEERING AND PACKAGING Effects of oxygen plasma surface treatment on biaxially oriented polypropylene film Miss Carolin Struller A diploma thesis (Diplomarbeit) submitted in partial fulfilment of the requirements for the degree of Diplom-Ingenieur in Technology and Biotechnology of Food
Synopsis Motivation for Carolin Struller s work Results from her work STEM thickness measurement sample preparation aluminum layers oxide layers at the substrate and the air interfaces X-ray diffraction measurement results crystallinity and orientation Summary
Schematic cross section of interfaces for aluminum deposited on plasma treated BOPP From Carolin Struller s thesis
From Carolin Struller s thesis
Oxygen concentration on the BOPP film surface as a function of plasma treatment level. XXX From Carolin Struller s thesis
Surface energy data as a function of plasma energy density XXX From Carolin Struller s thesis
Peel strength (adhesion) as a function of plasma energy density XXX From Carolin Struller s thesis
Summary of main results XXX XX X XXX XXX XXX XXX XXX XXX XXX XXX XXX From Carolin Struller s thesis
STEM imaging Quantification of aluminum and aluminum oxide layer thicknesses Atomic concentrations using x-ray fluorescence mapping
STEM images Sample at plasma treatment level 64% BOPP BOPP Substrate Oxide Substrate Oxide Surface Oxide Surface Oxide Al Al Embedding Medium Embedding Medium 100,000x instrument magnification 200,000x instrument magnification
STEM image STEM images with x-ray fluorescence maps Sample at plasma treatment level 0% STEM image The oxygen signal is also seen within the Al film implying internal oxide, likely along grain boundaries.
STEM images with x-ray fluorescence maps Sample at plasma treatment level 39% The oxygen signal is also seen within the Al film implying internal oxide, likely along grain boundaries.
Thickness (nm) 45 TEM thickness results 40 35 30 aluminum 25 20 15 10 5 0 surface oxide substrate oxide 0 1000 2000 3000 4000 5000 6000 Plasma treatment level
Thickness (nm) TEM oxide thickness results 4.0 3.5 surface oxide 3.0 2.5 2.0 substrate oxide Substrate oxide for Al on PET was 3.3 nm. Surface oxide for Al on PET was 3.0 nm. 1.5 0 1000 2000 3000 4000 5000 6000 Plasma treatment level
TEM thickness results Plasma treatment level Substrate oxide thickness (nm) Aluminum thickness (nm) Surface oxide thickness (nm) 0 2.7 40.0 2.9 14% 2.7 27.8 2.7 39% 2.9 27.1 3.0 64% 2.9 26.2 3.1 100% 2.8 26.1 2.7 Substrate oxide for Al on PET was 3.3 nm. Surface oxide for Al on PET was 3.0 nm.
X-ray diffraction Crystallinity of aluminum layers Orientation of crystalline domains Size of crystalline domains
Intensity (counts) X-ray scans 64% 39% 14% 100% 0%
X-ray Intensity and Crystallite Size (nm) 100 X-ray scans 90 80 70 60 50 40 30 20 10 intensity crystallite size crystallite size intensity 111 peaks 200 peaks 0 0 1000 2000 3000 4000 5000 6000 Plasma treatment intensity
Conclusion Samples of aluminum were deposited onto both untreated and plasma treated BOPP films Equal thickness aluminum oxide layers were found at the substrate-side and the air-surface-side of the aluminum layers The observed oxide layers thicknesses did not vary with plasma treatment level. This observation suggests that at least part of the oxide layers observed likely grow after deposition is complete. The cause of an increase in the crystallite size for the aluminum sample deposited onto an untreated BOPP film could not be assigned to the lack of plasma treatment due to the extra thickness of the aluminum layer in that sample.
Next steps Examine oxide layer film growth as a function of time after the deposition. The logistics of sample preparation for TEM make success unlikely if the oxide growth occurs in minutes but may be possible if the oxide growth occurs in hours.
Question? Can anyone explain why the apparent OD for aluminum, measured in the metallizer, decreases when the plasma treater is turned off?
Questions? Comments!