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Organic Electronics
Moisture Transport through Ultra-Low Permeation Barriers
Chemistry and Orientation with NEXAFS Spectroscopy
Nanoimprint Lithography
Pattern Transfer and Stability
Polymers for Next-Generation Lithography
Dissolution Fundamentals
Surface and Bulk Chemistry of Chemically Amplified Photoresists
NIST-Industry Partnerships
Dimensional Metrology with Small Angle X-ray Scattering
Sidewall Angle Metrology
Dimensional Changes during Fabrication
Characterization of Porous Low-k Dielectric Thin Films
Moisture Transport through Ultra-Low Permeation Barriers
Introduction
Organic light emitting diodes (OLEDs) show promise as a display technology
Greatest barrier to commercialization is the limited device lifetime
Most OLED materials are not stable in ambient due to moisture Encapsulate active materials to prevent degradation – < 10-6 g H2O/m2 day
Objective
Develop and apply new measurements for ultra-low moisture permeation rates and mechanisms
Quantify contribution of material and interfacial factors that control moisture permeation
Experimental Approach
X-ray Reflectivity (XR)
Measure thickness change due to moisture absorption
Mass density profile
Estimate permeation rate
Neutron Reflectivity (NR)
Isotopic sensitivity (1H vs 2H)
Measure water distribution within film
Results
Moisture induced swelling
Test condition: 60 °C, 100 % RH
Test structure 3 layers of alternating Al2O3 and polyacrylate
Swelling after 11 days: (7 ± 5) Å
Permeation rate:< 10-5 g/m2/day
Similar structure, but Al2O3 layers with defects
Test condition: 60 °C, 100 % RH
Swelling after 11 days: (107 ± 8) Å
Track swelling of each layer
Swelling rate similar for each layer
Permeation rate:1.7 x 10-3 g/m2/day
Direct observation of water break-through of the multilayer structure
Moisture distribution within model film
Model structure: UV cured polyacrylate on Al2O3
Equilibrium swelling is function of curing condition
NR measurement probes water distribution within film
Water accumulates at Al2O3 / polymer interface
Accumulation independent of cure condition
Water accumulation at interface slows apparent permeation through barrier
Al2O3 acts as built-in desiccant – potentially extending device lifetime
NIST Contributors
Bryan Vogt*
Wen-li Wu
Hae-Jeong Lee
Vivek Prabhu
Dean DeLongchamp
Eric Lin
Sushil Satija
Collaborators:
Nicole Rutherford
Lorenza Moro
Electronics Materials Group
Polymers Division
Materials Science and Engineering Laboratory
