REVIEW OF SCIENTIFIC INSTRUMENTS 85, 075102 (2014)
Internal sensor compensation for increased Ca test sensitivity Arrelaine A. Dameron,a),b) Michael D. Kempe,b) and Matthew O. Reeseb) National Renewable Energy Laboratory, 1617 Cole Blvd Golden, Colorado 80401, USA
(Received 10 March 2014; accepted 11 June 2014; published online 2 July 2014) The development of state-of-the-art barrier films and encapsulation schema for displays and photovoltaics requires precise measurement of water vapor permeation as quickly as possible. We have demonstrated improvements to our electrical, Ca-trace-based water vapor transmission rate measurement technique without introducing any additional cost or sample handling concerns. Most importantly, the contacting scheme was changed so that the effective length of the sensor traces can be more precisely determined making the contact resistance between the Ca and Au/Ti films far less likely to affect the results. A 4-pt contacting pattern was also applied to the internal (non-data) witness trace. This expanded the potential utility of the witness trace from just an indicator for the integrity of the sample assembly, to also being used to compensate for measurement error. Lastly, we increased the relative precision of our resistance measurements by implementing a Ca sensor trace with significantly higher resistance. Principally, these changes produce significant measurement improvements for permeation rates less than 10−4 g/m2 /day, by lowering the noise floor, reducing required measurement time, and increasing the reproducibility of this test method. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4884790] I. INTRODUCTION
A major technological and monetary obstacle to flexible electronics implementation is the development of flexible and transparent barriers for encapsulation.1–12 The high permeability of H2 O and O2 through typical polymer substrates requires significant modification strategies to make them suitable for flexible electronics applications. While display applications push the limits of current barrier technologies with water vapor transmission rates (WVTR) requirements of 10−6 g/m2 /day,11–13 flexible photovoltaic applications, requiring
Internal sensor compensation for increased Ca test sensitivity Arrelaine A. Dameron,a),b) Michael D. Kempe,b) and Matthew O. Reeseb) National Renewable Energy Laboratory, 1617 Cole Blvd Golden, Colorado 80401, USA
(Received 10 March 2014; accepted 11 June 2014; published online 2 July 2014) The development of state-of-the-art barrier films and encapsulation schema for displays and photovoltaics requires precise measurement of water vapor permeation as quickly as possible. We have demonstrated improvements to our electrical, Ca-trace-based water vapor transmission rate measurement technique without introducing any additional cost or sample handling concerns. Most importantly, the contacting scheme was changed so that the effective length of the sensor traces can be more precisely determined making the contact resistance between the Ca and Au/Ti films far less likely to affect the results. A 4-pt contacting pattern was also applied to the internal (non-data) witness trace. This expanded the potential utility of the witness trace from just an indicator for the integrity of the sample assembly, to also being used to compensate for measurement error. Lastly, we increased the relative precision of our resistance measurements by implementing a Ca sensor trace with significantly higher resistance. Principally, these changes produce significant measurement improvements for permeation rates less than 10−4 g/m2 /day, by lowering the noise floor, reducing required measurement time, and increasing the reproducibility of this test method. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4884790] I. INTRODUCTION
A major technological and monetary obstacle to flexible electronics implementation is the development of flexible and transparent barriers for encapsulation.1–12 The high permeability of H2 O and O2 through typical polymer substrates requires significant modification strategies to make them suitable for flexible electronics applications. While display applications push the limits of current barrier technologies with water vapor transmission rates (WVTR) requirements of 10−6 g/m2 /day,11–13 flexible photovoltaic applications, requiring
