A flatbed scanner for large-area thickness determination of ultra-thin layers in printed electronics

Abstract

Enabling solution-based printing techniques for sub-100 nm thin semiconductors for the application in large-area organic electronics is a challenging task. In order to optimize the process parameters, the layers have to be characterized on a large lateral scale while determining the nanometer thickness at the same time. We present a lateral and vertical resolving measurement method for large-area, semi-transparent thin films based on optical interference effects. We analyzed the RGB color images of up to 150 mm square-sized thin film samples obtained by a modified commercial flatbed scanner. Utilizing and comparing theoretical and measured color contrast values, we determined most probable thickness values of the imaged sample area pixel by pixel. Within specific boundary conditions, we found very good agreement between the presented imaging color reflectometry and reference methods. Due to its simple setup, our method is suitable to be implemented as part of a color vision inspection system in in-line printing and coating processes.

Printing Poly(p-phenyleneethynylene) PLEDs

“…Analysis by profilometry is disadvantageous because of long measuring times for stitching of continuous single measurements. We used reflectometric thin-film recordings (vide infra), supplemented by tactile profilometry for each printed sample. This optical method for evaluating the layers and their printing quality gives sufficient information about layer homogeneity including surface waviness or film defects and therefore gives an evaluation of the suitability of the printed films for OLED applications …”

“…We used reflectometric thin-film recordings (vide infra), supplemented by tactile profilometry for each printed sample. This optical method for evaluating the layers and their printing quality gives sufficient information about layer homogeneity including surface waviness or film defects and therefore gives an evaluation of the suitability of the printed films for OLED applications Figure shows the results of the printed toluene inks (Figure a–c, 50 g L –1 ), mesitylene/anisole inks (Figure d–f, 50 g L –1 ), and pure mesitylene inks (Figure g–i, 20 g L –1 ) printed on indium tin oxide (ITO)-covered PET sheets (15 × 5 cm 2 , SI, S5a–c).…”

“…As previous results indicate, PPEs featuring 2-ethylhexyl in combination with the dodecyl side chains displayed attractive printing behavior, and we chose farnesanyl as a branched homolog to the investigated linear dodecyl side chains. All of the GP layers of the PPEs were evaluated by a thin-film measurement technique developed by Bornemann et al A proof-of-principle PLED was printed.…”

On-Machine Measurement for Surface Flatness of Transparent and Thin Film in Laser Ablation Process

“…His method was applied to a dual-layer hard coating on a PET film. Bornemann presented thickness measurements for large-area and multi-layer printed devices using RGB scanning images and color contrast [15]. The method was tested using an organic semiconductor and showed sub-100 nm accuracy.…”

Printing PPEs: Fundamental Structure–Property Relationships

“…8,9 Even though the viscosity magnitude of 1 70 and 1 176 is appropriate for gravure printing, both samples show significant shear thinning at higher shear rates, which would make them less ideal as functional inks since the non-Newtonian nature of the fluid favors hydrodynamical instabilities during the printing process. 10,3 Moreover, it was observed that 1 70 and 1 176 gel at concentrations above 10 g L −1 and 5.4 g L −1 , respectively.…”