Articles you may be interested inEffect of the Al0.3Ga0.7As interlayer thickness upon the quality of GaAs on a Ge substrate grown by metalorganic chemical vapor deposition A method for the structural investigation of interior inverted GaAs/AlAs interfaces is presented which combines highly selective etching and subsequent atomic force microscopy. It provides three-dimensional mappings of interior GaAs interfaces on a lateral scale on the order of micrometers with angstrom z resolution. The perfection of this method is demonstrated, which allows the observation of the real interface monolayer island and terrace structure. Potential aluminum residues on the uncovered interfaces are below the detection limit of Auger electron spectroscopy, which is estimated to 16% of aluminum in a single monolayer on a GaAs crystal. The structure of an interior interface can differ significantly from that of a corresponding surface layer after cooling down from the growth temperature. The substantial restructuring of the interface morphology caused by growth interruptions is investigated in detail for metalorganic vapor phase epitaxy.
Inkjet printing (IJP) is on the rise to become a competitive production technology for organic light emitting diodes (OLEDs). Recent progress in printing technology with drop volumes down to the pL regime as well as constant performance improvements from material point of view have opened the way towards IT displays. Here target resolutions are 250 ppi and beyond. For this purpose, small molecules are highly suitable due to their low impact on ink viscosity and excellent device performance. Their current performance status is reviewed based on bottom and top emission. For the latter, crucial factors for high performance like film uniformity and precise thickness control are discussed.
In the recent years, displays for mobile electronic devices have been revolutionized, mostly driven by smartphones and tablets. Strongest trends are (besides growing sizes) the ever-increasing resolution, improved contrast, very good viewing angle and color performance. This went hand in hand with a trend to more "refined" display technologies, namely fringe field switching (FFS). Now, as the latest step, Ultra-Brightness (UB-) FFS is at the brink to widespread commercialization in mobile and IT displays. It can provide transmittance improvement of more than 15%. The Liquid Crystal (LC) plays a key role here, because UB-FFS uses LCs with negative dielectric anisotropy -whereas "traditional" FFS uses LCs with positive dielectric anisotropy. There are two key challenges. First is providing LCs with a fast switching speed. Second point is keeping the high reliability level of FFS even though completely different materials with much higher challenges on reliability are used. In this paper the recent progress for both key points will be discussed.
Flat and homogeneous films by ink jet printing of organic materials are proven to be essential for OLED application. The impact of ink formulation, film thickness, pixel size, bank layout and process conditions (i.e. drying parameters) have been investigated. Their severe impact on device performance is illustrated.
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