Designing micro-patterned Ti films that survive up to 10% applied tensile strain

Reducing the strain in brittle device layers is critical in the fabrication of robust flexible electronic devices. In this study, the cracking behavior of micro-patterned 500-nm-thick Ti films was investigated via uniaxial tensile testing by in situ SEM and 4-point probe measurements. Both visual observations by SEM and 4-pt resistance measurements showed that strategically patterned oval holes, off-set and rotated by 45°, had a significant effect on limiting the extent of cracking, specifically, in preventing cracks from converging. Failure with regard to electrical conduction was delayed from less than 2% to more than 10% strai

Modelling of layered cylindrical dielectric resonators with reference to whispering gallery mode resonators

Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: Keywords: Dielectric Resonators, Radial Mode Matching, Whispering Gallery Modes The aim of this investigation was to develop accurate modelling techniques to determine the resonant frequencies of dielectric resonators. These resonators could be simple dielectric posts, rings or combinations of these two. To do this, a radial mode matching technique was implemented and applied to a post resonator, a ring resonator and finally a combination of the two. The resulting method was used to develop a model of a high-Q whispering gallery mode resonator consisting of a post and a ring resonator combination with an spurious free region region.AFRIKAANSE OPSOMMING: Sleutelwoorde Dielektriese Resoneerders, Radiale Modale-Pas Tegniek, 'Whispering Gallery' Modus Die doel van hierdie navorsing was om 'n akkurate tegniek te ontwikkelom die resonante frekwensie van 'n dielektriese resoneerder vas te stel. Hierdie resoneerders kon eenvoudige resoneerders, ring resoneerders of kombinasies van die twee wees. 'n Radiale Modale-Pas tegniek is vir hierdie doel geïmplementeer en is op 'n eenvoudige resoneerder, 'n ring-resoneerder en kombinasies van die twee toegepas. Hierdie tegniek is dan gebruik om 'n hoë-Q resoneerder te ontwerp wat gebruik maak van 'n 'whispering gallery' modus. In hierdie geval is die resoneerder 'n kombinasie van 'n pil en 'n ring-resoneerder

The effects of mechanical bending and illumination on the performance of flexible IGZO TFTs

Amorphous indium-gallium-zinc-oxide (a-IGZO) is an interesting semiconducting material for use in flexible thin-film-transistor (TFT) fabrication due to the high carrier mobility and low deposition temperatures. To use these TFTs in flexible applications, their behavior under applied mechanical strain and changing illumination, as well as the influence of bending on reflattened TFTs, needs to be understood. We have fabricated a-IGZO TFTs on flexible substrates and measured their behavior under tensile and compressive strains down to bending radii <; 10 mm. Bending tests were applied in the dark, as well as under 90-lx illumination. Without illumination, the tensile and compressive strains caused a little change in the TFT performance, but the influence of the tensile strain combined with illumination causes changes in the TFT mobility of 15% and changes in threshold voltage of - 0.11 V. By comparison, the performance of illuminated TFTs under the applied compressive strain changes little compared with measurements in the dark. The impact of repeated tensile bending and reflattening shows a similar picture; bending tests carried out in the dark resulted in a nearly constant threshold voltage, but with illumination, we observed a shift of -0.1 V after 40 min of repeated bending

Designing micro-patterned Ti films that survive up to 10% applied tensile strain

ISSN:0947-8396ISSN:1432-0630ISSN:0340-379

Conformable, light emitting devices

While highly conformal electronics have always been of interest in case of medical applications, in the recent years also many light and lighting related applications are emerging which demand conformability. Well-being, automotive or smart clothing are just a few examples where these trends can be observed. We are finding that conformability could bring various benefits to both end users (improved comfort, biomimetics and haptics) as well as manufacturers (heterogeneous integration, more design freedom, differentiation and less stringent tolerancing). Application of SMI (Stretchable Molded Interconnect) technology, that attempts to address these demands, will be discussed. Some example realizations in the field of blue light therapy, automotive interior lighting and OLED lighting will be used to demonstrate the benefits and challenges resulting from use of conformable electronics

Effect of SiNx gate dielectric deposition power and temperature on a-Si:H TFT stability

The stability of thin-film transistors (TFTs) of hydrogenated amorphous-silicon (a-Si:H) against gate-bias stress is improved by raising the deposition power and temperature of the silicon nitride gate dielectric. We studied the effects of power density between 22 and 110 mW/cm2 and temperature between 150C and 300C. The time needed to shift the threshold voltage by 2 V varies by a factor of 12 between low power and low temperature, and high power and high temperature. These results highlight the importance of fabricating a-Si:H TFTs on flexible plastic with the SiNx gate dielectric deposited at the highest possible power and temperature

Locally Reinforced Polymer-Based Composites for Elastic Electronics

A promising approach to fabricating elastic electronic systems involves processing thin film circuits directly on the elastic substrate by standard photolithography. Thin film devices are generally placed onto stiffer islands on the substrate surface to protect devices from excessive strain while still achieving a globally highly deformable system. Here we report a new method to achieve island architectures by locally reinforcing polymeric substrates at the macro- and microscale using magnetically responsive anisotropic microparticles. We demonstrate that the resulting particle-reinforced elastic substrates can be made smooth enough for the patterning and successful operation of thin film transistors with transfer characteristics comparable to state-of-the-art device