Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy

Abstract

The development of new materials and devices for flexible electronics depends crucially on the understanding of how strain affects electronic material properties at the nano-scale. Scanning Kelvin-Probe Microscopy (SKPM) is a unique technique for nanoelectronic investigations as it combines non-invasive measurement of surface topography and surface electrical potential. Here we show that SKPM in non-contact mode is feasible on deformed flexible samples and allows to identify strain induced electronic defects. As an example we apply the technique to investigate the strain response of organic thin film transistors containing TIPS-pentacene patterned on polymer foils. Controlled surface strain is induced in the semiconducting layer by bending the transistor substrate. The amount of local strain is quantified by a mathematical model describing the bending mechanics. We find that the step-wise reduction of device performance at critical bending radii is caused by the formation of nano-cracks in the microcrystal morphology of the TIPS-pentacene film. The cracks are easily identified due to the abrupt variation in SKPM surface potential caused by a local increase in resistance. Importantly, the strong surface adhesion of microcrystals to the elastic dielectric allows to maintain a conductive path also after fracture thus providing the opportunity to attenuate strain effects.

Stretchable Low Impedance Electrodes for Bioelectronic Recording from Small Peripheral Nerves

“…The Hertizian model for a parabolic tip shape was used to fit the indentation curves and to provide the effective elastic modulus. Topographies during strain were obtained by clamping the sample in a tensile tester mounted on the AFM sample holder 51 .…”

Solvent-Dependent Electrical Characteristics and Mechanical Stability of Flexible Organic Ferroelectric Field-Effect Transistors

“…However, organic Fe-FETs fabricated on a flexible substrate still incur critical problems in electrical performance, even though useful performance from these Fe-FETs has been achieved when fabricated on a rigid substrate like glass or silicon. Generally, an unstable fabrication process, a low glass transition temperature, and a low water vapor transition rate caused by plastic substrates may lead to poor electrical properties in transistors, and repetitive mechanical stresses during flexible device use may cause unstable device operation by generating physical and chemical defects in thin-films and transistors [12,13,14,15]. Therefore, a deep understanding of the electrical characteristics and mechanical stability of flexible Fe-FETs are required for their utilization in flexible electronic applications.…”

Fabrication and Application of Highly Stretchable Conductive Fiber‐Based Electrode of Epoxy/NBR Electrospun Fibers Spray‐Coated with AgNW/PU Composites

“…In recent years, deformable (i.e., flexible and stretchable) electronic devices have attracted extensive research interest due to their potential applications in next‐generation wearable functional electronic devices . However, the device performance of deformable electronics under a large mechanical strain was limited by the deformability of electrodes and active materials as well as the compatibility of the surface between them . Although enormous efforts on fabricating electrodes based on flexible or stretchable thin film substrates have been made, it remains a significant challenge to attach those electronics onto a curved surface and fit into the human body comfortably .…”