Dic 222016
 

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

Tobias Cramer, Lorenzo Travaglini, Stefano Lai, Luca Patruno, Stefano de Miranda, Annalisa Bonfiglio, Piero Cosseddu, Beatrice Fraboni

Scientific Reports 6, 38203 (2016)

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.

 Scritto da in 22 dicembre 2016  Avvisi  Commenti disabilitati su NEW PUBLICATION: “Direct imaging of defect formation in strained organic flexible electronics by Scanning Kelvin Probe Microscopy”
Dic 222016
 

An Inkjet-Printed, Ultralow Voltage, Flexible Organic Field Effect Transistor

Silvia Conti, Stefano Lai, Piero Cosseddu, Annalisa Bonfiglio

Adv. Mater. Technol. 2016, 1600212

A very simple procedure for fabricating inkjet-printed organic field effect transistors (OFETs) is reported. A reliable process for the deposition of a thin and uniform polymeric dielectric film of poly(4-vinylphenol) (PVP) is established as a key factor for obtaining high performance devices operating at low voltages. To this aim, ink formulations, printing parameters, and cross-linking processes are investigated. Morphological characterization of the fabricated films by means of contact profilometry and atomic force micro­scopy is provided, as well as capacitive measurements proving ideal dielectric properties. OFET structures based on PVP gate dielectric are reported: in particular, inkjet-printed devices operated at voltages below 1 V with remarkable transistor performances such as high charge carrier mobility and low subthreshold swing are presented.

 Scritto da in 22 dicembre 2016  Avvisi  Commenti disabilitati su NEW PUBLICATION: “An Inkjet-Printed, Ultralow Voltage, Flexible Organic Field Effect Transistor”
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