Resonant reshaping of colloidal clusters on a current carrying wire

Colloids in confined geometries promise a path towards tailored microscopic superstructures. Yet, a major roadblock is posed by kinetically trapped states that prevent the assemblies from reaching their anticipated shapes. We investigate magnetic colloids trapped on a cylindrical surface of a current carrying wire. If kinetic traps could be avoided the wire’s surface would act as an ideal mold for colloidal rings and helical fibers. We devise here a way to dynamically shake down the clusters and avoid kinetic traps in their energy landscape. A low frequency magnetic modulation wave around the wire axis effectively eliminates defects from the clusters and stretches them into slender rings and helical filaments. A theoretical model is developed that qualitatively explains the observed resonant reshaping response of clusters

Thorough investigation of low frequency noise mechanisms in AlGaN/GaN and Al2_2O3_3/GaN HEMTs

International audienceThis paper investigates the AlGaN/GaN and Al2O3/GaN interface quality on GaN MIS-HEMT using low frequency noise (LFN) measurements. To address the issue of noise in the access resistance, we have also tested "non-gated" 2DEG devices. The LFN has a 1/f-like behaviour caused by trapping/de-trapping processes which has been well described by carrier number fluctuations (CNF) and correlated mobility fluctuation (CMF) models. The border trap density extracted in optimised devices is better than previously reported GaN data and close to silicon CMOS results. Finally, a noise model for GaN-HEMT with recessed MIS gate including a 2DEG access resistance noise source is proposed

New insights into low frequency noise (LFN) sources analysis in GaN/Si MIS-HEMTs

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