Structural transformations in pentagonal nanocrystals ... - Tartu

University of TartuInstitute of PhysicsPhysics ofMesostructuresPrincipal investigator: Prof. Jaak KikasResearchers: Dr. A.Lõhmus, Prof. A.Romanov,Dr. I.Kink, Dr. R.Lõhmus, Dr. K.Saal,Dr. S.Vlassov,Dr. M.Järvekülg, Dr. B.Polyakov,L. Dorogin, M. Timusk, A. Salundi,J. Jõgi, M. Paalo

Current state-of-the-art• Nanocrystals with fivefold symmetry exist and possessintrinsic mechanical stresses• Disclinations can be utilized to model the elastic stress inPNCs• Relaxation of mechanical stresses PNCs is predicted in theframework of the disclination approach and demonstratedexperimentally

Topic 2. Sol-gel method for variousapplications:‣Metal oxide fibers;‣CNT doped metal oxide fibers;‣Microscopic tubular oxide structures;‣GDLC films.4

12+solventFigure: Suggested route forobtaining tubular structures3‣ 2-10 μm in diameter;‣ 1 mm long;‣ shrink 30 % (up to 500 o C).Järvekülg, M., Välbe, R., Salundi, A., Reedo, V., Part, M., Mäeorg, U., Lõhmus, A.,A sol-gel approach to self-formation of microtubular structures from metal alkoxidegel films, Apply. Phys. Letters (manuscript)5

Jõgi, J., Järvekülg, M., Kalda, J., Salundi, A., Reedo, V., Lõhmus, A.,Simulation of cracking of metal alkoxide gel film formed on viscousprecursor layer using a spring-block model, EPL - A Letters JournalExploring the Frontiers of Physics, 95(6) (2011), 64005-p1 - 64005-p6.6

SubstrateElectrodesMatrix‣Crack free, large thickness‣Large change in transmittance‣Matrix with high refractive index (ideallythe dispersion curve of the matrix matcesthe dispersion curve of LC)Drying↓Sphere → EllipsoidAverage aspect ratio 0.476(ratio of the minor to major axis length)Timusk, M., Järvekülg, M., Lõhmus, R., Kink, I., Saal, K., Sol–gel matrix dispersedliquid crystal composite: Influence of methyltriethoxysilane precursor and solventconcentration, Materials Science and Engineering B, 172(1) (2010), 1 - 5.7

‣ Maximum conductivity 500S/m on fibers doped by 0,1wt % SWCNT.8

Task 3. Nanomanipulation experiments andmodellingManipulation of Gold nanoparticless:with a AFM tip inside SEM9

Measurements and modelling of mechanicalproperties of nanowiresA NW is half-suspended on an edge of trench cut by FIB – to be bent bytipAlso the static frictioncan be measured andmodelled