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Oulun yliopiston väitöskirjat

FERROELECTRIC PERFORMANCE FOR NANOMETER SCALED DEVICES, ACTA UNIVERSITATIS OULUENSIS C Technica 372

ISBN-13:	978-951-42-6392-7
Kieli:	englanti
Kustantaja:	Oulun yliopisto
Oppiaine:	Tekniikka, matematiikka
Painosvuosi:	2010
Sidosasu:	pehmeäkantinen
Sijainti:	Print Tietotalo
Sivumäärä:	140
Tekijät:	PLEKH MAXIM

20.00 €

The work deals with the experimental study of ferroelectric (FE) performance scaling fornanometer-sized devices. In the emerging and advanced devices, it is desirable to couple FEperformance with other functions. This requires integration of nanoscale FEs with other materials,which is especially promising in epitaxial heterostructures. Such heterostructures inevitablypossess a large lattice mismatch, the effect of which on FE properties is unknown and is in thefocus of the present work. In the study, heteroepitaxial thin and ultrathin films and superlattices of ABO3-type perovskitestructure FEs were used, with A = Pb, Ba, Sr, K, and N, and B = Ti, Zr, Nb, and Ta. FE domains and local polarization switching were explored on the nanometer scale usingpiezoresponse force microscopy. The experiment was modified that allowed achieving imageswith high contrast and lateral resolution, and also allowed analysis of nanodomains in lateralcapacitor configuration. Local properties were related to a macroscopic response. For this, themethod of simultaneous on-wafer low-frequency impedance measurements was optimizedallowing studies of thin and ultrathin (to 5 nm) films in a broad range of conditions and regimes. Experimental studies have reveled phenomena which cannot be explained in the frame of theexisting theories. The observed new effects are important for applications such as multistatememory devices, storage capacitors, and FE tunnel junction devices.

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