Thin-film heterostructures based on ferroelectrics, oxide wide-gap semiconductors, dielectrics, conductors.

Group participants:

Delimova L. A.

Cooperation:

The study is being done in cooperation with the colleagues from the Ioffe Institute: lab. of E. A. Tropp, (modeling and simulations), lab. of V. L. Berkovits (AFM-study), lab. of S. G. Lushnikov (XRD-study), and with the specialists from the MIREA-Russian Technological University, Scientific and Technological Center (heterostructure fabrication).

Field of studies:

• Thin-film ferroelectric heterostructures based on PZT and other ferroelectrics with different crystalline structure for application in micro- and nanoelectronics
• Nonvolatile Ferroelectric Random Access Memory (FeRAM)

Research objectives:

• Charge carrier transport in ferroelectric heterostructures
• Relaxation of the space-charge and polarization charge in the processes of repolarization and current passing in thin-film ferroelectric capacitor structures

Main achievements:

• A new approach of unsteady carrier transport in M/PZT/M structure is proposed. Based on this approach, a new drift-diffusion model is developed to account for the formation of unexpected current peaks, which are not caused by the domain switching and observed in the current–voltage curves in epitaxial or columnar-grain PZT films with nonconductive grain boundaries only when the bias and polarization directions coincide.
• The intergrain photovoltaic effect is found and explained in columnar-grain PZT films with conductive grain-boundaries. This photovoltaic effect can be used for nondestructive readout in ferroelectric memory.

Some publications:

• L.A. Delimova and V.S. Yuferev, “Transient carrier transport and rearrangement of Schottky barrier layers under the action of a bias applied to the M/PZT/M structure.” J. of Appl. Phys. 124, 184102 (2018).
• L.A. Delimova, E.V. Guschina, D.S. Seregin, K.A. Vorotilov, A.S. Sigov, “Unexpected behavior of transient current in thin PZT films caused by grain-boundary conduction.” J. of Appl. Phys. 121, 224104 (2017).
• L.A. Delimova ,  E.V. Guschina, N.V. Zaitseva, S.I. Pavlov, D.S. Seregin, K.A. Vorotilov, A.S. Sigov, “Effect of seed layer with low lead content on electrical properties of PZT thin films”. J. Mater. Res. 32, 1618 (2017).
• L.A. Delimova, V.S. Yuferev, I.V. Grekhov, “High retention of the polarization in polycrystalline M/PZT/M capacitors in the presence of the depolarization field near grain boundaries”. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 58, 2252 (2011).
• L.A. Delimova, V.S. Yuferev, I.V. Grekhov, P.V. Afanasjev, G.P. Kramar, A.A. Petrov, V.P. Afanasjev, “Origin of photoresponse in heterophase ferroelectric Pt/Pb(Zr,Ti)O₃/Ir capacitors”, Appl. Phys. Lett. 91, 112905 (2007).

Contacts:

L.A. Delimova	ladel@mail.ioffe.ru	+7 (812) 292-73-21