Wednesday, September 2, 2015

Nanocrystalline Ferroelectric BiFeO3 by Low-Temperature ALD

Joint research from Spain, Germany, UK, and USA present a low temperature process for ferroelectric BeFeO3 which opens possibilities for ferroelectric oxides on 3D substrates. BeFeO3 is a room temperature multiferroic material and due to its ferroelectric photovoltaic (FPV) effect bismuth ferrite have several applications in the field of magnetism, spintronics, photovoltaics etc.

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature Atomic Layer Deposition

Mariona Coll*†, Jaume Gazquez†, Ignasi Fina‡§, Zakariya Khayat∥, Andy Quindeau‡, Marin Alexe§, Maria Varela⊥, Susan Trolier-McKinstry∥, Xavier Obradors†, and Teresa Puig†

† Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193, Bellaterra, Catalonia, Spain
‡ Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), D-06120, Germany
§ Department of Physics, University of Warwick, Coventry CV 4 7AL, United Kingdom
∥ The Pennsylvania State University, N-227 Millennium Science Complex, University Park, Pennsylvania 16802, United States
⊥ Departamento de FĂ­sica Aplicada III, Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040, Madrid, Spain

Chem. Mater., Article ASAP
DOI: 10.1021/acs.chemmater.5b02093
Publication Date (Web): August 20, 2015

Abstract

In this work, ferroelectricity is identified in nanocrystalline BiFeO3 (BFO) thin films prepared by low-temperature atomic layer deposition. A combination of X-ray diffraction, reflection high energy electron diffraction, and scanning transmission electron microscopy analysis indicates that the as-deposited films (250 °C) consist of BFO nanocrystals embedded in an amorphous matrix. Postannealing at 650 °C for 60 min converts the sample to a crystalline film on a SrTiO3 substrate. Piezoelectric force microscopy demonstrates the existence of ferroelectricity in both as-deposited and postannealed films. The ferroelectric behavior in the as-deposited stage is attributed to the presence of nanocrystals. Finally, a band gap of 2.7 eV was measured by spectroscopic ellipsometry. This study opens broad possibilities toward ferroelectric oxides on 3D substrates and also for the development of new ferroelectric perovskites prepared at low temperature.

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