Wednesday, October 28, 2015

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature ALD

Here is a new interesting paper on ferroelectric BFO deposited in an Ultratech Cambridge Nanotech Savannah reactor Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC). The thermal ALD process at 250 °C by alternate pulsing of bismuth tris(2,2,6,6-tetramethyl-3,5-heptanedionate) (Bi(thd)3) and ferrocene (Fe(Cp)2) combined with ozone (O3)

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature ALD





Mariona Coll*, Jaume Gazquez, Ignasi Fina, Zakariya Khayat, Andy Quindeau, Marin Alexe, Maria Varela, Susan Trolier-McKinstry, Xavier Obradors, and Teresa Puig;
Chem. Mater., 2015, 27 (18), pp 6322–6328

DOI: 10.1021/acs.chemmater.5b02093

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 SrTiO3substrate. 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.