Anomalous response of supported few-layer hexagonal boron nitride to DC electric fields: a confined water effect?

• Published in: Nanotechnology 2012-05, Vol.23 (17), p.175703-1-6
• Main Authors: Oliveira, C K, Matos, M J S, Mazzoni, M S C, Chacham, H, Neves, B R A
• Format: Article
• Language: English
• Subjects: Bias; Boron nitride; Dielectric constant; Electric fields; Mathematical analysis; Oxides; Polarity; Silicon substrates
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/23/17/175703

We use electric force microscopy (EFM) to study the response of supported few-layer hexagonal boron nitride (h-BN) to an electric field applied by the EFM tip. Our results show an anomalous behavior in the dielectric response of h-BN atop Si oxide for different bias polarities: for a positive bias applied to the tip, h-BN layers respond with a larger dielectric constant than the dielectric constant of the substrate, while for a negative bias, the h-BN dielectric constant appears to be smaller. Based on ab initio calculations, we propose that this behavior is due to a water layer confined between the Si oxide substrate and h-BN layers. This hypothesis was experimentally confirmed by sample annealing and also by a comparative analysis with h-BN on a non-polar substrate.