Estudo de nanoestruturas de nitreto de boro hexagonal por microscopia de varredura por sonda

Abstract

In this thesis we present the results obtained in Laboratório de Nanoscopia at Physics Department (DF / UFMG) regarding the study of hexagonal boron nitride nanostructures. During these projects, we had an intense collaboration with Grupo de Estrutura Eletrônica do DF/UFMG. The behavior of boron nitride layers to the applied electric eld by an AFM probe was studied via Electric Force Microscopy (EFM). Our results show an anomalous behavior in dielectric response for h-BN layers for dierent orientations of the applied bias. Based on rst-principles calculations, we showed that this anomalous response may be interpreted as a macroscopic consequence of connement of a thin water layer between h-BN and substrate. These results were conrmed by sample annealing and also also by a comparative analysis with h-BN on a non-polar substrate. We also present a process of crystallographically oriented nanostructures deposition over the boron nitride layers. These structures are formed when samples of boron nitride containing metal nanoparticles are brought to the CVD furnace, with a hydrogen ow. The process is reproducible with dierent types of nanoparticles such as nickel, platinum and silver. In addition to the deposition of nanostructures, we demonstrate a method by which h-BN samples can be etched along crystallographic axes by thermally activated Ni nanoparticles.