Staff member

ZnO: Al thin films were deposited by spray pyrolysis onto glass substrates with 0, 0.5, 1.0, 2.0, 5.0 and 10.0% [Al3+/Zn2+] ratios in the deposition solution. Films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, UV–vis transmittance, conductive atomic force microscopy and the sheet resistance was measured. Aluminum contents in the films increases with the Al3+/Zn2+ ratio in the bath while the film deposition rate decreases due to the lower Al3+ surface mobility. Films were crystalline and display a varied morphology that evolves from flakes to mixtures between flakes and pencils and finally between triangles and hexagonal columns with increasing Al contents. Al3+ inclusion at the different sites within the ZnO lattice is proposed to direct the crystal habit and therefore the observed morphology and film texture. The optical band gap evolution and carrier density are related by the Burstein-Moss effect. The results show that film texture influences carrier mobility: increased presence of (112) planes originate a mobility increase while a predominant (110) or (100) texture reduces it. By Current sensing Atomic Force Microscopy (CAFM) the local surface current distribution was related with the observed film texture.

JTD

In the last years, nanoindentation by means of Atomic Force Microscopy-Force Spectroscopy (AFM-FS) or Nanoindenters has become a powerful tool to study the nanomechanics of all type of materials at micro-, nano- and also picometric scale, from soft metals, like copper, to brittle materials, as ceramics. The experimental basis of these techniques is the evaluation of the response of a material to an applied vertical load (in order to obtain the hardness, H, and the elastic modulus, E) or to a shear force (Lateral Force Microscopy, LFM) so as to obtain the friction coefficient, μ. In this work, the different methods to analyze friction, hardness and elastic modulus by means of AFM are explained for several examples as diamond single crystals, SiC single crystals, titanium dioxide coatings, mica and silicon oxide. Besides, examples of elastic deformation using nanoindentation are included. Moreover, several examples of results obtained by means of a Nanoindenter are also described in detail. A particular emphasis on ceramic coatings and advanced ceramic materials, such as YBaCuO superconductors, Yttria-stabilized zirconia, doped ceria electrolytes for fuel cells and yttria stabilized polycrystalline tetragonal zirconia, are reported and commented. The interest of these techniques is evidenced by the increasing quantity of nanomechanics-related papers published in the last decades, near a thousand of which appeared during the last five years. Unfortunately, a lot of practical information about nanomechanics of hard materials is still scarce in the literature (only one percent of the above mentioned publications are related to ceramic materials). This chapter aims to present the basic principles and methods applied to extract the different mechanical properties and also to review and comment real examples related to the cited techniques.

JTD