Modulation of charge transport in diamond-based layers

Doping of diamond by substitutional insertion of metallic species or production of diamond/metals nanocomposite layers has been obtained by a hybrid chemical vapor deposition based technique. The potential of such an approach makes it possible to obtain a wide class of purposely designed diamond-based structures characterized by specific properties of charge transport. Reflection high-energy electron diffraction, scanning electron microscopy and x-ray dispersive spectrometry have been used to study the structural and compositional characteristics of some Nd-, W- and Ti-containing diamond films. The peculiar electrical properties conferred to the host diamond layers by the insertion of various metals have been investigated in the range of 25-500 K by performing Hall effect and conductivity measurements. The mechanism of charge transport and the electrical properties of these materials are found to be mainly governed by organization of the metallic species, which can be in different forms, such as dispersion at the atomic scale and the distribution of isolated clusters or aggregates localized at grain boundaries. Depending on the microstructure, the resulting materials can behave as p-type semiconductors, characterized by resistivity values as low as 3.3x10(-3) Omega cm and high values of Hall mobility, or show metal-like conduction, with resistivity as low as 2.2x10(-1) Omega cm. The insertion of metallic species does not perturb the crystalline quality of the host diamond matrix and, consequently, the layers produced combine the outstanding properties of diamond with electrical behavior that can be modulated for specific applications. (C) 2003 American Institute of Physics.