VARIATION OF THE CELL PARAMETER OF POLYCRYSTALLINE BORON-DOPED DIAMOND FILMS

The lattice parameter of undoped and boron doped polycrystalline diamo nd films has been measured up to 8X10(20) B cm(-3). It varies slightly according to the three crystallographic directions [111], [220], and [311] investigated here. The cell parameters for the undoped films are within the published values for synthetic crystal and thin films. For the boron doped films, the cell parameter has a high expansion coeffi cient versus boron incorporation, with a mean value of Delta a/a=3X10( -24) [B], ([B] in cm(-3)), and a variation law in the [220] direction in striking agreement with a Russian work. The simplest Vegard model p redicts a smaller variation, while both the deformation potential (but with a high deformation potential on the boron impurity band of +19.5 eV) and a defect model might explain the experimental results. (C) 19 97 American Institute of Physics.