Growth and stability of CVD Ni3N and ALD NiO dual layers

Multilayers of combinations of NiO, Ni3N and Ni have been grown by ALD and CVD techniques at 250 degrees C. Layers of low thermodynamical stability have been modified to reach the target structures. The Ni layers have been formed by decomposition of metastable Ni3N layers, i.e., the Ni3N layers act as precursor for Ni film growth. This new reaction route enables production of Ni/NiO layer structures by chemical means for the first time. By choosing suitable low temperature annealing conditions like 180 degrees C in a 1 Torr hydrogen atmosphere, good control of the interfaces is obtained. It has also been shown that it is possible to grow multilayers which are ordered both with respect to each other, the substrate and the Ni films. For instance the following structure Ni (111)/NiO (111)/alpha-Al2O3 (001) has been grown. Moreover, another new reaction route is deposition of thin epitaxial seed layers of NiO (111) for subsequent growth of Ni3N at a high rate. Single phase Ni (111) films could then be obtained by decomposition at 350 degrees C of the Ni3N layers. The demonstrated reaction routes for film growth in the Ni-O-N system can also be applied in several similar systems. (C) 2010 Elsevier B.V. All rights reserved.