STUDIES OF NIO THIN-FILM FORMATION BY ATOMIC LAYER EPITAXY

Nickel oxide thin film formation by atomic layer epitaxy (ALE) was stu died including aspects of surface chemistry and structure of the prepa red films. The applied source materials were Ni(acac)(2), Ni(apo)(2), Ni(dmg)(2) and O-2, H2O, N2O, O-3, CH3COOH for Ni and O, respectively. The thermal behaviour of the Ni-containing precursors was studied by thermogravimetry and by experiments in the ALE reactor. The reactivity of the Ni-precursors towards various oxygen sources was studied at th e deposition temperature of 250 degrees C using soda-lime glass substr ates. The crystalline rocksalt-type NiO was obtained only when O-3 was used as an oxygen source. The him was in this case (100) oriented NiO independent on the applied Ni-precursor. The NiO ALE process was opti mized for the reaction between Ni(acac)(2) and O-3. The surface-satura ted growth rate was limited by the steric hindrance of the ligand and was 0.62 Angstrom cycle(-1). A slightly increased growth rate (0.72 An gstrom cycle(-1)) was observed, when H2O was supplied together with O- 3 as an oxygen source. Structure of the deposited films was studied by atomic force microscopy and X-ray diffraction techniques and some str uctural variations related to high ozone doses were observed. (C) 1998 Elsevier Science S.A. All rights reserved.