Controlled synthesis of Zirconium Oxide on graphene nanosheets by atomic layer deposition and its growth mechanism

Zirconium Oxide (ZrO2) was deposited on graphene nanosheets (GNS) by atomic layer deposition (ALD) using tetrakis(dimethylamido)zirconium(IV) and water as precursors. The results indicated that both morphology and crystallinity of the deposited ZrO2 were controllable in a temperature range of 150-250 degrees C. At all the temperatures studied, ZrO2 nanoparticles were formed with lower number of ALD cycles (<10 cycles at 150 degrees C and <30 cycles at 200 and 250 degrees C), while ZrO2 thin films were achieved uniformly with higher number of ALD cycles (>10 cycles at 150 degrees C and >30 cycles at 200 and 250 degrees C). The crystallinity of the deposited ZrO2 was highly dependent on the deposition temperature. The ZrO2 deposited at 150 degrees C exhibited mainly amorphous nature, whereas that prepared at 250 degrees C consisted of crystalline phase. At 200 degrees C, a mixture of amorphous and crystalline ZrO2 appeared in the ZrO2-GNS nanocomposite. In all cases, the growth of ZrO2 on GNS showed a transformation from an island growth mode to a layer-by-layer growth mode with increasing ALD cycle. Cyclic voltammetry measurement demonstrated that 10-cycle ZrO2-GNS nanocomposite exhibited evident electrochemical capacitance characteristics. (C) 2012 Elsevier Ltd. All rights reserved.