Paper GR+EM+MS+TF+MI-WeM11
In-situ X-ray Photoelectron Spectroscopy Studies of Ozone-based ALD Al₂O₃ Dielectrics on Graphite and Graphene

Wednesday, October 20, 2010, 11:20 am, Room Brazos

We present a study of ozone-based atomic layer deposition (ALD) of Al₂O₃ films on graphene and bulk graphite. Uniform deposition of scalable device-quality high-k dielectrics on graphene is a substantial hurdle for the implementation of conventional FET devices as well as novel device structures exploiting the unique transport properties of graphene. Trimethylaluminum (TMA) / O₃ processes are found to result in uniform Al₂O₃ depositions on graphite and graphene surfaces (1), in contrast to common TMA / H₂O-based processes which result in nonuniform nucleation at defects and step edges.

In order to further examine the nature of interactions between TMA / O₃ and graphene, we utilize in-situ x-ray photoelectron spectroscopy (XPS) coupled via a UHV transfer line to an ALD reactor. Morphology of deposited films is also examined ex-situ using atomic force microscopy (AFM). We examine the impact of several parameters on Al₂O₃ deposition. Choice of deposition temperature is critical, as etching of graphene by O₃ is observed at elevated temperatures (2) but dielectric quality is degraded at low temperature (3). We also examine the impact of surface condition on Al₂O₃ composition particularly with regard to partially reacted TMA precursor molecules; various surface treatments are employed to approximate realistic device processing conditions. Finally, the effect of variations in purge time between ALD precursor pulses is studied; a reduction in deposition with increased purge time indicates that weakly bonded precursor molecules (TMA and O₃) are easily desorbed from the graphene surface.

This work is supported by the NRI SWAN and MIND centers.

1: B. Lee, et. al., Appl. Phys. Lett. 92 (20), 203102 (2008)

2: G. Lee, et. al., J. Phys. Chem. C 113 (32), 14225 (2009)

3: S. K. Kim, et. al., J. Electrochem. Soc. 153 (5), F69 (2006)