title: Interface Electrical Properties of Al2O3Thin Films on Graphene Obtained by Atomic Layer Deposition with an in Situ Seedlike Layer.
abstract: High-quality thin insulating films on graphene (Gr) are essential for field-effect transistors (FETs) and other electronics applications of this material. Atomic layer deposition (ALD) is the method of choice to deposit high-κ dielectrics with excellent thickness uniformity and conformal coverage. However, to start the growth on the sp2Gr surface, a chemical prefunctionalization or the physical deposition of a seed layer are required, which can effect, to some extent, the electrical properties of Gr. In this paper, we report a detailed morphological, structural, and electrical investigation of Al2O3thin films grown by a two-steps ALD process on a large area Gr membrane residing on an Al2O3-Si substrate. This process consists of the H2O-activated deposition of a Al2O3seed layer a few nanometers in thickness, performed in situ at 100 °C, followed by ALD thermal growth of Al2O3at 250 °C. The optimization of the low-temperature seed layer allowed us to obtain a uniform, conformal, and pinhole-free Al2O3film on Gr by the second ALD step. Nanoscale-resolution mapping of the current through the dielectric by conductive atomic force microscopy (CAFM) demonstrated an excellent laterally uniformity of the film. Raman spectroscopy measurements indicated that the ALD process does not introduce defects in Gr, whereas it produces a partial compensation of Gr unintentional p-type doping, as confirmed by the increase of Gr sheet resistance (from ∼300 Ω/sq in pristine Gr to ∼1100 Ω/sq after Al2O3deposition). Analysis of the transfer characteristics of Gr field-effect transistors (GFETs) allowed us to evaluate the relative dielectric permittivity (ε = 7.45) and the breakdown electric field (EBD= 7.4 MV/cm) of the Al2O3film as well as the transconductance and the holes field-effect mobility (∼1200 cm2V-1s-1). A special focus has been given to the electrical characterization of the Al2O3-Gr interface by the analysis of high frequency capacitance-voltage measurements, which allowed us to elucidate the charge trapping and detrapping phenomena due to near-interface and interface oxide traps.
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Gabriele
authors.initials: G
authors.lastname: Fisichella
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Schilirò
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Di Franco
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Patrick
authors.initials: P
authors.lastname: Fiorenza
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Lo Nigro
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Roccaforte
authors.affiliation: STMicroelectronics , Stradale Primosole 50, Zona Industriale, 95121 Catania, Italy.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Ravesi
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto per la Microelettronica e Microsistemi , Strada VIII, n. 5, Zona Industriale, 95121 Catania, Italy.
authors.forename: Filippo
authors.identifier: http://orcid.org/0000-0002-0074-0469
authors.initials: F
authors.lastname: Giannazzo
keywords: aluminum oxide; atomic force microscopy; atomic layer deposition; graphene; interface states; top gate transistors