Parameter Space of Atomic Layer Deposition of Ultrathin Oxides on Graphene

Abstract

Atomic layer deposition (ALD) of ultrathin aluminum oxide (AlOx) films was systematically studied on supported chemical vapor deposition (CVD) graphene. We show that by extending the precursor residence time, using either a multiple-pulse sequence or a soaking period, ultrathin continuous AlOx films can be achieved directly on graphene using standard H2O and trimethylaluminum (TMA) precursors even at a high deposition temperature of 200 °C, without the use of surfactants or other additional graphene surface modifications. To obtain conformal nucleation, a precursor residence time of >2s is needed, which is not prohibitively long but sufficient to account for the slow adsorption kinetics of the graphene surface. In contrast, a shorter residence time results in heterogeneous nucleation that is preferential to defect/selective sites on the graphene. These findings demonstrate that careful control of the ALD parameter space is imperative in governing the nucleation behavior of AlOx on CVD graphene. We consider our results to have model system character for rational two-dimensional (2D)/non-2D material process integration, relevant also to the interfacing and device integration of the many other emerging 2D materials.

Graphene-based nanolaminates as ultra-high permeation barriers

“…2. In order to assure the initial ALD AlO x coating to be as uniform as possible, we use here a ALD process with 10 water prepulses, 28,31 which assists the nucleation of AlO x . Figure 3a, b shows SEM images of the as-deposited 10 nm AlO x film on G/Cu.…”

“…A conformal growth of AlO x on G/Cu was optimized by utilizing few water pulses which act as seed layer for the cyclic growth of the oxide. 28,31 Transfer The grown layers were transferred on planarized 125 µm thick PEN substrate (Teijin DuPont Films™, roughness <2 nm) with standard PMMAbased wet transfer method. 41 …”

“…The alternative is to decorate and block the defects in graphene with polymers and metal oxides. [26][27][28] These process steps are non-trivial considering that graphene is hard to coat/wet in particular once it has been exposed to ambient air. 29 Here, we combine catalytic CVD and ALD to create in scalable fashion few-layer graphene/aluminium oxide-based nanolaminates.…”

Bolometric detection of terahertz quantum cascade laser radiation with graphene-plasmonic antenna arrays

“…/ where g is the gap size, E gap is the electric field in the graphene channel and µ is the mobility that was assumed to be ~600 cm 2 V −1 s −1 [20]. The values obtained for the carrier transit time τ tr for Array A and B are 4.1 ps and 0.25 ps, respectively.…”

“…Each square has an area = 9 µm 2 shorting the gap between the antennas' arms. A final conformal di electric layer of 80 nm of Al 2 O 3 was then deposited on top of the sample via atomic layer deposition (ALD) in stop-flow mode using H 2 O/ TMA precursors, thus encapsulating the graphene [19,20]. This last step is crucial in order to reduce the hysteresis [21] and bring the Dirac point to bias voltages lower than 100-120 V which was observed in previous strongly p-doped samples.…”