The effect of surface functionalities of carbon Nanotubes in the Nucleation delay of Trimethylaluminum and water ALD cycles monitored by XPS

Published: 22-11-2018| Version 2 | DOI: 10.17632/pz7p5kdbnz.2
Contributor:
Gerardo Soto

Description

Atomic Layer Deposition (ALD) has become a very important technique to produce ultrathin coatings for a variety of applications. ALD has been successfully employed to produce standalone ceramic nanotubes using carbon nanotubes (CNTs) as template. The advantages of ALD are precise thickness control at the monolayer level since the self-limiting aspect of ALD leads to excellent step coverage and conformity on high aspect ratio structures [1,2]. The main factors influencing the ALD growth are the substrate morphology, density of reactive sites, precursor partial pressure, molecular mass and sticking coefficient, and exposure time. In first approximation, the growth rate for ALD depends on the number of ALD cycles. However, in the early stages of film growth, the ALD process may have nucleation difficulties, which delays the growth ratio of the film [3]. Consequently, the monitoring of the early nucleation stages must be known to all researchers who work with ALD. The data presented here correspond to the early nucleation by the ALD process on the surface of CNTs functionalized with common terminal groups (OH, COOH) or defects (Nx) monitored by XPS. XPS is a very surface sensitive technique that can be employed on irregular surfaces [4]. In this case the ALD cycles correspond to Trimethylaluminum (TMA) and deionized water (H2O), both kept at room temperature. The aim was to prepare alumina nanotubes by the CNTs template approach. This data is related to our previous report, “Optimal sidewall functionalization for the growth of ultrathin TiO2 nanotubes via atomic layer deposition” [4], where the same kind of experiments were carried out, but using tetrakis (dimethylamino) titanium (TDMAT) and water to yield TiO2 nanotubes. The data here indicates a regular trend, as compared with the above report, that affects the early nucleation of ALD. This phenomenon should be considered by all those who work with ALD to prepare ultra-fine ceramic nanotubes through the template approach.

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