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

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.原子层沉积 ALD (Atomic Layer Deposition) 现已成为面向多元应用场景制备超薄涂层的关键技术之一。该技术已成功以碳纳米管 CNTs (Carbon Nanotubes) 为模板，制备出独立式陶瓷纳米管。原子层沉积的优势在于可实现单原子层级别的精准厚度控制：其自限性特性可在高长径比结构上实现优异的台阶覆盖率与保形性[1,2]。影响原子层沉积生长的核心因素包括衬底形貌、活性位点密度、前驱体分压、分子质量、附着系数以及暴露时间。粗略而言，原子层沉积的生长速率取决于沉积循环次数。但在薄膜生长的初始阶段，该工艺可能面临成核难题，进而延缓薄膜生长速率[3]。因此，所有从事原子层沉积研究的科研人员都需掌握其初始成核阶段的监测方法。本次发布的数据聚焦于：以常见末端官能团（羟基OH、羧基COOH）或缺陷位点（氮掺杂Nₓ）功能化的碳纳米管表面，经原子层沉积工艺发生的初始成核过程，并由X射线光电子能谱 XPS (X-ray Photoelectron Spectroscopy) 进行监测。X射线光电子能谱是一种高表面灵敏度的表征技术，可用于不规则表面的分析[4]。本次实验中，原子层沉积的前驱体为室温下的三甲基铝 TMA (Trimethylaluminum) 与去离子水 H₂O。本研究的目标为通过碳纳米管模板法制备氧化铝纳米管。本次数据集与本团队此前发表的题为"Optimal sidewall functionalization for the growth of ultrathin TiO2 nanotubes via atomic layer deposition"[4]的研究相关：该研究开展了同类实验，但采用四(二甲氨基)钛 TDMAT (tetrakis(dimethylamino)titanium) 与水作为前驱体，以制备二氧化钛 TiO₂ 纳米管。与上述研究相比，本次数据集呈现出规律性变化趋势，该趋势会影响原子层沉积的初始成核过程。所有通过模板法制备超细陶瓷纳米管的原子层沉积研究者，均需重视这一现象。