Healy Brendan F M, Pain Sophie L, Grant Nicholas E, Murphy John D
School of Engineering, University of Warwick, Coventry, CV4 7AL, UK.
Nanoscale. 2025 Jun 26;17(25):15436-15447. doi: 10.1039/d5nr01144b.
High dielectric constant (high-) materials must be successfully integrated with single-layer transition metal dichalcogenides for future nanoscale device technologies. With high carrier mobility and relatively strong visible light emission, monolayer molybdenum disulfide (1L MoS) is a promising candidate for optoelectronic applications and is commonly synthesised chemical vapour deposition (CVD) to enable large-area device production. The growth of uniform high- dielectrics on bulk materials is routinely achieved thermal atomic layer deposition (ALD), but continuous deposition on MoS is notoriously challenging due to the absence of dangling bonds on the basal plane. The resulting unique nucleation and growth characteristics of high- dielectrics on 1L MoS are not fully understood, particularly on large-area CVD-1L MoS. In this work, we investigate the nucleation and growth of aluminium oxide (AlO) and hafnium dioxide (HfO) on CVD-1L MoS films direct thermal ALD at 200 °C. We vary the number of ALD cycles and monitor the morphology of the deposited high- layer atomic force microscopy, observing ALD-AlO and ALD-HfO films on CVD-1L MoS to exhibit island features for all cycle numbers investigated (up to 200 cycles). We reveal the development of AlO on CVD-1L MoS proceeds a three-dimensional growth mode, and we estimate the vertical and lateral growth rates to be 0.09 ± 0.01 nm per cycle and 0.06 ± 0.01 nm per cycle, respectively. In contrast, we find direct ALD of HfO on CVD-1L MoS exhibits negligible lateral growth, with a vertical growth rate of 0.14 ± 0.01 nm per cycle. We also investigate the thickness-dependent effects of ALD-AlO and ALD-HfO films on the Raman and photoluminescence character of CVD-1L MoS, and quantify changes in electron density. Our growth study offers valuable insights into the nucleation and development of high- dielectric films on CVD-1L MoS, enhancing the understanding of dielectric integration for MoS-based devices.
对于未来的纳米级器件技术而言，高介电常数（高κ）材料必须成功地与单层过渡金属二硫属化物集成。单层二硫化钼（1L MoS₂）具有高载流子迁移率和相对较强的可见光发射特性，是光电子应用的一个有前途的候选材料，并且通常通过化学气相沉积（CVD）来合成，以实现大面积器件的生产。在体材料上生长均匀的高κ电介质通常是通过热原子层沉积（ALD）来实现的，但由于MoS₂基面不存在悬空键，在其上进行连续沉积极具挑战性。高κ电介质在1L MoS₂上独特的成核和生长特性尚未得到充分理解，尤其是在大面积CVD生长的1L MoS₂上。在这项工作中，我们研究了在200℃下通过直接热ALD在CVD生长的1L MoS₂薄膜上氧化铝（Al₂O₃）和二氧化铪（HfO₂）的成核和生长情况。我们改变ALD循环次数，并通过原子力显微镜监测沉积的高κ层的形貌，观察到在CVD生长的1L MoS₂上的ALD-Al₂O₃和ALD-HfO₂薄膜在所有研究的循环次数（高达200次循环）下均呈现岛状特征。我们揭示了Al₂O₃在CVD生长的1L MoS₂上的生长过程遵循三维生长模式，并且我们估计其垂直生长速率和横向生长速率分别为每循环0.09±0.01 nm和每循环0.06±0.01 nm。相比之下，我们发现HfO₂在CVD生长的1L MoS₂上的直接ALD表现出可忽略不计的横向生长，垂直生长速率为每循环0.14±0.01 nm。我们还研究了ALD-Al₂O₃和ALD-HfO₂薄膜的厚度依赖性对CVD生长的1L MoS₂的拉曼和光致发光特性的影响，并量化了电子密度的变化。我们的生长研究为CVD生长的1L MoS₂上高κ介电薄膜的成核和生长提供了有价值的见解，增进了对基于MoS₂的器件的介电集成的理解。
