NER: Chemical Vapor Deposition of Carbon Nanotube/Diamond Composites

这个纳米级探索性研究项目的目标是使用化学气相沉积法生长碳纳米管和金刚石的复合膜，以广泛地表征这些膜，并通过对分子过程的详细模拟来了解原子水平上的膜生长过程。 碳纳米管（CNT）和金刚石具有各自独特的特性，但也具有互补性，因此由这些成分制成的复合材料应该具有真正独特的特性。预测CNT具有极高的杨氏模量值，同时还能够在轴向方向上维持大的应变。 它已被证明，使用AFM的尖端，多壁碳纳米管可以反复弯曲通过大角度，而不会导致任何明显的断裂。 另一方面，金刚石是已知最硬的材料，具有最高的室温热导率。其它性质包括非常低的摩擦系数、良好的电阻率和光学透明性，以及当适当掺杂时的一些上级半导体性质。 最近的研究表明，多晶金刚石可以容易地沉积在各种基底上作为膜。 这种金刚石膜主要用作耐磨涂层和散热装置，尽管膜的脆性显著限制了纯金刚石膜的使用。 为了利用金刚石的有利特性，同时解决脆性问题，制造CNT/金刚石复合材料，其应具有极高的硬度和出色的韧性。合成方法是化学气相沉积（CVD），其目前用于在类似条件下存款金刚石和CNT两者。通过仔细选择工艺条件，产生具有强界面的致密CNT/金刚石膜，其可以通过反应器参数的变化来控制和优化。 沉积实验在现有的CVD反应器中进行，该反应器稍微修改以允许CNT和金刚石沉积在同一晶片上。 在生成初始CNT膜之后，使用热丝CVD（HF-CVD）沉积金刚石。 复合膜的结构特性，其特征在于通过高分辨率透射电子显微镜。 研究了衬底和催化剂对碳纳米管和金刚石生长的影响，以及界面应力和膜内应力。 的复合材料的机械性能进行了研究与原子力显微镜使用金刚石探头。 一个互补的建模和仿真工作提供了基本现象的理解提供了深入了解补救措施和潜在的过程improvement. BroaderImpactThis工作提供了教育和经验，为大学生在纳米技术。 这项研究的结果通过会议和档案期刊出版物广泛传播。 如果这种薄膜合成的努力取得成功，将出现与新兴纳米技术产业进行技术转让的巨大潜力。 来自代表性不足的群体的学生的参与是通过招聘工作，以及通过大学的正式浪涌计划促进。该项目所需的设施升级将改善基础设施，提高在纳米材料领域开展研究的能力。

PROJECT SUMMARY The objectives of this nanoscale exploratory research project are the growth of composite films of carbon nanotubes and diamond using chemical-vapor deposition, to extensively characterize these films, and to understand the film-growth process at the atomistic level through detailed simulations of the molecular processes. Carbon nanotubes (CNT) and diamond have properties that are individually exceptional but also complementary in a fashion such that a composite material made of these components should have truly unique properties. CNT are predicted to have extremely high values of Young's modulus while also being able to sustain large strain in the axial direction. It has been demonstrated that, using the tip of an AFM, multiwalled CNT can be bent repeatedly through large angles without causing any apparent fracture. On the other hand, diamond is the hardest known material and has the highest room-temperature thermal conductivity. Other properties include a very low coefficient of friction, good resistivity and optical transparency, and some superior semiconducting properties when appropriately doped. Recent research has shown that polycrystalline diamond can be readily deposited as a film on various substrates. Such diamond films have found applications primarily as wear-resistant coatings and heat-spreading devices, though film brittleness significantly limits the use of pure diamond films. In order to capitalize on the favorable properties of diamond while addressing the brittleness problem, a CNT/diamond composite material is manufactured that should have extreme hardness combined with outstanding toughness. The synthesis method is chemical vapor deposition (CVD) which is currently used to deposit both diamond and CNT under similar conditions. By careful selection of process conditions, a dense CNT/diamond film with a strong interface is produced that can be controlled and optimized by variation of reactor parameters. Deposition experiments are conducted in an existing CVD reactor, which is slightly modified to allow for CNT and diamond deposition on the same wafer. After the initial CNT film is generated, diamond is deposited using hot-filament CVD (HF-CVD). The structural properties of the composite films are characterized by high-resolution transmission electron microscopy. The roles of the substrate and catalyst on the growth of CNT and diamond, and the interface and internal film stresses are investigated. The mechanical properties of the composite are studied with atomic-force microscopy using a diamond-tipped probe. A complementary modeling and simulation effort provides understanding of the fundamental phenomena offers insight into remedial measures and potential process improvement.Broader impactThis work provides education and experience for university students in nanotechnology. Results obtained in this study are widely disseminated through conferences and archival journal publications. Should this effort at film synthesis be successful, a great potential for technology transfer with the emerging nanotechnology industry will be present. The involvement of students from under-represented groups is promoted through recruiting efforts, as well as through the university's formal SURGE program. Facility upgrades required for this project improve the infrastructure and enhance the ability to conduct research in the area of nanomaterials .