Building three dimensional structures from two dimensional materials, novel approaches for the creation of van der Waals heterostructures

我们最近开发了一种制造范德华异质结构的新工艺，这是一种最近才构思和制造的材料系统。我们的方法价格低廉、通用且可扩展。该项目的重点是提高我们对支撑该方法的科学的理解，并研究通过该方法产生的新型异质结构。范德华异质结构（vdWHSs）是一种源自单层二维固体的层状材料，如石墨烯及其非碳类似物（如过渡金属二硫族化合物、黑磷等）。这些超薄的三维结构可以通过将一个或多个不同的二维材料层堆叠在纳米尺度上，相当于一个层饼。由此产生的体系结构是新颖的“智能”材料，它结合了各种二维构建块的独特性能，能够创造从光电探测器、吸光涂层到柔性电子设备的新功能。由于需要精确匹配每层的晶格结构，传统的半导体异质结构在材料组合方面受到限制-在vdWHSs中，层之间的弱范德华相互作用和强层内键合完全放松了层在结构上相称的要求，并且可以使用广泛的二维材料产生干净，无缺陷的界面。目前生产vdWHSs的方法昂贵、耗时且难以规模化。第一批vdwhs是通过“透明胶带”技术的扩展生产的，通过这种技术，手工剥离材料的各个层，并以微米级精度手动定位，这是一种不可能缩放的费力方法。最近，化学气相沉积（CVD）方法在这些结构的生长方面取得了一些进展，但它们仍然局限于可获得的固体范围和所产生的异质结构的质量。此外，热预算使得CVD方法昂贵且难以扩展。我们的液体悬浮沉积（LSD）方法已经在初步研究中得到了证实，它涉及到在几乎任何材料表面上，通过有限的（甚至可能不需要）预处理，从容易产生的液相悬浮液中精确和可控地组装vdWHsS。LSD方法的物理学尚未完全理解，仍然需要优化所生产结构的质量，并扩大所使用材料的范围。解决这些问题将是拟议博士项目的核心活动，为工业合作和未来的资金应用提供平台。低成本、快速和可扩展的vdWHSs生产将彻底改变其可用性，并使其能够融入制成品。参考文献[1]a.g.m.m athieson， M. Zulqurnain， M. Szablewski和M.R.C. Hunt（未发表，准备中）。“通过剪切剥离在液体中大规模生产无缺陷的少层石墨烯”K.R. Paton等人。“石墨烯以外二维材料的进展、挑战和机遇”，S.Z. Butler等。中国化学工程学报，2013,28 (1):387 - 398

We have recently developed a novel process for the fabrication of van der Waals heterostructures, a materials system which has only recently been conceived and fabricated. Our method is inexpensive, generic and scalable. The focus of this project is to improve our understanding of the science underpinning the approach and investigate novel heterostructures produced via this method. Van der Waals heterostructures (vdWHSs) are layered materials derived from monolayer two-dimensional solids such as graphene and its non-carbon analogues (such as the transition metal dichalcogenides, black phosphorous etc.). These ultra-thin three-dimensional structures can be built up by stacking units made up of one or more layers of different two-dimensional materials in a nanoscale equivalent to a layer cake. The resulting architectures are novel 'smart' materials which combine the individual, outstanding properties of the various two-dimensional building blocks, enabling the creation of new functionality ranging from photodetectors and light-absorbing coatings to flexible electronic devices. vdWHSs offer great advantages over conventional semiconductor heterostructures which are limited in their materials combinations due to the need to match the lattice structure of each layer precisely - in vdWHSs the weak van der Waals interactions between layers and strong intra-layer bonding fully relaxes the requirement that layers be commensurate in structure and can produce clean, defect-free interfaces using a wide palette of two-dimensional materials. Current methods of producing vdWHSs are expensive, time consuming and difficult to scale. The first vdWHSs were produced by an extension of the 'Scotch tape' technique, by which individual layers of material are peeled off by hand, and positioned manually with micron-scale precision, a laborious approach which is impossible to scale. More recently, some advances have been made with chemical vapour deposition (CVD) approaches to the growth of these structures, but they are still limited in the range of solids accessible and the quality of the heterostructure produced. Moreover, the thermal budget makes CVD approaches expensive and difficult to scale. Our liquid suspension deposition (LSD) approach, which has been proven in preliminary studies [1], involves the precise and controlled assembly of vdWHsS from easily produced liquid phase suspensions [2] on almost any materials surface with limited (and potentially no) pre-treatment. The physics of the LSD approach is not yet fully understood and work is still required to optimise the quality of the structures produced and widen the range of materials employed [3]. Addressing these issues would be the core activity of the proposed PhD project, providing a platform for industrial collaboration and future funding applications. The low-cost, rapid and scalable production of vdWHSs will revolutionise their availability and enable incorporation into manufactured goods. References [1] A.G.M. Mathieson, M. Zulqurnain, M. Szablewski and M.R.C. Hunt (unpublished, in preparation). [2] 'Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids' K.R. Paton et al. Nature Materials 13 (2014) 624 [3] 'Progress, Challenges and Opportunities in Two-Dimensional Materials Beyond Graphene' S.Z. Butler et al. ACS Nano 7 (2013) 2898-2926