The synthesis of two-dimensional materials for post-Moore integrated circuits
面向后摩尔集成电路的二维材料合成
–Manuscript Draft–  –手稿草稿–

Centered on Complementary Metal-Oxide-Semiconductor (CMOS) technology,
以互补金属氧化物半导体（CMOS）技术为中心，
integrated circuits have become essential components in microprocessors, Static Random-Access Memory (SRAM), and various digital logic circuits ${}^{[1,2]}$${}^{[1,2]}$^([1,2]){ }^{[1,2]}. However, as channel lengths approach the 5 -nm regime, traditional three-dimensional stacked chip architectures exhibit unit-area thermal densities that surpass silicon’s transient thermal capacitance limit, thereby destabilizing channel materials. Furthermore, with continued scaling of channel dimensions, short-channel effects and quantum tunneling phenomena become pronounced, leading to elevated leakage currents in semiconductor devices and a significant increase in power consumption ${}^{[3-6]}$${}^{[3-6]}$^([3-6]){ }^{[3-6]}. As a result, Moore’s Law faces imminent limitations, posing severe challenges to the future advancement of integrated circuits ${}^{[7]}$${}^{[7]}$^([7]){ }^{[7]}.
集成电路已成为微处理器、静态随机存取存储器（SRAM）和各种数字逻辑电路中的关键组件 ${}^{[1,2]}$${}^{[1,2]}$^([1,2]){ }^{[1,2]} 。然而，随着沟道长度接近 5 纳米级别，传统的三维堆叠芯片架构表现出超过硅瞬态热容极限的单位面积热密度，从而导致沟道材料不稳定。此外，随着沟道尺寸的持续缩小，短沟道效应和量子隧穿现象变得显著，导致半导体器件的漏电流增加，功耗显著上升 ${}^{[3-6]}$${}^{[3-6]}$^([3-6]){ }^{[3-6]} 。因此，摩尔定律面临迫在眉睫的限制，对集成电路的未来发展构成严峻挑战 ${}^{[7]}$${}^{[7]}$^([7]){ }^{[7]} 。

In recent years, 2D materials have garnered significant attention from researchers due to their unique properties and ultrathin thickness ${}^{[8-11]}$${}^{[8-11]}$^([8-11]){ }^{[8-11]}. 2D semiconductor materials, including transition metal sulfur compounds (TMDCs) and black phosphorus, have seen remarkable advancements in high-frequency electronic devices ${}^{[12,}{}^{13]}$${}^{[12,}{}^{13]}$^([12,)^(13]){ }^{[12,}{ }^{13]}, and optoelectronic integration ${}^{[14-16]}$${}^{[14-16]}$^([14-16]){ }^{[14-16]}, leveraging their atomic-scale thickness to exhibit quantum confinement effect, ultra-high carrier mobility, and in-surface anisotropy ${}^{[17}$${}^{[17}$^([17){ }^{[17}, ${}^{18]}$${}^{18]}$^(18]){ }^{18]}. Unlike conventional semiconductor devices, the naturally passivated surface of 2D semiconductor eliminates dangling bonds, thereby significantly reducing interfacial scattering and impurity trap scattering ${}^{[19]}$${}^{[19]}$^([19]){ }^{[19]}. Moreover, 2D semiconductors possess sub-threshold swing (SS) values approaching the Boltzmann limit, offering a transformative technological pathway for achieving ultra-low power consumption and high integration density in the post-Moore era ${}^{[20-22]}$${}^{[20-22]}$^([20-22]){ }^{[20-22]}. Additionally, their ultrathin nature effectively suppress the short-channel effect, enhancing switching speed and minimizing power consumption ${}^{[23,24]}$${}^{[23,24]}$^([23,24]){ }^{[23,24]}. The compatibility of 2D materials with flexible substrates further promotes the development of flexible electronics and enables opportunities for 3D heterogeneous integration ${}^{[25,26]}$${}^{[25,26]}$^([25,26]){ }^{[25,26]}. Furthermore, the bandgap of certain 2D semiconductor materials is tunable, which is important for optimizing the performance of logic circuits, holding great potential for ultra-high-density 3D integration ${}^{[27]}$${}^{[27]}$^([27]){ }^{[27]}. In this context, 2D materials emerge as promising candidates for overcoming the limitations of Moore’s law.
近年来，二维材料因其独特的性质和超薄厚度受到研究人员的广泛关注 ${}^{[8-11]}$${}^{[8-11]}$^([8-11]){ }^{[8-11]} 。二维半导体材料，包括过渡金属硫化物（TMDCs）和黑磷，在高频电子器件 ${}^{[12,}{}^{13]}$${}^{[12,}{}^{13]}$^([12,)^(13]){ }^{[12,}{ }^{13]} 和光电子集成 ${}^{[14-16]}$${}^{[14-16]}$^([14-16]){ }^{[14-16]} 方面取得了显著进展，利用其原子级厚度展现出量子限域效应、超高载流子迁移率和面内各向异性 ${}^{[17}$${}^{[17}$^([17){ }^{[17} ， ${}^{18]}$${}^{18]}$^(18]){ }^{18]} 。与传统半导体器件不同，二维半导体的自然钝化表面消除了悬挂键，从而显著减少了界面散射和杂质陷阱散射 ${}^{[19]}$${}^{[19]}$^([19]){ }^{[19]} 。此外，二维半导体具有接近玻尔兹曼极限的亚阈值摆幅（SS）值，为实现后摩尔时代的超低功耗和高集成度提供了变革性的技术路径 ${}^{[20-22]}$${}^{[20-22]}$^([20-22]){ }^{[20-22]} 。另外，其超薄特性有效抑制了短沟道效应，提高了开关速度并最小化了功耗 ${}^{[23,24]}$${}^{[23,24]}$^([23,24]){ }^{[23,24]} 。 二维材料与柔性基板的兼容性进一步促进了柔性电子的发展，并为三维异质集成提供了机会 ${}^{[25,26]}$${}^{[25,26]}$^([25,26]){ }^{[25,26]} 。此外，某些二维半导体材料的带隙是可调的，这对于优化逻辑电路的性能非常重要，具有超高密度三维集成的巨大潜力 ${}^{[27]}$${}^{[27]}$^([27]){ }^{[27]} 。在此背景下，二维材料成为克服摩尔定律限制的有前景的候选材料。

2D transistors continue to evolve, yet numerous challenges remain to be addressed. For the post-Moore-era transistor technology of 2D semiconductor materials, the growth of high-quality, large-area 2D semiconductor materials is a critical aspect ${}^{[28,29]}$${}^{[28,29]}$^([28,29]){ }^{[28,29]}. However, 2D materials exhibit randomly distributed nucleation points and equivalence between antiparallel islands during growth. Additionally, their growth modes are highly susceptible to perturbations from various factors, including temperature gradients and airflow, which significantly hinder the continuous growth of high-quality thin films ${}^{[30,}{}^{31]}$${}^{[30,}{}^{31]}$^([30,)^(31]){ }^{[30,}{ }^{31]}. Currently, integrated devices based on 2D semiconductors necessitate high dielectric constant and wide bandgap gate insulators to reduce the gate leakage and enhance the overall gate controllability, and provide high interface quality and dielectric reliability. Moreover, the integration of traditional 3D dielectric materials often results in a significant number of dangling bonds at the interface, which can degrade the carrier mobility of semiconductor material ${}^{[32,33]}$${}^{[32,33]}$^([32,33]){ }^{[32,33]}. Achieving optimal contact between 2D semiconductor materials and metal electrodes at the nanoscale remains a substantial challenge. Specifically, Fermi level pinning and pronounced Schottky barriers adversely impact the electrical properties and contact resistance of 2D semiconductor materials, thus hindering their industrial applications ${}^{[34,35]}$${}^{[34,35]}$^([34,35]){ }^{[34,35]}. In this review, we focus on 2D transistors, and presenting the latest advancements in the growth of 2D semiconductor materials and 2D dielectric materials. We then explore strategies for enhancing the contact between 2D semiconductors and metal electrodes. Subsequently, we highlight the progress of 2D transistors in large-scale integration and advanced applications. Finally, we offer conclusions and outlooks on 2D transistors.
二维晶体管持续发展，但仍有许多挑战需要解决。对于后摩尔时代的二维半导体材料晶体管技术，高质量、大面积二维半导体材料的生长是关键方面 ${}^{[28,29]}$${}^{[28,29]}$^([28,29]){ }^{[28,29]} 。然而，二维材料在生长过程中表现出随机分布的成核点和反平行岛屿之间的等效性。此外，其生长模式极易受到温度梯度和气流等多种因素的扰动，这显著阻碍了高质量薄膜的连续生长 ${}^{[30,}{}^{31]}$${}^{[30,}{}^{31]}$^([30,)^(31]){ }^{[30,}{ }^{31]} 。目前，基于二维半导体的集成器件需要高介电常数和宽带隙的栅极绝缘体，以减少栅极泄漏并增强整体栅极控制能力，同时提供高界面质量和介电可靠性。此外，传统三维介电材料的集成通常会在界面产生大量悬挂键，可能降低半导体材料的载流子迁移率 ${}^{[32,33]}$${}^{[32,33]}$^([32,33]){ }^{[32,33]} 。 在纳米尺度上实现二维半导体材料与金属电极之间的最佳接触仍然是一个重大挑战。具体来说，费米能级钉扎和显著的肖特基势垒对二维半导体材料的电学性能和接触电阻产生不利影响，从而阻碍了其工业应用 ${}^{[34,35]}$${}^{[34,35]}$^([34,35]){ }^{[34,35]} 。在本综述中，我们聚焦于二维晶体管，介绍二维半导体材料和二维介电材料生长的最新进展。随后，我们探讨了增强二维半导体与金属电极接触的策略。接着，我们重点介绍了二维晶体管在大规模集成和先进应用中的进展。最后，我们对二维晶体管的发展进行了总结和展望。

Based on the mechanistic analysis of the chemical vapor deposition (CVD) process, in which the thermodynamic driving force is regulated by the temperature field, the enhanced atomic diffusion capability can significantly improve the growth rate at higher growth temperatures. The kinetic limitation mainly originates from the
基于对化学气相沉积（CVD）工艺的机理分析，其中热力学驱动力由温度场调控，增强的原子扩散能力可以显著提高较高生长温度下的生长速率。动力学限制主要来源于
substrate surface interface characteristics, which is manifested as the competitive relationship between the mean free range of adsorbed atoms $(\lambda )$$(\lambda )$(lambda)(\lambda) and the substrate step spacing ( L ): when $\lambda >\mathrm{L}$$\lambda >\mathrm{L}$lambda > L\lambda>\mathrm{L}, most adsorbed atoms desorb before migrating to the step edge, resulting in a significant reduction of the growth rate; when $\lambda <\mathrm{L}$$\lambda <\mathrm{L}$lambda < L\lambda<\mathrm{L}, the adsorbed atoms can efficiently arrive at the edge of the nucleus and realize the growth rate close to the theoretical limit. It is worth noting that under fixed thermodynamic parameters, $\lambda$$\lambda$lambda\lambda and L are completely determined by the substrate properties, and thus the interfacial interactions between the substrate and precursor atoms become a key parameter in regulating the nucleation kinetics. Based on this, substrate engineering has been shown to be an effective strategy to achieve controlled preparation of 2D materials at the water level, especially for single-crystal thin film growth by constructing seamless splicing structures. In this section, we take atomic surface smoothness, lattice matching, and space group symmetry as typical systems, and systematically review the research progress of substrate engineering in wafer-scale 2D materials preparation in recent years, and deeply analyze the design principles and implementation paths of different substrate engineering strategies, from the atomic-scale interface regulation mechanism to the macroscopic-scale experimental validation ${}^{[36-38]}$${}^{[36-38]}$^([36-38]){ }^{[36-38]}.
基底表面界面特性表现为吸附原子平均自由程 $(\lambda )$$(\lambda )$(lambda)(\lambda) 与基底台阶间距 (L) 之间的竞争关系：当 $\lambda >\mathrm{L}$$\lambda >\mathrm{L}$lambda > L\lambda>\mathrm{L} 时，大多数吸附原子在迁移到台阶边缘之前脱附，导致生长速率显著降低；当 $\lambda <\mathrm{L}$$\lambda <\mathrm{L}$lambda < L\lambda<\mathrm{L} 时，吸附原子能够高效到达成核边缘，实现接近理论极限的生长速率。值得注意的是，在固定热力学参数下， $\lambda$$\lambda$lambda\lambda 和 L 完全由基底性质决定，因此基底与前驱体原子之间的界面相互作用成为调控成核动力学的关键参数。基于此，基底工程已被证明是一种实现二维材料水准受控制备的有效策略，尤其是通过构建无缝拼接结构实现单晶薄膜生长。 在本节中，我们以原子表面光滑度、晶格匹配和空间群对称性作为典型体系，系统回顾了近年来基底工程在晶圆级二维材料制备中的研究进展，深入分析了不同基底工程策略的设计原则和实施路径，从原子尺度的界面调控机制到宏观尺度的实验验证 ${}^{[36-38]}$${}^{[36-38]}$^([36-38]){ }^{[36-38]} 。

While CVD technology on transition metal-catalyzed substrates allows for the controlled preparation of wafer-scale single-crystal 2D materials, its industrial application requires the transfer of 2D materials to dielectric substrates for electrical functionalization. However, the mechanical transfer process inevitably introduces defects such as folds, cracks and interfacial contamination, leading to significant degradation of electrical properties. Therefore, the development of direct epitaxy of 2D materials on insulating substrates has become a key path to break through the bottleneck of industrialization. The Fang team has successfully realized the highly oriented epitaxial growth of 2D semiconductor single crystals on c-surface sapphire substrates (Figure 1a). By rotating the crystal orientation by ${30}^{\circ }$${30}^{\circ }$30^(@)30^{\circ}, the compressive and tensile stresses are effectively regulated, and strain tolerance is realized, resulting in a controlled interfacial strain between the heterogeneous epitaxial single crystal with different lattice constants and the sapphire substrate. Photodetectors based on this
虽然基于过渡金属催化基底的 CVD 技术可以实现晶圆级单晶二维材料的可控制备，但其工业应用需要将二维材料转移到介电基底上以实现电功能化。然而，机械转移过程不可避免地引入折叠、裂纹和界面污染等缺陷，导致电学性能显著下降。因此，开发二维材料在绝缘基底上的直接外延成为突破工业化瓶颈的关键路径。Fang 团队成功实现了二维半导体单晶在 c 面蓝宝石基底上的高度定向外延生长（图 1a）。通过将晶体取向旋转 ${30}^{\circ }$${30}^{\circ }$30^(@)30^{\circ} ，有效调节了压缩和拉伸应力，实现了应变容忍，从而控制了具有不同晶格常数的异质外延单晶与蓝宝石基底之间的界面应变。基于此的光电探测器
heterogeneous epitaxial material show better photodetection performance than non-epitaxial devices ${}^{[39]}$${}^{[39]}$^([39]){ }^{[39]}. A similar strategy has also been validated in the system of TMDCs: Lo’s group utilized the ultra-low surface energy property of molten glass to successfully prepare 2.5 mm -scale single-crystal ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} triangular flakes (Figure 1b), which showed a $40\mathrm{\%}$$40\mathrm{\%}$40%40 \% enhancement of photoluminescence intensity compared with mechanically exfoliated samples ${}^{[40]}$${}^{[40]}$^([40]){ }^{[40]}. liu et al. proposed a double-coupled synergistic tuning of the two-dimensional material with the intra-insulating substrate surface by van der Waals’ coupling interaction and step interactions in a new mechanism of dual-coupling synergistic regulation, realizing the epitaxial preparation of 2 -inch single-layer monocrystalline ${\mathrm{WS}}_2{}^{[41]}$${\mathrm{WS}}_2{}^{[41]}$WS_(2)^([41])\mathrm{WS}_{2}{ }^{[41]}. kong et al. proposed a new strategy to realize the epitaxial growth of 2D semiconductor monocrystalline wafers represented by molybdenum disulfide on commercial insulator substrates, which provides a solid material foundation for the large-scale industrial application of 2D semiconductor-based semiconductors ${}^{[42]}$${}^{[42]}$^([42]){ }^{[42]}. These advances demonstrate that insulator substrate engineering offers innovative solutions for device-level integration of 2D materials with both interface quality and process compatibility.
异质外延材料表现出比非外延器件更好的光电探测性能 ${}^{[39]}$${}^{[39]}$^([39]){ }^{[39]} 。类似的策略也在 TMDCs 系统中得到了验证：Lo 团队利用熔融玻璃的超低表面能成功制备了 2.5 mm 级单晶 ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} 三角形薄片（图 1b），其光致发光强度相比机械剥离样品表现出 $40\mathrm{\%}$$40\mathrm{\%}$40%40 \% 倍的增强 ${}^{[40]}$${}^{[40]}$^([40]){ }^{[40]} 。刘等人提出了一种通过范德华耦合相互作用和阶梯相互作用对二维材料与绝缘基底表面进行双耦合协同调控的新机制，实现了 2 英寸单层单晶 ${\mathrm{WS}}_2{}^{[41]}$${\mathrm{WS}}_2{}^{[41]}$WS_(2)^([41])\mathrm{WS}_{2}{ }^{[41]} 的外延制备。孔等人提出了一种新策略，实现了以二硫化钼为代表的二维半导体单晶晶圆在商业绝缘基底上的外延生长，为基于二维半导体的半导体器件的大规模工业应用提供了坚实的材料基础 ${}^{[42]}$${}^{[42]}$^([42]){ }^{[42]} 。 这些进展表明，绝缘体基板工程为二维材料的器件级集成提供了创新的解决方案，兼顾了界面质量和工艺兼容性。

The epitaxial growth mechanisms of 2D materials and 3D bulk thin films are fundamentally different, although both are based on heterogeneous nucleation on the substrate surface. In the 3D thin-film system, the material is strongly coupled to the substrate through oriented chemical bonding, and the epitaxy process has stringent requirements for lattice symmetry matching and lattice constant agreement (typically $\mathrm{\Delta }\mathrm{a}/\mathrm{a}<5\mathrm{\%})$$\mathrm{\Delta }\mathrm{a}/\mathrm{a}<5\mathrm{\%})$Deltaa//a < 5%)\Delta \mathrm{a} / \mathrm{a}<5 \%). In contrast, the growth mechanism of 2D layered materials exhibits unique cross-dimensional properties: atoms within the layers build a stable 2D lattice through strong covalent/ionic bonds (binding energy $\sim 2-8\mathrm{eV}/$$\sim 2-8\mathrm{eV}/$∼2-8eV//\sim 2-8 \mathrm{eV} / atom), while interlayer and layer-substrate interactions are dominated by weak van der Waals (vdW) forces, which are 1-2 orders of magnitude lower than the energy scale of chemical bonds. The energy scale is 1-2 orders of magnitude lower than that of chemical bonding. This weak interfacial coupling property allows the epitaxial growth of 2D materials to break through the rigid constraints of conventional lattice matching and exhibit significant non-strict lattice matching dependence ${}^{[43-45]}$${}^{[43-45]}$^([43-45]){ }^{[43-45]}. The ${\mathrm{Bi}}_2{\mathrm{Te}}_3$${\mathrm{Bi}}_2{\mathrm{Te}}_3$Bi_(2)Te_(3)\mathrm{Bi}_{2} \mathrm{Te}_{3} can even form
二维材料和三维体薄膜的外延生长机制从根本上不同，尽管两者都基于基底表面的异质成核。在三维薄膜系统中，材料通过定向化学键与基底强耦合，外延过程对晶格对称性匹配和晶格常数一致性有严格要求（通常为 $\mathrm{\Delta }\mathrm{a}/\mathrm{a}<5\mathrm{\%})$$\mathrm{\Delta }\mathrm{a}/\mathrm{a}<5\mathrm{\%})$Deltaa//a < 5%)\Delta \mathrm{a} / \mathrm{a}<5 \%) ）。相比之下，二维层状材料的生长机制表现出独特的跨维性质：层内原子通过强共价/离子键（结合能 $\sim 2-8\mathrm{eV}/$$\sim 2-8\mathrm{eV}/$∼2-8eV//\sim 2-8 \mathrm{eV} / 原子）构建稳定的二维晶格，而层间及层-基底相互作用主要由弱范德华（vdW）力主导，其能量尺度比化学键低 1-2 个数量级。这种弱界面耦合特性使二维材料的外延生长能够突破传统晶格匹配的刚性限制，表现出显著的非严格晶格匹配依赖性 ${}^{[43-45]}$${}^{[43-45]}$^([43-45]){ }^{[43-45]} 。 ${\mathrm{Bi}}_2{\mathrm{Te}}_3$${\mathrm{Bi}}_2{\mathrm{Te}}_3$Bi_(2)Te_(3)\mathrm{Bi}_{2} \mathrm{Te}_{3} 甚至可以形成
high-quality heterogeneous epitaxial structures on FeTe substrates with very different lattice structures (Figure 1c) ${}^{[46]}$${}^{[46]}$^([46]){ }^{[46]}. Controlling the thickness of two-dimensional materials is crucial for regulating the properties of two-dimensional materials, so the ability to grow large-area two-dimensional channel materials with different layers is of great significance for the development of two-dimensional semiconductors, and most of the current growth methods are unable to achieve stable growth of large-area, multilayer two-dimensional channel materials. Liu et al. proposed an edge-aligned double-layer nucleation strategy based on an edge nucleation mechanism. By employing a CVD method, they achieved uniform nucleation and epitaxial growth of bilayer ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} on a sapphire substrate with step height precisely controlled through high-temperature annealing. Furthermore, compared to traditional single-layer ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} thin films, the bilayer ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} devices synthesized by this method exhibit significantly enhanced mobility and improved short-channel current density, demonstrating superior performance characteristics ${}^{[47]}$${}^{[47]}$^([47]){ }^{[47]}. It is worth noting that although the energy scale of the vdW interaction is low, its spatial distribution characteristics are decisive for the growth morphology of the 2D material: by tuning the lattice symmetry, step density, and other parameters on the substrate surface, the crystal orientation, domain size, and layer distribution of the 2D epitaxial layer can be precisely manipulated. This weak coupling-strong regulation dialectic provides a unique physical basis for heterogeneous integration of 2D materials.
在晶格结构差异很大的 FeTe 基底上实现高质量的异质外延结构（图 1c） ${}^{[46]}$${}^{[46]}$^([46]){ }^{[46]} 。控制二维材料的厚度对于调节二维材料的性质至关重要，因此能够生长不同层数的大面积二维通道材料对于二维半导体的发展具有重要意义，而目前大多数生长方法无法实现大面积、多层二维通道材料的稳定生长。Liu 等人提出了一种基于边缘成核机制的边缘对齐双层成核策略。通过采用 CVD 方法，他们在通过高温退火精确控制台阶高度的蓝宝石基底上实现了双层 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 的均匀成核和外延生长。此外，与传统的单层 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 薄膜相比，该方法合成的双层 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 器件表现出显著增强的迁移率和改进的短沟道电流密度，展示了优越的性能特征 ${}^{[47]}$${}^{[47]}$^([47]){ }^{[47]} 。 值得注意的是，尽管范德华相互作用的能量尺度较低，但其空间分布特性决定了二维材料的生长形貌：通过调节基底表面的晶格对称性、台阶密度等参数，可以精确控制二维外延层的晶体取向、晶域大小和层分布。这种弱耦合-强调控的辩证关系为二维材料的异质集成提供了独特的物理基础。

Figure 1. Two-dimensional material epitaxial growth technology based on precise regulation of nucleation orientation, interface strain, and defect density. a) Schematic illustration of the procedure to fabricate ${\mathrm{Cs}}_3{\mathrm{Bi}}_2{\mathrm{X}}_9{}^{[39]}$${\mathrm{Cs}}_3{\mathrm{Bi}}_2{\mathrm{X}}_9{}^{[39]}$Cs_(3)Bi_(2)X_(9)^([39])\mathrm{Cs}_{3} \mathrm{Bi}_{2} \mathrm{X}_{9}{ }^{[39]}. b) Synthesis process and morphology of ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} monolayers. Scheme showing CVD process for the synthesis of ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} crystalson molten glass. Photograph of ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} crystals grown on moltenglass ${}^{[40]}$${}^{[40]}$^([40]){ }^{[40]}. c) Scanning transmission electron microscope micrographs of a ${\mathrm{Bi}}_2{\mathrm{Te}}_3/\mathrm{FeTe}$${\mathrm{Bi}}_2{\mathrm{Te}}_3/\mathrm{FeTe}$Bi_(2)Te_(3)//FeTe\mathrm{Bi}_{2} \mathrm{Te}_{3} / \mathrm{FeTe} heterostructure. HADDF image. Annular bright field image. Higher-magnification HADDF image shows atomically sharp interface between ${\mathrm{Bi}}_2{\mathrm{Te}}_3$${\mathrm{Bi}}_2{\mathrm{Te}}_3$Bi_(2)Te_(3)\mathrm{Bi}_{2} \mathrm{Te}_{3} and ${\mathrm{FeTe}}^{[46]}$${\mathrm{FeTe}}^{[46]}$FeTe^([46])\mathrm{FeTe}^{[46]}. d) Thermodynamic analysis of monolayer and bilayer ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} growth in C-surface sapphire, as well as optical maps of large-area growth of monolayers and bilayers of ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} and optical maps of the initial nucleation stage of bilayer ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} domains with Atomic Force Microscope (AFM) images ${}^{[47]}$${}^{[47]}$^([47]){ }^{[47]}. a) Reproduced with permission ${}^{[39]}$${}^{[39]}$^([39]){ }^{[39]}.
图 1. 基于对成核取向、界面应变和缺陷密度的精确调控的二维材料外延生长技术。a) 制备 ${\mathrm{Cs}}_3{\mathrm{Bi}}_2{\mathrm{X}}_9{}^{[39]}$${\mathrm{Cs}}_3{\mathrm{Bi}}_2{\mathrm{X}}_9{}^{[39]}$Cs_(3)Bi_(2)X_(9)^([39])\mathrm{Cs}_{3} \mathrm{Bi}_{2} \mathrm{X}_{9}{ }^{[39]} 的工艺示意图。b) ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} 单层的合成过程及形貌。展示在熔融玻璃上合成 ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} 晶体的 CVD 工艺示意图。 ${\mathrm{MoSe}}_2$${\mathrm{MoSe}}_2$MoSe_(2)\mathrm{MoSe}_{2} 晶体在熔融玻璃 ${}^{[40]}$${}^{[40]}$^([40]){ }^{[40]} 上的照片。c) ${\mathrm{Bi}}_2{\mathrm{Te}}_3/\mathrm{FeTe}$${\mathrm{Bi}}_2{\mathrm{Te}}_3/\mathrm{FeTe}$Bi_(2)Te_(3)//FeTe\mathrm{Bi}_{2} \mathrm{Te}_{3} / \mathrm{FeTe} 异质结构的扫描透射电子显微镜图像。HADDF 图像。环形明场图像。高倍放大 HADDF 图像显示 ${\mathrm{Bi}}_2{\mathrm{Te}}_3$${\mathrm{Bi}}_2{\mathrm{Te}}_3$Bi_(2)Te_(3)\mathrm{Bi}_{2} \mathrm{Te}_{3} 与 ${\mathrm{FeTe}}^{[46]}$${\mathrm{FeTe}}^{[46]}$FeTe^([46])\mathrm{FeTe}^{[46]} 之间的原子级锐利界面。d) C 面蓝宝石上单层和双层 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 生长的热力学分析，以及 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 单层和双层大面积生长的光学图谱和双层 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 域初始成核阶段的光学图谱及原子力显微镜（AFM）图像 ${}^{[47]}$${}^{[47]}$^([47]){ }^{[47]} 。a) 经许可转载 ${}^{[39]}$${}^{[39]}$^([39]){ }^{[39]} 。

Although the heterogeneous epitaxial growth of 2D materials can be realized in a
尽管二维材料的异质外延生长可以实现于一个...
variety of substrate systems, the evolution of its crystallographic orientation is strictly limited by the symmetry matching principle at the substrate-film interface. Analyzed from the thermodynamic perspective of interfacial energy optimization, the 2D epitaxial process is essentially a dynamic selection mechanism of the coupling of adsorbed atoms with the potential field on the substrate surface, and the 2D crystal core edges tend to extend along the direction of low interfacial energies determined by the substrate lattice symmetry, resulting in the formation of a stable domain structure with a specific crystallographic orientation ${}^{[48]}$${}^{[48]}$^([48]){ }^{[48]}. Based on the principle of lattice symmetry subgroup matching, Ma demonstrates a versatile method for the growth of dense, aligned arrays of ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} nanoribbons by CVD on anisotropic sapphire substrates without the need for customized surface steps. This method is capable of synthesizing nanoribbons with widths below 10 nm and longitudinal axes parallel to the sawtooth direction, and can be extended to the growth of ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} nanoribbons and ${\mathrm{MoS}}_2-{\mathrm{WS}}_2$${\mathrm{MoS}}_2-{\mathrm{WS}}_2$MoS_(2)-WS_(2)\mathrm{MoS}_{2}-\mathrm{WS}_{2} heterogeneous nanoribbons, as shown in Figure 2a ${}^{[49]}$${}^{[49]}$^([49]){ }^{[49]}. The mechanism is also validated in the tetragonal symmetric system, where the lattice orientation of the quadruple-symmetric ${\mathrm{Bi}}_2{\mathrm{O}}_2\mathrm{Se}$${\mathrm{Bi}}_2{\mathrm{O}}_2\mathrm{Se}$Bi_(2)O_(2)Se\mathrm{Bi}_{2} \mathrm{O}_{2} \mathrm{Se} film is confined to be aligned along the [100]/[010] direction of the substrate when the film is grown on a cubic-symmetric ${\mathrm{SrTiO}}_3(001)$${\mathrm{SrTiO}}_3(001)$SrTiO_(3)(001)\mathrm{SrTiO}_{3}(001) substrate, as shown in Figure 2b. This stems from the uniaxial orientation-locking effect due to the interfacial energy anisotropy of tetragonal-phase films with cubic substrates ${}^{[50]}$${}^{[50]}$^([50]){ }^{[50]}. It is worth noting that although the symmetry matching strategy exhibits universality in centrosymmetric material systems, the epitaxial orientation regulation mechanism for complex interfacial systems with asymmetric surface reconstruction or mirror-symmetry breaking requires further decoupling of the nonlinear correlation between the interfacial potential field distribution and the dynamic growth process.
在各种基底系统中，其晶体取向的演变严格受限于基底-薄膜界面处的对称性匹配原则。从界面能优化的热力学角度分析，二维外延过程本质上是吸附原子与基底表面势场耦合的动态选择机制，二维晶体核边缘倾向于沿基底晶格对称性决定的低界面能方向延伸，形成具有特定晶体取向的稳定晶域结构 ${}^{[48]}$${}^{[48]}$^([48]){ }^{[48]} 。基于晶格对称子群匹配原理，Ma 展示了一种通过 CVD 在各向异性蓝宝石基底上生长致密、排列整齐的 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 纳米带阵列的通用方法，无需定制表面台阶。该方法能够合成宽度低于 10 纳米且纵轴平行于锯齿方向的纳米带，并可扩展至 ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} 纳米带和 ${\mathrm{MoS}}_2-{\mathrm{WS}}_2$${\mathrm{MoS}}_2-{\mathrm{WS}}_2$MoS_(2)-WS_(2)\mathrm{MoS}_{2}-\mathrm{WS}_{2} 异质纳米带的生长，如图 2a 所示 ${}^{[49]}$${}^{[49]}$^([49]){ }^{[49]} 。 该机制也在四方对称系统中得到了验证，当薄膜生长在立方对称的 ${\mathrm{SrTiO}}_3(001)$${\mathrm{SrTiO}}_3(001)$SrTiO_(3)(001)\mathrm{SrTiO}_{3}(001) 基底上时，四重对称 ${\mathrm{Bi}}_2{\mathrm{O}}_2\mathrm{Se}$${\mathrm{Bi}}_2{\mathrm{O}}_2\mathrm{Se}$Bi_(2)O_(2)Se\mathrm{Bi}_{2} \mathrm{O}_{2} \mathrm{Se} 薄膜的晶格取向被限制为沿基底的[100]/[010]方向排列，如图 2b 所示。这源于四方相薄膜与立方基底界面能各向异性引起的单轴取向锁定效应 ${}^{[50]}$${}^{[50]}$^([50]){ }^{[50]} 。值得注意的是，尽管对称中心材料系统中的对称匹配策略表现出普适性，但对于具有非对称表面重构或镜像对称破缺的复杂界面系统，其外延取向调控机制仍需进一步解耦界面势场分布与动态生长过程之间的非线性关联。

Preparation of TMDCs with non-centrosymmetric lattice structures faces the key challenge of compatibility between symmetric substrates and catalytic substrates, which has prompted researchers to explore novel substrate design strategies from an energy-modulation perspective. Crystal nucleation tends to occur at step edges rather than flat surfaces, which stems from the fact that step sites have the lowest interface
制备具有非中心对称晶格结构的 TMDCs 面临的关键挑战是对称基底与催化基底之间的兼容性，这促使研究人员从能量调控的角度探索新型基底设计策略。晶体成核倾向于发生在阶梯边缘而非平坦表面，这源于阶梯位点具有最低的界面能。
formation energy. By designing and processing substrates with controllable step structures, the unidirectional orientation of two-dimensional crystal domains can be effectively guided. kim et al. obtained Au (111), (110), and (100) crystal faces, providing a universal platform for the growth of materials with different symmetries ${}^{[51]}$${}^{[51]}$^([51]){ }^{[51]}. Liu et al. grew wafer-scale single-crystal monolayers of ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} with dual symmetry as shown in Figure $2{\mathrm{c}}^{[41]}$$2{\mathrm{c}}^{[41]}$2c^([41])2 \mathrm{c}^{[41]}. Wang et al. optimized the direction of miscutting of c-face sapphire to the a-axis, and successfully grew 2-inch single-crystalline ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} thin films, whose crystalline quality and electrical properties meet the standards for industrial applications, as shown in Figure $2{\mathrm{d}}^{[52]}$$2{\mathrm{d}}^{[52]}$2d^([52])2 \mathrm{~d}^{[52]}. Together, these results show that the step-edge-induced nucleation control and symmetry-breaking design based on step edges can break through the limitations of traditional centrosymmetric substrates on the intrinsic physical properties of materials.
形成能。通过设计和加工具有可控阶梯结构的衬底，可以有效引导二维晶体域的单向取向。Kim 等人获得了 Au (111)、(110) 和 (100) 晶面，提供了一个适用于不同对称性材料生长的通用平台 ${}^{[51]}$${}^{[51]}$^([51]){ }^{[51]} 。Liu 等人如图 $2{\mathrm{c}}^{[41]}$$2{\mathrm{c}}^{[41]}$2c^([41])2 \mathrm{c}^{[41]} 所示，生长了具有双重对称性的 ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} 晶圆级单晶单层。Wang 等人优化了 c 面蓝宝石相对于 a 轴的错切方向，成功生长了 2 英寸单晶 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 薄膜，其晶体质量和电学性能达到工业应用标准，如图 $2{\mathrm{d}}^{[52]}$$2{\mathrm{d}}^{[52]}$2d^([52])2 \mathrm{~d}^{[52]} 所示。这些结果表明，基于阶梯边缘的阶梯边缘诱导成核控制和对称性破缺设计，可以突破传统中心对称衬底对材料内在物理性质的限制。

This paper systematically describes the key role of substrate-assisted growth in CVD technology for the controlled preparation of two-dimensional materials at the wafer level. These advances not only reveal the mechanisms of substrate-material interface interactions on the regulation of nucleation kinetics at the atomic scale, but also promote the device-level integration of 2D semiconductors with topological insulators and other materials at the macroscopic scale. Through the synergistic thermodynamic optimal orientation and kinetic path design, substrate engineering provides innovative solutions for breaking through the mechanical transfer defects and realizing the large-scale preparation of high-performance 2D materials, which lays the foundation for its application in the future electronics and optoelectronics fields.
本文系统地描述了基底辅助生长在化学气相沉积（CVD）技术中对二维材料晶圆级可控制备的关键作用。这些进展不仅揭示了基底-材料界面相互作用在原子尺度上调控成核动力学的机制，还促进了二维半导体与拓扑绝缘体及其他材料在宏观尺度上的器件级集成。通过协同的热力学最优取向和动力学路径设计，基底工程为突破机械转移缺陷和实现高性能二维材料的大规模制备提供了创新解决方案，为其在未来电子学和光电子学领域的应用奠定了基础。
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Figure 2. Two-dimensional material epitaxial growth technology via substrate symmetry matching, interface energy optimization, and symmetry-breaking design. a) Lattice-guided growth of ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} NRs. Model of the aligned ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} NRs on a-sapphire. scanning electron microscope (SEM) image of the as-grown NRs. Distribution of the width versus the length of $\sim 150$$\sim 150$∼150\sim 150 NRs, measured by SEM. The color of the markers indicates the aspect ratio (L/W) of the given NR. AFM image of the as-grown NRs. High magnification AFM images of isolated narrow NRs, with widths down to $\sim 24$$\sim 24$∼24\sim 24 nm . Scale bar, 500 nm . SEM image ${}^{[49]}$${}^{[49]}$^([49]){ }^{[49]}. b) Characterization of single-crystal Cu (110) obtained by annealing an industrial Cu foil ${}^{[53]}$${}^{[53]}$^([53]){ }^{[53]}. c) Growth and characterization of single-crystal ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} monolayer on vicinal a-plane sapphire ${}^{[41]}$${}^{[41]}$^([41]){ }^{[41]}. d) Sapphire (0001) substrate and epitaxial relationship. Four possible edge configurations during the nucleation stage on the $\mathrm{C}/\mathrm{A}$$\mathrm{C}/\mathrm{A}$C//A\mathrm{C} / \mathrm{A} and $\mathrm{C}/\mathrm{M}$$\mathrm{C}/\mathrm{M}$C//M\mathrm{C} / \mathrm{M} substrates. Inset: AFM image of a sample at the early growth stage, showing that the nucleation is along the step edges. Scale bar, $500{\mathrm{nm}}^{[52]}$$500{\mathrm{nm}}^{[52]}$500nm^([52])500 \mathrm{~nm}^{[52]}.
图 2. 通过基底对称匹配、界面能量优化和破对称设计实现的二维材料外延生长技术。a) ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 纳米线的晶格引导生长。在 a-蓝宝石上的对齐 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 纳米线模型。生长后纳米线的扫描电子显微镜（SEM）图像。通过 SEM 测量的 $\sim 150$$\sim 150$∼150\sim 150 纳米线宽度与长度的分布。标记颜色表示给定纳米线的长宽比（L/W）。生长后纳米线的原子力显微镜（AFM）图像。孤立窄纳米线的高倍 AFM 图像，宽度低至 $\sim 24$$\sim 24$∼24\sim 24 纳米。比例尺，500 纳米。SEM 图像 ${}^{[49]}$${}^{[49]}$^([49]){ }^{[49]} 。b) 通过退火工业铜箔获得的单晶 Cu（110）表征 ${}^{[53]}$${}^{[53]}$^([53]){ }^{[53]} 。c) 在斜切 a 面蓝宝石上生长和表征单晶 ${\mathrm{WS}}_2$${\mathrm{WS}}_2$WS_(2)\mathrm{WS}_{2} 单层 ${}^{[41]}$${}^{[41]}$^([41]){ }^{[41]} 。d) 蓝宝石（0001）基底及外延关系。成核阶段在 $\mathrm{C}/\mathrm{A}$$\mathrm{C}/\mathrm{A}$C//A\mathrm{C} / \mathrm{A} 和 $\mathrm{C}/\mathrm{M}$$\mathrm{C}/\mathrm{M}$C//M\mathrm{C} / \mathrm{M} 基底上的四种可能边缘构型。插图：早期生长阶段样品的 AFM 图像，显示成核沿阶梯边缘进行。比例尺， $500{\mathrm{nm}}^{[52]}$$500{\mathrm{nm}}^{[52]}$500nm^([52])500 \mathrm{~nm}^{[52]} 。

Although step-guided epitaxy growth provides a promising approach for the synthesis of wafer-scale single-crystalline 2D materials with a single orientation, the need for meticulous substrate and inevitable transfer process pose challenges for
尽管阶梯引导外延生长为合成具有单一取向的晶圆级单晶二维材料提供了一种有前景的方法，但对基底的精细处理和不可避免的转移过程带来了挑战
commercial integrate circuits. To overcome these problems, a seed assisted technique was used for homogeneous epitaxial growth of large area 2D materials ${}^{[54]}$${}^{[54]}$^([54]){ }^{[54]}. Xu et al. successfully prepared 1 -inch single crystal $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} films by pre-implanting small area single crystal $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} seeds on the surface of polycrystalline $1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2{}^{[55]}$$1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2{}^{[55]}$1T^(')-MoTe_(2)^([55])1 \mathrm{~T}^{\prime}-\mathrm{MoTe}_{2}{ }^{[55]}. Figure 3a shows the schematic diagram of in-plane seed-induced epitaxy growth of wafer-scale single-crystalline 2 H MoTe 2 . Due to the abundance of Te vacancies in $1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2$$1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2$1T^(')-MoTe_(2)1 \mathrm{~T}^{\prime}-\mathrm{MoTe}_{2}, the continuous introduction of external Te atoms induces the phase transition and recrystallization of ${\mathrm{MoTe}}_2$${\mathrm{MoTe}}_2$MoTe_(2)\mathrm{MoTe}_{2} from 1 T ’ to 2 H . Meanwhile, a dense ${\mathrm{Al}}_2{\mathrm{O}}_3$${\mathrm{Al}}_2{\mathrm{O}}_3$Al_(2)O_(3)\mathrm{Al}_{2} \mathrm{O}_{3} film covers the wafer surface, with a small hole created in the seed area as the sole channel for Te atoms, preventing the spontaneous disorderly nucleation of $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} (Figure 3b). As the epitaxial growth of $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} is triggered by a pre-implanted single-crystal seed as the template and the growth process does not rely on the substrate structure, large-scale device arrays can be directly fabricated on the target substrate without an additional transfer process, thereby ensuring the integrity and electrical performance of the channel material. In addition, scalable single-crystalline 2D p-type $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} transistor arrays were fabricated using the similar epitaxial strategy, achieving high on-state currents $(\sim 7.8\mu \mathrm{A}/\mu \mathrm{m})$$(\sim 7.8\mu \mathrm{A}/\mu \mathrm{m})$(∼7.8 muA//mum)(\sim 7.8 \mu \mathrm{~A} / \mu \mathrm{m}) and on/off ratio $(\sim {10}^5)$$\left(\sim {10}^5\right)$(∼10^(5))\left(\sim 10^{5}\right), promoting the development of next-generation 2D electronics for both front and back-end applications ${}^{[56]}$${}^{[56]}$^([56]){ }^{[56]}. The traditional CVD preparation of large-area ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} typically requires prolonged processing times, posing significant barriers for industrial applications. Liu et al. have developed a novel two-dimensional Czochralski (2DCZ) growth method that enables seamless growth of centimeter-scale single-crystal ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} domains by constructing a two-dimensional liquid precursor film on a molten glass substrate and combining it with a rapid sulfidation process. This approach exploits the molten glass’s low nucleation barrier and surface tension to inhibit polycrystalline nucleation while promoting lateral crystallization, thereby achieving a grain-boundary-free single-crystal structure. Notably, the method achieves an ultrafast growth rate of up to $75\mu \mathrm{m}/\mathrm{s}$$75\mu \mathrm{m}/\mathrm{s}$75 mum//s75 \mu \mathrm{~m} / \mathrm{s} through rapid diffusion of the liquid-phase precursor, overcoming the critical limitation of conventional techniques in terms of processing efficiency (Figure 3c,d) ${}^{[57]}$${}^{[57]}$^([57]){ }^{[57]}. Han et. al fabricated centimeter-scale 2D ${\beta }^6$${\beta }^6$beta^(6)\beta^{6} - ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} films
商业集成电路。为了解决这些问题，采用了种子辅助技术进行大面积二维材料的均匀外延生长 ${}^{[54]}$${}^{[54]}$^([54]){ }^{[54]} 。Xu 等人通过在多晶 $1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2{}^{[55]}$$1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2{}^{[55]}$1T^(')-MoTe_(2)^([55])1 \mathrm{~T}^{\prime}-\mathrm{MoTe}_{2}{ }^{[55]} 表面预植入小面积单晶 $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} 种子，成功制备了 1 英寸单晶 $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} 薄膜。图 3a 显示了晶圆级单晶 2H MoTe2 的面内种子诱导外延生长示意图。由于 $1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2$$1{\mathrm{T}}^{\prime }-{\mathrm{MoTe}}_2$1T^(')-MoTe_(2)1 \mathrm{~T}^{\prime}-\mathrm{MoTe}_{2} 中 Te 空位丰富，持续引入外部 Te 原子诱导 ${\mathrm{MoTe}}_2$${\mathrm{MoTe}}_2$MoTe_(2)\mathrm{MoTe}_{2} 从 1T’相向 2H 相的相变和再结晶。同时，一层致密的 ${\mathrm{Al}}_2{\mathrm{O}}_3$${\mathrm{Al}}_2{\mathrm{O}}_3$Al_(2)O_(3)\mathrm{Al}_{2} \mathrm{O}_{3} 薄膜覆盖晶圆表面，种子区域形成一个小孔作为 Te 原子的唯一通道，防止了 $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} 的自发无序成核（图 3b）。由于 $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} 的外延生长是由预植入的单晶种子作为模板触发，且生长过程不依赖于衬底结构，因此可以直接在目标衬底上制造大规模器件阵列，无需额外的转移工艺，从而保证了通道材料的完整性和电性能。 此外，利用类似的外延策略制备了可扩展的单晶二维 p 型 $2\mathrm{H}-{\mathrm{MoTe}}_2$$2\mathrm{H}-{\mathrm{MoTe}}_2$2H-MoTe_(2)2 \mathrm{H}-\mathrm{MoTe}_{2} 晶体管阵列，实现了高开态电流 $(\sim 7.8\mu \mathrm{A}/\mu \mathrm{m})$$(\sim 7.8\mu \mathrm{A}/\mu \mathrm{m})$(∼7.8 muA//mum)(\sim 7.8 \mu \mathrm{~A} / \mu \mathrm{m}) 和开关比 $(\sim {10}^5)$$\left(\sim {10}^5\right)$(∼10^(5))\left(\sim 10^{5}\right) ，推动了下一代二维电子器件在前端和后端应用中的发展 ${}^{[56]}$${}^{[56]}$^([56]){ }^{[56]} 。传统的 CVD 制备大面积 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 通常需要较长的处理时间，这对工业应用构成了重大障碍。Liu 等人开发了一种新颖的二维 Czochralski（2DCZ）生长方法，通过在熔融玻璃基底上构建二维液态前驱体薄膜并结合快速硫化工艺，实现了厘米级单晶 ${\mathrm{MoS}}_2$${\mathrm{MoS}}_2$MoS_(2)\mathrm{MoS}_{2} 区域的无缝生长。该方法利用熔融玻璃的低成核势垒和表面张力抑制多晶成核，同时促进横向结晶，从而实现了无晶界的单晶结构。 值得注意的是，该方法通过液相前驱体的快速扩散，实现了高达 $75\mu \mathrm{m}/\mathrm{s}$$75\mu \mathrm{m}/\mathrm{s}$75 mum//s75 \mu \mathrm{~m} / \mathrm{s} 的超快生长速率，克服了传统技术在加工效率方面的关键限制（图 3c,d） ${}^{[57]}$${}^{[57]}$^([57]){ }^{[57]} 。Han 等人制造了厘米级的 2D ${\beta }^6$${\beta }^6$beta^(6)\beta^{6} - ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} 薄膜。
by introducing InSe seed crystals ${}^{[58]}$${}^{[58]}$^([58]){ }^{[58]}. Density functional theory (DFT) calculations reveal that when atoms are fully relaxed, the energy difference between $\beta$$\beta$beta\beta-phase and ${\beta }^{\prime }$${\beta }^{\prime }$beta^(')\beta^{\prime}-phase monolayer ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} monotonically increases with the rise in selenium vacancy concentration (Figure 3e). This indicates the ${\beta }^{\prime }$${\beta }^{\prime }$beta^(')\beta^{\prime}-phase is more stable under selenium-deficient conditions. Consequently, at elevated temperatures, $\beta$$\beta$beta\beta-InSe acts as a seed crystal, facilitating the nucleation of ${\beta }^{\prime }-{\mathrm{In}}_2{\mathrm{Se}}_3$${\beta }^{\prime }-{\mathrm{In}}_2{\mathrm{Se}}_3$beta^(')-In_(2)Se_(3)\beta^{\prime}-\mathrm{In}_{2} \mathrm{Se}_{3}. Benefited from controllable seed-induced epitaxy growth and phase-transition transfer methods, large -area synthesis of three phases of ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} was achieved (Figure 3f), rendering 2D ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\operatorname{In}_{2} \mathrm{Se}_{3} a promising candidate for memory transistors and heterophase junctions. Due to independence from highly modulated substrates, seed-induced epitaxy growth provides a promising way for integration of 2D materials with other function materials or architectures for the fabrication of integrated devices. In 2022, Pan et. al achieved a direct synthesis of heteroepitaxy of single-crystal 2 D MoTe 2 on highly lattice-mismatched substrates and 3D architectures ${}^{[59]}$${}^{[59]}$^([59]){ }^{[59]} (Figure 3g). As shown in Figure $1\mathrm{h},2\mathrm{H}-{\mathrm{MoTe}}_2$$1\mathrm{h},2\mathrm{H}-{\mathrm{MoTe}}_2$1h,2H-MoTe_(2)1 \mathrm{~h}, 2 \mathrm{H}-\mathrm{MoTe}_{2} single-crystal domains nucleated in the continuous polycrystalline 1 T ’ background and grew through in-plane seed-induced epitaxy process and across the 3D fin structures. Meanwhile, a wafer-scale p-n heterojunction array was fabricated on an n-type silicon substrate (Figure 3i), showing spatial uniformity of the electrical performance of the devices on a large scale.
通过引入 InSe 种子晶体 ${}^{[58]}$${}^{[58]}$^([58]){ }^{[58]} 。密度泛函理论（DFT）计算表明，当原子完全弛豫时， $\beta$$\beta$beta\beta 相和 ${\beta }^{\prime }$${\beta }^{\prime }$beta^(')\beta^{\prime} 相单层 ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} 之间的能量差随着硒空位浓度的增加单调上升（图 3e）。这表明 ${\beta }^{\prime }$${\beta }^{\prime }$beta^(')\beta^{\prime} 相在缺硒条件下更稳定。因此，在高温下， $\beta$$\beta$beta\beta -InSe 作为种子晶体，促进了 ${\beta }^{\prime }-{\mathrm{In}}_2{\mathrm{Se}}_3$${\beta }^{\prime }-{\mathrm{In}}_2{\mathrm{Se}}_3$beta^(')-In_(2)Se_(3)\beta^{\prime}-\mathrm{In}_{2} \mathrm{Se}_{3} 的成核。得益于可控的种子诱导外延生长和相变转移方法，实现了 ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\mathrm{In}_{2} \mathrm{Se}_{3} 三相的大面积合成（图 3f），使二维 ${\mathrm{In}}_2{\mathrm{Se}}_3$${\mathrm{In}}_2{\mathrm{Se}}_3$In_(2)Se_(3)\operatorname{In}_{2} \mathrm{Se}_{3} 成为存储晶体管和异相结的有前景候选材料。由于不依赖高度调制的衬底，种子诱导外延生长为二维材料与其他功能材料或结构的集成提供了有希望的途径，用于集成器件的制造。2022 年，Pan 等人实现了在高度晶格失配的衬底和三维结构 ${}^{[59]}$${}^{[59]}$^([59]){ }^{[59]} 上直接合成单晶二维 MoTe2 的异质外延（图 3g）。 如图 $1\mathrm{h},2\mathrm{H}-{\mathrm{MoTe}}_2$$1\mathrm{h},2\mathrm{H}-{\mathrm{MoTe}}_2$1h,2H-MoTe_(2)1 \mathrm{~h}, 2 \mathrm{H}-\mathrm{MoTe}_{2} 所示，单晶域在连续的多晶 1T'背景中成核，并通过面内种子诱导外延过程穿过三维鳍结构生长。同时，在 n 型硅衬底上制备了晶圆级 p-n 异质结阵列（图 3i），显示出器件电性能在大尺度上的空间均匀性。