Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS) , Suzhou 215123, P. R. China.
Suzhou Nanowin Science and Technology Co., Ltd. , Suzhou 215123, P. R. China.
ACS Appl Mater Interfaces. 2017 Dec 20;9(50):44001-44009. doi: 10.1021/acsami.7b14494. Epub 2017 Dec 11.
"Volmer-Weber" island nucleation and step-flow growth model are the classical processes of the conventional epitaxy of films. However, a growth model of van der Waals epitaxy (vdWE) of films is still not very well-documented. Here, we present an example of vdWE of AlN films on multilayer graphene (MLG)/SiC by hydride vapor phase epitaxy at a high temperature of 1100 °C and reveal the orientation relationship of AlN, MLG, and SiC as (0001)[1-100]||(0001)[1-100]||(0001)[11-20], which suggests that the vdWE heterointerface is not an usual covalent bond and no excessive strain during the growth process owing to the incommensurate in-plane lattices. Remarkably, zigzag cracks are formed because of the anisotropy of strain after the films are cooled down to room temperature, indicating that the growth model of vdWE is different from that of conventional epitaxy. It is a layer-by-layer epitaxy, and a planar substrate without a miscut angle is essential for obtaining single-crystalline films. Additionally, the films can be transferred to foreign substrates by direct mechanical exfoliation without any stressor layer. An ultraviolet photosensor device illustrates an example of III-nitride heterogeneous integration application. Our work demonstrates an excellent step toward the vdWE of varieties of compound films on 2D materials for the applications of transferrable heterogeneous integration in future.
“Volmer-Weber”岛状成核和阶跃流生长模型是传统薄膜外延的经典过程。然而，范德华外延（vdWE）的薄膜生长模型仍然没有得到很好的记录。在这里，我们通过高温（1100°C）的氢化物气相外延展示了多层石墨烯（MLG）/SiC 上 AlN 薄膜的 vdWE 示例，并揭示了 AlN、MLG 和 SiC 的取向关系为（0001）[1-100]||（0001）[1-100]||（0001）[11-20]，这表明 vdWE 异质界面不是通常的共价键，并且由于面内晶格失配，在生长过程中没有过度的应变。值得注意的是，由于应变的各向异性，薄膜冷却到室温后会形成锯齿状裂纹，表明 vdWE 的生长模型与传统外延不同。它是一种逐层外延，具有平面衬底且没有偏角对于获得单晶薄膜是必不可少的。此外，通过直接机械剥落可以将薄膜转移到外国衬底上，而无需任何应变量层。一个紫外光传感器器件说明了 III 族氮化物异质集成应用的一个例子。我们的工作展示了在二维材料上外延各种化合物薄膜的 vdWE 的一个很好的进展，为未来可转移的异质集成应用铺平了道路。
