Bansal Anushka, Hilse Maria, Huet Benjamin, Wang Ke, Kozhakhmetov Azimkhan, Kim Ji Hyun, Bachu Saiphaneendra, Alem Nasim, Collazo Ramon, Robinson Joshua A, Engel-Herbert Roman, Redwing Joan M
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
2D Crystal Consortium─Materials Innovation Platform, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
ACS Appl Mater Interfaces. 2021 Nov 17;13(45):54516-54526. doi: 10.1021/acsami.1c14591. Epub 2021 Nov 8.
A comparison of hexagonal boron nitride (hBN) layers grown by chemical vapor deposition on -plane (0001) versus -plane (112̅0) sapphire (α-AlO) substrate is reported. The high deposition temperature (>1200 °C) and hydrogen ambient used for hBN deposition on sapphire substantially alters the -plane sapphire surface chemistry and leaves the top layer(s) oxygen deficient. The resulting surface morphology due to H etching of -plane sapphire is inhomogeneous with increased surface roughness which causes non-uniform residual stress in the deposited hBN film. In contrast to -plane, the -plane of sapphire does not alter substantially under a similar high temperature H environment, thus providing a more stable alternative substrate for high quality hBN growth. The E Raman mode full width at half-maximum (FWHM) for hBN deposited on -plane sapphire is 24.5 ± 2.1 cm while for hBN on -plane sapphire is 24.5 ± 0.7 cm. The lesser FWHM standard deviation on -plane sapphire indicates uniform stress distribution across the film due to reduced undulations on the surface. The photoluminescence spectra of the hBN films at 300 and 3 K, obtained on -plane and -plane sapphire exhibit similar characteristics with peaks at 4.1 and 5.3 eV reported to be signature peaks associated with defects for hBN films deposited under lower V/III ratios. The dielectric breakdown field of hBN deposited on -plane sapphire was measured to be 5 MV cm, agreeing well with reports on mechanically exfoliated hBN flakes. Thus, under the typical growth conditions required for high crystalline quality hBN growth, -plane sapphire provides a more chemically stable substrate.
本文报道了通过化学气相沉积法在面（0001）和面（112̅0）蓝宝石（α - Al₂O₃）衬底上生长的六方氮化硼（hBN）层的比较。用于在蓝宝石上沉积hBN的高沉积温度（>1200°C）和氢气环境会显著改变面蓝宝石的表面化学性质，并使顶层缺氧。由于面蓝宝石的H蚀刻导致的表面形态不均匀，表面粗糙度增加，这会在沉积的hBN薄膜中产生不均匀的残余应力。与面相比，蓝宝石的面在类似的高温H环境下基本不变，因此为高质量hBN生长提供了更稳定的替代衬底。沉积在面蓝宝石上的hBN的E拉曼模式半高宽（FWHM）为24.5±2.1 cm⁻¹，而沉积在面蓝宝石上的hBN的E拉曼模式半高宽为24.5±0.7 cm⁻¹。面蓝宝石上较小的FWHM标准偏差表明由于表面起伏减少，薄膜上的应力分布均匀。在面和面上的蓝宝石上获得的hBN薄膜在300 K和3 K时的光致发光光谱具有相似的特征，峰值分别为4.1和5.3 eV，据报道这些峰值是与在较低V/III比下沉积的hBN薄膜中的缺陷相关的特征峰。测量沉积在面蓝宝石上的hBN的介电击穿场为5 MV/cm，与关于机械剥离的hBN薄片的报道非常吻合。因此，在高质量hBN生长所需的典型生长条件下，面蓝宝石提供了一种化学性质更稳定的衬底。
