Epitaxial growth of homogeneous single-crystalline AlN films on single-crystalline Cu (111) substrates

• Published in: Applied surface science Vol. 294; pp. 1 - 8
• Main Authors: Wang, Wenliang, Yang, Weijia, Liu, Zuolian, Lin, Yunhao, Zhou, Shizhong, Qian, Huirong, Gao, Fangliang, Yang, Hui, Li, Guoqiang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.03.2014
• Subjects: Atomic force microscopy; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cracks; Cross-disciplinary physics: materials science; rheology; Ellipsometry; Epitaxial growth; Exact sciences and technology; High resolution; Lasers; Physics; Single crystals; Substrates; AlN; Inorganic compounds; Semiconductor materials; Laser rastering program; Epitaxy; Hetero-interfaces; Aluminium nitride; Pulsed laser deposition; Cu substrates; Film growth
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.12.179

The homogeneous and crack free single-crystalline AlN thin films have been epitaxially grown on single-crystalline Cu (111) substrates with an in-plane alignment of AlN [11-20]//Cu [1-10] by pulsed laser deposition (PLD) technology with an integrated laser rastering program. The as-grown AlN films are studied by spectroscopic ellipsometry, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), polarized light microscopy, high-resolution X-ray diffraction, and high-resolution transmission electron microscopy (HRTEM). The spectroscopic ellipsometry reveals the excellent thickness uniformity of as-grown AlN films on the Cu (111) substrates with a root-mean-square (RMS) thickness inhomogeneity less than 2.6%. AFM and FESEM measurements indicate that very smooth and flat surface AlN films are obtained with a surface RMS roughness of 2.3nm. The X-ray reflectivity image illustrates that there is a maximum of 1.2nm thick interfacial layer existing between the as-grown AlN and Cu (111) substrates and is confirmed by HRTEM measurement, and reciprocal space mapping shows that almost fully relaxed AlN films are achieved only with a compressive strain of 0.48% within 321nm thick films. This work demonstrates a possibility to obtain homogeneous and crack free single-crystalline AlN films on metallic substrates by PLD with optimized laser rastering program, and brings up a broad prospect for the application of acoustic filters that require abrupt hetero-interfaces between the AlN films and the metallic electrodes.