Abstract
This paper investigates the formation and propagation of defects in the heteroepitaxial growth of single-crystal diamond with a thick film achieving 500 µm on Ir (001)/Al2O3 substrate. The growth of diamond follows the Volmer–Weber mode, i.e., initially shows the islands and subsequently coalesces to closed films. The films’ strain imposed by the substrate gradually relaxed as the film thickness increased. It was found that defects are mainly located at the diamond/Ir interface and are then mainly propagated along the [001] direction from the nucleation region. Etching pits along the [001] direction formed by H2/O2 plasma treatment were used to show defect distribution at the diamond/Ir/Al2O3 interface and in the diamond bulk, which revealed the reduction of etching pit density in diamond thick-film surface. These results show the evident impact of the thickness on the heteroepitaxially grown diamond films, which is of importance for various device applications.
Highlights
Diamond is a promising material for high power and high frequency electronic devices owing to its excellent material properties, e.g., ultra-wide band gap (5.5 eV), high thermal conductivity (2200 W/m·K), high breakdown voltage (107 V/cm), high electron and hole mobility (4500 cm2 /V·s and 3800 cm2 /V·s), and low dielectric constant (5.7) [1,2,3,4,5].Heteroepitaxially grown single-crystal diamond is considered a promising method for realizing large-area diamond substrate [6]
Transmission electron microscope (TEM) is used to observe the cross-section of the diamond/Ir (001) interface which is fabricated by FIB
The diamond film formed a complete closed film as shown in Figure 1d, which provided a precondition for the thick-film growth of S5
Summary
Diamond is a promising material for high power and high frequency electronic devices owing to its excellent material properties, e.g., ultra-wide band gap (5.5 eV), high thermal conductivity (2200 W/m·K), high breakdown voltage (107 V/cm), high electron and hole mobility (4500 cm2 /V·s and 3800 cm2 /V·s), and low dielectric constant (5.7) [1,2,3,4,5]. Grown single-crystal diamond is considered a promising method for realizing large-area diamond substrate [6]. Heteroepitaxial diamond on Ir/Al2 O3 substrates has been performed by MPCVD (microwave plasma chemical vapor deposition) with different thickness. Methods such as scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray diffraction (XRD) are introduced to analyze the morphology and crystallinity of initial diamond growth. It is clear that the etching pit density at the diamond/Ir interface is larger due to lattice mismatch. With the increase in film thickness, the diamond is coalesced to the closed film combined with strain relaxation so that the etching pit density reduces a lot. This research could provide important evidence for the understanding of the dislocation distribution of heteroepitaxial diamond thick films, both at the interface and in the film bulk
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