A review of crystallographic textures in chemical vapor-deposited diamond films

Abstract

Diamond is one of the most important functional materials for film applications due to its extreme physical and mechanical properties, many of which depend on the crystallographic texture. The influence of various deposition parameters matters to the texture formation and evolution during chemical vapor deposition (CVD) of diamond films. In this overview, the texture evolutions are presented in terms of both simulations and experimental observations. The crystallographic textures in diamond are simulated based on the van der Drift growth selection mechanism. The film morphology and textures associated with the growth parameters α (proportional to the ratio of the growth rate along the〈100〉direction to that along the 〈111〉direction) are presented and determined by applying the fastest growth directions. Thick films with variations in substrate temperature, methane concentration, film thickness, and nitrogen addition were analyzed using high-resolution electron back-scattering diffraction (HR-EBSD) as well as X-ray diffraction (XRD), and the fraction variations of fiber textures with these deposition parameters were explained. In conjunction with the focused ion beam (FIB) technique for specimen preparation, the grain orientations in the beginning nucleation zones were studied using HR-EBSD (50 nm step size) in another two sets of thin films deposited with variations in methane concentration and substrate material. The microstructures, textures, and grain boundary character were characterized. Based on the combination of an FIB unit for serial sectioning and HR-EBSD, diamond growth dynamics was observed using a 3D EBSD technique, with which individual diamond grains were investigated in 3D. Microscopic defects were observed in the vicinity of the high-angle grain boundaries by using the transmission electron microscopy (TEM) technique, and the advances of TEM orientation microscopy make it possible to identify the grain orientations in nano-crystalline diamond.

Tunable Thermal Energy Transport across Diamond Membranes and Diamond–Si Interfaces by Nanoscale Graphoepitaxy

“…As a result, grains with (110) orientation are longer (wider) in the film thickness (cross-plane) direction than grains with (111) orientation. Similarly, it has been reported that the (110) grain orientation is a preferred grain orientation for CVD diamond growth under certain conditions. − As discussed above, these long (wide) grains scatter phonons less extensively in the cross-plane direction, resulting in longer phonon mean-free path and correspondingly higher thermal conductivity.…”

“…Similarly, it has been reported that the (110) grain orientation is a preferred grain orientation for CVD diamond growth under certain conditions. [62][63][64] As discussed above, long grains scatter phonons less extensively in the cross-plane direction, resulting in longer phonon mean free path and correspondingly higher thermal conductivity. To assess the cross-plane preferred grain orientation, Samples A1, B1, and ref1 were measured using XRD 2: scans.…”

Diamond/GaN HEMTs: Where from and Where to?

“…The size of the diamond grains is typically a few nm close to the substrate and increases with the thickness of the film. The evolution of the grain size has been studied computationally [171,172] and experimentally [173]; it has been shown that, depending on the growth conditions, the lateral size of the grains and their aspect ratio are strongly changing with the film thickness. As a consequence, the grain boundary density varies with the depth of the PCD layer, translating into an inhomogeneous κ in-plane .…”

Morphology and Structure Properties of Boron-doped Diamond Films Prepared by Hot Cathode Direct Current Plasma Chemical Vapor Deposition

“…In general, the deposited CVD films consisted primarily of (111) and (100) facets, depending on the growth velocity ratio of the <100> and <111> directions. It has been previously posited that substrate temperatures higher than 1170 K benefited the growth in the <100> direction while substrate temperatures lower than or equal to 1070 K benefited the growth in the <111> direction [8]. Experimental results of HCDC-PCVD were in keeping with that conclusion, considering the substrate temperature of 800 °C (1073 K) and the faceted grains which were dominated by the (111) texture as shown in Besides, there were ridges and steps oriented parallel to one other, manifesting twinning bands within the grains intersecting with the surface.…”