Sintered tantalum carbide coatings on graphite substrates: Highly reliable protective coatings for bulk and epitaxial growth

Abstract

Highly reliable low-cost protective coatings have been sought after for use in crucibles and susceptors for bulk and epitaxial film growth processes involving wide bandgap materials. Here, we propose a production technique for ultra-thick (50–200 μmt) tantalum carbide (TaC) protective coatings on graphite substrates, which consists of TaC slurry application and subsequent sintering processes, i.e., a wet ceramic process. Structural analysis of the sintered TaC layers indicated that they have a dense granular structure containing coarse grain with sizes of 10–50 μm. Furthermore, no cracks or pinholes penetrated through the layers, i.e., the TaC layers are highly reliable protective coatings. The analysis also indicated that no plastic deformation occurred during the production process, and the non-textured crystalline orientation of the TaC layers is the origin of their high reliability and durability. The TaC-coated graphite crucibles were tested in an aluminum nitride (AlN) sublimation growth process, which involves extremely corrosive conditions, and demonstrated their practical reliability and durability in the AlN growth process as a TaC-coated graphite. The application of the TaC-coated graphite materials to crucibles and susceptors for use in bulk AlN single crystal growth, bulk silicon carbide (SiC) single crystal growth, chemical vapor deposition of epitaxial SiC films, and metal-organic vapor phase epitaxy of group-III nitrides will lead to further improvements in crystal quality and reduced processing costs.

Simple and quick enhancement of SiC bulk crystal growth using a newly developed crucible material

“…We previously proposed highly reliable low-cost TaCcoated graphite materials prepared via a wet ceramic process, 12) which we call "SinTaC" (Sintered Tantalum carbide Coatings on graphite). Furthermore, we have already demonstrated their excellent reliability and durability under extremely corrosive AlN sublimation growth conditions.…”

“…Furthermore, we have already demonstrated their excellent reliability and durability under extremely corrosive AlN sublimation growth conditions. 12) Here, we demonstrate the use of SinTaC crucibles in SiC sublimation growth to evaluate their effectiveness. Promising results were obtained, especially in terms of the increases in the growth rate and size of the crystals.…”

High‐entropy yttrium pyrochlore ceramics with glass‐like thermal conductivity for thermal barrier coating application

“…Phase composition was analyzed by X‐ray diffraction (XRD, D/max 2200 PC, Rigaku, Tokyo, Japan) using Cu Ka radiation at the diffraction angles 2θ ranging from 10° to 90° with a scan speed of 4°/min. Some specimens and Si powders used as external standard were analyzed by XRD with a slow scan speed of 1°/min and a scan step of 0.02°, in order to perform Rietveld refinement by FullProf software and calculate the lattice strain by MDI Jade software (Version 6.5, Materials Data, Inc., USA) based on the Williamson–Hall (W‐H) equation: 44,45 $$\begin{equation}{\beta }_{hkl}\cos \theta = k\lambda /D + 4\sin \theta \end{equation}$$where β hkl is the peak full width at half maximum intensity (FWHM) excluding the instrumental FWHM, D , k , λ , and ε are crystallite size, shape factor, the wavelength of CuK α1 radiation, and lattice strain, respectively. The phases were further identified by Raman spectroscopy (Renishaw‐InVia, Renishaw, UK) with the 532 nm argon laser.…”

Non‐Polar a‐Plane AlN Growth on Nitrided r‐Plane Sapphire by Ga–Al Liquid‐Phase Epitaxy

“…AlN is a good candidate as a substrate material for AlGaN‐based DUV‐LEDs because of its high UV transparency, high thermal conductivity, and small lattice mismatch with AlGaN. A number of groups have fabricated bulk AlN single crystals through sublimation, alumina reduction, and solution growth using Li 3 N as a source material . Kumagai et al grew a homoepitaxial AlN layer by hydride vapor‐phase epitaxy (HVPE) on a bulk AlN substrate fabricated by sublimation.…”