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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2026
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2605.16583 |
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| _version_ | 1866913134166409216 |
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| author | Crites, Evan N. Mahatara, Sharad Hummel, Joshua R. Laywell, Sydney R. Raihan, Ahamed Gowda, Shivashree S. Scott, Ethan A. Thakur, Amitayush Jha McChesney, Jessica L. Hopkins, Patrick E. Chandrashekhar, MVS Spencer, Michael G. Lany, Stephan Kushwaha, Satya K. McQueen, Tyrel M. |
| author_facet | Crites, Evan N. Mahatara, Sharad Hummel, Joshua R. Laywell, Sydney R. Raihan, Ahamed Gowda, Shivashree S. Scott, Ethan A. Thakur, Amitayush Jha McChesney, Jessica L. Hopkins, Patrick E. Chandrashekhar, MVS Spencer, Michael G. Lany, Stephan Kushwaha, Satya K. McQueen, Tyrel M. |
| contents | Incorporation of $\mathrm{Al_{y}Ga_{1-y}N}$ (AGN) semiconductors into high power electronics offers efficiency improvements in power transmission, generation, and use, if approaches to eliminate the defects arising from film-lattice mismatch can be established. Here, we report the optical floating zone crystal growth of $\mathrm{Ta_{1-x}Hf_{x}C_{0.5}}$ (x = 0.2), a new metallic substrate material family lattice matched to the ultra-wide-band-gap, Al-rich side (y = 0.91) of the AGN solid solution. Laue diffraction demonstrates large single crystal domains in the as-grown boule. Single crystal x-ray diffraction at T = 213 K in conjunction with first principles calculations shows that the material adopts a layered crystal structure with AA-type stacking of (Ta/Hf)-C-(Ta/Hf) trilayers described in the trigonal space group P-3m1 (#164), with a = 3.1168(4) Å, c = 4.9644(4) Å, and $β$ = 120.0°. X-ray photoelectron spectroscopy (XPS) measurements show the Hf:Ta ratio to be close to the nominal value of 0.8:0.2 in the grown crystal. Density Functional Theory calculations reveal that this structure is stabilized by the low energy of carbon-vacancy formation of a hypothetical $\mathrm{(Ta/Hf)_{1}C_{1}}$ anti-NiAs structure type, and imply flexibility in interface structure with an overlayer nitride film. A surface preparation/polishing procedure is developed that reduces root mean square (RMS) surface roughness from as-cut 130 nm to 7 nm as measured by atomic force microscopy. Scanning electron microscopy shows the presence of a native surface oxide, removed by polishing, along with carbon-rich pits. Time-domain thermoreflectance measurements show a room temperature thermal conductivity of $κ$ = 18.1(4) W m-1 K-1. These results provide key first steps for utilizing metallic, lattice matched, substrates for the growth of Al-rich AGN semiconductors. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_16583 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Crystal growth and characterization of the ultra-high temperature substrate $\mathrm{Ta_{1-x}Hf_{x}C_{0.5}}$ Crites, Evan N. Mahatara, Sharad Hummel, Joshua R. Laywell, Sydney R. Raihan, Ahamed Gowda, Shivashree S. Scott, Ethan A. Thakur, Amitayush Jha McChesney, Jessica L. Hopkins, Patrick E. Chandrashekhar, MVS Spencer, Michael G. Lany, Stephan Kushwaha, Satya K. McQueen, Tyrel M. Materials Science Incorporation of $\mathrm{Al_{y}Ga_{1-y}N}$ (AGN) semiconductors into high power electronics offers efficiency improvements in power transmission, generation, and use, if approaches to eliminate the defects arising from film-lattice mismatch can be established. Here, we report the optical floating zone crystal growth of $\mathrm{Ta_{1-x}Hf_{x}C_{0.5}}$ (x = 0.2), a new metallic substrate material family lattice matched to the ultra-wide-band-gap, Al-rich side (y = 0.91) of the AGN solid solution. Laue diffraction demonstrates large single crystal domains in the as-grown boule. Single crystal x-ray diffraction at T = 213 K in conjunction with first principles calculations shows that the material adopts a layered crystal structure with AA-type stacking of (Ta/Hf)-C-(Ta/Hf) trilayers described in the trigonal space group P-3m1 (#164), with a = 3.1168(4) Å, c = 4.9644(4) Å, and $β$ = 120.0°. X-ray photoelectron spectroscopy (XPS) measurements show the Hf:Ta ratio to be close to the nominal value of 0.8:0.2 in the grown crystal. Density Functional Theory calculations reveal that this structure is stabilized by the low energy of carbon-vacancy formation of a hypothetical $\mathrm{(Ta/Hf)_{1}C_{1}}$ anti-NiAs structure type, and imply flexibility in interface structure with an overlayer nitride film. A surface preparation/polishing procedure is developed that reduces root mean square (RMS) surface roughness from as-cut 130 nm to 7 nm as measured by atomic force microscopy. Scanning electron microscopy shows the presence of a native surface oxide, removed by polishing, along with carbon-rich pits. Time-domain thermoreflectance measurements show a room temperature thermal conductivity of $κ$ = 18.1(4) W m-1 K-1. These results provide key first steps for utilizing metallic, lattice matched, substrates for the growth of Al-rich AGN semiconductors. |
| title | Crystal growth and characterization of the ultra-high temperature substrate $\mathrm{Ta_{1-x}Hf_{x}C_{0.5}}$ |
| topic | Materials Science |
| url | https://arxiv.org/abs/2605.16583 |