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1. Band offset between cubic boron nitride and nitrogen-plasma terminated boron-doped diamond (111)

   https://doi.org/10.1063/5.0278816  

   Ebadi_Yekta, Ali; McCartney, Martha_R; Smith, David_J; Tokuda, Norio; Nemanich, Robert_J (October 2025, Applied Physics Letters)

   Diamond electronics has attracted attention for high power and high frequency device applications. Cubic boron nitride (c-BN) may be considered as a suitable dielectric layer for electron channel diamond metal–insulator–semiconductor field effect transistors (MISFETs) provided that its valence band edge can be positioned above that of diamond. This study reports experimental measurement of the valence band offset (VBO) between c-BN and nitrogen-plasma terminated boron-doped diamond (111). Nitrogen plasma processing was used to produce C–N bonding at the diamond surface. Electron cyclotron resonance plasma enhanced chemical vapor deposition was then used to deposit epitaxial c-BN films on the N-terminated diamond substrate, as confirmed by cross-sectional high-resolution electron microscopy. X-ray and ultraviolet photoemission spectroscopies indicated that the valence band maximum of c-BN is positioned 0.4 eV above that of diamond resulting in a type II staggered band alignment. This result is consistent with theoretical predictions of the VBO between the two materials in the (111) surface orientation, indicating that c-BN with C–N interface bonding can be used as a dielectric layer for electron channel diamond (111) MISFET devices. 

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2. Mechanical properties of cubic boron nitride and diamond at dynamical pressure and temperature

   https://doi.org/10.1063/5.0172885  

   Kastuar, Srihari M.; Liu, Zhong-Li; Najmaei, Sina; Ekuma, Chinedu E. (December 2023, Applied Physics Letters)

   We report the mechanical properties of cubic boron nitride (c-BN) and diamond under the combined impact of dynamical pressure and temperature, calculated using ab initio molecular dynamics. Our study revealed a pronounced sensitivity of the mechanical properties of c-BN to applied pressure. Notably, c-BN undergoes a brittle-to-ductile transition at ∼220 GPa, consistent across various dynamical temperatures, while diamond exhibits no such transition. Furthermore, the Vickers hardness profile for c-BN closely mirrors that of diamond across a spectrum of temperature–pressure conditions, highlighting c-BN's significant mechanical robustness. These results underscore the superior resilience and adaptability of c-BN compared to diamond, suggesting its potential as an ideal candidate for applications in extreme environments. 

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3. Nucleation of cubic boron nitride on boron-doped diamond via plasma enhanced chemical vapor deposition

   https://doi.org/10.1063/5.0145771  

   Brown, Jesse M.; Vishwakarma, Saurabh; Smith, David J.; Nemanich, Robert J. (June 2023, Journal of Applied Physics)

   Cubic boron nitride (c-BN), with a small 1.4% lattice mismatch with diamond, presents a heterostructure with multiple opportunities for electronic device applications. However, the formation of c-BN/diamond heterostructures has been limited by the tendency to form hexagonal BN at the interface. In this study, c-BN has been deposited on free standing polycrystalline and single crystal boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD), employing fluorine chemistry. In situ x-ray photoelectron spectroscopy (XPS) is used to characterize the nucleation and growth of boron nitride (BN) films as a function of hydrogen gas flow rates during deposition. The PECVD growth rate of BN was found to increase with increased hydrogen gas flow. In the absence of hydrogen gas flow, the BN layer was reduced in thickness or etched. The XPS results show that an excess of hydrogen gas significantly increases the percent of sp2 bonding, characteristic of hexagonal BN (h-BN), particularly during initial layer growth. Reducing the hydrogen flow, such that hydrogen gas is the limiting reactant, minimizes the sp2 bonding during the nucleation of BN. TEM results indicate the partial coverage of the diamond with thin epitaxial islands of c-BN. The limited hydrogen reaction is found to be a favorable growth environment for c-BN on boron-doped diamond. 

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4. Optical and acoustic phonons in turbostratic and cubic boron nitride thin films on diamond substrates

   https://doi.org/10.1016/j.diamond.2023.110452  

   Guzman, Erick; Kargar, Fariborz; Patel, Avani; Vishwakarma, Saurabh; Wright, Dylan; Wilson, Richard B; Smith, David J; Nemanich, Robert J; Balandin, Alexander A (December 2023, Diamond and Related Materials)
5. Cubic and hexagonal boron nitride phases and phase boundaries

   https://doi.org/10.1039/D4TC00039K  

   Biswas, Abhijit; Alvarez, Gustavo A; Tripathi, Manoj; Lee, Jonghoon; Pieshkov, Tymofii S; Li, Chenxi; Gao, Bin; Puthirath, Anand B; Zhang, Xiang; Gray, Tia; et al (February 2024, Journal of Materials Chemistry C)

   We used temperature-dependent spark plasma sintering to induce phase transformations of metastable 3D c-BN to mixed-phase 3D/2D c-BN/h-BN and ultimately to the stable 2D h-BN phase at high temperature, useful for extreme-temperature technology. 

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