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Y 2 O 3 anti-reflection films were deposited on freestanding CVD diamond substrates by radio frequency magnetron sputtering. The thermal shock resistance and oxidation resistance of Y 2 O 3 /diamond/Y 2 O 3 samples at 727 °C and 800 °C in atmospheric air were investigated. No delamination of the Y 2 O 3 films occurred after thermal shock, thereby demonstrating extreme adhesion to freestanding diamond substrates. After thermal shock, Y atoms in the films were almost fully oxidized. Moreover, the majority of monoclinic phase in the Y 2 O 3 films transformed into cubic phase, crystallinity was enhanced, and the average grain size significantly increased. The maximum transmittance in the 8–12 μm long-wave IR range of the Y 2 O 3 /diamond/Y 2 O 3 samples increased from 81.3% ± 0.3% to 84.7% ± 0.2% and 83.6% ± 0.4%. These findings indicated that the Y 2 O 3 anti-reflection films displayed good resistance to thermal shock and provided sufficient protection for diamond substrates against elevated temperature oxidation. [ABSTRACT FROM AUTHOR]

The addition of titanium (Ti) interlayer was verified to reduce the residual stress of diamond films by self-fracturing and facilitate the harvest of a crack-free free-standing diamond film prepared by direct current (DC) arc plasma jet. In this study, the evolution of the Ti interlayer between large-area diamond film and substrate was studied and modeled in detail. The evolution of the interlayer was found to be relevant to the distribution of the DC arc plasma, which can be divided into three areas (arc center, arc main, and arc edge). The formation rate of titanium carbide (TiC) in the arc main was faster than in the other two areas and resulted in the preferred generation of crack in the diamond film in the arc main during cooling. Sandwich structures were formed along with the growth of TiC until the complete transformation of the Ti interlayer. The interlayer released stress via self-fracture. Avoiding uneven fragile regions that formed locally in the interlayer and achieving cooperatively released stress are crucial for the preparation of large crack-free diamond films. [ABSTRACT FROM AUTHOR]