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1. Analysis of surface integrity of orthogonal diamond cut single-crystal Calcium Fluoride for ultraviolet and vacuum ultraviolet wavelength applications

   Rickens, Kai; Riemer, Oltmann; Lucca, Don A. (June 2020, Proceedings of the 20th euspen International Conference and Exhibition)

   Single-crystal calcium fluorite (CaF2) is widely used for transmissive optics in ultraviolet and vacuum ultraviolet (UV and VUV) wavelength applications because of its exceptional transmission performance. Generally, products using CaF2 are manufactured through finishing processes such as chemo-mechanical polishing (CMP), magnetorheological finishing (MRF) or ion-beam figuring (IBF) after performing precision cutting and grinding processes for profiling. However, CaF2 is known as a brittle material with high anisotropy, and subsurface damage is induced by each cutting process. But, the effects of surface integrity on the optical and functional performance of precision machined CaF2 has not been reported yet. In this research, a newly developed multiaxial adjustment system that can precisely align specimens is used in single-axis orthogonal cutting experiments with zero degree and negative rake angle diamond radius tools to prevent pre-machining and thus pre-damaging of single-crystal CaF2 specimens. Cutting forces evaluation via piezoelectric dynamometer acquisition as well as surface analysis by atomic force microscopy and white light microscopy has been performed. Finally, smooth surfaces due to ductile material removal mechanisms could be determined on all machined specimen surfaces. 

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2. Influence of hydrogen and oxygen surface termination on the mechanism of sub-bandgap photoelectron emission from diamond(111) into vacuum and into water

   https://doi.org/10.1016/j.diamond.2025.112011  

   Saucedo, Cesar; Rieders, Nathaniel; Hamers, Robert J (January 2025, Diamond and Related Materials)

   Wide-bandgap semiconductors have unique electron emission properties by virtue of having high-lying conduction bands. Among these, diamond stands out because of its chemical stability, allowing it to serve as a solid-state electron source in vacuum and non-vacuum environments, including water. However, the underlying mechanisms of electron emission are not well understood. Here, we report investigations of the mechanisms of electron emission from H-terminated and oxidized surfaces of single-crystal boron-doped diamond(111) in vacuum and in water using both sub-bandgap (4.75 eV and 3.05 eV) and above-bandgap (21.2 eV) excitation. Energy-resolved photoemission spectra in vacuum using different incident photon energies reveal two distinct energy distributions, reflecting different emission pathways. While oxidation greatly reduces electron emission into vacuum using both sub-bandgap and above-bandgap sources, facile electron emission into water persists on the oxidized samples using sub-bandgap excitation and is directly observed through transient optical absorption measurements using sub-bandgap excitation. Low-energy inverse photoemission spectroscopy shows that oxidation leads to broad distribution of surface states throughout the diamond bandgap. Our studies highlight 

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3. Development of a manual multi-axes workpiece adjustment system for ultraprecision diamond machining

   Shizuka, H.; Rickens, K.; Riemer, O.; Lucca, D.A. (July 2019, Proc. 19th Int. Conference & Exhibition of the European Society for Precision Engineering & Nanotechnology)

   This paper describes the development and performance evaluation of a manual multi-axes workpiece adjustment system for ultra-precision diamond machining that is capable of holding a CaF2 specimen with high positioning accuracy without pre-machining. Experiments revealed that the specimen alignment system developed in this study has sub-micrometer adjustment resolution and demonstrates a stiffness that can withstand diamond cutting forces. Applying this system to diamond cutting of CaF2 produced an error of nominal cut thickness of at most 10 nm on both ends of the 10.5 mm cutting length and achieved a defect-free finished surface. 

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4. Curvature polishing for light-weight, thin reflective optics

   https://doi.org/10.1117/12.2691385  

   Romer, Nikolas; Kuhn, Jeff R; Rolland, Jannick P (November 2023, Joint poster session at Optica Design and Fabrication)

   DeGroote_Nelson, Jessica; Unger, Blair L (Ed.)

   Traditional optical manufacturing techniques such as abrasive polishing and diamond turning create precise surfaces by removing material from the optical surface of a mirror. Such techniques often require many cycles of removal and metrology and can leave surface roughness or tool marks that negatively affect the straylight properties of an optical system. These residual artifacts often necessitate expensive postprocessing such as ion beam finishing. Limiting straylight is particularly crucial in the design of reflecting coronagraphs or optical systems that are sensitive to scattered light, for example for exoplanet detection, where even low-level scattering can degrade contrast ratios below the sensitivity needed to detect exoplanets. We introduce a non-contact method for shaping thin front-surface mirrors to avoid tool artifacts. Using laser techniques to alter local surface stresses, we deterministically introduce ≥ 8 waves (632.8 nm) of shape to 2 mm thick substrates. A deterministic method for creating arbitrary surface figures is under development and calibration. 

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5. Ion‐Implantation, Epilayer Growth, and Lift‐Off of High‐Quality Diamond Films

   https://doi.org/10.1002/adfm.202423174  

   Zhang, Xiang; Pieshkov, Tymofii_S; Chen, Di; Nonis, Suresh; Ngan, Kinfung; Oliveira, Eliezer_F; Gray, Tia; Biswas, Abhijit; Puthirath, Anand_B; Pate, Bradford_B; et al (April 2025, Advanced Functional Materials)

   Abstract The development of high‐quality diamond films is pivotal for driving advances in quantum technology, power electronics, and thermal management. The ion implantation and lift‐off technique has emerged as a crucial method for fabricating diamond films with controlled thickness and scalable production of large‐area diamond wafers. This study advances the understanding of critical interface dynamics during diamond epilayer growth on ion‐implanted commercial diamond substrates. Leveraging high‐resolution cross‐sectional electron microscopy and spectroscopic analyses, the direct transformation of the damaged diamond layer is revealed into a graphitic layer during epilayer overgrowth, eliminating the need for high‐temperature annealing. Raman and photoluminescence spectroscopy mappings along the side section highlight the exceptional quality and purity of the epilayer, showcasing nitrogen‐vacancy center densities comparable to electronic‐grade diamond, making it highly suitable for quantum and electronic applications. Finally, the epilayer detaches efficiently via electrochemical etching, leaving a substrate with low surface roughness that is reusable for multiple growth cycles. These results provide valuable insights into refining the ion implantation and lift‐off process, bridging critical gaps in interface evolution, and establishing a foundation for sustainable, high‐performance diamond films across diverse technological applications. 

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