Large Diffraction-Grade Single Crystal Diamond for Applications at New Generation Synchrotron and FEL X-ray Sources

As the capabilities of synchrotron and free electron laser FEL) sources increase, so too do the technical requirements of materials utilized for the x-ray optics in these sources. Due to its low atomic number and extremely high thermal diffusivity, x-ray transparency, radiation resistance, and mechanical strength, diamond is an ideal material for synchrotron and FEL optics. However, improvement to crystalline quality are necessary in order to prevent distortion of the x-rays and subsequent loss of monochromaticity, flux or other desired beamline requirements. Single crystal silicon is most commonly used today due to its wide availability and high crystalline quality. However, the previously mentioned physical properties are far superior for diamond compared to that of silicon. Additionally, silicon optics need to be cryogenically cooled via liquid nitrogen, necessitating additional equipment complexity whereas diamond optics do not. The problem with diamond optics available today is that the crystalline quality remains too low for diffraction applications. This phase I project aims to develop a prototype process capable of manufacturing single crystal diamond optics of sufficient size and crystalline quality to meet the stringent requirements for an x-ray optic. To achieve these results a chemical vapor deposition process is proposed to grow diamond via traditional homoepitaxy and novel heteroepitaxial methods that iteratively improve the crystalline lattice until near-perfect lattice constants and quality are achieved. This will be achieved through reduction in impurities and thermal gradients during the growth process, resulting in lower stress and fewer defects in the final material. At the conclusion of Phase I, a single crystal diamond will be produced possessing a thermal conductivity of no less than 1800 W/m·K) with a size of at least 6x6x4mm^3. Development of pristine quality diamond bodies of significant size has great commercial potential in a wide range of areas. As an ultra-wide bandgap material, diamond LEDs have the potential to replace toxic and expensive mercury vapor lamps in water purification, as well as for deep-UV lithography for nano-scale device fabrication. Additionally, diamond has already proven to be a superior material for semiconductor substrates in high-frequency and high-power applications, including power infrastructure, communications and military radar. Diamond also has great potential for room- temperature quantum computing by exploiting NV centers within the diamond body. Due to high rigidity, diamond is also an ideal material for a number of MEMS devices, include SAW devices used for transmitting and receiving signals in mobile phones and other mobile devices.