Abstract <p>Single crystal diamond is a material of tremendous interest for a wide range of advanced applications due to its unmatched properties. Despite the potential of diamond-based devices, commercialization has been hindered by significant technological challenges, particularly the need for high-quality, technological-grade materials to fully realize their advantages. It is widely accepted that high-quality single crystal diamonds grown by MPCVD are classified as type IIa, meaning their nitrogen concentration is less than 1 ppm. In this study, an attempt was made to grow high-quality single crystal diamonds with nitrogen impurities below 1 ppm, using welding material to maintain the substrate temperature at the optimum growth temperature. The quality and nitrogen-related defects were evaluated by examining optical properties through Raman, UV–Vis, and FT-IR spectroscopy. Raman spectroscopy confirmed the presence of the pure diamond phase in the spectra of sample, peak was observed at 1332.5 cm^–1 with FWHM 1.5 cm^–1, while FT-IR spectroscopy confirms a nitrogen concentration of less than 1 ppm. UV–Vis spectroscopy at 502 nm revealed the presence of an H3 defect, quantified at 206 parts per billion (ppb). Our findings indicate strong dependency of controlled growth parameters over nitrogen concentrations during the synthesis process of single crystal diamonds.</p>