Early studies have demonstrated the possibility of synthesizing diamonds at atmospheric pressure via halogen-assisted CVD [1,2]. This method enables diamond growth on a wide range of substrates at lower temperatures. In this talk, I will discuss our effort on revisiting the method reported over three decades ago towards a deeper understanding of reaction mechanisms and improving diamond growth. We use a thermal CVD process involving halogen-containing gases under ambient pressure. Reaction parameters were varied, including reaction time, temperature, gas composition, mixing ratios, flow rates, substrate, and seeding conditions. The samples are characterized to reveal the impact of reaction conditions on the composition, size, and morphology of the products. We observed the formation of crystals made of carbon and fluorine on substrates at lower temperature zones (300-700 °C). We also noted that higher hydrogen-to-carbon ratios in the gas mixture led to a lower amount of non-diamond carbon. We hypothesize that halogen atoms stabilize sp3-hybridized carbon, likely facilitating diamond formation. We are currently working on identifying the nature of those crystals, and investigating substrate and seeding effects to promote diamond nucleation and growth.