Density functional theory analysis and novel green chemical mechanical polishing for potassium dihydrogen phosphate

Potassium dihydrogen phosphate (KDP) has recently emerged as a promising candidate for the frequency con-verter and giant laser. Despite the great efforts to process the ultra-smooth surface of KDP, it is still elusive to remove the flaws precisely, resulting in fatal defects, such as cracks, dissolved cave and embedded grits, inducing the low performance of devices. In this study, a novel green chemical mechanical polishing (CMP) was developed for KDP, consisting of silica, graphene oxide, ethylene glycol and triethanolamine. The CMP developed effec-tively avoids the defects to KDP. Graphene oxide in slurry promotes the formation of complexes on KDP, which is proved by X-ray photoelectron spectroscopy and infrared Fourier transformation. The experimental results are in good agreement with those of density functional theory calculations using successive O-P bonds. Using the novel CMP, surface roughness Ra of 0.66 nm is achieved with a scanning area of 70 x 50 mu m2, and the thickness of damaged layer is 18.27 nm. To the best of our knowledge, this is the lowest surface roughness on KDP after CMP under such a large area of measurement. These findings provide a new pathway to fabricate sub-nanometer ultrasmooth surface of KDP with soft-brittle, deliquescent and temperature-sensitive characteristics.