Femtosecond laser-induced surface structuring for improved surface characteristics of single crystal diamond

Laser-induced periodic surface structures (LIPSS) were formed on a single crystal diamond using an ultrashort pulse femtosecond laser, enabling the modification of its surface characteristics and optical properties, thereby enhancing its functionality. A femtosecond laser operating at a central wavelength of 1035 nm, a pulse width of 275 fs, and a repetition rate of 0.5 kHz was used to create a highly periodic LIPSS structure on a single crystal diamond surface. The resulting LIPSS pattern exhibited a ripple periodicity of approximately 300-330 nm, which is smaller than the irradiation wavelength of the laser. The laser parameters for LIPSS were optimized to prevent the complete conversion of the diamond to the graphite phase. This process forms diffraction grating-like structures, which induce different colours as the light impinges onto the sample from various angles. The microstructural characterization of the LIPSS was studied using scanning electron microscopy and Raman spectroscopy. Raman spectroscopy revealed strong diamond peaks in the range between 1333.1 and 1334.5 cm-1 in the modified region, along with weaker non-diamond peaks in the range of 1559.22-1595.2 cm-1, indicating the presence of sp2-bonded carbon. The surface characteristics and the roughness of the modified surface were also studied using an atomic force microscopy technique. The studies showed an approximate 20 % increase in surface area with a surface roughness of around 42 nm on the modified diamond. Further, the wettability tests were also done on the patterned sample. The test showed that the contact angle decreased from 70 degrees to 44.7 degrees in the laser-irradiated regions, enhancing the hydrophilicity of the textured sample. The LIPSS-engineered diamond surfaces offer a versatile platform for applications such as biosensing, microfluidics, and advanced diagnostic techniques.