Fabrication of diamond drum resonators via laser engraving and Si wet etching for high precision temperature sensing

Diamond has attracted considerable attention in microelectromechanical systems (MEMS) due to its outstanding mechanical, thermal, and optical properties. We report here a novel strategy for facile fabrication of diamond drum resonators on silicon (Si) wafer for high precision temperature sensing. To accomplish this, nanodiamonds (NDs) colloids were first treated with cerium ammonium nitrate, a potent single-electron oxidant, to achieve a positive Zeta potential (+37 mV). The NDs seeds were then electrostatically adsorbed onto Si (100) wafer, followed by microwave plasma chemical vapor deposition (MPCVD) at 1103 K for 2 h. A continuous, pinhole-free diamond film with uniformly distributed residual stress (∼451 MPa) and low surface roughness (∼70 nm) was obtained. Diamond drum resonator was fabricated by a combination of laser engraving and wet chemical etching. Circular pattern of various diameters was first engraved onto the backside of the Si wafer using a 355 nm nanosecond pulse laser. Subsequent Si wet etching with 25 wt% KOH yielded square diamond drums of various sizes. We find that the etching process reduced the residual stress by 208 MPa, and enhance the SiV photoluminescence emission by 47 %. The drum resonators exhibit relatively high quality factors up to ∼2496 and high Young's modulus of ∼812 GPa, with a power sensitivity of 427 Hz/mW and a temperature sensitivity of 907 Hz/K (1396 ppm/K). This approach offers a rapid, cost-effective method for batch fabrication of diamond drum resonators on Si wafers.