Microwave hydrogen plasma etching on the laser-cut surface of single crystal diamond: Phases, etching morphology, stress evolution and the effect of etching on the subsequent homoepitaxial growth

In order to improve the pretreating efficiency of single crystal diamond (SCD) before its homoepitaxial growth, a strategy coupling laser cutting and microwave hydrogen plasma etching was proposed to replace the traditional pretreatment steps, which underwent laser cutting, mechanical polishing, acid cleaning, and microwave plasma etching in order. The feasibility of this idea has been studied by growing SCD after directly etching its laser-cut surface using microwave hydrogen plasma. The effect of the etching time on the SCD including surface phase, etching morphology, etching pit shape, residual stress, growth morphology, and quality of SCD are investigated and analyzed. The results show that microwave hydrogen plasma etching can quickly (within 10 min) remove the residual graphite carbon on the SCD surface caused by laser cutting. The extension of the etching time mainly affects the surface morphology and the internal stress of SCD. Etching pits with different shapes (square, trapezoid, inverted pyramid) and sizes can be found on the hydrogen plasma etched surface under different etching times. Fortunately, these etching pits do not introduce polycrystals on the SCD during subsequent homoepitaxial growth. All the hydrogen plasma etched laser cut SCD samples exhibit typical step-flow growth morphology after 20 h of homoepitaxial growth. Moreover, the step-flows are orderly and parallel, which is better than the disorderly step-flows on the polished SCD. Besides, a higher growth quality and a lower residual stress are obtained for the etched SCD. The above results indicate that replacing the traditional complex pretreatment steps with laser cutting and etching pretreatment is feasible. The new approach can effectively improve the pretreatment efficiency and result in superior quality of SCD after homoepitaxial growth.