Anisotropic damage mechanism in water-jet guided laser processing of CdZnTe single crystals

The inherent brittleness and thermal sensitivity of infrared semiconductor CdZnTe (CZT) present significant limitations for conventional laser micromachining. To overcome this limitation, we employed a water-jet guided laser (WJGL) for processing CZT wafers, leveraging the continuous water jet to dissipate heat and thereby suppressing adverse thermal effects. A comparison between measured and predicted kerf depth and width demonstrates a consistent increase with laser intensity, with deviations within 5 μm. Notably, Increasing the traverse speed reduces kerf width, depth, and taper by minimizing pulse overlap and heat accumulation, while higher laser intensity increases these dimensions. Moreover, Surface roughness decreases sharply above 15 mm/s, reaching values as low as 1 μm due to more efficient molten material ejection. Additionally, traverse speed has a greater effect on material removal rate and cutting efficiency than laser intensity. Higher speeds reduce total cutting time and enhance material removal. At a traverse speed of 30 mm/s, thermomechanical damage exhibits strong anisotropy. Specifically, the cut surface develops directional cracks, which are confined to the {110} cleavage planes of CZT, independent of the laser cutting path. These cracks extend up to 500 nm deep, and the surrounding area forms a polycrystalline structure due to rapid thermal cycles. These findings provide valuable insights into damage formation and establish a solid foundation for advancing WJGL technology in the precision fabrication of soft and brittle semiconductor materials.