CZT sub-surface damage assessment using electrical leakage measurements

Electrical measurements of sidewall leakage are used to quantify the degree of sub-surface damage created by cutting CZT. High leakage is found at freshly cut surfaces but not at control surfaces. Dramatic reduction of leakage is demonstrated by subsequent polishing of cut sidewall surfaces to a point matching the control surfaces. CZT parts were cut using outer-diameter saw (OD), wire saw and laser machining methods. An important practical finding is that laser machined surfaces can achieve low leakage performance by the appropriate surface processing, in spite of large initial subsurface damage level. This is of interest, because the laser method provides a random-access cutting capability, whereas wire saw and OD cutting is restricted to linear directional cuts. A comparison of roughness and surface morphology imply differences in the otherwise unseen sub-surface damage that are characteristic of the machining process methods. Leakage measurements with step-wise polishing trials are used to test the depth to which cutting damage extends into the crystal.