Motion of etch defects on (0 0 1) Li₂B₄O₇ single crystal wafer

Three types of etch defects were observed on a (001) lithium tetraborate (Li₂B₄O₇:LB4) single crystal wafer. Type I appeared all over the +c plane taking a four-sided pyramidal shape. The etch defects on the -c plane were differentiated into two types; Type II corresponded to dislocation arrays and presented a four-sided pyramidal shape while Type III was distributed all over the -c plane, forming a eight-sided hillock. After annealing the wafer at 850 °C in several different atmospheres, the density of Types I and II did not change while that of Type III was reduced by two order of magnitude in the oxygen atmosphere. This might suggest that the formation mechanism of each of these defects was different and they showed the various motions for the thermal treatment.