By applying a new quenching method, we determined the formation energy of:v
acancies in high-purity silicon. Specimens were heated in H-2 gas at high t
emperatures for 1 h followed by quenching in water. By this method, vacanci
es are quenched in the form of complexes with hydrogen and the vacancy form
ation energy can be determined from the quenching temperature dependence of
the intensity of the optical absorption peak due to the complexes. The vac
ancy formation energy of silicon was determined to be about 4.0 eV. This va
lue is in good agreement with results of recent theoretical calculation.