| 摘要 |
PURPOSE:To calculate the density of impurities indicating excitation of a non- harmonic vibration element, by measuring an elastic constant of a crystal sample at a low temperature for which effect of non-harmony of a lattice vibration can be ignored to be compared with an elastic constant of a highly pure semiconductor. CONSTITUTION:A measuring bar 5 having a sample measuring box 4 at the lower end thereof is inserted into a liquid helium tank 13 made up of three low-temperature tanks of a low-temperature cryostal 1. When a pulse signal from a pulse generator 31 is applied, a transducer 31a generates an ultrasonic vibration by piezoelectric effect and causes one end of a crystal sample 2 in the sample measuring box 4 to vibrate. A transducer 32a converts the ultrasonic vibration transmitted to the other end of the crystal sample 2 into an electrical pulse and a sound velocity of the ultrasonic pulse transmitted through the crystal sample 2 is measured with an ultrasonic pulse detector 32. An elastic coefficient is calculated from the sound velocity to be compared with an elastic coefficient of a highly pure crystal thereby calculating the density of inpurities in the crystal sample. |
