Iwase Y, Uedono A, Tanigawa S, Suzuki T
Radioisotopes. 1985 Apr;34(4):195-200. doi: 10.3769/radioisotopes.34.4_195.
The precision measurement system of the Doppler broadening profiles of positron annihilation radiations using a simultaneous and comparative detection technique has been developed and was applied to the study of grown-in defects in indium phosphide (InP). Annihilation energy spectra in the specimen to be examined and in a standard one were simultaneously measured by a single pure Ge detector. Each specimen incorporated a 22Na positron source in a sandwiched form between two identical samples. The colinear directional correlation of two photon annihilation allows us to route the output of ADC (analogue to digital converter) to different memory sections. For the purpose of discrimination which source emitted the analysed gamma ray, two auxiliary NaI(Tl) detectors were used. Such a simultaneous and comparative measurement was found to be free of drift in electronics during the course of experiments over 10 weeks. Furthermore, the coincidence measurement reduced the background due to 1.28 MeV prompt gamma rays. This technique was applied to the detection of a positional distribution of grown-in defects in an InP wafer, which was slivered along a plane involving growth axis from the single crystal ingot grown by a liquid encapsulated Czochralski technique. The narrowing of Doppler broadening profiles was observed at the center and at the periphery of the wafer. This result well resembles the positional distribution of dislocations observed by the etch pit counting.
采用同步比较探测技术的正电子湮没辐射多普勒展宽谱精密测量系统已研制成功，并应用于磷化铟（InP）中生长缺陷的研究。用一个高纯锗探测器同时测量待检测样品和标准样品中的湮没能谱。每个样品都将一个22Na正电子源以夹心形式置于两个相同样品之间。双光子湮没的共线方向相关性使我们能够将模数转换器（ADC）的输出路由到不同的存储部分。为了区分哪个源发射了被分析的伽马射线，使用了两个辅助碘化钠（铊）探测器。在超过10周的实验过程中，这种同步比较测量被发现电子设备中没有漂移。此外，符合测量减少了1.28 MeV瞬发伽马射线产生的本底。该技术应用于检测InP晶片内生长缺陷的位置分布，该晶片是从通过液封直拉法生长的单晶锭上沿包含生长轴的平面切片得到的。在晶片的中心和边缘观察到多普勒展宽谱变窄。这一结果与通过蚀坑计数观察到的位错位置分布非常相似。
