Positron beam studies of transients in semiconductors

Coincidence Doppler broadening spectroscopy in polyvinyl chloride after doping with Al2O3

“…The width of the gamma ray annihilation spectrum depends on Doppler broadening effects and reflects the momentum distribution of the electrons with which the positrons annihilate. [19][20][21][22] When a positron source is surrounded by a material, the electron and the positron cannot be regarded as entirely free because of the action of an electromagnetic field produced by their surrounding. The most frequent partner for positron, in such annihilation case, is a bound electron.…”

“…Because the positron is sensitive to defects, vacancy, surface and interface, it has been turned into the best probe for defect research 19. The positron annihilation technique has been extensively applied in areas of polymers, solid physics, chemistry, medicine and materials science and so on 20, 21. Since the emerging gamma photons produced by the annihilation of thermal positron with electrons provide information of both momentum distribution and the electron density of materials, the related spectrum can be used to study the microstructure of materials.…”

“…Since the emerging gamma photons produced by the annihilation of thermal positron with electrons provide information of both momentum distribution and the electron density of materials, the related spectrum can be used to study the microstructure of materials. The width of the gamma ray annihilation spectrum depends on Doppler broadening effects and reflects the momentum distribution of the electrons with which the positrons annihilate 19–22…”

Direct Observation of Electron Capture and Reemission by the Divacancy via Charge Transient Positron Spectroscopy

“…Because positrons are efficiently trapped by divacancies in Si, and their trapping rate depends on the charge state of the defect [12,13] [14] Beling et al, recognizing this potential, proposed an approach they termed ''vacancy-sensing positron DLTS (PDLTS),'' which they considered to be the one variation of PDLTS with great potential use. To overcome the main barrier against successful implementation of the technique-that the electric field required to change the charge state of the vacancy defects also drifts the positron away from the volume of interest-they proposed, but did not implement, the use of a Schottky diode with high injection, under forward bias, to provide free carriers from the rear of the sample to be trapped in defects.…”