K P Gopinathan
Articles written in Pramana – Journal of Physics
Volume 13 Issue 6 December 1979 pp 625-636 Solids
Positron lifetime has been measured as a function of temperature in Sidoped GaAs single crystals subjected to various heat treatments. Defects produced by these heat treatments trap positrons. In all the GaAs samples containing defects positron lifetime was found to decrease with temperature in the range from 375 K to 16 K. The decrease is explained as due to the decrease in the trapping rate. The trapping rate is mainly controlled by the diffusion of the positron to the trap. The diffusion constant is determined mainly by the scattering from charged Si impurities.
Volume 40 Issue 5 May 1993 pp 391-398
Time differential perturbed angular correlation measurements of the 133–482 keV
Volume 49 Issue 5 November 1997 pp 535-546
Time differential perturbed angular correlation measurements done on the 482 keV level of181Ta probe nuclei in well annealed reference foil samples of
Volume 52 Issue 2 February 1999 pp 219-233
181Ta time differential perturbed angular correlation (TDPAC) and positron lifetime measurements were carried out on homogeneously α-implanted CuHf samples. TDPAC measurements indicate the trapping of vacancy clusters and helium associated defect complexes by Hf atoms. The presence of helium-vacancy complexes and helium stabilised voids has been identified by positron lifetime measurements. Further the nucleation and growth stages of helium bubbles have been identified. TDPAC and positron lifetime measurements indicate that Hf atoms act as heterogeneous nucleating centers for helium bubbles. Hf atoms are found to suppress the bubble growth in CuHf as indicated by the results of positron lifetime measurements.
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