Fast neutron irradiation of 1T and 2H tantalum disulfides (TaS2)

Measurements of the electrical conductivity of 1 T—Ta S2 and 2 H—TaS2 irradiated with fast neutrons are presented. A recent calculation by one of the authors enables an estimation of the defect production rates in these binary compounds. The irradiation induced defects have large effects on the charge density waves' (CDW) contribution to the resistivity. In 1T—TaS, these defects qualitatively behave like substitutional impurities in doped samples but they are about two orders at magnitude more effective in changing the resistivity. 2H—TaS2, in its low temperature phase, behaves under irradiation like a semi-metal. A qualitative explanation for the observed effects in both polytypes is proposed : The irradiation produces defects in the Van der Waals gaps which increase the 3-dimensional interaction between layers. These defects are more effective than the substitutional doping impurities in disturbing the CDW states.