Study on the crystallization by an electrical resistance measurement in Ge₂Sb₂Te₅ and N-doped Ge₂Sb₂Te₅ films

Abstract

An electric resistance measurement was used to study the crystallization process of Ge₂Sb₂Te₅ (GST) and N-doped Ge₂Sb₂Te₅ (N-GST) films. The relation between onductivity and annealing time was investigated and the crystallization parameters were determined directly by resistance measurement during isothermal crystallization process in the amorphous GST and the N-GST films. The results show that the crystallization processes in both GST and N-GST films are layer by layer. Their conductivities satisfy the equation σ = σc−(σc−σa)exp(−ktⁿ), at t>r , where r is a temperature-dependent time in the process of crystallization. The activation energy for crystallization of amorphous GST films was 2.11±0.18 eV and the Avrami coefficient was between 2 to 4, in close agreement with previous studies using different techniques. After N doping the Avrami coefficient decreased, while the activation energy increased. The formation of a strain induced by the distortion of unit cell after N doping was used to explain the observed results.