Influence of hydrogen incorporation on the optical properties and crystallization of GeTe2 thin films

Thin films of GeTe2 were deposited on glass substrates using radio-frequency magnetron sputtering with various hydrogen flow rates in the growth chamber. Transmission data of deposited films were taken and used to determine optical constants refractive index n , extinction coefficient , and absorption coefficient and the energies corresponding to absorption coefficients of 104 and 103 cm−1 E04,E03 , Tauc band gap ETauc, and Urbach energy EU. An increase in these energies was observed as a function of the hydrogen flow rate. An increase in the disorder in the hydrogenated GeTe2 thin films was determined from Tauc’s slope B 1/2 parameter, Urbach energy, and full width at half maximum of Raman vibrational modes. Crystallization of GeTe2 occurs via a phase separation into Te and GeTe crystalline phases. The crystallization temperature increases with the addition of hydrogen. A large change 60% decrease in the optical transmission occurs after the phase change from amorphous to crystalline. © 2008 American Institute of Physics. DOI: 10.1063/1.3041660