<title>Effects of preparation parameters on the optical constants of Ge2Sb2Te5 thin films</title>

Abstract

Effects of preparation parameters on the optical constants (n,k) of Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> thin films in the wavelength range of 300 - 830 nm were studied. The results show: (1) When the sputtering power is constant, the refractive index (n) first increases and then decreases with increasing Ar gas pressure, whereas the extinction coefficient (k) changes with Ar gas pressure in a contrary way to that of n. (2) When the Ar gas pressure is constant, for the amorphous thin films in the wavelength range of 300 nm - 500 nm, the refractive index (n) first increases and then decreases with increasing power, whereas the extinction coefficient (k) decreases monotonically. In the wavelength range of 500 nm - 830 nm, the refractive index (n) decreases with sputtering power, while the extinction coefficient (k) first decreases and then increases. For the crystalline thin films, in the wavelength range of 300 nm - 830 nm the refractive index (n) first decreases and then increases, whereas the extinction coefficient (k) decreases. (3) The extent of the influence of preparation parameters on n and k also changes with wavelength, it is greater in the long wavelength region than in the short wavelength region. The mechanism by which the optical constants of the Ge<SUB>2</SUB>Sb<SUB>2</SUB>Te<SUB>5</SUB> thin films are affected by the preparation parameters is analyzed.