Compositional dependence of electrical conduction in solution grown Zn sub(1-x)Cr sub(x)Se thin films: a correlation

Zinc selenide (ZnSe) has a typical band gap of 2.7 eV suitable for window application and can easily be synthesized using a liquid phase chemical bath deposition. An attempt is made to tune its band gap and other characteristics to cope with a maxima of the solar spectrum by deliberate addition of Cr super(3+). ZnSe and Zn sub(1-x)Cr sub(x)Se (0 less than or equal to x less than or equal to 0.35) thin films were obtained under the controlled deposition conditions (temperature=70 degree C, time=210 min, pH=10, etc). The compositional analysis showed Zn super(2+) replacement by Cr super(3+). The X-ray photoelectron spectroscopy revealed chemical states of the constituents Zn, Cr and Se as 2 super(+), 3 super(+) and 2 super(-) respectively. The electrical conductivity and thermo-power measurements in the 300-550 K temperature range showed semiconducting nature of the material and that the electrical conduction is of the n-type. The electrical conductivity is found to be increased continuously up to x=0.05 and then decreased for further increase in x. The Hall-probe measurements also confirmed n-type conduction. The average Hall coefficient for pure ZnSe is -1.0310 super(7) cm super(3)/C whereas, it is -4.5510 super(6) cm super(3)/C for a sample with x=0.35.