Growth of Pd4S, PdS and PdS2 films by controlled sulfurization of sputtered Pd on native oxide of Si

• Multichamber sulfurization setup designed for preparing thin films of Pd–S.
• S vapor activated at 550, 600 and 700 °C results in Pd4S, PdS and PdS2 phases.
• The Seebeck coefficient of Pd–S phases shows their n-type conducting behavior.
• Transport properties of Pd4S phase show that it is a metallic phase.
• High resistivity and thermopower of PdS and PdS2 show semiconducting nature.

Thin films of different Pd–S phase, namely Pd4S, PdS and PdS2, have been reproducibly grown by the sulfurization of Pd films deposited on native oxide of (111) Si substrates by radio frequency sputtering method. In order to achieve controlled sulfurization, a three-stage sulfurization setup consisting of evaporation chamber, activation chamber and sulfurization chamber has been developed. The sulfurization of Pd films (kept at a constant temperature of 500 °C) was carried out using sulfur vapors activated to different temperature between 550 and 700 °C. The results of X-ray diffraction and X-ray photoelectron spectroscopy measurements show that formation of Pd4S, PdS and PdS2 phases takes place for the activation temperatures of 550, 600 and 700 °C, respectively. The room temperature resistivity of Pd, Pd4S, PdS and PdS2 were found to be respectively 0.1, 15.9, 15,000 and 20,000 μΩ cm. The temperature-dependent electrical resistivity measurements showed metallic conduction for Pd and Pd4S films. The Seebeck coefficient measured at 300 K for these Pd–S phases showed their n-type conducting behavior.