Correlation between hardness and embedded argon content of magnetron sputtered chromium films

Abstract Chromium films were produced on steel substrates by d.c. magnetron sputtering in pure argon at a target power density of 2, 4, 10 or 16 W/cm 2 applying a negative substrate bias voltage, V s , ranging from 4 to 1000 V. The substrate temperature varied from 158 to 600°C. Some experiments were conducted at a constant temperature of 600°C. The film hardness was measured by Vickers microindentation. Gas content in the films was analyzed by electron probe microanalysis. The film microstructure was investigated by X-ray diffraction and transmission electron microscopy. At constant deposition rate, while increasing the substrate bias, first the film hardness remained constant and beyond a threshold bias value increased from 4 to 11.7 GPa. The threshold bias value increased with the target power density. The temperature series performed at V s =−500 V and a target power density of 4 W/cm 2 revealed that the film hardness decreased from 12 GPa to 8 GPa when increasing the substrate temperature from 300 to 600°C. The microstructure of the films was found to vary with the deposition parameters. However, over the results for all the experiments performed here, a clear relationship has been established between the microhardness and the argon content of the films. Furthermore, a relationship between the argon content and the deposition rate was established for the films produced at V s =−500 V and T s =600°C.