Reduction of thin oxide layer on Fe60Ni40 substrates in hydrogen plasmas

The method of low temperature reduction of thin oxide layers in hydrogen pl asmas is described. Samples made of Fe60Ni40 alloys were picked from the pr oduction line for housings of electronic devices. During thermal treatment a layer of brownish oxide was formed on the surface. The thickness of the o xide layer was estimated from AES depth profiles of the samples and it was about 30 nm. Samples were fixed on small thermocouples and exposed to hydro gen plasmas with a density of 8 x 10(15) m(-3); an electron temperature of 6 eV, and the dissociation degree of the hydrogen molecules of 30%. Samples were treated in hydrogen plasmas for different periods. During the treatme nt, the temperature of samples was raised to about 185 degrees C, then was dropped to 30 degrees C, and then remained constant for as long as the RF g enerator was on. The appearance of the maximum temperature coincided with t he change of the sample colour. After plasma treatment, the samples were an alyzed with AES. Depth profiles of the samples exposed to the plasma for le ss than 17 s showed hardly any change in surface composition. The AES depth profiles of samples exposed to plasmas for more than 20 a, however, showed no presence of oxygen. The composition of the surface layer was the same a s that of the bulk material, 60% iron and 40% nickel. Complete reduction of the oxide layer on the samples therefore occurred in a short time (less th an 3 s) after 17 s exposure of the samples to the hydrogen plasma. (C) 1999 Elsevier Science S.A. All rights reserved.