Chemical Modification of B₄C Films and B₄C/Pd Layers Stored in Different Environments

B₄C/Pd multilayers with small d-spacing can easily degrade in the air, and the exact degradation process is not clear. In this work, we studied the chemical modification of B₄C films and B₄C/Pd double layers stored in four different environments: a dry nitrogen environment, the atmosphere, a dry oxygen-rich environment, and a wet nitrogen environment. The XANES spectra of the B₄C/Pd layers placed in a dry oxygen-rich environment showed the most significant decrease in the σ* states of the B-C bonds and an increase in the π* states of the B-O bonds compared with the other samples. X-ray photoelectron spectroscopy (XPS) measurements of the samples placed in a dry oxygen-rich environment showed more intensive B-O binding signals in the B₄C/Pd layers than in the single B₄C film. The results of the Fourier-transform infrared spectroscopy (FTIR) showed a similar decrease in the B-C bonds and an increase in the B-O bonds in the B₄C/Pd layers in contrast to the single B₄C film placed in a dry oxygen-rich environment. We concluded that the combination of palladium catalysis and the high content of oxygen in the environment promoted the oxidization of boron, deteriorated the B₄C composition.