Figure 1. X-ray diffraction pattern of Cu3N films
deposited at different RF Power and the working pressure of 3.5 Pa
(left) and 5.0 Pa (right).
The stoichiometry of Cu3N is studied in the films
deposited on silicon by using FTIR and Raman techniques. These two
techniques give information on the vibrational state of the molecular
bonds that are found in the films. Both techniques are considered as
complementary. As shown the Figure 2 and Figure 3, the FTIR and Raman
peaks reveal the formation of Cu3N. The Figure 2 shows
the FTIR spectra of the films as function of the RF power values, where
a band around the wavenumber of 650 cm-1 was observed,
being the typical peak of the stretching vibrations attributed to Cu-N
bonds. The peaks at 5.0 Pa are wider than the ones obtained at 3.5 Pa
and closer to 650 cm-1; while the band of the samples
deposited at 150 and 200 W is quite far from the ≈ 650
cm-1, revealing the change in their structure. On the
other hand, the Figure 3 depicts the Raman spectra where the typical
bands of Cu3N thin films, found at the wavelength of ≈
634cm-1 [19], are the characteristic ones of Cu-N
bonds [20] . A slight shift to lower wavenumbers is observed when
the RF power increases, attributed to deviation from the stoichiometric
level more evident at high RF powers where the Cu3N
structure is Cu-rich [21]. Whereas, the sample deposited at 200 W
and 5.0 Pa presents a Raman spectrum completely different, which can be
attributed to the appearance of CO2 and/or CO absorption
bands [22].