Rutherford Backscattering Spectroscopy (RBS) is an analytical method to study the composition of the thin films. This technique do the quantification without the use of reference standards and is a non destructive. The RBS analysis is the bombardment of high-energy (MeV) He2+ ions (i.e. alpha particles) directed unto the surface of the specimens and the backscattered particle’s yield and distribution of energy is measured at a given specific angle. The information about the backscattering cross section for each element can be obtain from literature review and is known for each sample so it is possible to get the knowledge of quantitative compositional depth profile from the obtained spectrum of RBS. The beam energy used was 2.085 MeV while the beam current was set to 29 nA with charge of 20 µC was used in the data collection. The bounced ions after striking the surface were detected by Si detector and the angle was set to 1700. The figure.1 is depicting the simulation and experimental yields of the relative concentration of elements present in the sample against the channel.
SIMNRA (SIMulation of Nuclear Reaction Analysis) is a windows program using for the simulation of charged particle energy spectra and gamma ray yields gamma-ray yields for ion beam analysis with incident ions from about 100 keV to many MeV. The films parameters were evaluated using RBS analysis when fitted with SIMNRA. The used input parameters set in the SIMNRA calculations in order to do the fitting of experimental and simulated curves were scattering angles θ (deg), calibration offset (keV), exit angle β (deg), detector resolution (keV) and energy per channel (keV/ch) are given by respectively 1700, 35.41, 100, 20.99 and 1.15. The films composition obtained from the RBS spectroscopy are shown in table. 1.
Table 1
Percent Composition and thickness of the film
Al | N | O | Cr | Thickness (nm) |
34.2 | 17.6 | 45.9 | 2.1 | 400 |
In order to study the chemical bonds existing in the specimens and to detect the optical vibrations we conducted the Fourier Transform Infrared (FTIR) Spectroscopy using the FT/IR-6600 type setup. This spectroscopy informs us that each molecule within the samples has an associated frequency whereby reflecting or transmitting the rest of the existing frequencies which could carry the information about the strength and nature of the bond [14]. These vibration motions consist of vibrational transitions with distinct energies. The goal of this experiment was to find the amount of light that to be transmitted. Figure. 3 is contrasting the transmittance in percent value against the wavenumber for the thin film Cr doped AlN thin films.
The result concluded that the transmittance has been lowered with the irradiation and the number and positions of the peaks have been altered. The transmittance has been lowered down by almost 3 orders of magnitude. The existence of peaks in the range from 2270–2420 cm− 1 represents CO2, which is due to the spectrometer path and is not from composition of the films [15, 16] while the peaks at 1067 cm− 1 represents Si-O-Si [17, 18].
X Ray Diffraction (XRD) is an analytical technique conducted in this study for the identification of phase of a crystalline material as well for the information about the dimension of the unit cell. The structural information of the films was obtained by using XRD. The source of x-rays was copper with wavelength of 1.5418 A0.
The peaks at (003), (012) and (111) are the corresponded crystallographic axes of Si. No change in the peaks has been found with the irradiation other than slight increase in the intensity which is informing us about the enhanced crystalline behavior while the peaks at (200), (110) and (101) correspond to AlN. The sharpness of the peaks is almost unaffected with the physical treatment.