Nitrogen doped ZrO2 thin films: synthesis and characterization

Abstract

To obtain ZrO2 and ZrO2+N2 thin films was used magnetron sputtering in radio frequency mode in a 10-6 mbar high vacuum deposition chamber. Silicon and carbon substrates measuring 12x15mm were used for deposition. The used magnetron system was composed of a single water-cooled cathode, provided with one circular targets of ZrO2 (2 mm thick and 50 mm in diameter) of high purity (99.95%). TDS Analysis of the films was performed. The desorbed species were observed with a QMG 220 Mass spectrometer provided with a W filament. It can be observed that in the case of the ZnO2 film, nitrogen desorption registers two maxima with signal intensity of 9.7x10-12 and 9.0x10-12, reached after 2000s and 4900s respectively. In the case of ZrO2+N2 film, nitrogen desorption shows a pronounced maximum with a signal intensity of 2.4x10-11 reached after 6000s. . The topology the ZrO2 and ZrO2+N2 samples deposited on Si substrates have been investigated by scanning electron microscopy (SEM) using a FEI Inspect S scanning electron microscope ( Hillsboro, Oregon, OR, USA) in high-vacuum modes. For the ZrO2 deposition, the surface appears to have grain-like topology, with a mean dimension of around 150 nm. These structures do not appear for the ZrO2+N2 deposition. Instead, for the ZrO2+N2 sample, small blisters (between 300 nm and 1.000nm) have formed on the surface, as a consequence of injecting N2 during the deposition. Cross-section measurements were also performed to establish the layer thickness. The ZrO2 sample has a measured thickness of 1950nm, while the introduction of N2 gas for the ZrO2+N2 sample had a poisoning effect on the magnetron target that led to a decrease (5 times) in deposition rate, giving this sample a final thickness of 365nm (compared to 1950nm) for the same deposition The crystalline structure was investigated using X-Ray Diffraction (XRD) method. The experimental set-up was composed of a diffractometer equipped with a Cu-Kα X-ray sourse, with a specific wavelength of 0.154nm, in a Bragg-Bretano type geometry. In this way, a crystalline phase corresponding to ZrO2 with a group symmetry Fm-3m (225)-face centered cubic was identified. At the same time, it is observed that the films deposited in the reactive atmosphere show a pronounced amorphization, this most likely being due to the retention of nitrogen which leads to the modification of the network parameters.