Preparation and Characterization of Silicon Nitride Nanostructures Prepared by DC Reactive Sputtering Technique with Novel Design of Closed-Field Unbalanced Dual Magnetron Assembly


In this work, novel design of closed-field unbalanced dual magnetrons system was employed in a DC reactive sputtering system to prepare silicon nitride nanostructures. Two types of silicon wafers (n- and p-type) were sputtered in presence of nitrogen gas to deposit nanostructured silicon nitride thin films on glass substrates. The prepared nanostructured were polycrystalline with six dominant crystal planes: (101), (110), (200), (232), (301) and (321). The surface roughness of the sample prepared at inter-electrode distance of 4cm was higher than other samples prepared at smaller or larger distances and the average and R.M.S roughness were 0.777 and 1.03 nm, respectively. The nanoparticles of minimum size of 30nm were formed and recognized as individual accumulated particles. Two bands of significant absorption were observed around 960 and 1086 cm-1, those are attributed to the Si-N-Si vibration mode in Si3N4 molecule. An absorption peak was observed at 389nm, which is attributed to the quantum size effect of nanostructures. The refractive index of the prepared Si3N4 samples was determined to be 1.38-2.1 and the energy band gap was ranging in 5.1-5.2 eV. The energy band gap was found to increase with decreasing thickness of the prepared film. The wide energy band gap of Si3N4 nanostructures makes them good candidate, as similar as AlN, BN and GaN, for power electronics and optoelectronics operating at high temperatures.