Preparation And Characterization Of Modulation Structure For Fe/Ti Nanometer-scale Multilayers

The nanometer-scale Fe/Ti multilayers of nominal bilayer thickness of 4-200 nm with alternating Fe and Ti sublayers thickness ratio of 1:1 are deposited by direct current magnetron sputtering onto Si(100) substrates in the duplex chamber magnetron sputtering apparatus. The typical sputtering deposition parameters are the magnetron sputtering targets supply power of 60-80 W, the working pressure of 0.3-0.9 Pa and the separation distance between target and substrate of 90-120 mm and 85-105 mm for Fe and Ti respectively. The modulation structure of the nanometer-scale Fe/Ti multilayers is investigation using Rutherford backscattering spectroscopy (RBS), small/wide angle X-ray diffraction (SA/WAXRD), high-resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). The bilayer thickness of nanometer-scale Fe/Ti multilayers is measured as a modulation wavelength of 4.2-214.7 nm. With the smaller modulation wavelength of 4.2 nm, an amorphous-like modulation structure is obtained. For the modulation wavelengths larger than 4.2 nm, the nanometer-scale multilayers are composed of pure metallic a-Fe and a-Ti with a clear interface between the alternating Fe and Ti sublayers which is planar between the inner sublayers and waved between the outer sublayers. There is an amorphous layer with the thickness of 2 nm between the substrate and the multilayer. The preferred orientation of a-Fe (110) and a-Ti (100) is observed for the Fe/Ti multilayer with modulation wavelength of 19.0 nm deposited at the working pressure of 0.9 Pa and the magnetron sputtering targets supply power of 80 W. For the else Fe/Ti multilayers, the preferred orientation of a-Fe (110) and a-Ti (002) is detected. As the modulation wavelength increases from 9.5 nm to 214.7 nm, the lattice parameter a of Fe sublayer is decrease from 0.2874 nm to 0.2851 nm which is closed to that of the bulk a-Fe. The lattice parameter c of Ti sublayers with the modulation wavelength of 37.0 nm is same as that of the bulk a-Ti and its maximum deviation of -1.6% and +1.1% is respectively achieved with the modulation wavelength of 9.5 nm and 56.5 nm. With the work pressure increases from 0.3 Pa to 0.9 Pa, the lattice parameter a of Fe sublayer is maintained 0.2866 nm as the value of the bulk a-Fe and the lattice parameter c of Tisublayer is increased from 0.4703 to 0.4768 nm. The average clusters size on the surface of the Fe/Ti nanometer-scale multilayers increases from 70-100 nm to 250-300 nm with increasing the modulation wavelengths from 19.0 to 95.5 nm and the surface roughness is 4.3 nm and 4.6 nm, respectively. The modulation structure of the nanometer-scale multilayers is significantly influenced by the sputtering deposition parameters of magnetron sputtering.