Comparison of magnetic and structural properties of permalloy Ni₈₀Fe₂₀ grown by dc and high power impulse magnetron sputtering

Abstract

We study the microstructure and magnetic properties of Ni80Fe20 thin films grown by high power impulse magnetron sputtering (HiPIMS), and compare with films grown by dc magnetron sputtering (dcMS). The films were grown under a tilt angle of 35 • to identical thickness of 37 nm using both techniques, at different pressure (0.13 − 0.73 Pa) and substrate temperature (room temperature and 100 • C). All of our films display effective in-plane uniaxial anisotropy with square easy axis and linear hard axis magnetization traces. X-ray diffraction reveals that there is very little change in grain size within the pressure and temperature ranges explored. However, variations in film density, obtained by X-ray reflectivity measurements, with pressure have a significant effect on magnetic properties such as anisotropy field (H k ) and coercivity (Hc). Depositions where adatom energy is high produce dense films, while low adatom energy results in void-rich films with higher H k and Hc. The latter applies to our dcMS deposited films at room temperature and high pressure. However, the HiPIMS deposition method gives higher adatom energy than the dcMS and results in dense films with low H k and Hc. The surface roughness is found to increase with increased pressure, in all cases, however it showed negligible contribution to the increase in H k and Hc.

Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20

“…Such a short time is enough to define uniaxial anisotropy in the polycrystalline film using both dcMS and HiPIMS. 30 However, it appears that for the epitaxial film deposited by dcMS, our deposition geometry is not enough to induce uniaxial anisotropy along the [100] direction in agreement with the previous study of Schuhl et al 35 .…”

“…lower pressures results in non-linear increase of delay time for current onset and increase time from current onset to peak current which is nearly constant at higher pressures. 30 Thus pressure is low enough to capture the third stage of the current evolution but, the short pulse length here does not allow it to appear. It is worth mentinong that, although we have tried to maintain the HiPIMS average power the same as dcMS power (at 150 W), the HiPIMS pulse voltage and peak current (465 V and 25 A) are well above dcMS counterparts (321 V and 463 mA).…”

“…28,29 We have also demonstrated growth of polycrystalline Py films under an angle using high power impulse magnetron sputtering (HiPIMS) and compared with films deposited by conventional dc magnetron sputtering (dcMS). 30 During HiPIMS deposition high power pulses of low frequency and low duty cycle are applied to a magnetron target which results in highly ionized sputtered material. 31 The HiPIMS discharge provides a highly ionized flux of the metallic species and the averaged ion energy is significantly higher in the HiPIMS discharge than in dcMS discharge and this energetic metallic ions are created during the active phase of the discharge pulse.…”

Oblique angle deposition of nickel thin films by high-power impulse magnetron sputtering

“…By employing an ionized deposition flux (i.e., using HiPIMS in GLAD), the angular distribution of the deposited material can be influenced [40–42]. Earlier we have explored the microstructure and magnetic properties of polycrystalline [43] and epitaxially [44] deposited permalloy (Ni 80 Fe 20 atom %) thin films deposited under 35° tilt using dcMS and HiPIMS. The films prepared by HiPIMS present a lower anisotropy field ( H k ) and coercivity ( H c ) than films deposited with dcMS.…”

On the role of ion potential energy in low energy HiPIMS deposition: An atomistic simulation

“…One may think this will generate deposition rate several orders of magnitude larger than in a typical experiment. We would like to remark that, considering the pulse duration, the instantaneous deposition rate of HiPIMS is 1 -2 orders of magnitude higher than for dcMS [54]. Besides, experimental measurements indicate a variable intensity of the ion flux during the pulse, reaching its peak within a fraction of the pulse [55].…”