Effect of Voltage Pulse Width and Synchronized Substrate Bias in High-Power Impulse Magnetron Sputtering of Zirconium Films

Abstract

The Zr film microstructure is highly influenced by the energy of the plasma species during the deposition process. The influences of the discharge pulse width, which is the key factor affecting ionization of sputtered species in the high-power impulse magnetron sputtering (HiPIMS) process, on the obtained microstructure of films is investigated in this research. The films deposited at different argon pressure and substrate biasing are compared. With keeping the same average HiPIMS power and duty cycle, the film growth rate of the Zr film decreases with increasing argon pressure and enhancing substrate biasing. In addition, the film growth rate decreases with the elongating HiPIMS pulse width. For the deposition at 1.2 Pa argon, extending the pulse width not only intensifies the ion flux toward the substrate but also increases the fraction of highly charged ions, which alter the microstructure of films from individual hexagonal prism columns into a tightly connected irregular column. Increasing film density leads to higher hardness. Sufficient synchronized negative substrate biasing and longer pulse width, which supports higher mobility of adatoms, causes the preferred orientation of hexagonal α-phase Zr films from (0 0 0 2) to (1 0 1¯ 1). Unlike the deposition at 1.2 Pa, highly charged ions are also found during the short HiPIMS pulse width at 0.8 Pa argon.

Effects of the Ethyne Flow Ratio on Structures and Mechanical Properties of Reactive High Power Impulse Magnetron Sputtering Deposited Chromium-Carbon Films

“…After argon glow discharge plasma cleaning, the pressure was further reduced to 0.8 Pa. The HiPIMS plasma was initiated on the Cr target and the −1000 V substrate bias voltage was switched to the unipolar pulsed mode and synchronized with the target HiPIMS pulses to proceed the Cr ion bombardment for 40 s. The reasons to apply the synchronized substrate bias can be seen in the other research [32,38] and our previous works [31,36,37]. Due to the recycling of ions and the flight delay of ions [33,38,39], the pulse width of the substrate bias voltage was set to 1.75-fold of HiPIMS pulses to optimally accelerate the Cr ion flux.…”

“…The hardness and the modulus of elasticity of Cr-C films were evaluated by applying the nanoindentation (TTX-NH3, Anton Paar, Graz, Austria). Settings of the analysis instruments were as the same as described in the previous works [31,36,37]. Notes: high-power impulse magnetron sputtering (HiPIMS).…”

“…It was found that the main structure of all the obtained films in the previous work is hydrogenated amorphous carbon. Although applying synchronized substrate bias successfully prevented the substrate voltage drop and inhibited arc discharge on deposited film [31,36,37]. A part of films presents loosen structures which seemed contrary to above-mentioned features of denser films via HiPIMS.…”

Impact of Coating Defects on Performance of Coated Zirconium Cladding

“…ORNL procured several hundred meters of Zry-4 from Cameco Fuel Manufacturing (Port Hope, Ontario, Canada) in FY20. The material was stress relieved annealed and conformed to the typical geometry of a PWR cladding, conforming to ASTM B353-12 and stress relieved per ASTM B350-11, with a surface finish of 0.81 micrometer R-average (Ra) or better [21]. Product certifications are on file at ORNL.…”

“…A recent report has highlighted those properties with the highest priorities [19]. A higher substrate bias leads to a dense coating, which potentially protects the cladding against oxidation and grid-to-rod-fretting [20,21]. Nanoindentation in combination with XRD to investigate the interface and residual stress will be performed in FY22.…”