Effects of Cathode Voltage Pulse Width in High Power Impulse Magnetron Sputtering on the Deposited Chromium Thin Films

Chin-Chiuan Kuo,Yu-Tse Lin,Chun-Hui Lin,Jing-Tang Chang

doi:10.3390/coatings10060542

Abstract

Environmentally-safe high-power impulse magnetron sputtering (HiPIMS) technology was utilized to deposit chromium films. This research focused on the influences of the HiPIMS pulse widths on the microstructure of films deposited at different deposition pressures and substrate bias voltages. Under the conditions of the same average HiPIMS power and duty cycle, the deposition rate of the Cr thin film at working pressure 0.8 Pa is slightly higher than at 1.2 Pa. Also, the difference between deposition rates under two pressures decreases with the discharge pulse width. The deposition rate of the short pulse width 60 μs is lowest, but those of 200 and 360 μs are approximately the same. With no or small direct current substrate biasing, the microstructure of films coated at short pulse width is similar to the typical magnetron sputtering deposited films. Elongating the pulse width enhances the ion flux toward the substrate and changes the film structure from individual prism-like columns into tangled 3-point/4-point star columns. Substantial synchronized substrate biasing and longer pulse width changes the preferred orientation of Cr films from Cr (110) to Cr (200) and Cr (211). The films deposited at longer pulse width exhibit a higher hardness due to the reducing of intercolumn voids.

Highlights

Chromium coatings are commonly used as decorative and corrosion-protective surface finishing for metallic mirrorlike product parts [1]
This research focuses on the effects of discharge pulse width on chromium films deposited by using high power impulse magnetron sputtering
With the conditions of same average power and pulse duty cycle, the microstructure of Cr films deposited at different working pressure, voltage pulse width, and substrate biasing were compared

Summary

Introduction

Chromium coatings are commonly used as decorative and corrosion-protective surface finishing for metallic mirrorlike product parts [1]. The high-power density pulses enable a high ionization ratio of the sputtered materials, which provides the feasibility of altering the kinetic energy of incident ions, migration of adatoms, and consequent film microstructure, through controlling substrate biasing [8,9]. This widens the region of choosing the workpiece temperature, the deposition pressure, and associated film properties [9,10,11]. The commercial HiPIMS coating systems have been promoted for years Most of these works are focused on nitride, oxide, and carbide hard coating applications. This work investigated the influences of the deposition pressure, the discharge voltage pulse width, and the substrate bias voltage on the microstructure of HiPIMS-deposited Cr thin films

Materials and Methods

Results and Discussion

Conclusions