Sputtering Bias Voltage Research Articles

Effect of Sputtering Bias Voltage on the Microstructure and Lead-Bismuth Eutectic Corrosion Resistance of the FeCrAlY Coating

FeCrAlY coatings deposited on the outer surface of the cladding tube by the magnetron sputtering with varying bias voltages (0 V to −500 V) were corroded at 550°C to 600°C in oxygen-saturated and oxygen-poor lead-bismuth eutectic for 500 h to 1,000 h. The increased bias voltage led to the Al content decreased and the Y content increased. The coating changed from columnar crystals to equiaxed crystals with increased bias voltage. The decreased bias voltage makes an improved corrosion resistance. The fundamental process governing the evolution of microstructure and corrosion resistance in the FeCrAlY coatings was discussed.

Structure, mechanical properties and tribological behavior of sp2-C:Ti/sp3-C:Ti multilayer films deposited by magnetron sputtering

Amorphous carbon (a-C), one of the most studied carbon-based films, has been widely applied in the filed of artificial joints due to its excellent mechanical and tribological properties and high corrosion resistance. However, low adhesive strength and poor fatigue resistance are fatal shortcomings of this kind of films. In this study, carbon (sp2-C:Ti/sp3-C:Ti) nano-multilayer films (MFs) with sequential sp3-rich and sp2-rich layers were deposited on Ti6Al4V and c-Si substrate by DC magnetron sputtering. X-ray diffraction, scanning electron microscopy, the X-ray photoelectron spectroscopy and the transmission electron microscopy were used to characterize the composition, structure and morphologies of the MFs. In the sp2-C:Ti/sp3-C:Ti MFs, the sp3-C rich layer and the sp2-C rich layer exhibit amorphous features and onion-like structure, respectively. Moreover, the layered structure is continuous in a relatively clear region but with a rough layer interface. The mechanical and the scratch behaviors were elaborately characterized by nanoindentation and scratch tests. The results revealed that the sp2-C:Ti/sp3-C:Ti MFs possess hardness of 21.9 GPa and excellent scratch behavior at sputtering bias voltage −220 V, which are significantly better than single-layer films. Furthermore, the adhesion and tribological behaviors of the sp2-C:Ti/sp3-C:Ti MFs were obtained by Rockwell and ball-on-disk tribometer tests. It was found that the sp2-C:Ti/sp3-C:Ti MFs synthesized under a sputtering bias of −220 V not only exhibit relatively low coefficient of friction (only 0.11) in humid air, but also present lower coefficient of friction (0.085) and wear rate (7.5 × 10−17m3N−1 m−1) of Si3N4 balls in Fetal bovine serum (FBS) solution. In conclusion, the critical loads and wear resistance of the sp2-C:Ti/sp3-C:Ti-MFs were effected by the sputtering bias and the mechanical properties of the MFs. And when sputtering bias is −220 V, the sp2-C:Ti/sp3-C:Ti MFs exhibited the improved mechanical properties, the lowest coefficient of friction (CoF) and the highest wear resistance.

Strain rate-dependent hardness and deformation behavior in the nanocrystalline/amorphous Ti2AlNb film

Abstract Building nanocrystalline/amorphous biphase nanostructure has recently emerged as a new strengthening-toughening route that can combine the strengthening benefits of nanocrystallinity and amorphization. Therefore, it is required exploring on the strain rate-dependent deformation behavior with above different nanostructure in certain system. Herein, three typical nanostructures: polycrystalline, uniform nanocrystalline/amorphous core-shell nanostructure and amorphous matrix with nanoclusters, have been achieved in the sputtered Ti2AlNb films by individually regulating the sputtering bias voltage (Ubias). Note that a high Ubias can promote formation of Nb–rich amorphous tissues via Al preferential resputtering and Nb segregation. Moreover, microstructural evolution and strain rate-dependent hardness and deformation behavior were further explored. Firstly, at a low Ubias (−40 V), Ti2AlNb film exhibited polycrystalline character; it yielded a relatively low hardness (~10.0 GPa) but a high strain sensitivity coefficient of 0.1505. Subsequently, the novel nanocrystalline/amorphous core-shell nanostructure consisting of Ti2AlNb nanocrystalline cores uniformly encapsulated by thin amorphous shells was achieved at a higher Ubias (−120 V); this nanostructure provided a remarkable hardness enhancement (~15.2 GPa) without sacrificing its ductility and intermediate strain sensitivity coefficient of 0.1382. Finally, a transition to amorphous matrix with nanoclusters occurred with further increasing Ubias to −200 V, thus yielding slight decrease in hardness (~12.5 GPa) and a minimum strain sensitivity coefficient of 0.0915 when shear-band deformation was activated.

단일 복합 타겟으로 스퍼터 코팅된 CIGS 박막의 형성과 열처리에 따른 미세구조 변화

Thin film solar cells have attracted much attention due to their high cell efficiency, comparatively low process cost, and applicability to flexible substrates. In particular, CIGS solar cells have been widely studied and produced because they demonstrated the highest cell efficiency. However, the deposition process of CIGS films generally includes the selenization process conducted at elevated temperature using toxic <TEX>$H_2Se$</TEX> gas. To avoid this selenization process, CIGS thin films were, in this study, deposited by RF sputtering using single composite CIGS target. In addition, the effects of sputtering bias voltage and heat treatment on the microstructural and morphological changes in deposited CIGS films were investigated and discussed.

Effect of sputtering bias voltage on the structure and properties of Zr–Ge–N diffusion barrier films

The diffusion barrier properties of Zr–Ge–N thin films are reported, focusing on issues relevant to their application as diffusion barriers for Cu interconnections in Si devices. The Zr–Ge–N films were prepared by reactive r.f. magnetron sputtering with different bias voltage. The analyses of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) indicate that the final structure and composition of Zr–Ge–N film are very sensitive to the sputtering bias voltage. The N content in Zr–Ge–N film changes very little, and only decreases from 51.6 to 48.4at.% when sputtering bias voltage increases from 0V to −150V. However, the correlation between bias voltage change and the atomic ratio of Zr and Ge is very remarkable. These results clearly show that the Ge atoms are preferentially resputtered with increasing substrate bias voltage. The high sputtering bias appears to be in favor of the growth of ZrN grains. The copper diffusion barrier properties of Zr–Ge–N on Si have been examined and compared to ZrN. XRD and four-point probe method (FPP) both showed the onset of formation of copper silicide crystallites for ZrN barriers annealed at 650°C. In contrast, TEM on a Zr–Ge–N barriers annealed even at high annealing temperatures of 800°C revealed sharp interfaces and the energy dispersive X-ray spectroscopy (EDS) line scan showed no Cu diffusion through the barrier into Si substrate. The results suggest that Zr–Ge–N is superior to ZrN as a copper diffusion barrier on Si.

Deposition of dense and smooth Ti films using ECR plasma-assisted magnetron sputtering

We report high quality Ti films grown in a novel electron cyclotron resonance (ECR) plasma-assisted magnetron sputtering (PMS) deposition system. The films are compared with films deposited by conventional direct current (DC) magnetron sputtering. Using ECR-PMS, the argon plasma bombardment energy and Ti film deposition rate can be controlled separately, with the substrate bias voltage under feedback control. Results from SEM, AFM, XRD and PAS (scanning electron microscopy, atomic force microscopy, X-ray diffraction and positron annihilation spectroscopy) show that the properties of Ti films prepared by ECR-PMS are greatly improved compared with conventional sputtering. SEM and AFM confirmed that ECR-PMS Ti films have a dense, smooth, mirror-like surface. Increasing the substrate bias of the ECR plasma from − 23 V to − 120 V while keeping a fixed sputtering bias voltage of − 40 V, the intensity of the (100) reflection of Ti film was a little strengthened, but (002) remained strongly preferred orientation. The XRD peak broadening of ECR-PMS Ti films is more than for conventional magnetron sputtering, due to grain refinement induced by Ar ion bombardment. Doppler broadening of PAS analysis reveals that the Ti films have fewer vacancy defects compared with films prepared by the conventional magnetron.

The characterization of Zr–Si–N diffusion barrier films with different sputtering bias voltage

Zr–Si–N diffusion barriers were sputtered by RF reactive magnetron sputtering with different bias voltage. The Cu films were subsequently sputtered onto the Zr–Si–N films without breaking vacuum. Energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Auger electron spectroscopy, transmission electron microscopy, atomic force microscope, and four-point probe method were employed to characterize the microstructure and properties of the Zr–Si–N films. The results reveal that as the bias voltage increases the Zr/Si ratio and the surface roughness increase, but the resistivity of the film decreases. High sputtering bias is in favor of the growth of ZrN grains in Zr–Si–N film. With the decrease of sputtering bias, the microstructure of Zr–Si–N film changes from composite consisting of nano-grain ZrN and amorphous SiN x to one consisting of amorphous phases of both ZrN and SiN x . The Zr–Si–N film can effectively prevent diffusion of Cu to Si wafer even at high temperature of 850 °C.