Closed Field Unbalanced Magnetron Research Articles

Influence of Pulsed-DC Power Frequency on Mechanical Properties and High Speed Drilling Application of a-C:H:Zr-x Coatings

The a-C:H:Zr-x coatings are deposited on micro-drills using a closed field unbalanced magnetron (CFUBM) sputtering system with pulsed-DC power frequencies in the range 30 kHz to 110 kHz (the x in the term a-C:H:Zr-x is the frequency varied in the deposition process). The hardness of the various coatings is systematically explored. Additionally, the machining performance of the coated micro-drills is investigated by conducting high-speed through-hole drilling tests utilizing Printed Circuit Board (PCB) specimens. The experimental results reveal that the a-C:H:Zr-70 coating has the highest hardness (42 GPa), while the a-C:H:Zr-110 coating has the lowest hardness (26 GPa). In addition, it is shown that the a-C:H:Zr-70 coating increases the life of the micro-drill by a factor of three compared to that of an uncoated micro-drill.

Tribological properties of Zr-C:H:Nx% coatings with different amounts of nitrogen addition

A closed field unbalanced magnetron (CFUBM) sputtering system is used to deposit Zr-C:H:N x% coatings with nitrogen contents ranging from 0 to 29 at.% on AISI M2 steel disks. The microstructures of the various coatings are analyzed using Raman spectrometry, while the hardness and adhesion strength are measured via nanoindentation tests and scratch tests, respectively. The tribological properties of the coatings are tested against AISI 52100 steel balls under loads of 0.5–10 N using a ball-on-disk wear tester. The wear testing results reveal that the Zr-C:H:N 12% coating has excellent tribological properties, including a low wear depth, a low friction coefficient and an extended lifetime.

Microstructure and mechanical properties of Ti-B-C-N nanocomposite coatings

Ti-B-C-N nanocomposite coatings with different C quantities are deposited on Si(100) and high speed steel (W18Cr4V) substrates by the closed-field unbalanced reactive magnetron sputtering in the mixture of argon, nitrogen and acetylene gases. The microstructures of Ti-B-C-N nanocomposite coatings are characterized by X-ray diffraction and high-resolution transmission electron microscopy; while the nanohardness and elastic modulus values are measured by the nano-indention method. The results indicate that in the studied composition range, the deposited Ti-B-C-N nanocomposite coatings are found still only in the TiN base nanocrystalline. When the C2H2 flux is small, adding C can promote crystallization of Ti-B-C-N nanocomposite coatings, and the grain can be increased to improve the mechanical properties, when the grain size of about 6 nm (C2H2 flux rate 2 cm3/min), hardness, elastic modulus and fracture toughness of Ti-B-C-N nanocomposite coatings achieve the maximum, respectively, 35.7 GPa, 363.1 GPa and 2.46 MPa m1/2; the further increase of the C content of Ti-B-C-N nanocomposite coating can reduce mechanical properties of coating dramatically.

Optimizing the tribological properties and high-speed drilling performance of a-C:H coatings via nitrogen addition

a-C:H:N x % coatings with various levels of nitrogen addition ranging from 0 to 29 at.% are deposited on high-speed steel substrates and micro-drills utilizing a Closed Field Unbalanced Magnetron (CFUBM) sputtering technique. The tribological properties of the various coatings are evaluated by performing reciprocating sliding wear tests against an AISI 1045 steel cylinder under an applied load of 100 N. Additionally, the machining performance of the coated micro-drills is investigated by conducting high-speed through-hole drilling tests utilizing Printed Circuit Board (PCB) specimens. The experimental results reveal that the a-C:H:N 8% coating possesses the best tribological properties, namely the lowest wear depth, the lowest friction coefficient and the longest lifetime. In addition, it is shown that the a-C:H:N 8% coating increases the lifetime of the micro-drill by a factor of three compared to that of an uncoated micro-drill.

Tribological properties and high-speed drilling performance of Zr–C:H:Nx% coatings with different amounts of nitrogen addition

Zr-C:H:Nx% coatings with nitrogen additions ranging from 0 to 29 at.% are deposited on AISI M2 steel substrates and micro-drills using a closed field unbalanced magnetron (CFUBM) sputtering technique. The tribologi- cal properties of the coatings are tested against AISI 52100 steel balls under loads of 10 and 100 N, respectively, using an oscillating friction and wear tester. The drilling perfor- mance of the coated micro-drills is evaluated by performing high-speed through-hole drilling tests using printed circuit boards as a test material. The wear testing results reveal that the Zr-C:H:N8% coating has excellent tribological properties, including a low wear depth, a low friction coefficient, and an extended lifetime. Meanwhile, the dril- ling tests reveal that the Zr-C:H:N8% coating increases the tool life of the micro-drill by a factor of five compared to an uncoated micro-drill when used for the high-speed through- hole drilling of PCBs and yields a considerable improve- ment in the machining quality of the drilled hole.

Characterization of Nanocrystalline Conductive a-C as the Electrode Used in the Bottom-Gated Structure of a Pentacene-Based Organic Thin Film Transistor

Nanocrystalline amorphous carbon (nc a-C) films recently prepared in our laboratory exhibited very low resistivity (< 1 momega x cm) and good conductivity without any dopant. They also showed properties such as good adhesion to glass and plastic substrates, smooth surface, low friction coefficient, thermal stability, and high transparency. We applied nc a-C films to the bottom-gated electrodes of organic thin film transistors (OTFTs). In this work, we describe the characterization of conductive nc a-C films synthesized by closed-field unbalanced magnetron (CFUBM) sputtering and fabricate OTFTs of a bottom gate structure using pentacene as the active layer and polyvinylphenol (PVP) as the gate dielectric on the nc a-C gate electrode. We investigated the surface and electrical properties of each layer using an AFM method and estimated the device properties of OTFTs including I(D)-V(D), I(D)-V(G), threshold voltage V(T), on/off ratio, and field effect mobility.

High-speed drilling performance of coated micro-drills with Zr–C:H:N x% coatings

A closed field unbalanced magnetron (CFUBM) sputtering system is used to deposit Zr–C:H:N x% coatings with nitrogen contents ranging from 0 to 25 at.% on M2 steel disks and micro-drills. The microstructures of the various coatings are analyzed using Raman spectrometry, while the hardness and adhesion strength are measured by performing nanoindentation tests and scratch tests, respectively. The drilling performance of the coated micro-drills is evaluated by conducting high-speed through-hole drilling tests using printed circuit board (PCB) specimens. The service life of the coated micro-drills is assessed utilizing four different criteria, namely the nail head ratio and surface roughness of the drilled hole, and the corner wear and flank wear of the cutting edge, respectively. Overall, the results show that the Zr–C:H:N 17% coating has the optimal high-speed machining performance, i.e. it extends the tool life by a factor of at least four compared to the uncoated micro-drill and yields a significant improvement in the machining quality.

Growth of carbon nanotubes using nanocrystalline carbon catalyst

The basic growth of carbon nanotubes (CNTs) involves dissociation of hydrocarbon molecules over a metal layer as a catalyst. Generally, the metals used for the catalyst include nickel, cobalt, gold, iron, platinum, and palladium. However, the metal catalyst used with CNTs could have a harmful influence on the electrical properties of electronic devices. Therefore, we propose the use of nanocrystalline carbon (nc-C) as the catalyst for the growth of CNTs. We used a nc-C catalyst layer deposited by the closed-field unbalanced magnetron (CFUBM) sputtering method, and CNTs were grown by the hot filament plasma-enhanced chemical vapor deposition (HF-PECVD) method with ammonia (NH 3) as a pretreatment and acetylene gas (C 2H 2) as a carbon source. The CNTs were grown on the nc-C layers pretreated with a variation of the pretreatment time. The characteristics of the pretreated nc-C layers and the grown CNTs were investigated by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) measurements. Also, the structural variation of the pretreated nc-C layers was investigated by Raman measurement. We used the nc-C catalyst without metal, and we confirmed that our CNTs were composed with only carbon elements through an EDS measurement. Also, the pretreatment time was attributed to the growth of CNTs.

Characteristics of sputtered amorphous carbon films prepared by a closed-field unbalanced magnetron sputtering method

We discuss the tribological performance of sputtered amorphous carbon (a-C) films deposited by closed-field unbalanced magnetron (CFUBM) sputtering with a graphite target using a mixture of helium (He) and argon (Ar) as sputtering gases. We investigated the effects of the graphite target power density on the micro-structural and physical properties. In the Raman spectra, the G-peak position moved to the higher wavenumbers. The ID/IG ratio increased with the increase of target power density in the fixed DC bias voltage. This was the result of the structural change in the a-C film that resulted with the increase in sp2 bonding fraction. Also, the maximum hardness of the a-C film was 23 GPa, the friction coefficient was 0.1, and the critical load was 25.9 N on the Si wafer. In addition, the compressive residual stress of the film increased a little with increasing target power density. Consequently, the various properties of a-C films, with an increase of the target power density, were associated with the increase of cross-linked sp2 bonding fraction and the cluster size. The tribological properties of a-C film showed clear dependence on the energy of ion bombardment with the increase of plasma density during film growth.

The effect of thermal annealing on the structural and mechanical properties of a-C:H thin films prepared by the CFUBM magnetron sputtering method

a-C:H films were prepared by closed-field unbalanced magnetron (CFUBM) sputtering on silicon substrates using argon (Ar) and acetylene (C 2H 2) gases, and the effects of post-annealing temperature on structural and mechanical properties were investigated. Films were annealed at temperatures ranging from 300 °C to 700 °C in increments of 200 °C using rapid thermal annealing equipment in vacuum ambient. Variations in microstructure were examined using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Surface and mechanical properties were investigated by atomic force microscopy (AFM), nano-indentation, residual stress tester, and nano-scratch tester. We found that the mechanical properties of a-C:H films deteriorated with increased annealing temperature.

The Characteristics and Thermal Stability of CrN/AlSiN Multilayer Coatings

CrN/AlSiN multilayer coatings with bilayer period (Λ) between 2.3 nm and 8.0 nm were synthesized from Cr and AlSi (Si=20 and 66 at.%) targets by using a closed-field unbalanced magnetron sputtering (CFUBMS) and their crystal structure, chemical composition and mechanical properties have been investigated by glow discharge optical emission spectroscopy (GDOES), Xray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and nano-indenter. In order to evaluate the thermal stability of the coatings annealing treatments for 30 min at temperature between 800 °C and 1000 °C were performed in air. The thermal stability of the CrN/AlSiN multilayer coatings was improved with increasing Si content. In case of the coating with Si content of 18.2 at.%, a superior thermal stability was exhibited even after annealed at 1000 °C and the relatively high hardness of 25 GPa was maintained without a significant decrease in hardness. The reduced oxidation rate of the coatings at high temperature could be attributed to the formation of the amorphous Si3N4 phase around the crystalline AlN phase.

Ion-beam analysis of the structure and composition of nanocomposite nc-TiC/a-C:H coatings

The structure and composition of nanocomposite nc-TiC/a-C:H thin films prepared by closed-field unbalanced reactive magnetron sputtering in an argon-acetylene atmosphere have been investigated. The concentrations of carbon and heavier elements have been obtained by Rutherford backscattering and nuclear backscattering. The hydrogen concentration in the films has been determined by elastic recoil detection analysis. Based on the data obtained, a scheme has been proposed to evaluate the C:H matrix mass density and the sp 3 and sp 2 fractions in the matrix.

Tribological properties of a-C:H:N thin films prepared using C 2H 2 and N 2 by CFUBM sputtering method

In this work, nitrogenated a-C:H (a-C:H:N) films were prepared using the closed-field unbalanced magnetron (CFUBM) sputtering method on Si substrate with graphite target in a Ar + C 2H 2 + N 2 plasma. We changed the ratio of nitrogen and acethylene gases used as reaction gas and applied the negative DC bias voltage of – 200 V. The tribological properties of a-C:H:N films were observed. In the result, the increase of N 2 as the reaction gas in the plasma showed the growth rate and the N atomic ratio in the films increased markedly. Raman spectroscopy and X-ray photoelectron spectroscopy were used to investigate the chemical bonding structure and sp 3 fraction in the film. As a result, the film had the improvement of the physical properties such as the high hardness of 29 GPa, elastic modulus of 276 GPa and good adhesion of 35 N between a-C:H:N films and substrate. Also, N incorporated a-C:H films exhibited lower friction coefficient than a-C:H film without N. Consequently, the addition of N atoms in the a-C:H film was observed to improve the tribological properties of the film.

비대칭 마그네트론 스퍼터링법에 의한 비정질 질화탄소 박막의 합성 및 윤활 특성

The incorporation of N in a-C film is able to improve the friction coefficient and the adhesion to various substrates. In this study, a-C:N films were deposited on Si and steel substrates by closed-field unbalanced magnetron (CFUBM) sputtering system in <TEX>$Ar/N_2$</TEX> plasma. The lubricant characteristics was investigated for a-C:N deposited with total working pressure from 4 to 7 mTorr. We obtained high hardness up to 24GPa, friction coefficient lower than 0.1 and the smooth surface of having the extremely low roughness (0.16 nm). The physcial properties of a-C:N thin film are related to the increase of cross-linked <TEX>$sp^2$</TEX> bonding clusters in the film. However, the decrease of hardness, elastic modulus and the increase of surface roughness, friction coefficient with the increase of <TEX>$N_2$</TEX> partial pressrue might be due to the effect of energetic ions as a result of the increase of ion bombardment with the increase of ion density in the plasma.

CFUBM Sputtering법으로 증착시킨 티타늄이 첨가된 비정질 탄소 박막의 기계적 특성 연구

Ti-containing amorphous carbon (a-C:Ti) films shows attractive mechanical properties such as low friction coefficient, good adhesion to various substrate and high wear resistance. The incorporation of titanium in a-C films is able to improve the electrical conductivity, friction coefficient and adhesion to various substrates. In this study, a-C:Ti films were depositied on Si wafer by closed-field unbalanced magnetron (CFUBM) sputtering system composed two targets of carbon and titanium. The tribological properties of a-C:Ti films were investigated with the increase of DC bias voltage from 0 V to - 200 V. The hardness and elastic modulus of films increase with the increase of DC bias voltage and the maximum hardness shows 21 GPa. Also, the coefficient of friction exhibites as low as 0.07 in the ambient. In the result, the a-C:Ti film obtained by CFUBM sputtering method improved the tribological properties with the increase of DC bias volatage.

마그네트론 스퍼터링법에 의해 합성되어진 비정질 탄소박막들의 구조적, 물리적 특성

본 연구에서는 비정질 탄소박막들(a-C, a-C:H, a-C:N)을 흑연타겟이 부착되어진 비대칭 마그네트론 스퍼터링법을 이용하여 증착하였으며, 음의 DC 바이어스 전압의 효과를 알아보기 위해 증착가스 압력내에서 200 V를 인가하여 탄소박막들을 제작하였다. 수소화된 비정질 탄소박막과 질화탄소박막은 각각 스퍼터링 가스로써 아세틸렌과 질소를 주입하여 제작하였다. 결과적으로 26.5 GPa의 높은경도와 0.1 nm의 낮은 거칠기 그리고 접착력은 30.5 N를 가지는 수소화된 비정질 탄소박막을 합성하였으며, 32 N의 좋은 접착 특성을 나타내는 질화 탄소 박막을 합성하였다. 본 논문에서는 아세틸렌과 질소 가스의 효과와 음의 DC 바이어스 전압에 따른 비정질 탄소박막들의 구조적 특성과 물리적 특성과의 관계를 규명하였다. In this research, amophous carbon films (a-C, a-C:H, a-C:N) were synthesized by closed-field unbalanced magnetron (CFUBM) sputtering using graphite target. We also fabricated amorphous carbon films with applying negative DC bias voltage of 200 V in during the deposition in working pressure. Also, a-C:H and a-C:N films was synthesized by adding acethylene(<TEX>$C_{2}H_{2}$</TEX>) and nitrogen(N) gases of 4 and 3 sccm into Ar pressure. The a-C:H film synthesized at -200 V exhibited the maxumum hardness of 26.3 GPa, the smooth surface of 0.1 nm and the good adhesion of 30.5 N. And a-C:N film synthesized at -200 V exhibited at -200 V exhibited the best adhesion of 32 N. This paper examined the effect of <TEX>$C_{2}H_{2}$</TEX> gas, <TEX>$N_{2}$</TEX> gas and negative DC bias voltage as the parameter for improving the physical properties and the relation between structral and physical properties of carbon films.

The low temperature process design for Al doped ZnO film synthesis on polymer

In order to deposit Al doped ZnO (AZO) films on a polymer substrate, we designed two types of low temperature process with a CFUBM (Closed Field Unbalanced Magnetron) sputtering system. The first one is a reactive magnetron sputtering process using a single ZnO:Al 2O 3 target. The second is a co-magnetron sputtering system using Al + ZnO targets. In the first process, due to the characteristics of formation of the AZO film in which the presence of Al prevents the ZnO grain growth, a high temperature is needed in order to enlarge the crystallite size. However, in the second process, it is easy not only to synthesize the ZnO film on the polymer due to the low heat of formation of ZnO, but also to control the Al content in the film. In addition, by controlling the hydrogen partial pressure, we obtained highly conductive AZO films with a minimum resistivity of 8 × 10 − 4 Ω·cm and a maximum transmittance of 83.2% at a hydrogen partial pressure of 1 mTorr.

The low temperature synthesis of Al doped ZnO films on glass and polymer using pulsed co-magnetron sputtering: H2 effect

It has been reported that a small amount of hydrogen in argon plasma induces an increase in the crystallite size of the as-deposited films. In addition, control of the hydrogen partial pressure is expected to improve the carrier mobility by increasing the crystallinity of the film (larger crystal size and lower grain boundary effects). Al doped ZnO (AZO) films were deposited by co-CFUBM (closed field unbalanced magnetron) sputtering. The ultimate aim was to deposit transparent films on a polymer substrate with a low electrical resistivity. Therefore, the structural, optical and electrical properties of AZO films were investigated as a function of the hydrogen partial pressure. A minimum resistivity and maximum transparency of 8 × 10 − 4 Ω cm and 88.1% were obtained, respectively. A critical P H2 was expected to improve the carrier mobility by increasing the crystallinity of the film. However, above this value, conductivity reduced due to the formations of oxides such as ZnO and Al 2O 3 in the AZO films.

The low temperature synthesis of Al doped ZnO films on glass and polymer using magnetron co-sputtering: Working pressure effect

Transparent conductive Al doped ZnO thin films were prepared on glass and polymer substrates by unipolar pulsed d.c. co-CFUBM (Closed Field Unbalanced Magnetron) sputtering at ZnO and Al targets without introducing any oxygen at room temperature. The lowest resistivity of 1.2 mΩ cm as well as the transmittance of above 84% was obtained by controlling working pressure. But the resistivity is slightly increased up to 6.8 mΩ cm with time passing due to the unstable microstructure caused by the low temperature process.

The electrical and structural properties of the hydrogenated amorphous carbon films grown by close field unbalanced magnetron sputtering

Carbon-based materials, i.e., amorphous hydrogenated and nonhydrogenated forms of carbon, have attracted much attentions for application in microelectronic devices due to their importance in electrical, optical, and tribological properties. In this work, the hydrogenated amorphous carbon films were deposited by close field unbalanced magnetron (CFUBM) sputtering method with a graphite target in a mixed Ar (80%) and C 2H 2 (20%) plasma. We have observed a systematic variation for the properties of these films with the increase of DC bias voltage from 0 to −200 V. The investigation of the composition and structure was performed by Raman analysis, FT-IR (Fourier transform infrared) spectroscopy, and AFM (Atomic Force Microscopy). The electrical properties were observed by current–voltage ( I– V) measurement and electrical resistivity.