Bipolar Pulsed DC Magnetron Sputtering Research Articles

Asymmetric Bipolar Pulsed dc Sputtered Nanocrystalline VN Coatings for Electrode Materials in Lithium Battery.

Nanocrystalline vanadium nitride (VN) coatings for electrode materials for lithium battery with various deposition parameters have been prepared using dc and asymmetric bipolar pulsed dc magnetron sputtering. The deposition parameters such as pulse frequency and the duty cycle were varied from 0 to 50 kHz and 100 to 75%, respectively. Microstructural, crystallographic and electrical characterizations were performed by FE-SEM, AFM, XRD and 4-point probe method. With an increase in pulse frequency, coating microstructure evolved from a porous columnar structure to a highly dense one. Single- phase cubic (FCC) VN coatings with different preferential orientations were obtained as a function of pulse frequency. Minimum resistivity of 108 μΩ-cm was obtained for the coatings deposited at pulse frequency of 25 kHz.

Measurement of deposition rate and ion energy distribution in a pulsed dc magnetron sputtering system using a retarding field analyzer with embedded quartz crystal microbalance.

A compact retarding field analyzer with embedded quartz crystal microbalance has been developed to measure deposition rate, ionized flux fraction, and ion energy distribution arriving at the substrate location. The sensor can be placed on grounded, electrically floating, or radio frequency (rf) biased electrodes. A calibration method is presented to compensate for temperature effects in the quartz crystal. The metal deposition rate, metal ionization fraction, and energy distribution of the ions arriving at the substrate location are investigated in an asymmetric bipolar pulsed dc magnetron sputtering reactor under grounded, floating, and rf biased conditions. The diagnostic presented in this research work does not suffer from complications caused by water cooling arrangements to maintain constant temperature and is an attractive technique for characterizing a thin film deposition system.

Omnidirectional photonic band gap in magnetron sputtered TiO2/SiO2 one dimensional photonic crystal

One dimensional photonic crystal (1DPC) of TiO2/SiO2 multilayer has been fabricated by sequential asymmetric bipolar pulsed dc magnetron sputtering of TiO2 and radio frequency magnetron sputtering of SiO2 to achieve wide omnidirectional photonic band in the visible region. The microstructure and optical response of the TiO2/SiO2 photonic crystal have been characterized by atomic force microscopy, scanning electron microscopy and spectrophotometry respectively. The surface of the photonic crystal is very smooth having surface roughness of 2.6nm. Reflection and transmission spectra have been measured in the wavelength range 300 to 1000nm for both transverse electric and transverse magnetic waves. Wide high reflection photonic band gap (∆λ=245nm) in the visible and near infrared regions (592–837nm) at normal incidence has been achieved. The measured photonic band gap (PBG) is found well matching with the calculated photonic band gap of an infinite 1DPC. The experimentally observed omnidirectional photonic band 592–668nm (∆λ=76nm) in the visible region with band to mid-band ratio ∆λ/λ=12% for reflectivity R>99% over the incident angle range of 0°–70° is found almost matching with the calculated omnidirectional PBG. The omnidirectional reflection band is found much wider as compared to the values reported in literature so far in the visible region for TiO2/SiO2 periodic photonic crystal.

듀티 싸이클 및 펄스 주파수가 TiAlN 코팅막의 미세구조와 기계적 특성에 미치는 영향에 관한 연구

This paper presents the effects of pulse plasma parameters such as duty cycle and pulse frequency on the properties of TiAlN coatings deposited by asymmetric bipolar pulsed DC magnetron sputtering systems. The results show that, with decreasing duty cycle and increasing pulse frequency, the coating morphology changes from a columnar structure to a dense structure with finer grains. Pulsed sputtered TiAlN coatings showed higher hardness, higher residual stress, and smaller grain sizes than did DC prepared TiAlN coatings. Moreover, residual stress and nanoindentation hardness of pulsed sputtered TiAlN coatings increased with increasing pulse frequency. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 50 kHz.

Thermoelectricity of p-NCO and n-ZAO Thin Films

Thin films of sodium cobalt oxide and zinc aluminium oxide were prepared onto ceramic substrates by a bipolar pulsed-dc magnetron sputtering system using a NaCoO2target and a ZnAlO target, respectively, under an argon atmosphere. Energy dispersive spectroscopy analysis revealed that the as-deposited films from the NaCoO2target comprised Na, Co, O elements, while those from the ZnAlO target contained Zn, Al, O elements. Cross-sectional view estimation by the scanning electron microscope indicated that the as-deposited Na-Co-O (NCO) and Zn-Al-O (ZAO) films had the thickness of 0.63 μm and 0.58 μm, respectively. X-ray diffraction analysis showed that the NCO thin films were grown in amorphous phase while the ZAO thin films exhibited hexagonal structure. From thermoelectric properties measurement, the p-NCO and n-ZAO films were found to exhibit the thermoelcectric power factor of 0.03 and 14.39 μW/mK2, respectively. A thermoelectric module made from three pairs of the p-n thin film stripes provided the open-circuit voltage up to 26.0 mV for a temperature difference of 79.3 K. However, the module was unable to produce useful electrical current due to its high internal series resistance contributed from the NCO films.

Thermoelectricity of p-CCO and n-ZAO Thin Films

Thin films of calcium cobalt oxide and zinc aluminium oxide were prepared onto ceramic substrates by a bipolar pulsed-dc magnetron sputtering system using a Ca3Co4O9 target and a ZnAlO target, respectively, under an argon atmosphere. Energy dispersive spectroscopy analysis revealed that the as-deposited films from the Ca3Co4O9 target comprised Ca, Co, O elements, while those from the ZnAlO target contained Zn, Al, O elements. Cross-sectional view estimation by the scanning electron microscope indicated that the as-deposited Ca-Co-O (CCO) and Zn-Al-O (ZAO) films had the thickness of 0.55μm and 0.58μm, respectively. X-ray diffraction analysis showed that the CCO thin film was grown in amorphous phase while the ZAO thin film exhibited hexagonal structure. From measurement of the properties, the p-CCO and n-ZAO films were found to exhibit the power factor of 0.13 and 14.39μW/mK2, respectively. A thermoelectric module made from three pairs of the p-n thin film stripes provided the open circuit voltage and short circuit current up to 55.6mV and 0.04μA for a temperature difference of 101.40K, respectively.

Investigation on the Enhancement of the Thermoelectric Power Factor of ZnO Thin Films by Al-doping using Asymmetric Bipolar Pulsed-DC Magnetron Sputtering Technology

ZnO and Al-doped ZnO thin films were deposited on ceramic substrate by using an asymmetric bipolar pulsed-DC magnetron sputtering system under Ar atmosphere. Compacted ZnO powder and ZnO:Al2O3 premixed powder in copper supports were used as sputtering targets for the deposition of ZnO and Al-doped ZnO thin films, respectively. Optical emissions from the plasma during the deposition, measured using a high resolution spectrometer in the wavelength range of 360-800 nm, showed that the constituents of each target were successfully sputtered off. X-ray diffraction (XRD) analysis confirmed the formation of ZnO and Al-doped ZnO thin films of hexagonal crystal structure. The deposition rates of 24 and 15 nm/min were obtained for the ZnO and Al-dopoed ZnO thin films, respectively. The electrical conductivity and Seebeck coefficient of the thin films were measured at room temperature by the steady state and the Van der Pauw four probe methods, respectively. The increase in thermoelectric power factor of about 2 orders of magnitude was observed for the Al-doped ZnO thin films.

Resistivity improvement of Al-doped ZnO film by bipolar pulsed dc magnetron sputtering with high Ar flow rate

Aluminum-doped ZnO (AZO) films were deposited on a glass substrate of 400 mm × 400 mm area by bipolar pulse dc magnetron sputtering with various Ar flow rate. The working pressure was kept at 3 mTorr by controlling pumping speed (69–1564 l/s) during the change of Ar rate from 15 sccm to 340 sccm. And the sputtering power density was 1.48 W/cm2 at 150 kHz without intentional heating of the substrate. The resistivity of films was improved from 3.2 × 10−3 Ω cm to 1.50 × 10−3 Ω cm by increasing Ar flow rate. The mobility and carrier concentration increased from 13.7 cm2/V s to 17.8 cm2/V s and from 2.29 × 1020 #/cm3 to 2.46 × 1020 #/cm3, respectively. The mobility depended on the grain size at different Ar flow rate atmosphere, regardless of the preferred orientation and type of crystal plane. And the variation of the contents inside thin film was found by AES and TPD. The average transmittance of both films was almost same in visible range, but the band gap by high flow rate deposition was improved up to 3.52 eV as compared with that by low flow rate one and pure ZnO (3.3 eV).

Preparation of Thin Films by a Bipolar Pulsed-DC Magnetron Sputtering System Using Ca<sub>3</sub>Co<sub>4</sub>O<sub>9</sub> and CaMnO<sub>3</sub> Targets

The thin films were deposited on the glass substrates by an asymmetric bipolar pulsed-dc magnetron sputtering system using the Ca3Co4O9 and CaMnO3 Targets (n-type) targets of 60 mm diameter and 2.5 mm thickness. The targets were prepared from powder precursors, which obtained by a solid state reaction. Optical emissions from plasmas during sputter depositions of films were detected using a high resolution spectrometer. Thickness of thin film was estimated by Tolansky’s Fizeau fringe method and ellipsometic measurement. Crystal structures were studied from X-ray diffraction. The thermoelectric properties were assessed from Seebeck coefficient and electrical resistivity measurements at room temperature. The power factors were calculated. It was found that the optical emission spectrums showed that the Ca, Mn, Co and O atoms were sputtered from the targets onto glass substrates. As-deposited Ca-Co-O and Ca-Mn-O films thickness values were 0.435 ?m and 0.449 ?m, respectively. The X-ray diffraction patterns clearly showed amorphous nature of the as-deposited films. Determining thermoelectric properties of Ca-Co-O film gave Seebeck coefficient of 0.146 mV/K, electrical resistivity of 0.473Ω.cm, and power factor of 4.531 μW/m?K at room temperature. Ca-Mn-O film baring a high resistance was not the experimental determination of thermoelectric properties.

Ion flux-film structure relationship during magnetron sputtering of WO3

In this work, we have investigated the influence of the magnetic field configuration during magnetron sputtering of WO 3 in order to establish the ion flux-film structure relationship. An asymmetric bipolar pulsed DC magnetron sputtering (PDMS) was used with two magnetic field configurations: balanced (BM) and unbalanced (UMB) magnetic configurations. Ion Energy Distribution Functions (IEDFs) of the main ion populations (Ar + , O + ) were recorded. The IEDFs are broad with, in addition of the thermalized distribution around 2 eV, two peaks with available ion kinetic energy up to 40–100 eV associated with the positive part of the pulse. Comparing the BM and UBM data, we calculated an increase by a factor of 5 of the ionic current while the average energy per ion was kept constant (~44 eV). X-ray diffraction demonstrates the influence of the magnetic configuration on the coating phase constitution. The films are crystallized in the WO 3 monoclinic phase with preferential orientations along the c axis using the BM configuration and along the a axis using the UBM one’s. On the other hand, it has been demonstrated that the grain size increases with the thickness using the BM configuration (up to 18 nm) while it remains constant using the UBM one’s (~7 nm).

Influence of bilayer period and thickness ratio on the mechanical and tribological properties of CrSiN/TiAlN multilayer coatings

Nanostructured CrSiN/TiAlN multilayer coatings were deposited by a bipolar asymmetric reactive pulsed DC magnetron sputtering system. The thickness ratio of CrSiN to TiAlN layers was fixed at 1:1. The bilayer periods of the coatings were controlled to be from 6 to 40nm. Furthermore, two CrSiN/TiAlN multilayer coatings with the same bilayer period (20nm) but different CrSiN/TiAlN thickness ratios (2:8 and 8:2) were also deposited to explore the influence of thickness ratio on the mechanical properties of the multilayer coatings. The crystalline structures of the coatings were determined by a glancing angle X-ray diffractometer. The microstructures of thin films were examined by a scanning electron microscopy and a transmission electron microscopy, respectively. A nanoindenter, a micro Vickers hardness tester, and a pin-on-disk wear tester were used to evaluate the hardness, the toughness and the tribological properties of the thin films, respectively. The maximum hardness of the multilayers was obtained when the bilayer period was at 10nm for the coating with the same thickness ratio of CrSiN to TiAlN layers (1:1). Meanwhile, the thickness ratio of CrSiN to TiAlN layer had great influence on the hardness and the toughness properties of the multilayer coatings. The hardness and the toughness of the CrSiN/TiAlN multilayer coatings increased as the individual TiAlN layer thickness increased.

Nano-scratching and nano-machining in different environments on Cr 2N/Cu multilayer thin films

Five nanostructured Cr 2N/Cu multilayer coatings were deposited by a bipolar asymmetric reactive pulsed DC magnetron sputtering system, and various bilayer periods (Λ) were achieved by controlling the holding time of Si substrates in the plasma of Cr or Cu. The hardness and elastic modulus of multilayer coatings were investigated by means of a nanoindenter. Nano-scratch and nano machining experiments on multilayered coatings were conducted using atomic force microscopy (AFM) in air and DI-water, respectively. According to the groove depth, width , and coefficient of friction (COF) obtained from nano-scratch tests, influences of scratch cycle numbers and bilayer periods on the scratchability of Cr 2N/Cu multilayered thin films were examined. It was observed that after nano-scratch experiments in air and water, the COF values and the amount of removed material increased with increasing bilayer period. After nano-machining tests in air and water, different types of the cutting chip pile-ups were observed. In this work, the surface tribological properties and machinability of Cr 2N/Cu multilayered thin films when using an AFM are discussed.

Ultrathin chromium transparent metal contacts by pulsed dc magnetron sputtering

AbstractOptoelectronic technology frequently demands optically transparent materials. In this paper we present an overview of the development of ultrathin chromium films of above 80% optical transparency and 102–103 µΩ cm resistivity using bipolar pulsed dc magnetron sputtering. The surface morphology and film resistivity are investigated using atomic force microscopy (AFM) and four point probe, respectively. The variation of the electrical properties of the film with thickness, pulse duty cycle and target power are examined. An optimal experimental condition is suggested for developing transparent metal contacts, which can be used for the realisation of optoelectronic devices including organic light‐emitting diodes on flexible, low cost polymeric substrates. This process does not require high temperature and post‐deposition annealing unlike other transparent conducting oxides.

Electrical resistivity change in Al:ZnO thin films dynamically deposited by bipolar pulsed direct-current sputtering and a remote plasma source

The Al-doped ZnO (AZO) thin films for a transparent conducting oxide in solar cell devices were deposited by bipolar pulsed dc magnetron sputtering. This work was performed in an in-line type system and investigated AZO films in a static deposition mode and dynamic one, which is more important in the practical fields. Because of this dynamic deposition process, the zigzagged columnar structure was observed. This resulted in the decreasing electrical property, optical properties, and surface roughness. As a deposition in the dynamic mode, the resistivity increased from 1.64×10−3 to 2.50×10−3 Ω cm, as compared to that in the static mode, and the transmittance also decreased from 83.9% to 78.3%. To recover the disadvantage, a remote plasma source (RPS) was supported between the substrate and target for reducing zigzagged formation during the deposition. The deposition rate decreased by using RPS, but the electrical and optical properties of films got better than only dynamic mode. The resistivity and transmittance in the dynamic mode using RPS were 2.1×10−3 Ω cm and 85.5%, respectively. In this study, the authors found the possibility to advance the electrical and optical properties of AZO thin films in the industry mode.

LOW TEMPERATURE FABRICATION AND PHYSICAL PROPERTIES OF 5 at.% Ga-DOPED ZnO FILMS FOR TRANSPARENT ELECTRODE APPLICATIONS

Transparent conductive 5 at.% Ga -doped ZnO (GZO) thin films are deposited on a glass substrate by an asymmetrical bipolar-pulsed DC magnetron sputtering at various substrate temperatures. All the GZO films have nanocrystalline structure and compact surface morphology. A highly c-axis oriented GZO film was grown perpendicular to the substrate at the 200C. The measured work function of GZO film deposited at 200°C shows slightly lower value of 4.37 eV than a commercial ITO film of 4.6 eV. The GZO film showed the lowest sheet resistance of 35 Ω/□, a carrier concentration of 1.2 ×1021 cm -3, a mobility of 9.9 cm2/Vs, and high optical transmittance of over 85% in the visible range. It indicates that the GZO films at 200°C can be promising as an alternative to ITO thin film for transparent electrode applications.

Evaluation of antimicrobial abilities of Cr 2N/Cu multilayered thin films

Nine kinds of nanostructured Cr 2N/Cu multilayer thin films were deposited by the bipolar asymmetry reactive pulsed DC magnetron sputtering system. The antibacterial tests of coatings with various bilayer periods ( Λ) and different Cr 2N/Cu thickness ratios were performed to evaluate the bactericidal ability by E. coli, S. aureus and P. aeruginosa, respectively. The Λ value, thickness values of Cr 2N to Cu layers significantly affected the bactericidal rates. The 100% bactericidal rates were achieved when the Λ value reached 20 nm. For the same Λ = 12 nm Cr 2N/Cu multilayered coatings, the thickness ratio of Cr 2N to Cu also showed strong influence on the bactericidal rates.

Deposition and characterization of titania–silica optical multilayers by asymmetric bipolar pulsed dc sputtering of oxide targets

Titania–silica (TiO2/SiO2) optical multilayer structures have been conventionally deposited by reactive sputtering of metallic targets. In order to overcome the problems of arcing, target poisoning and low deposition rates encountered there, the application of oxide targets was investigated in this work with asymmetric bipolar pulsed dc magnetron sputtering. In order to evaluate the usefulness of this deposition methodology, an electric field optimized Fabry Perot mirror for He–Cd laser (λ = 441.6 nm) spectroscopy was deposited and characterized. For comparison, this mirror was also deposited by the reactive electron beam (EB) evaporation technique. The mirrors developed by the two complementary techniques were investigated for their microstructural and optical reflection properties invoking atomic force microscopy, ellipsometry, grazing incidence reflectometry and spectrophotometry. From these measurements the layer geometry, optical constants, mass density, topography, surface and interface roughness and disorder parameters were evaluated. The microstructural properties and spectral functional characteristics of the pulsed dc sputtered multilayer mirror were found to be distinctively superior to the EB deposited mirror. The knowledge gathered during this study has been utilized to develop a 21-layer high-pass edge filter for radio photoluminescence dosimetry.

Characteristics of Cr 2N/Cu multilayered thin films with different bilayer thickness

Nanostructured Cr 2N/Cu multilayer coatings were deposited periodically by a bipolar asymmetric reactive pulsed DC magnetron sputtering system. The crystalline structure of multilayer coatings was determined by a glancing angle X-ray diffractometer. Microstructures of thin films were examined by an atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. A nanoindenter, a micro Vickers hardness tester and pin-on-disk wear tests were used to evaluate the hardness, fracture toughness and tribological properties of the thin films, respectively. Electrochemical tests in 3.5 wt.% NaCl aqueous solution were performed to evaluate the corrosion resistance of multilayered coatings . The bilayer period of the nanostructured multilayer coatings were controlled within the range from 5 to 40 nm. It was found that the hardness increased with decreasing bilayer period and leveled off at small periods around 6–12 nm. The Cr 2N/Cu multilayered coatings with bilayer periods of 5 and 6 nm exhibited a combination of high hardness, good tribological and good anticorrosion performance in this study.

Heat Transfer Analysis in ICP-Assisted Bipolar Pulsed DC Magnetron Sputtering

March 2009 Special Issue on 17th World Interfinish Congress Heat Transfer Analysis in ICP-Assisted Bipolar Pulsed DC Magnetron Sputtering Wonkyun YANG and Junghoon JOO .........971 Etch Characteristics of TiO2 Etched by Using an Atomic Layer Etching Technique with BCl3 Gas and an Ar Neutral Beam Jae Beom PARK, Woong Sun LIM, Sang Duk PARK, Byoung Jae PARK and Geun Young YEOM .........976 Characteristics of SiOx Thin Films Deposited by Using Direct-Type Pin-to-Plate Dielectric Barrier Discharge with PDMS/He/O2 Gases at Low Temperature J. H. LEE, Y. S. KIM, S. J. KYUNG, J. T. LIM and G. Y. YEOM .........981 An Application of Plasma Treatment to Improve Shear and Bending Behavior of HDPE/Steel Composites Ji Hoon LEE and Kyong Yop RHEE .........986 Effect of Process Parameters on Plasma Equipment in a Cl2 Inductively Coupled Plasma Sanghee KWON and Byungwhan KIM .........992 Effects of Pulsating Bias Power on Deep Si Vias Etching Seung-Hwan LEE, Young-Dae LIM and Won Jong YOON .........998 Chemical Reaction on the Surface of As-Doped ZnO Thin Films during the Dry Etching Process Chan-Min KANG, Dong-Pyo KIM, Doo-Seung UM and Chang-Il KIM.........1002 Effects of a Sandwich-Like Catalyst on the Vertical Growth of Carbon Nanotubes Synthesized by Using Chemical Vapor Deposition Hyeongkeun KIM, Cheesung LEE, Jaeboong CHOI, Kyoung-Yong CHUN,Youngjin KIM and Seunghyun BAIK.........1006 Different Behaviors of Catalytic Nanoparticles during Carbon Nanotube Growth by Chemical Vapor Deposition Goo-Hwan JEONG and Yoshihiro KOBAYASHI.........1011 Effects of Nanostructures Formed by Plasma Etching on the Reflectance of Solar Cells Seung-Heon RYU, Cheng YANG, Won Jong YOO, Dong-Ho KIM and Teak KIM.........1016 Formation of Silicon Nanoparticles Using SiH4 Pyrolysis at Atmosphericand Low-Pressure Kwangsu KIM, Daekwang WOO, Jin-Hwan PARK, Seok-Gwang DOO and Taesung KIM.........1021 Effect of Electrolyte Conductivity on the Formation of a Nanotubular TiO2 Photoanode for a Dye-Sensitized Solar Cell Kiyoung LEE, Jiyoung KIM, Hyeyoung KIM, Yujin LEE, Yongsug TAK, Doohun KIM and Patrik SCHMUKI.........1027 ISSN 0374-4884 Online ISSN 1976-8524

Influence of bipolar pulsed DC magnetron sputtering on elemental composition and micro-structure of Ti–Al–Y–N thin films

Single-phase cubic Ti 1 − x Al x N thin films with high Al content are preferred in industrial applications as they combine superior mechanical properties with good oxidation protection. Recently we showed that yttrium, which can further increase the oxidation resistance by the reactive element effect, shifts the cubic stability range of Ti 1 − x Al x N to lower AlN mole fractions. Already the addition of 1 at.% Y to single-phase cubic Ti 0.45Al 0.55N promotes the hexagonal phase formation. Based on X-ray diffraction and transmission electron microscopy studies we reveal that DC magnetron sputtering (DC-MS) from Ti 0.49Al 0.49Y 0.02 compound targets in Ar–N 2 atmosphere results in the formation of mixed cubic-hexagonal structured (Ti 1 − x Al x ) 1 − y Y y N films, whereas the cubic structure can be stabilized by employing bipolar pulsed magnetron sputtering. This can be correlated to an increase in the Ti/Al ratio of the film and increased ion bombardment with increasing pulse duration, triggered by increases in the plasma electron temperature and ion fluxes. For pulsed DC-MS with 80 kHz and increasing pulse duration from 0 (DC-MS) to 4976 ns the composition of the coatings changes from Ti 0.41Al 0.57Y 0.02N to Ti 0.46Al 0.52Y 0.02N and the structure from a mixed cubic-hexagonal to a single-phase cubic, resulting in hardness increases from 23.5 to 34.6 GPa, respectively.