Electron Cyclotron Resonance Microwave Plasma Research Articles

Nitridation of steel using a microwave ECR plasma

Plasma nitriding of En-41B steel samples has been performed using electron cyclotron resonance (ECR) plasma of (N 2+H 2) gas mixtures at substrate temperature of 420°C in an ECR plasma reactor. A nitriding time of only 30 min has been found to produce a compact surface nitride layer composed of γ′ (Fe 4N) and ε(Fe 2–3N) with a thickness of around 7–12 μm. The thickness of ε phase was found to be only about 2 μm. Microhardness measurements showed significant increase in the hardness from 220 HV (for untreated samples) up to 1000 HV (for nitrided sample). Structural investigations for the surfaces were carried out using grazing incidence X-ray diffraction methods. A scanning electron microscope was used for obtaining the microstructural details of plasma nitrided samples. These results were augmented by surface compositional analysis using X-ray photoelectron spectroscopy.

Effect of gradient a-SiCx interlayer on adhesion of DLC films

Diamond-like carbon films were prepared on radio-frequency (RF) biased substrates of silicon wafer and Corning 7059 glass at low temperature substrate by electron cyclotron resonance microwave plasma chemical vapor deposition using CH4–H2 and CH4–Ar as reactant gases. The effects of a-SiCx interlayer prepared by RF-PECVD on the adhesion and failure mode of DLC films were investigated. In CH4–H2 system with the a-SiCx interlayer and RF bias applied to −90 V, the adherence of DLC films was improved significantly and the critical load was increased from 2 N without RF bias to 80 N. The failure mode transferred from spalling failure at lower substrate bias to conformal cracking at higher substrate bias. In CH4–Ar system with a-SiCx interlayer, the critical load was increased to 20 N at RF bias −90 V and the spalling failure mode was revealed. Comparing the DLC films obtained in the two system coated with a-SiCx interlayer and RF bias applied to −90 V, the one deposited in CH4–H2 system exhibited less damage which demonstrates that the films obtained has a better adherence behavior.

The Structure and I-V Property of a-C:F Thin Film

Fluorinated amorphous carbon (a-C:F) thin film has been deposited by microwave electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) using C6H6 and CHF3 as source gases. The result of x-ray photoelectron spectroscopy (XPS) shows that the main bonds in the film as-deposited are C-C, C-F and CF2. The measurement of postive I-V property indicates that the conductance of the film presents Omic characteristic at a lower electric field, and follows Schotty emission at a higher electric field.

High coercivity ferrite thin-film tape media for perpendicular recording

Reactive sputtering using an electron–cyclotron-resonance microwave plasma was introduced to prepare ferrite thin-film media at substrate temperatures lower than 150°C without oxidation process after their deposition. The ferrite thin-films deposited on glass substrates had perpendicular magnetic anisotropy, high coercivity of about 3000 Oe and very smooth surface. The ferrite thin-films deposited on organic flexible film substrates such as polyimide and PET films also showed perpendicular magnetic anisotropy and high coercivity of 1700–2000 Oe.

Nanotribology of amorphous hydrogenated carbon films using scanning probe microscopy

Nanotribological characterization of amorphous hydrogenated carbon (a-C:H) films is performed by scanning probe microscopy. The a-C:H films are produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD). The influences of different percentages of hydrogen (H 2) and methane (CH 4) in the gas-discharge plasmas on the nanotribological characteristics are investigated. Scanning probe nanotribological tests, including the nano-friction, nano-wear and nano-scratch, are carried out. Large quantitative variations of the friction coefficient as well as the wear depth are found for different H 2 content percentages in source gas. The results indicate that a higher H 2 content in the source gas is beneficial to wear and scratch resistance, and produces a lower friction coefficient and that source gas H 2 content plays an important role in the tribological characteristics of diamond-like films.

Mechanical properties of DLC films prepared in acetylene and methane plasmas using electron cyclotron resonance microwave plasma chemical vapor deposition

Diamond-like carbon (DLC) films were deposited on silicon using methane and acetylene plasma induced by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD). The mechanical properties of DLC films were characterized by micro-Raman system, atomic force microscope, tribometer, nano-indenter used for both hardness and nano-scratch test measurements. The mechanical properties of both DLC films, prepared in methane and acetylene plasmas, respectively, strongly depended on the kinetic energy of impinging particles. The deposition at −120 V substrate bias gave rise to DLC films with the best mechanical properties for both methane and acetylene plasmas. The hardness measurements with variable indentation depth showed the characteristic changes in hardness values implying elastic deformations of supporting substrates. The maximum hardness value of DLC M films was 20 GPa while that of DLC A films was 28 GPa. However, the hardness dropped when DLC films were prepared at substrate biases more negative than −120 V due to the thermal graphitization. The improvement in DLC properties usually provided the films with smaller hydrogen content and higher density of sp 3 bondings. These parameters were engineered through controlling the deposition parameters. Particularly, the bombardment of growing DLC films by energetic ions showed to be extremely important to yield films with lower internal stress.

Film thickness effects on mechanical and tribological properties of nitrogenated diamond-like carbon films

Nanoindentation, nanoscratch and ball-on-disk tests were used to determine the film thickness effect on the mechanical and tribological properties of nitrogenated diamond-like carbon (CN x ) films, which were deposited on Si (100) substrates by an electron cyclotron resonance microwave plasma chemical vapor deposition (ECR MP-CVD) system. Except for the film with a thickness of 20 nm, there existed peak values of hardness for all films thicker than 44 nm. When the thickness ranged from 44 to 235 nm, the peak values of hardness and the corresponding indentation depth increased along with increasing film thickness. The results of scratch resistance tests showed that the critical loads of the fracture were independent of thickness for thinner films, however, they increased rapidly with increasing thickness for thicker films. Ball-on-disk sliding tests indicated that the friction coefficient decreased with increasing thickness for thinner films, while there was no obvious thickness dependence of the friction coefficient for relatively thicker films. The formation of transferred layer and graphitization of the films during sliding resulted in the decrease of friction coefficients at early stages of sliding.

Tunneling spectroscopy in Fe-GaN-Fe trilayer structures grown by MBE using ECR microwave plasma nitrogen source

Epitaxy of Fe on GaAs by the MBE technique has a long tradition in magnetism research. This paper deals with the growth of epitaxial Fe–GaN–Fe trilayer structures whose intriguing magnetic properties were exploited for the evaluation of GaN as a spin-dependent tunneling barrier. The trilayers were grown on semi-insulating (0 0 1) GaAs using an ultra-high vacuum deposition chamber equipped with electron cyclotron resonance (ECR) microwave plasma nitrogen source.

Growth characterization and properties of diamond-like carbon films by electron cyclotron resonance chemical vapor deposition

Diamond-like carbon (DLC) films were deposited on radio-frequency (RF) biased substrates at low temperature by electron cyclotron resonance microwave plasma chemical vapor deposition using CH 4-Ar as reactant gas. The effects of gas composition ratio, microwave power and RF bias on growth rate, structure and hardness of the films were investigated. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Vickers microhardness tests were used to determine the structural change and properties of the DLC films. By changing the microwave power, the growth rate shows a maximum value of 1.6 μm/h at 150 W. From Raman spectra of the films deposited at different microwave power and RF bias, the peaks centered at 1540±20 cm −1 for the deposited films, which was the characteristic peak of DLC coatings. By increasing the RF bias the CH n peaks in the FTIR spectra decreased because of hydrogen evolution. The film hardness increased with the increase in microwave power and RF bias. DLC films synthesized at a bias voltage of −(100–250) V and CH 4/Ar gas ratio of 2/7 exhibited extreme hardness of more than 3000 kg mm −2. The role of adding Ar in reactant gases on DLC deposition was also discussed.

Characterization of CN x films prepared by twinned ECR plasma source enhanced DC magnetron sputtering

The DC discharge of a planar magnetron was enhanced by twinned microwave electron cyclotron resonance plasma source. The magnetic cusp geometry formed in the processing chamber was used for plasma confinement. The sputtering discharge characteristics was investigated and a combined mode of voltage and current was observed at a pressure as low as 0.007 Pa. Carbon nitride thin films were synthesized using this method. Characterization of the films showed that the deposition rate was high, and the films were composed of a single amorphous carbon nitride phase with N/C ratio close to that of C 3N 4, with the bonding mainly of CN type.

Transport properties of epitaxial Fe–GaN–Fe tunnel junctions on GaAs

Using an ultra-high vacuum deposition system equipped with an electron cyclotron resonance microwave plasma nitrogen source, epitaxial Fe–GaN–Fe layers were grown on GaAs for the evaluation of GaN as a spin-dependent tunneling barrier. The tunnel junction conductance was strongly temperature dependent. Above 10 K thermionic emission over the barrier was the dominant transport mechanism, while at lower temperature direct tunneling prevailed. At 4 K, the I– V characteristics were non-linear as expected for metal–insulator–metal systems. To date present, spin-dependent tunneling was not observed.

Characteristics of a large diameter reactive ion beam generated by an electron cyclotron resonance microwave plasma source

A new ion source with a large beam diameter generated by an electron cyclotron resonance microwave plasma source is presented. Ion beams with a beam diameter of >160 mm and a maximum argon-ion current density of 2.1 mA/cm2 are obtained. For this large two-electrode silicon-ion extraction optics are mounted into an electron cyclotron resonance microwave plasma source. With ion extraction optics installed an electron temperature up to three times higher than without optics was observed. Due to this high electron temperature (up to 12 eV) the O+ concentration as compared to the O2+ concentration is enhanced in an oxygen plasma. Therefore, a very reactive oxygen ion beam with an ion current density of 1.1 mA/cm2 can be generated. Ion energies of 1 keV corresponding to the screen grid voltage are obtained with a small energy spread of 10 eV full width at half maximum or less. The low working pressure (about 10−4 mbar) is well suited for low-pressure ion-beam processes.

Plasma enhanced direct current planar magnetron sputtering technique employing a twinned microwave electron cyclotron resonance plasma source

The dc discharge of a planar magnetron was enhanced by a twinned microwave electron cyclotron resonance plasma source. The magnetic cusp geometry formed in the processing chamber was used for plasma confinement. The sputtering discharge characteristics were investigated and a combined mode of voltage and current was observed at a pressure as low as 0.007 Pa. Carbon–nitride thin films were synthesized using this method. Characterization of the films show that deposition rate was high, the films were composed of a single amorphous carbon nitride phase with N/C ratio close to that of C3N4, and the bonding was mainly of C–N type.

Fracture resistance enhancement of diamond-like carbon/nitrogenated diamond-like carbon multilayer deposited by electron cyclotron resonance microwave plasma chemical vapor deposition

Diamond-like carbon (DLC), nitrogenated diamond-like carbon (CNx) and multilayered DLC/CNx films of 350 nm overall thickness were deposited on Si (100) substrates by using an electron cyclotron resonance microwave plasma chemical vapor deposition system. The deposited films were investigated for the fracture resistance using nanoindentation and nanoscratch methods in combination with scanning electron microscopy. In nanoindentation fracture tests, the film fracture was detected by the discontinuities in the load-displacement curves. The abrupt increase in the friction force between the tip and films during nanoscratch fracture tests was taken as a criterion for film fracture. Both the nanoindentation and nanoscratch fracture tests revealed that the DLC/CNx multilayer exhibited substantially higher critical load than that measured for either DLC or CNx films, though there was no obvious enhancement in the multilayer hardness and elastic modulus while the multilayer internal stress was between that of DLC and CNx. This study suggests that the fracture resistance of hard coatings can be improved by the design of a suitable multilayer structure.

CVD Diamond Coating on WC Cutting Tool Using Electrophoresis.

CVD diamond films were deposited on commercial WC cutting tools. An electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD) apparatus was used to deposit diamond films. Methane and hydrogen were used as gaseous source for CVD, and WC-Co (JIS standard: K-10) was used as a substrate for CVD. Cobalt on the surface of the WC cutting tool prevented CVD diamond from depositing on the WC cutting tool. Scratching with diamond particles on the surface of the WC cutting tool, which is one of the most popular pretreatments for enhancing the nuclei density of CVD diamond, was ineffective on the WC cutting tool without removing surface cobalt. On the other hand, Electrophoresis treatment was effective for increasing diamond nuclei density on the WC cutting tool without removing surface cobalt. However, CVD diamond films synthesized on the WC cutting tool (from which surface cobalt was removed) using electrophoresis pretreatment separated from the surface of the WC cutting tool. To improve the adhesion between CVD diamond film and WC cutting tool, heat treatment was performed after electrophoresis pretreatment. The heat treatment condition was 500°C for 1h in Ar flow. The heat treatment after electrophoresis treatment was effective for improving adhesion between WC surface and CVD diamond film. Vickers hardness test was carried out for estimating the adhesion. The Vickers hardness of the CVD diamond film obtained by the electrophoresis-heat pretreatment, was as hard as that of a CVD diamond film obtained with conventional scratching pretreatment. From the results of Vickers hardness test, it was found that heat treatment after electrophoresis process is effective for improving the strength of the adhesion layer.

磁性材料 有機可塑基板上に堆積させたＣｏ含有酸化鉄薄膜

Co-containing ferrite thin films were successfully deposited on organic flexible substrates by the reactive sputtering method using-an electron cyclotron resonance microwave plasma at a temperature lower than 150°C. The ferrite thin films had an amorphous-like structure, perpendicular magnetic anisotropy and high perpendicular coercivity of about 170kA/m. The perpendicular coercivity increased with increasing substrate thickness. Inserting SiO2 underlayer between organic flexible substrate and ferrite thin films enhanced the perpendicular coercivity.

OPTICAL PROPERTIES OF AMORPHOUS FLUORINATED CARBON FILMS PREPARED BY ELECTRON CYCLOTRON RESONANCE PLASMA

The optical property of amorphous fluorinated carbon (α-C∶F) films are investigated, which are prepared by microwave electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) using trifluromethane (CHF3) and benzene (C6H6) as source gases. The optical energy gap Eg of the α-C∶F films deposited at 140—700W powers and CHF3∶C6H6=1∶1—10∶1 are between 1.76 and 2.85eV. The amount of fluorine in the films has an effect on optical absorption and energy gap. The absorption edge increases as the amount of fluorine is raised. The optical energy gap Eg is mainly determined by CF bond in the films, which results in the change of the density of states in band tail of the valence band.

Some growth peculiarities of a-C:H films in ECR microwave plasma

The chemical vapor deposition (CVD) process of a-C:H films from methane and argon gas mixtures in an electron cyclotron resonance (ECR) microwave plasma has been studied. The formation of a-C:H films in a wide range of basic parameters has been investigated. The basic parameters are the following: the total pressure of the working gas mixture, the composition of the gas mixture, the magnitude of microwave power absorbed in a plasma, the location of the substrate L ECR-S with respect to the position of ECR and substrate material (Si, ceramic). We found that extremely low or zero growth rate of the a-C:H films takes place in the cases when (i) the substrate is placed in the ECR plane or its close vicinity and (ii) a high microwave power is used; the latter situation occurs when the power is about 300 W or greater. The increase in deposition rate takes place under the increase of the L ECR-S distance or under the decrease of the microwave power. The deposition rate of a-C:H films on the ceramic substrate was higher than that on the silicon substrate for all values of operating pressure. These peculiarities are explained in terms of additional heating of Si substrates by microwave power absorption outside the ECR region. A later (latent) parameter should be taken into account in the analysis of the deposition process and choice of the substrate material. The mechanism leading to a very high growth rate of a-C:H polymer-like films is discussed.

Relative Irradiance Measurement and Bonding Configurations of Amorphous Fluorinated Carbon Films Deposited by Electron Cyclotron Resonance Plasma

α-C:F films are deposited by microwave electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) using trifluoromethane (CHF3) and benzene (C6H6) as source gases at different microwave powers. The radicals in plasma originating from source gases dissociation are analyzed by relative irradiance measurement. The bonding configurations and binding state of α-C:F films are measured with Fourier-transformed infrared spectrometer (FTIR) and x-ray photoelectron spectroscopy (XPS). The results show that α-C:F films are mainly composed of CF radical at lower powers but of CF2 radical at higher powers. The deposition of films is related to the radicals generated in plasma and the main bonding configurations are dependent on the ratio of CF to CF2 radicals in films.

Physical properties of a-C:H films prepared by electron cyclotron resonance microwave plasma chemical vapor deposition

a-C:H films have been deposited on silicon and glass using electron cyclotron resonance microwave plasma decomposition of CH 4 diluted with Ar gas at 0–160 V rf negative bias and 65–250 W microwave power. The deposition rates, absorption coefficients, optical bandgaps, refractive indices and internal stresses of the a-C:H films grown under varying preparation parameters have been measured. The microstructure of the carbon films has been evaluated by Raman spectroscopy. It has been found that the properties and structure of the carbon films are strongly dependent upon the rf substrate bias voltage. At lower rf biases (0 and 40 V), the films are transparent polymer-like carbon films with lower refractive indices, lower internal stresses, and higher optical bandgaps; at higher rf biases (80, 120 and 160 V), they are semi-transparent diamond-like carbon films with higher refractive indices, higher internal stresses and lower optical bandgaps. Microwave power has little influence on the properties and structure of the a-C:H films.