Room-temperature deposition of transparent conducting Al-doped ZnO films by RF magnetron sputtering method

Transparent conductive Al-doped zinc oxide (AZO) films with highly (0 0 2)-preferred orientation were deposited on quartz substrates at room temperature by RF magnetron sputtering. Optimization of deposition parameters was based on RF power, Ar pressure in the vacuum chamber, and distance between the target and substrate. The structural, electrical, and optical properties of the AZO thin films were investigated by X-ray diffraction, Hall measurement, and optical transmission spectroscopy. The 250 nm thickness AZO films with an electrical resistivity as low as 4.62 × 10⁻⁴ Ω cm and an average optical transmission of 93.7% in the visible range were obtained at RF power of 300 W, Ar flow rate of 30 sccm, and target distance of 7 cm. The optical bandgap depends on the deposition condition, and was in the range of 3.75-3.86 eV. These results make the possibility for light emitting diodes (LEDs) and solar cells with AZO films as transparent electrodes, especially using lift-off process to achieve the transparent electrode pattern transfer.     

Effects of deposition parameters on the structure and mechanical properties of high-entropy alloy nitride films

High-entropy alloy (AlCrNbSiTiV)N nitride films are prepared using direct current (dc) reactive magnetron sputtering, with an equiatomic AlCrNbSiTiV alloy target. Experiments using the grey-Taguchi method are conducted to determine the effect of deposition parameters (dc power, substrate temperature, N₂/(N₂+Ar) flow rate and substrate bias) on the microstructure, mechanical and tribological properties. Orthogonal array (L₉ 3⁴), signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. The coated films are examined using scanning electron microscopy, an atomic force microscope, transmission electron microscopy (TEM), a tribometer and a nanoindenter. The TEM patterns confirm that the (AlCrNbSiTiV)N nitride films have a simple face-center-cubic structure. The experimental results show that a (AlCrNbSiTiV)N film coating significantly improves the mechanical properties. In the confirmation runs, using grey relational analysis, the improvement in friction coefficient is 32.5%, in corrosion current is 28.6%, in hardness H is 29.4%, in elastic modulus E is −18.3%, in H/E is 57.1 and in H³/E² is 225.0%. The samples with (AlCrNbSiTiV)N film coating are classified as HF1 and exhibit good adhesive strength.     

Influence of sputtering power and Ar–N2 flow on the structure and optical properties of indium nitride films prepared by magnetron sputtering

ABSTRACT

This paper discusses the deposition of indium nitride (InN) thin films on Si (100) substrates by using pulsed DC magnetron sputtering. Effects of varying sputtering power and Ar–N₂ flow ratio on the structural, morphological, and optical properties of indium nitride (InN) films were investigated. The structural characterization indicated nanocrystalline InN film with preferred orientation towards (101) plane that exhibited the optimum crystalline quality at 130?W and for 40:60 Ar–N₂ ratio. The surface morphology of InN, as observed through FESEM, contained irregularly shaped nanocrystals with size that increases with higher sputtering power and Ar:N₂ flow ratio. The optical properties of InN films were studied using ellipsometer at room temperature. The band gap of InN was decreased with the increase of sputtering power to 130?W, whereas an increase in the band gap was noticed with the increase of the Ar:N₂ flow ratio.     

Influence of oxygen on structural and optoelectronic properties of CdS thin film deposited by magnetron sputtering technique

In this study, CdS thin films with thicknesses of approximately 100 nm were deposited at a substrate temperature of 100 °C by a sputtering technique under two different ambient conditions—pure Ar ambient and Ar/O₂ (99:1) ambient—at deposition power densities of 1.0 and 2.0 W/cm², respectively The films were polycrystalline with a preferential orientation along the (002) crystal plane; however, the films deposited in the Ar/O₂ ambient exhibited reduced crystallinity. Furthermore, the crystallite sizes, micro-strains, and dislocation densities of the films were significantly affected by oxygen diffusion into the films’ crystal structures. The CdS films deposited in the Ar/O₂ ambient demonstrated higher optical transmittance and higher bandgaps. Morphologies observed from scanning electron microscopy images revealed that the grains of the films were also significantly affected by the oxygen present in the deposition ambient. Additionally, photoluminescence analysis revealed that the sulfur vacancies in the CdS films were partially filled by oxygen atoms, causing significant variations in the electrical properties of the films.     

Microstructure, chemical bonds, and friction properties of nanocrystalline diamond films deposited in two different plasma media

Nanocrystalline diamond films with the properties dependent on the composition of the gaseous medium have been prepared using the microwave plasma enhanced chemical vapor deposition (MPECVD) method. A nanocrystalline film formed in the Ar/CH₄ plasma is characterized by a high crystallinity factor, a small grain size, a large fraction of sp ²-amorphous carbon, and, consequently, by an increase in the hardness and elastic modulus. The low value of the friction coefficient of this film is associated with the small grain size and large fraction of the sp ²-amorphous carbon boundary phase that ensures an easy sliding. The contact angle of the film is small (hydrophilic properties) in the case when the plasma consists of an Ar/CH₄ mixture. It has been shown that the wetting properties of the films are provided by a thin layer of carboxyl and hydroxyl functional groups passivating the dangling bonds at the surface that are responsible for the boundary lubrication mechanism. It has also been found that the friction coefficient of these films is inversely proportional to the contact pressure dependent on the diameter of the sliding counterbody ball.     

Influence of deposition pressure and power on characteristics of RF-Sputtered Mo films and investigation of sodium diffusion in the films

Mo films deposited by DC sputtering are widely used as back contact in CIGS and CZTS based thin film solar cells. However, there have been only a few studies on the deposition of Mo films by RF sputtering method. In this context, Mo films on SLG substrates were prepared as a function of deposition pressure and power by using RF magnetron sputtering method to contribute to this shortcoming. Mo films were deposited at 250 °C substrate temperature by using 20, 15, 10 mTorr Ar pressures at 120 W RF power and 10 mTorr Ar pressure at 100 W RF power. Structural, morphological and reflectivity properties of RF-sputtered Mo films were clarified by XRD, AFM, FE-SEM and UV–Vis measurements. In addition, due to sodium incorporation from SLG substrate to the absorber layer through Mo back contact layer is so essential in terms of improving the conversion efficiency values of CIGS and CZTS thin film solar cell devices, the effects of Na diffusion in the films were analyzed with SIMS depth profile. The electrical properties of the films such as mobility, carrier density and resistivity were determined by Hall Effect measurements. It was found that Mo films prepared at 120 W, 10 mtorr and 250 °C substrate temperature and then annealed at 500 °C for 30 min, had resistivity as low as 10⁻⁵ Ω cm, as well as higher amount of Na incorporation than other films.     

玉米蛋白质基底上射频磁控溅射法制备ZnO薄膜

采用射频磁控溅射方法在蛋白质基底上成功地制备了ZnO薄膜,研究了不同靶基距、氩氧比和溅射功率条件对ZnO薄膜性质的影响。结果表明,较小的靶基距有助于ZnO薄膜的c轴择优取向生长。我们还发现,沉积于玉米蛋白质基底的ZnO薄膜存在不同程度的张应力,当Ar/（Ar+O₂）为0.7时,ZnO薄膜内的张应力最小。ZnO近带边发光峰有不同程度的红移,我们认为,这是由于晶界势垒和氧空位V_o造成的。随着溅射功率的增大,薄膜生长速率显著加快,晶粒尺寸增大,ZnO的近带边发光峰位逐渐趋向于理论值。     

The influence of H2/(H2 + Ar) ratio on microstructure and optoelectronic properties of microcrystalline silicon films deposited by plasma-enhanced CVD

Hydrogenated microcrystalline silicon films were deposited by glow discharge decomposition of SiH₄ diluted in mixed gas of Ar and H₂. By investigating the dependence of the film crystallinity on the flow rates of Ar and H₂, we showed that the addition of Ar in diluted gas markedly improves the crystallinity due to an enhanced dissociation of SiH₄. The infrared-absorption spectrum reveals that the fraction of SiH bonding increases with increasing the rate ratio of H₂/(H₂ + Ar). The surface roughness of the films increases with increasing the flow rate ratio of H₂/(H₂ + Ar), which is attributed to the decrease of massive bombardment of Ar ions in the plasma. Refractive index and absorption coefficient of the films were obtained by simulating the optical transmission spectra using a modified envelope method. Electrical measurements of the films show that the dark conductivity increases and the activation energy decreases with the ratio of H₂/(H₂ + Ar). A reasonable explanation is presented for the dependence of the microstructure and optoelectronic properties on the flow rate ratio of H₂/(H₂ + Ar).     

Determination of the element distribution in films deposited using the plasma focus facility by Rutherford backscattering

The C, Cu and W element profiles in films deposited using a plasma focus facility are studied by the Rutherford backscattering of 2-MeV He⁺ ions. The films are deposited onto glass substrates in Ar plasmaforming gas. The element profiles are found to depend significantly on the kinetic energy of particles. The penetration depth of particles with the velocity ~10⁵ m/s is about 1.5 μm. The corresponding element profiles showing the distribution of elements over the thickness of the glass are non-linear. For each element, the maximum layer depth is observed under the glass surface. The formation of Cu, W and C layers under the glass surface and their overlapping is a feature of films deposited using the plasma focus facility. Such an arrangement of layers evidences the significant difference between this method of film deposition and conventional techniques at low rates of atom deposition, as well as diffusion-based methods. The obtained films are found to have dielectric properties.     

Growth and thermoelectric properties of FeSb<Subscript>2</Subscript> films produced by pulsed laser deposition

Thermoelectric FeSb₂ films were produced by pulsed laser deposition on silica substrates in a low-pressure Ar environment. The growth conditions for near phase-pure FeSb₂ films were confirmed to be optimized at a substrate temperature of 425°C, an Ar pressure of 2 Pa, and deposition time of 3 h by ablating specifically prepared compound targets made of Fe and Sb powders in atomic ratio of 1:4. The thermoelectric transport properties of FeSb₂ films were investigated. Pulsed laser deposition was demonstrated as a method for production of good-quality FeSb₂ films.     

Pulsed magnetron sputtering and ion-induced annealing of carbon films

Thin carbon films are deposited on a silicon substrate at room temperatures via the biased pulsed magnetron sputtering of graphite in the physical (Ar, Kr, Xe) and reactive (Ar: CH4) modes at a different sputtering power density varying from 40 to 550 W/cm². To ensure ion-assistance, negative bias of the substrate is set during film deposition by means of both DC and pulsed power sources. Some deposition parameters lead to a high hardness of the films (12.5 GPa), optical transparency, a surface resistance of RS > 10⁹ Ω/h, and developed nanomorphology of the sample surface which bears visible inclusions with a lateral size of 35 nm. Some of the films are annealed after deposition with a C⁺-ion beam with an energy of 20 keV. A correlation between the parameters of magnetron deposition and ion-beam modification and the examined characteristics of the films is found. Different R _S values in a wide range can be achieved by means of simple adjustment of the parameters and modes during magnetron sputtering and ion-beam modification.     

等离子体发射光谱诊断用于射频磁控溅射GaP薄膜的工艺参数优化

以GaP为靶材、Ar为工作气体,采用射频磁控溅射法制备了厚层GaP膜.对沉积过程中的辉光放电等离子体进行了发射光谱诊断,发现只有ArⅠ发射谱线.研究了工艺参数对发射谱线强度的影响规律,并在此基础上通过同时改变射频功率、Ar气流量及工作气压,使ArⅠ发射谱线强度保持相同.发现通过增大射频功率、减小工作气压而保持ArⅠ发射谱线强度不变可以提高GaP膜的沉积速率,并使GaP膜的沉积工艺参数得到优化.在优化后的工艺参数下制备出了符合化学计量比、红外透过性能好的厚层GaP膜. 关键词： GaP薄膜 射频磁控溅射 等离子体发射光谱 红外透射     

The characterization of fluorocarbon films on NiTi alloy by magnetron sputtering

Fluorocarbon films were deposited on nickel-titanium (NiTi) alloy substrate by radio-frequency (RF, 13.56 MHz) magnetron sputtering using a polytetrafluoroethylene (PTFE) target. The deposition parameters of fluorocarbon films including the RF power, the working gas pressure and Ar flow rate were systematically studied. The structure of the deposited films was studied by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The surface morphology of the deposited films was measured by atomic force microscopy (AFM). The mechanical properties of the deposited films were characterized by a nanoindenter. C-Fx and C-C units were found in the deposited fluorocarbon films, which corresponded to the results of XPS. The surface roughness of the fluorocarbon film was 7.418 nm (Ra).     

Development of conductive transparent indium tin oxide (ITO) thin films deposited by direct current (DC) magnetron sputtering for photon-STM applications

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 °C and the effects of thermal annealing in air between 200 and 400 °C for between1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of ∼1.7×10^-3 Torr by DC power sputtering (100 W) at substrate temperatures between 40 and 400 °C exhibited resistivities in the range 3.0–5.7×10^-5 Ω m and transmissions in the range 71–79%. After deposition and annealing in air at 300 °C for 1 h, the films showed resistivities in the range 2.9–4.0×10^-5 Ω m and transmissions in the range 78–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 °C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 °C, and up to 400 °C, had domains with crystalline structures. After deposition and annealing in air at 300 °C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 °C to 300 °C, and annealing in air at 300 °C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 °C and annealing in air at 300 °C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated. Received: 10 July 2000 / Accepted: 27 October 2000 / Published online: 9 February 2001     

Optical,electrical, structural and microstructural characteristics of rf sputtered ITO films developed for art protection coatings

Transparent and conductive tin-doped indium oxide (ITO) films have been prepared by rf sputtering in an Ar and Ar+O₂ gas mixture, both with and without additional substrate heating. The influence of both deposition conditions and post-annealing treatment on optical, electrical, structural and microstructural properties of the ITO films has been investigated. The optical constants have been calculated in the range 320–2500 nm using a combination of several theoretical models. A schematic diagram for the film properties change versus composition has been proposed in terms of a generalized parameter characterising the energy efficiency of the film formation. The deposition conditions and the optical and electrical properties of the films have been optimized with respect to the requirements for their application in art protection coatings. PACS 78.66-w; 68.55.Jk; 81.15.Cd; 81.40-z     

Deposition of MgO films by pulsed mid-frequency magnetron sputtering

MgO films were deposited by pulsed mid-frequency magnetron sputtering from metallic targets in the mixture of Ar and O₂ gas. The surface morphology, crystalline structure, and optical properties were characterized by using atomic force microscopy (AFM), X-ray diffraction (XRD), and spectroscopic ellipsometry, respectively. The secondary electron emission coefficients of MgO films were measured by using a self-made apparatus in He gas. A pronounced hysteresis phenomenon of target voltage, current, and deposition rate with increasing and decreasing O₂ flow rate was observed. The structure of films deposited at a metallic mode changes from Mg phase to the mixed Mg and MgO phase, and the films have a very rough surface. All the films deposited at oxide mode have high transparency and smooth surface, and show (2 2 0) preferred orientation growth. The refractive index and extinction coefficient at a wavelength of 670 nm for MgO films deposited at oxide mode with a O₂ flow rate of 3 sccm are 1.698 and 1.16×10⁻⁴, respectively. The secondary emission coefficient at a E/p of 57.8 V/(cm Torr) for MgO films deposited at a O₂ flow rate of 3 sccm is 0.16, which is higher than that of MgO films deposited by e-beam evaporation.     

Optical emission spectroscopy during fabrication of indium-tin-oxynitride films by RF-sputtering

Indium-tin-oxide (ITO) and indium-tin-oxynitride (ITON) films have been deposited on glass by rf-sputtering from an ITO target, using Ar plasma and N₂ plasma, respectively, and different rf-power. Optical emission spectroscopy (OES) was employed to identify the species present in the plasma and to correlate them with the properties of the ITO and ITON thin films. Emission lines of ionic In could only be detected in N₂ plasma, whereas in the Ar plasma additional lines corresponding to atomic In and InO, were detected. The deposition rate of thin films was correlated with the In species, rather than the nitrogen species, emission intensity in the plasma. The higher resistivity and lower carrier concentration of the ITON films, as compared to the respective properties of the ITO films, were attributed to the incorporation of nitrogen, instead of oxygen, in the ITON structure.     

Mechanical properties and platelet adhesion behavior of diamond-like carbon films synthesized by pulsed vacuum arc plasma deposition

Diamond-like carbon (DLC) is an attractive biomedical material due to its high inertness and excellent mechanical properties. In this study, DLC films were fabricated on Ti6Al4V and Si(1 0 0) substrates at room temperature by pulsed vacuum arc plasma deposition. By changing the argon flow from 0 to 13 sccm during deposition, the effects of argon flow on the characteristics of the DLC films were systematically examined to correlate to the blood compatibility. The microstructure and mechanical properties of the films were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) surface analysis, a nano-indenter and pin-on-disk tribometer. The blood compatibility of the films was evaluated using in vitro platelet adhesion investigation, and the quantity and morphology of the adherent platelets was investigated employing optical microscopy and scanning electron microscopy.The Raman spectroscopy results showed a decreasing sp³ fraction (an increasing trend in I_D/I_G ratio) with increasing argon flow from 0 to 13 sccm. The sp³:sp² ratio of the films was evaluated from the deconvoluted XPS spectra. We found that the sp³ fraction decreased as the argon flow was increased from 0 to 13 sccm, which is consistent with the results of the Raman spectra. The mechanical properties results confirmed the decreasing sp³ content with increasing argon flow. The Raman D-band to G-band intensity ratio increased and the platelet adhesion behavior became better with higher flow. This implies that the blood compatibility of the DLC films is influenced by the sp³:sp² ratio. DLC films deposited on titanium alloys have high wear resistance, low friction and good adhesion.     

Effect of Ar in the source gas on the microstructure and optoelectronic properties of microcrystalline silicon films deposited by plasma-enhanced CVD

Hydrogenated microcrystalline silicon films have been prepared by plasma-enhanced chemical vapor deposition technique using silane diluted in H₂ or H₂ + Ar. The microstructures for silicon films have been evaluated by Raman scattering spectroscopy, X-ray diffraction and Fourier-transform infrared spectroscopy. Optical characterization has been done by UV-vis spectroscopy. It is found that the addition of Ar in diluent gases efficiently improves the deposition rate and crystallinity due to an enhanced dissociation of the source gas and the energy of deexcitation of Ar* released within the growth zone. Meanwhile, the enhanced crystallinity and the reducing of hydrogen ion bombardment with increasing Ar dilution lead to the polymerization and also a bad passivation of the hydrogen which cause the widening of the optical gap and increase of defect states in the μc-Si films. The absorption coefficient and dark conductivity are found to decrease basically with increasing Ar dilution corresponding to the widening optical gap and more defects. That the activation energy increases with increasing Ar dilution or decreasing hydrogen dilution is due to the fact that more defect states lead to a pulling down of the Fermi level.     

A magnetron sputtering technique to prepare a-C:H films: Effect of substrate bias

Amorphous hydrogenated carbon (a-C:H) films were deposited by magnetron sputtering with a mixture gas of Ar and CH₄. The a-C:H films deposited by this method have relatively low internal stress (<1 GPa) compared to some films deposited by conventional deposition process. The effects of substrate bias voltage on microstructure, surface morphology and mechanical properties of the films were investigated by various techniques. It has been found that the polymer-like structure is dominated at low bias voltage (−100 V), while the diamond-like structure with the highest hardness and internal stress is the main feature of the a-C:H films deposited under high bias voltage (−300 V). With increasing the bias voltage further, the feature of diamond-like structure decreases associating with the increase of graphitization. The frictional test shows that the friction coefficient and wear rate of the a-C:H films are depended strongly on structure and mechanical properties, which were ultimately influenced by the deposition method and bias voltage.