Sputtering Gas Research Articles

Effect of lack of oxygen on optical and electrical properties of RF magnetron sputtering deposited CuFeO2−x thin films

Delafossite CuFeO[Formula: see text] thin films were fabricated on quartz substrate using radio-frequency sputtering deposition under low O2 flow ratios from 9% to 0% at room temperature. The as-deposited films were in amorphous phase and crystallized into rhombohedral 3R (R3m) delafossite structure after post annealing at 900[Formula: see text]C for 2 h in flowing N2 atmosphere. SEM images showed that the films were composed of nano-sized crystallized grains, thin film composed of smoother surface and higher oxygen content was obtained under higher oxygen percentage in sputtering gas. The optical transmission spectra of these films were studied in the wavelength range 200–1500 nm and the results revealed a narrowing trend of direct bandgap from 3.09 eV to 2.98 eV with the decrease of oxygen flow ratio during deposition. All of the post-annealed CuFeO[Formula: see text] thin films exhibited p-type conductivity and linear ohmic contact feature with Cu electrodes. The carrier concentration of thin films increased from [Formula: see text] to [Formula: see text] whereas the carrier mobility decreased from [Formula: see text] to [Formula: see text] as the oxygen flow ratio reduced from 9% to 0%. The ability of controlling compound composition enables tuning of carrier concentration and mobility in CuFeO[Formula: see text] and offering essential technical basis in engineering photoelectronic devices.

Development of the Aluminum Powder Composite Based on the Al–Si–Ni System and Technology of Billet Fabrication of This Composite

Results of an investigation into the development of the composition and fabrication technology of compact billets of the aluminum powder composite material based on the Al–Si–Ni system for space-rocket hardware are presented. The composite production was performed as follows: initially the powder of the matrix alloy is prepared by gas sputtering, and then a mixture of the matrix alloy powder and alloying dispersed additives is subjected to mechanical alloying in high-energy apparatuses. The method of degassing the mechanically alloyed composition in a thin layer (in order to exclude material ejection from a container when degassing a larger volume of powder) and process regimes of composition compaction are developed using the unique equipment available at OAO Kompozit (Korolev, Moscow oblast)—a vacuum press. Using this technology, cylindrical briquettes up to 100 mm in diameter and up to 120 mm in height are fabricated. Newly developed and patented Kompal-301 composite material has substantial advantages over SAS-1-50 power alloy applied for similar purposes. Its thermal linear expansion coefficient is lower by a factor of 1.5, while the precision limit of elasticity is higher by a factor of 2–3 upon similar strength characteristics. The final structure of a compact briquette is a matrix in which dispersed particles of excess silicon are distributed rather uniformly against the background of the aluminum solid solution. Coarser isolated silicon particles are met in separate regions of the structure. Unfortunately, they are the cause of low plasticity of briquettes, which prevents the formation of semifinished products by plastic deformation; however, such low plasticity does not immediately negatively affect the fabrication of the briquettes themselves.

NTC thin film temperature sensors for cryogenics region with high sensitivity and thermal stability

HfOxNy thin films were deposited on polished and oxidized silicon wafers at different nitrogen-oxygen gas flow rates by DC magnetron reactive sputtering, and temperature sensors based on these HfOxNy thin films were fabricated using a microelectromechanical system micromachining process. The resistance–temperature dependencies of these sensors were studied in the temperature range of 4.2 K–300 K, and the effect of the sputtering gas flow rate on the initial resistivity and sensitivity [temperature coefficient of resistance and absolute sensitivity (Sa)] was discussed. One of these sensors was subjected to 15 cycles between 300 K and 4.2 K for thermal cycle stability testing. The performances of these sensors were compared to the now available negative temperature coefficient thin film temperature sensors (ZrNx, CrNx, RuO2, and ZrOxNy), and they show very outstanding sensitivity and thermal cycle stability. Furthermore, the conduction mechanism of HfOxNy thin films in the cryogenic region was studied for the first time.

Fluorinated tin oxide (FTO) deposited at room temperature: Influence of hydrogen and oxygen in the sputtering gas on the optical and electrical properties

The optical and electrical properties of fluorinated tin oxide (FTO) films deposited at room temperature by sputtering were investigated. In addition to small amount of oxygen to preserve highly transparent films, electrical resistivity become decreased two orders of magnitude by using appropriate hydrogen content in the sputtering gas. Films deposited with Ar(93%)/O2(5%)/H2(2%) gas mixture show maximal values of conductivity, charge carrier density and mobility as well as excellent transparency. Taking into account the film characterization carried out by Rutherford backscattering spectrometry (RBS), a mechanism is proposed to explain the observed optical and electrical dependence with the hydrogen content in the film.

Apparatus and method for the growth of epitaxial complex oxides on native amorphous SiO2 surface of (001) oriented single crystal silicon

The design, fabrication, and performance of an apparatus for the deposition of complex oxides with highly uniform thicknesses at controllable deposition rates over large area, even on the native amorphous SiO2 layer of (001) oriented single crystal Si, are described. The apparatus makes use of the lateral port of a spherical chamber. The port is maintained at uniform temperature, and it houses a substrate heater. The deposition process is controlled by varying different parameters such as target-to-substrate distance, sputtering power, sputtering gas atmosphere, substrate temperature, and pulsed plasma growth. The system has been tested by growing a series of La0.7Sr0.3MnO3 thin films on Si. The systematic strain relaxation and thus the tunable magnetic properties along with the presence of high-quality surface morphology of the films indicate that the designed system could be used to fabricate different components of oxide electronics-based devices over larger area.

Deposition and characterization of diamond-like carbon films by electron cyclotron resonance microwave plasma enhanced unbalanced magnetron sputtering

We introduce the structure and operational principles of an electron cyclotron resonance microwave enhanced plasma source ion implantation/deposition system for the creation of diamond-like carbon (DLC) film. Using an unbalanced magnetron sputtering process, DLC film was deposited on the silicon substrate using high-purity graphite as the carbon source and argon as the sputtering gas. We used Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy characterization methods to study the structure and chemical ratio of the film under different deposition parameters. The results show that the optimal substrate bias and target-substrate distance are 50 V and 150 mm, respectively; when the deposition bias is increased, the film can be made denser and smoother. We also discuss the formation mechanism of DLC film based on the results of structural characterization.

High-performance polycrystalline RuOx cathodes for thin film Li-ion batteries

A process for sputter deposition of RuOx films with high volumetric Li capacities and good cyclability was developed, demonstrating the potential for use of RuOx films as cathodes in high-performance thin-film microbatteries. Using a stoichiometric RuO2 sputtering target, the effects of oxygen content within the Ar/O2 plasma on the stoichiometry of thin films deposited at room temperature was investigated and correlated with electrochemical performance. The oxygen content of the films was found to increase with the O2 to Ar ratio of the sputtering gas. RuOx thin films with x ≥ 1.92 delivering capacities of ∼550 μAh/cm2μm in the 0.75–3.6 V vs. Li/Li+ voltage range, which is much higher than that of under-stoichiometric RuOx (320 μAh/cm2μm). The capacities obtained for RuOx films significantly exceed the capacity of LiCoO2 films (∼60 μAh/cm2μm) typically used in thin-film microbatteries. Given that high capacity RuOx films can be obtained using only room temperature processing, their use in thin-film microbatteries will also allow integration with silicon-based integrated circuits.

Electrical properties of ZnO:H films fabricated by RF sputtering deposition and fabrication of p-NiO/n-ZnO heterojunction devices

A high-transparency ZnO thin film of high carrier concentration was grown by conventional RF sputtering, where the carrier concentration was continuously varied from 1016 to 1019 cm−3 by controlling the amounts of O2 and H2 sputtering gases. To prevent the formation of a Schottky junction at the contact with In–Zn–O, and to improve the fill factor of a visible-light-transparent solar cell, a Ag-paste/NiO/ZnO/ZnO:H/IZO p–n diode structure with the carrier concentration of the ZnO:H layer of 1019 cm−3 was fabricated. It is possible to reduce the depletion width and inverse the rectification action around ZnO/IZO by controlling the carrier concentration of the ZnO layer while maintaining the high transparency.

The variation of propagation velocity according to substrate material of band pass filter

Background/Objectives: The SAW filter has a frequency characteristic determined by the geometry of the IDT electrode, and is widely used as a band-pass filter for passing only a signal having a specific frequency.Methods/Statistical analysis: The features of this filter are high stability and reliability and enable mass production using semiconductor processes.Findings: The MCB process lift off method was used to fabricate the filter to solve the difficulties of the SAW filter process. In particular, we fabricated ZnO thin films with excellent c-axis preferential orientation, high resistivity of more than 106Ωcm, and flat surfaces, and fabricated SAW filters using ZnO thin films as deposition conditions suitable for application to SAW filters. ZnO thin films deposited under conditions of RF power of 150W, chamber pressure of 10mTorr, substrate temperature of 200 ° C and gas mixture ratio of Ar/O2 of 50/50 as sputtering gas have excellent c-axis preferential orientation, high specific resistance and flat surface shape. Then, ZnO piezoelectric thin film was deposited on SiO2 substrate by RF magnetron sputtering method and the SAW filter was fabricated by the MCB lift off method to analyze the frequency characteristics. In addition, compared with the SAW filter fabricated on the LiNbO3 substrate, which is a piezoelectric substrate.Improvements/Applications: The propagation speed of the SAW filter using the ZnO thin film was determined by the variation of the center frequency due to the deposition of the ZnO thin film.

How the sputtering process influence structural, optical, and electrical properties of Zn3N2 films?

Abstract

Structural, morphological, electrical and optical properties of PbSe thin films sputtered at various pressures

Optical band gap control of lead selenide (PbSe) thin films is essential for realizing the practical applications. In this paper, PbSe thin films have been deposited by radio frequency (RF) magnetron-sputtering with varied sputtering gas pressures from 0.5 to 4.0 Pa. A systematical investigation of the film properties was carried on. X-ray diffractometry, atomic force microscopy, Hall effects measurements and UV–vis spectroscopy analyses were performed to investigate the crystal structural, morphological, electrical and optical properties of the films. The sputtering pressure has a significant effect on the structure and properties of the PbSe thin films. The intensity of the preferred orientation (200) increases with sputtering pressure up to 3.0 Pa, and then decreases at 4.0 Pa. The films are composed of equiaxed spherical crystals, whose roughness tends to increase with pressure. According to the Hall effect measurements, the resistivity linearly decreases from 1.6 Ω cm to 0.02 Ω cm, and the carrier concentration decreases from 1.19 × 1020 cm−3 (0.5 Pa) to 4.0 × 1017 cm−3 (4.0 Pa). The optical band gap ranges from 1.22 to 1.52 eV. The suitable pressure range is 2.0–3.0 Pa in this study.

Hybrid high power impulse and radio frequency magnetron sputtering system for TiCrSiN thin film depositions: Plasma characteristics and film properties

TiCrSiN thin films were successfully grown using a hybrid approach in which a high power impulse magnetron sputtering (HiPIMS) power was combined with a radio frequency (RF) power. Different Si contents were obtained by changing the RF power of Si target. The ion energy distribution functions (IEDFs) showed that the energy tails of all sputtered ions from the targets and sputtering gases shifted to a higher energy tails when the Si target power increased from 50 to 150 W. The peak power density of the TiCr target powered by HiPIMS and the corresponding Si content in the films increased from 1214 to 1350 W/cm2 and from 0.2 to 17.9 at.%, respectively, as the Si target power increased from 50 to 150 W. The Si atoms were in the form of amorphous Si3N4 phase. The Si content showed a major influence on the microstructure, adhesion and mechanical properties of TiCrSiN film. Although a nanocomposite microstructure was formed when the Si content was 17.9 at.%, lower hardness and acceptable adhesion property were obtained due to a microstructure consisting of small TiN nanograins embedded in a large amount of soft amorphous silicon nitride matrix. The hardness of TiCrSiN film reached a maximum hardness of 31.1 GPa at Si = 6.7 at.% due to the refined microstructure and grain boundary hardening effect.

Electron Scattering from Disordered Grain Boundaries in Degenerate Polycrystalline Al‐Doped ZnO Thin Films

This paper describes the influence of electron scattering from disordered grain boundaries on the carrier transport in polycrystalline Al‐doped ZnO (AZO) thin films prepared with electron concentrations on the order of 1020 cm−3. It is found that in degenerate AZO thin films prepared on glass substrates by various magnetron sputtering depositions, the mobility–carrier concentration (µHall–nHall) relationship with a positive slope (µHall increases as nHall increases) is always obtained when measured by changing the sputter gas pressure and the substrate temperature, the location on the substrate surface, and the exposure time in a moisture‐resistance test. The main scattering mechanism, which limits the carrier transport in AZO thin films, is attributed to grain boundary scattering caused by the reflection of electrons from the potential barrier at the grain boundary between crystallites. The measured µHall–nHall relationship demonstrates fair agreement with the relationship calculated using the Mayadas and Shatzkes (MS) theory. However, conceptual and other difficulties to apply the semi‐classical MS theory to degenerate semiconductors must be considered. The results of this quantum theory‐based investigation show that the positively sloped µHall–nHall relationship attributes to Anderson localization, induced by electron grain boundary scattering from disordered successive grains.

Characteristics of carbon‑nickel nanocomposite thin films prepared by reactive sputtering under different radio frequency powers and their applications for electronic devices

The carbon‑nickel nanocomposite thin films (C-Ni films) were deposited on n-type silicon (n-Si) wafers using reactive sputtering from a pure nickel target in methane/argon sputtering gas. Six kinds of C-Ni films were prepared with the rf power being 50, 100, 150, 200, 250, and 300 W, and the effect of different rf powers on the characteristics of C-Ni films is studied. The measured results show that the carbon-hydrogen bonds in C-Ni films decrease with increasing the rf power from 50 to 100 W, but no carbon‑hydrogen bonds were found in C-Ni films with the rf power above 150 W. When the rf power increases from 50 to 300 W, the Ni/C ratio in C-Ni films increases from 0.2 to 55.8% and the sp2/(sp2 + sp3) carbon ratio in C-Ni films also increases from 40 to 84%. Additionally, the degree of crystallinity of C-Ni films increases with increasing the rf power from 50 to 300 W, and the structure of C-Ni films changes from amorphous carbons to containing an amount of rhombohedral Ni3C compounds. The Ni/C ratio and degree of graphitization of C-Ni films increase with increasing the rf power from 50 to 300 W, so the optical band gap of C-Ni films decreases from 2 to 0 eV and the electrical resistivity of C-Ni films decreases from 3.6 × 104 to 8.6 × 10−5 Ω·m. The current density-voltage behavior displays that the C-Ni/n-Si device has the rectifying characteristic. As the C-Ni film was prepared at the rf power of 150 W, the C-Ni/n-Si device has the best ideality factor of 2.6. One can predict that the C-Ni/n-Si device has the potential to be applied in the electronic/optoelectronic fields.

The role of thermal processes and target evaporation in formation of self-sputtering mode for copper magnetron sputtering

The main focus of the article is the study of function mechanisms of a magnetron sputtering system (MSS) with a heat-insulated metal target in a self-sputtering gasless mode. A distinctive feature of the studied case is that the target evaporation takes place along with its sputtering. The research has been carried out on a copper target sample in molybdenum crucible. It has been found that because of evaporation the MSS can function stably using metal vapors without sputtering gas. The pressure in the chamber is 0.01 Pa. The current-voltage characteristics and spatial distribution of the copper atoms concentration near the target have been determined at the power density from 14 to 72 W/cm2. The minimum power density necessary for a stable gasless self-sputtering mode is 19.4 W/cm2. Herewith the evaporated particles constitute approximately 87% of the total number of copper atoms near the target.It has been found that the erosion coefficients of metal targets at evaporation reach several tens of atoms per ion, which is an order of magnitude higher than the sputtering yield. Due to this, the coatings deposition under self-sputtering conditions takes place without reducing a deposition rate as compared to the case with sputtering gas.

Effect of sputter pressure on Ta thin films: Beta phase formation, texture, and stresses

The metastable tetragonal beta phase of tantalum can be made in thin film form by sputter deposition and has very different properties from the stable BCC alpha phase. Both phases are important in thin film technologies. However, despite fifty years of study, the mechanism of phase selection remains unknown. To evaluate the role of energetic deposition, we prepared a series of films under varying Ar sputter pressures. Measurements of film stress as a function of sputter gas pressure allow us to unambiguously index diffraction peaks to determine phase and texture. This peak indexing allows us to confirm that β-Ta has a distorted Frank-Kasper sigma structure (P4¯21m), rather than the β-U structure (P42/mnm) that is usually assumed. We find only the beta phase in our films in the form of a dominant (002) β-Ta fiber component that becomes broader as the pressure increases. Based on calculations of the energy of incident Ta atoms and Ar neutrals, we show that resputtering could account for the changes in texture distribution. By comparing these results with a detailed review of the literature, we are able to propose a phase selection mechanism that is consistent with the vast majority of published results, namely that β-Ta grows epitaxially on a TaOx layer, possibly TaO2, that forms during the initial phase of deposition. Oxygen is not required in the growing film to maintain the beta structure.

The effect of different radio-frequency powers on characteristics of carbon-titanium nanocomposite thin films prepared by reactive sputtering

The effect of radio-frequency (rf) powers on the characteristics of carbon-titanium nanocomposite thin films (C-Ti films) prepared by reactive sputtering is investigated. The C-Ti films were prepared on n-type silicon (n-Si) wafers by reactive sputtering, which was the combination of rf plasma enhanced chemical vapor deposition (rf-PECVD) and sputtering. Pure methane was used as the precursor gas to form the amorphous carbon (a-C) film by rf-PECVD, and argon was used as the sputtering gas to bombard the titanium target surface to dope titanium in a-C films by sputtering. Seven kinds of C-Ti films were prepared with the rf power being 50, 100, 150, 200, 250, 300, and 350 W, and all the thickness of C-Ti films were fixed at 100 nm at various rf powers. The measured results indicate that the carbon-hydrogen bonds in C-Ti films decrease with increasing the rf power from 50 to 350 W, but the degree of graphitization of C-Ti films increases. The Ti/C ratio of C-Ti films increases from 0.3 to 116% with increasing the rf power from 50 to 350 W, and the sp2 / (sp2 + sp3) carbon ratio of C-Ti films also increases from 14.7 to 44%. On the other hand, the C-Ti films are amorphous at the rf power from 50 to 250 W, but nano-crystalline titanium carbide grains are encapsulated in a-C matrix at the rf powers of 300 and 350 W. Furthermore, the optical band gap of C-Ti films decreases from 2.6 to 0 eV with increasing the rf power from 50 to 350 W, and the electrical resistivity of C-Ti films decreases from 2.1 × 103 to 5 × 10−6 Ω·m. This implies that the C-Ti film changes from semiconductor to conductor with increasing the rf power from 50 to 350 W. The current density-voltage results show that the C-Ti/n-Si device prepared at various rf powers exhibits the rectifying behavior. The C-Ti/n-Si device prepared at the rf power of 300 W has a best ideality factor of 2.1. The C-Ti/n-Si device has the potential to be applied in the electronic/optoelectronic fields.

Development of high-polarization Fe/Ge neutron polarizing supermirror: Possibility of fine-tuning of scattering length density in ion beam sputtering

The multilayer structure of Fe/Si and Fe/Ge systems fabricated by ion beam sputtering (IBS) was investigated using X-ray and polarized neutron reflectivity measurements and scanning transmission electron microscopy with energy-dispersive X-ray analysis. The obtained result revealed that the incorporation of sputtering gas particles (Ar) in the Ge layer gives rise to a marked reduction in the neutron scattering length density (SLD) and contributes to the SLD contrast between the Fe and Ge layers almost vanishing for spin-down neutrons. Bundesmann et al. (2015) have shown that the implantation of primary Ar ions backscattered at the target is responsible for the incorporation of Ar particles and that the fraction increases with increasing ion incidence angle and increasing polar emission angle. This leads to a possibility of fine-tuning of the SLD for the IBS, which is required to realize a high polarization efficiency of a neutron polarizing supermirror. Fe/Ge polarizing supermirror with m=5 fabricated under the same condition showed a spin-up reflectivity of 0.70 at the critical momentum transfer. The polarization was higher than 0.985 for the qz range where the correction for the polarization inefficiencies of the beamline works properly. The result of the polarized neutron reflectivity measurement suggests that the “magnetically-dead” layers formed at both sides of the Fe layer, together with the SLD contrast, play a critical role in determining the polarization performance of a polarizing supermirror.

Corrosion studies of DC reactive magnetron sputtered alumina coating on 304 SS

AbstractAluminum oxide films on SS 304 deposited by DC reactive magnetron sputtering technique were studied with respect to the composition of the sputter gas (Ar:O

Competitive Reactivity of Nitrogen and Oxygen with Nickel When an Argon/Air Mixture is Used as Sputtering Gas

Competitive Reactivity of Nitrogen and Oxygen with Nickel When an Argon/Air Mixture is Used as Sputtering Gas