Increasing Sputtering Power Research Articles

Face–centered cubic p–type NiO films room–temperature prepared via direct-current reactive magnetron sputtering–Influence of sputtering power on microstructure, optical and electrical behaviors

High–quality p–type NiO films are crucial for NiO–based heterojunction solar cells. Herein, a series of face-centered cubic, p–type NiO films was prepared at room temperature through DC reactive magnetron sputtering. The increased sputtering power (SP) improves the film crystallization. The film's lattice strain is increased and a microstress transition from compressive to tensile stress occurs with increased SP. The film's lattice strain reduces the LO and 2LO phonon frequency. The blueshifted optical absorption edge with increased SP is caused by the improved film crystallization. The film's free hole concentration is slightly increased and subsequently reduced with increased SP. The former is mainly due to the increased number of the nickel vacancies, whereas the latter to the improved film crystallization that reduces the content of the nickel vacancies and interstitial oxygen. The hole mobility is strongly affected by the scatterings by the crystal lattice and point defects.

Optical properties of amorphous Ta2O5 thin films deposited by RF magnetron sputtering

Optical properties including refractive indices, extinction coefficient, thickness and both optical direct and indirect band gaps of the Ta2O5 thin films deposited by RF magnetron sputtering were determined in this work. The influence of sputtering power, which varies from 70 to 130 W, on microstructure and optical properties of the films were investigated as well. Phase structure, surface morphology, optical transmittance and optical constants of the samples were characterized by X-ray diffraction, atomic force microscopy, spectrophotometry and ellipsometry, respectively. The results show that deposition rate of the films increases with increasing sputtering power, and the maximum deposition rate, 2.1 nm/min, is achieved at 130 W, while the minimum one, 0.84 nm/min, is obtained at 90 W. The as-deposited thin films are amorphous according to the X-ray diffraction. Good surface quality featured by dense and compact microstructure is obtained at lower and higher sputtering powers while some micro-pores are found in the film deposited at medium sputtering powers. The optical constants, such as refractive index, extinction coefficient, and thickness of the Ta2O5 thin films were determined as a function of wavelength based on the ellipsometry measurements and fittings, and the dispersive refractive index was obtained for each sputtering power. The optical constants have been verified by comparing the measured transmittance spectra with the simulated ones, as they are consistent well with each other. Direct bandgap ranging from 4.05 to 4.18 eV and indirect bandgap ranging from 4.53 to 4.66 eV were acquired for the films deposited with the aforementioned sputtering powers.

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

ABSTRACTThis 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.

An interplay among the Mg2+ ion coordination, structural order, oxygen vacancies and magnetism of MgO thin films

The magnetic properties of MgO thin films were discussed as an interplay among the oxygen vacancies, Mg2+ ion coordination and structural order deposited using radio frequency (RF) sputtering method by varying substrate temperature and deposition power followed by in-situ annealing. Rutherford backscattering spectrometry (RBS) and high resolution transmission electron microscopic (HRTEM) performed for these films showed decrease of film thickness with increase of substrate temperature. Films are thicker for higher sputtering powers at corresponding substrate temperatures. Spectral features in Mg K-edge near edge X-ray absorption fine structure (NEXAFS) spectra are characteristics of MgO for both sputtering powers at substrate temperature of room temperature (RT) and 350 °C. O K-edge NEXAFS spectra exhibited onset of oxygen vacancies as inferred from pre-edge region. Magnetization versus applied magnetic field curves for these films showed onset of do ferromagnetism. This behavior ceased with increase of substrate temperature, however, become dominant with increase of sputtering power. Magnetic behavior was dominant for the films which had slightly distorted Mg2+ ion co-ordination. The existence of oxygen vacancies was not observed to be consistent with magnetization. Thus, this study envisaged the role of Mg2+ ion coordination, long range structural order and oxygen vacancies in order to determine magnetism in these systems.

Effects of carbon concentration on high-hardness plasma-polymer-fluorocarbon film deposited by mid-range frequency sputtering

We propose a method for fabricating high-hardness plasma-polymer-fluorocarbon (PPFC) thin films with controllable optical and surface properties via manipulation of the target composition design and sputtering power density. The carbon/polytetrafluoroethylene (PTFE) composite polymeric material targets with the low electrical resistance were prepared by press-molding using a mechanically mixed powder of PTFE, carbon nanotubes, and graphite. The composite targets showed electrical sheet resistances of 0.1–100 Ω/sq. PPFC thin films were deposited by mid-range frequency (MF) sputtering at power densities within 0.62~4.92 W/cm2. The maximum surface hardness of the PPFC thin film was 4.75 GPa, which was 21.6 times higher than that of fluorocarbon thin film sputtered from PTFE under the same conditions. With the increase of the carbon concentration in the target, the carbon cross-linking density of the PPFC thin film increased but the fluorine concentration decreased. The concentration of fluorine in the PPFC thin films grew with increasing sputtering power density. The MF sputtered carbon-rich PPFC thin films are controllable with physical properties of optical transmittance, surface hardness and surface water repellency which could be applied as protective layers for transparent flexible devices.

Structural, magnetic, and electrical properties of collinear antiferromagnetic heteroepitaxy cubic Mn3Ga thin films

We report the structural, magnetic, and electrical properties of antiferromagnetic cubic Mn3Ga thin films, in comparison with ferrimagnetic tetragonal Mn3Ga. The structural analyses reveal that cubic Mn3Ga is heteroepitaxially grown on a MgO substrate with a disordered Cu3Au-type cubic structure, which transforms to tetragonal Mn3Ga as the RF sputtering power increases. In cubic Mn3Ga, the Mn moments aligned ferromagnetically in layers are stacked antiferromagnetically between layers, compared to the theoretical prediction. The magnetic and magnetotransport data show the antiferromagnetic transition at TN = 400 K for cubic Mn3Ga and the ferrimagnetic transition at TC = 820 K for tetragonal Mn3Ga. Furthermore, we find that the antiferromagnetic cubic Mn3Ga exhibits a higher electrical resistivity than the ferrimagnetic tetragonal Mn3Ga, which can be understood by the spin-dependent scattering mechanism.

The relationship between carrier mobility and bicrystalline grains boundary of rutile TiO2 film

The rutile titanium dioxide (TiO2) has attracted enormous interest in sensor field owing to its stability at high temperature. But less is known about electron transfer efficiency of rutile TiO2, which is mainly influenced by the electron mobility. The aim of this study is to investigate the relationship between carrier mobility and bicrystalline grains boundary of rutile TiO2 film. In this study, TiO2 film was deposited by the direct current pulsed magnetron sputtering technology with sputtering power from 150 to 900 W. Then the TiO2 films were annealed at [Formula: see text] in air atmosphere. By this way, the rutile TiO2 films were obtained. Special attention was paid to the carrier mobility of rutile TiO2 films. The Hall measurement results showed that with the increase of sputtering power from 150 to 900 W, the carrier mobility of rutile TiO2 films increased from 0.75 to [Formula: see text], gradually. Taking the TEM and SAED results together, our data indicated that the carrier mobility of rutile TiO2 film was influenced by the bicrystalline grains boundary. The large angle bicrystalline grain boundary seriously deteriorates the carrier mobility of rutile TiO2 film. On the contrary, the low angle bicrystalline grain boundary has little influence on the carrier mobility of rutile TiO2 film.

Structural and optical properties of doped amorphous carbon films deposited by magnetron sputtering

Amorphous carbon films containing oxygen and bismuth were deposited by direct current magnetron sputtering. The microstructure and optical properties of the films were measured as a function of magnetron sputtering power by atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–VIS–NIR spectrophotometry, and null-ellipsometry. The oxygen concentration in the films was in the range of 19–21 at.%. It was determined that the deposition rate of amorphous carbon films increased and the surface roughness of the films changed from 1.2 nm to 1.7 nm with the increase of magnetron sputtering power. The microRaman analysis demonstrated that the D band shifted to a lower wavenumbers range and the fraction of the sp2 carbon sites decreased as the power increased. X-ray photoelectron spectroscopy revealed that sp3/sp2 ratio in the films varied between 0.74 and 0.98. The optical transmission of the films in the visible region was in the range of 60–90%. The optical band gap and the refractive index of the films depend on the dopant concentration and the sp2 site fraction.

Impact of Sputtering Power on Amorphous In–Al–Zn–O Films and Thin Film Transistors Prepared by RF Magnetron Sputtering

High-performance In–Al–Zn–O (IAZO) films and thin film transistors (TFTs) were fabricated using RF magnetron sputtering. The influence of sputtering power (90–250 W) on the film properties and device performance was investigated. All the IAZO films were in the amorphous state both before and after annealing, with a decrease in surface roughness observed with the increase of sputtering power. The Hall mobility of the annealed IAZO films degraded as the sputtering power increased. The highest Hall mobility of 63.6 cm2/ $\text{V}\cdot \text{s}$ and a proper carrier concentration of ${3.22} \times {10}^{{14}}$ /cm3 were obtained for the 90-W-deposited film. All the IAZO films exhibited high average visible transmittances (above 92%) and large optical bandgaps (4.10 ± 0.03 eV). The IAZO TFT prepared at 90 W had the best electrical properties with a high saturation mobility of 12.08 cm2/ $\text{V}\cdot \text{s}$ , a high ON–OFF current ratio of ${7.75} \times {10}^{{7}}$ , a low hysterisis of −0.19 V, and a low subthreshold swing (SS) of 0.55 V/dec.

Microstructure, morphology, wettability and mechanical properties of Ho2O3 films prepared by glancing angle deposition

Hydrophobic materials based on ceramic have attracted significant attentions in recent years owing to their high hardness, good wear resistance and high thermal stability. Rare earth oxide (REO) ceramics are recently reported to show hydrophobic properties. In this context, a series of Ho2O3 films were deposited at different sputtering power using glancing angle deposition (GLAD) technology. The microstructure, morphology, wettability and mechanical properties of the films were systematically investigated. With the increase of sputtering power, the film grows into a cubic microstructure, and the roughness increases monotonously owing to the enhancement of shadowing effects and island growth. Wettability characterization shows that the films exhibit hydrophilic properties after exposure to laboratory environment for 0.1 and 24 h, but they transform to hydrophobic as exposure time increases to 240 h. XPS measurement demonstrates that this transformation is attributed to three successive reactions: i) formation of holmium hydroxide; ii) formation of holmium carbonate and iii) adsorption of volatile organic compounds (VOCs) on carbonate saturated surface. Mechanical characterization shows that the films provide maximum hardness and elastic modulus values as sputter power increases to an optimal value of 100 W.

Plasma Spectroscopy Diagnostics of V2O5 at a Variable of Operating Power and Pressure With Radio Frequency Magnetron Sputtering.

In this paper, we investigate the basic characteristics of "magnetron sputtering plasma" using the target V2O5. The "magnetron sputtering plasma" is produced using "radio frequency (RF)" power supply and Argon gas. The intensity of the light emission from atoms and radicals in the plasma measured by using "optical emission spectrophotometer", and the appeared peaks in all patterns match the standard lines from NIST database and employed are to estimate the plasma parameters, of computes electron temperature and the electrons density. The characteristics of V2O5 sputtering plasma at multiple discharge provisos are studied at the "radio frequency" (RF) power ranging from 75 - 150 Watt and gas pressure (0.03, 0.05 and 0.007) torr. One can observe that the intensity of the emission lines increases with increasing the sputtering power. We find that the electron temperature excess drastically from 0.95 eV to 1.11eV when the emptying gas pressure excess from 0.03 to 0.05 Torr. On other hand excess electron temperature from 0.9 to 1.01 eV with increasing sputtering power from 100 to 125 Watt, while the electron density decrease from 5.9×1014 to 4.5×1014 cm-3 with increasing sputtering power. and electron density decrease with increasing of pressure from 4.25×1014 to 2.80×1014 cm-3, But the electron density maximum values 5.9×1014 at pressure 0.03 Torr.

Plasma Spectroscopy Diagnostics of V2O5 at a Variable of Operating Power and Pressure With Radio Frequency Magnetron Sputtering.

In this paper, we investigate the basic characteristics of "magnetron sputtering plasma" using the target V2O5. The "magnetron sputtering plasma" is produced using "radio frequency (RF)" power supply and Argon gas. The intensity of the light emission from atoms and radicals in the plasma measured by using "optical emission spectrophotometer", and the appeared peaks in all patterns match the standard lines from NIST database and employed are to estimate the plasma parameters, of computes electron temperature and the electrons density. The characteristics of V2O5 sputtering plasma at multiple discharge provisos are studied at the "radio frequency" (RF) power ranging from 75 - 150 Watt and gas pressure (0.03, 0.05 and 0.007) torr. One can observe that the intensity of the emission lines increases with increasing the sputtering power. We find that the electron temperature excess drastically from 0.95 eV to 1.11eV when the emptying gas pressure excess from 0.03 to 0.05 Torr. On other hand excess electron temperature from 0.9 to 1.01 eV with increasing sputtering power from 100 to 125 Watt, while the electron density decrease from 5.9×1014 to 4.5×1014 cm-3 with increasing sputtering power. and electron density decrease with increasing of pressure from 4.25×1014 to 2.80×1014 cm-3, But the electron density maximum values 5.9×1014 at pressure 0.03 Torr.

Optical nonlinear enhancement through interaction between Ag nanoparticles and CdSe quantum dots

The CdSe/Al2O3/Ag composite films were prepared on quartz glass substrate by magnetron sputtering and spin coating with the CdSe oily quantum dots. The absorption experiments and analysis results show that all of the CdSe quantum dots, Ag films, and Al2O3 contribute to the absorption peak, and the absorption peak of the CdSe/Al2O3/Ag composite films shifts to the ultraviolet region (356 nm). The transmission TZ-scan results illustrate that the nonlinear absorption effect of the CdSe/Al2O3/Ag composite films exhibits reverse-saturated absorption characteristic, and the third-order nonlinear refractive index of the CdSe/Al2O3/Ag composite films is approximately 105 times greater than that of the CdSe quantum dots. With the increase in the CdSe quantum dots concentration, the nonlinear absorption and refraction properties of the CdSe/Al2O3/Ag composite films are enhanced. However, the nonlinear absorption and refractive index of the CdSe/Al2O3/Ag composite films decrease with the increase in sputtering power of Ag. The reverse-saturated absorption characteristic is explained by the three-level system. The composite films could be applied to new optical control fields, for example, optical phase recovery.

Optimal target sputtering mode for aluminum nitride thin film deposition by high power pulsed magnetron sputtering

Low surface roughness, low residual stress, and (002) textured aluminum nitride (AlN) thin films are favored for applications in microelectronic and optoelectronic devices. In this paper, AlN thin films were deposited by reactive high power pulsed magnetron sputtering (HPPMS). The effect of aluminum target sputtering mode and sputtering power on thin film residual stress, crystalline structure, surface roughness, and morphology of AlN thin films was studied. The results indicate that, with Al target sputtering mode transfer from metallic mode to transitional and compound modes, respectively, the number of Al species decrease, and ion-to-neutral ratio of Al species increase. Comparing the AlN thin film deposited in compound mode with that deposited in transitional mode, the latter exhibited lower surface roughness and residual stress. In addition, AlN thin film with (002) texture and lower residual stress is obtained by increasing sputtering power in transitional mode. For fabricating AlN film via reactive HPPMS with a particular (002) texture, low surface roughness, and residual stress, sputtering the target in the transitional mode with high sputtering power is optimal.

Sputtered cobalt doped CuO nano-structured thin films for photoconductive sensors

Pure and cobalt (Co) doped CuO thin films have been deposited by DC and AC reactive magnetron sputtering technique. The doping ratio has been controlled by the RF power of the AC sputtering unit. The sputtering power ranges from 0 to 50 W. The crystal structure of the films has been identified by X-ray diffraction. One of the peaks has been shifted toward the high diffraction angle. Energy dispersive analysis shows cationic deficiency of the pure and doped samples. Morphology of the films has been investigated by atomic force microscopy. Film roughness decrease with the increase of sputtering power. Spectrophotometry studies reveal that films darken with the increase of sputtering power. The current–voltage curves show Ohmic contacts and an enhancement in the conductivity with the increase of Co concentrations. Photoresponse measurements have shown that the film doped at 50 W is the best photodetector sensor.

Reactively Magnetron Sputter-Deposited Ti (C,N) Nanocomposite Thin Films: Composition and Thermal Stability

Titanium carbonitride thin films were grown by reactive magnetron sputtering deposition of titanium carbide target in Ar/N2 gas mixture on p-type silicon (100) substrates. With the increase of sputtering power up to 125W, the deposition rate and films thickness reached a maximum of 14nm/min and 430nm, respectively. A thick film of about 2200nm could be deposited for 120 min at the optimum deposition pressure of 20mTorr. Cathode current decreased from about 290mA to reach a value of about 235mA as the N2 flow percentage increased from 0 to 100%. X-ray diffraction analyses of the deposited films confirmed the formation of titanium carbide and carbonitride layers as the nitrogen gas concentrations in the process gas were increased. SEM image of the deposited titanium carbonitride thin film for 5 min deposition time showed that the film started to grow as tiny particles of size as low as about 140nm, which in later stage coalesced together to form bigger grains and finally a continuous film. The deposited film shows good thermal stability upon annealing in air and in vacuum at 700oC for 2 hours.

Structural properties and surface topography of MgO films prepared on Si (100) by pulsed DC magnetron sputtering

This work deals with the preparation of MgO films on Si (100) substrate by using pulsed DC magnetron sputtering of pure Mg target in reactive oxygen environment at room temperature. The sputtering power was varied in the range 100 W to 150 W while keeping the deposition time fixed at 4 h. In the next step, deposition time was changed from 1 h to 3 h by maintaining the sputtering power at 150 W. The results obtained were analyzed by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) techniques. The XRD pattern at 100 W exhibited MgO2 diffraction peak along (211) plane. However, with increase of power to 125 W and 150 W, MgO diffraction peak corresponding to (200) plane appeared. The crystallinity of MgO was improved with increase of the sputtering power. On contrary, the crystalline quality of MgO film was degraded with increase of the deposition time. The FTIR analysis displayed peaks around 860 cm−1 and 740 cm−1 corresponding to the characteristic of cubic MgO. With increase of deposition time from 1 h to 3 h, the peaks at 860 cm−1 and 740 cm−1 were disappeared, indicating a decrease in the strength of chemical bond between Mg and O. The AFM results revealed a decrease in the surface roughness with increase of both sputtering power and the deposition time.

Deposition and Electrical Resistivity of Oxygen-Deficient Tin Oxide Films Prepared by RF Magnetron Sputtering at Different Powers

A series of oxygen-deficient tin oxide thin films were deposited by radio frequency magnetron sputtering a sintered tin oxide ceramic target under pure argon atmosphere at different sputtering powers (80-160 w) under the based pressure of no more than 2.0×10-4 Pa, sputtering pressure of 2.0 Pa and deposition time of 20 min. It was revealed that all the as-deposited films were oxygen-deficient tin oxide films, and the main defect in films was oxygen vacancy (VO), whose concentration gradually decreased with the increase of sputtering power. The films prepared at a power of no more than 120 w were amorphous, and as the sputtering power increased to 140 and 160 w, the deposited thin films exhibited polycrystalline characteristics with (110), (101) and (211) diffraction peaks of tin oxide. The grain size, deposition rate as well as thickness of the obtained films rose up with increasing sputtering power. In addition, as the sputtering power raised, the electrical resistivity of the films increased, due to the electron conducting mechanism controlled by VO in the samples.

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes

Effect of Pd overlayer and mixed gases on hydrogen permeation of Pd/Nb30Hf35Co35/Pd composite membranes was investigated. The diameter of Pd particle increases with increasing sputtering power. With this change, the membrane shows a signification reduction in hydrogen permeability/or flux, but its durability and stability increases significantly, which can be mainly attributed to a decrease in hydrogen solubility coefficient. In addition, H2S impurity in mixed gases can greatly degrade membrane performance, especially the hydrogen permeability, whereas the Ar impurity content has less effect in the temperature range of 523–673 K. Lowering of permeability caused by the change of gas purity can be attributed to a decrease in hydrogen solubility, which is closely related to the stronger adsorption of H2S molecules to the Pd overlayer of the membrane. Thus, it is concluded that aside from the optimum design for composition of Nb-based hydrogen permeable alloy to improve their permeability, the control of Pd overlayer film on membrane surface and gas purity in the feed gas is important.

Study on the optical properties and electrochromic applications of LTO/TaOx ion storage-transport composite structure films

In this paper, the morphological and optical properties of LTO/TaOx composite structure films and electrochromic properties of “ITO/NiOx/LTO/TaOx/WOx/ITO” electrochromic devices (ECDs) based on LTO/TaOx composite structure films are reported. The composite films are deposited on the ITO substrate by reactive magnetron sputtering. The results of XRD, SEM, and AFM show that LTO film is amorphous and the performance of films prepared by sputtering power of 100 W for 5 h is the best. The optical transmittance of the multilayer structure is tested using an ultraviolet-visible spectrum and the refractive index dispersion is calculated using the relationship between the peaks in the spectrum based on equal inclination interference theory. Optical transmittance and refractive index dispersion are changed with the increase of magnetron sputtering power. Electrochromic tests show that all-solid-state ECDs based on composite films have 13 s coloring and 14 s fading response time, and the average optical modulation amplitude is 58%.