Radio Frequency Magnetron Sputtering Method Research Articles

Oxygen partial pressure effects on the RF sputtered p-type NiO hydrogen gas sensors

NiO thin films were grown by Radio Frequency (RF) Magnetron Sputtering method under different oxygen partial pressures, which are 0.6 mTorr, 1.3 mTorr and 2.0 mTorr. The effects of oxygen partial pressures on the thin films were analyzed through Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Hall measurements. The change in the surface morphology of the thin films has been observed with the SEM and AFM measurements. While nano-pyramids have been obtained on the thin film grown at the lowest oxygen partial pressure, the spherical granules lower than 60 nm in size has been observed for the samples grown at higher oxygen partial pressures. The shift in the dominant XRD peak is realized to the lower two theta angle with increasing the oxygen partial pressures. XPS measurements showed that the Ni2p peak involves satellite peaks and two oxidation states of Ni, Ni2+ and Ni3+, have been existed together with the corresponding splitting in O1s spectrum. P-type conductivity of the grown NiO thin films are confirmed by the Hall measurements with concentrations on the order of 1013 holes/cm−3. Gas sensor measurements revealed minimum of 10% response to the 10 ppm H2 level. Enhanced responsivity of the gas sensor devices of NiO thin films is shown as the oxygen partial pressure increases.

Preparation and thermal volatility characteristics of In2O3/ITO thin film thermocouple by RF magnetron sputtering

In2O3/ITO thin film thermocouples for high temperature measurement (up to 1250 °C) were prepared by radio frequency magnetron sputtering method with different annealing temperatures from 1100 °C to 1250 °C. The changes with microstructure characteristics and the thickness of the thin film thermocouples were investigated as a function of sintering temperature in the range of 1100 °C -1250 °C and annealing time from 2 hrs to 10 hrs at 1200 °C by using XRD and SEM techniques. The thermoelectric output was measured and its results indicated that this thermocouple had a steady and constant voltage output from room temperature to 1247 oC. The thermoelectric voltage and Seebeck coefficient of In2O3/ITO thermocouples measured at 1247 oC were 166.7 mV and 136.3 μV/oC, respectively.

MANIPULATING THE STRUCTURAL AND ELECTRICAL PROPERTIES OF ZINC OXIDE THIN FILMS BY CHANGING THE SPUTTERING POWER OF RADIO FREQUENCY MAGNETRON SPUTTERING

Oxygen-deficient zinc oxides thin films with different levels of defects were prepared by using radio frequency magnetron sputtering method with sintered zinc oxide disk as target at different sputtering powers. The composition, structure and electrical properties of the prepared films were investigated. Under the present conditions, all the obtained films possessed würtzite structure, which were growing preferentially along the [Formula: see text]-axis. The thickness of the films, the size of the zinc oxide grains and the content of Zn atoms increased with increasing sputtering power. In the films deposited at a sputtering power from 52[Formula: see text]W to 212[Formula: see text]W, the main defect was interstitial zinc. With increasing sputtering power, due to the enhanced number of interstitial zinc in the films, their room-temperature electrical resistivity would decrease, which was controlled by electron conduction. At increasing measurement temperature, their electrical resistivity would increase, owing to the decrease of defect concentration caused by oxidization.

Effects of period number and sputtering time on optical properties of Si/Ge multilayer films deposited by magnetron sputtering

Si/Ge multilayer films were deposited by radio frequency magnetron sputtering method, and effects of period number and sputtering time on structure and optical absorption properties of the films were investigated by XP-1 profilometer, XRD, SEM, AFM, Ramman and UV–Vis techniques. Results indicated that the films exhibited the incomplete crystallization, and the appropriate period number benefited the ordering of the Si. Simultaneously, the films showed smooth growth, and the islands were spread all over the surface, and changing of the roughness was attributed to the interface effects. Strong absorption range in the UV–Vis spectra was enlarged with increasing period numbers, and there was a general trend for the band gaps to decrease with increasing period numbers, accompanied the gradually decreasing amplitude. Theoretical calculation and analysis displayed that the ECB value gradually increased and the EVB value gradually decreased with the increasing period number, eventually resulting in the decreasing band gap, and the corresponding values remained stable at different sputtering time when period number was 5.

Enhanced magnetic and microwave absorption properties of FeCo-SiO2 nanogranular film functionalized carbon fibers fabricated with the radio frequency magnetron method

Abstract The combination of carbon materials with magnetic materials to fabricate new composites has attracted widespread attention due to their strong potential applications as microwave absorbing materials. Here, combining the excellent physical properties of carbon fibers (CFs) with the unique magnetic properties of FeCo-SiO 2 nanogranular films, we report a new type of nano-micrometer composite, which is fabricated by a radio frequency magnetron sputtering method at low temperature and high vacuum. The microstructures, phase compositions, mechanical performances, and magnetic and microwave absorption properties of the composites were successfully characterized. After modification with FeCo-SiO 2 nanogranular films, the CFs still maintained high strength. The CF/FeCo-SiO 2 nanogranular film composites exhibited magnetic properties, where the maximum value of saturation magnetization reached 56 emu/g, and the minimum coercivity reached 95 Oe. In particular, the CF/FeCo-SiO 2 nanogranular film composites exhibited strong electromagnetic absorption properties in the range of 2–18 GHz. The absorption bandwidth lower than −10 dB was in the frequency range of 4.08–18 GHz, and the reflection loss reached −43.78 dB at 4.64 GHz with a thickness of 5 mm. The strategy utilized here for the preparation of functionalized CFs paves the way for the development of wave-absorption composites with excellent performances.

Enhanced microwave-absorbing properties of FeCo magnetic film-functionalized silicon carbide fibers fabricated by a radio frequency magnetron method

Silicon carbide (SiC) fibers have potential application in microwave absorption materials in recent years. In this study, we provide a new method for improving the microwave-absorbing properties of SiC fibers. Magnetic FeCo films were fabricated on SiC fibers at low temperature and high vacuum by a radio frequency magnetron sputtering method. The properties of FeCo film/SiC fiber (FeCo/SiCf) composites were investigated. When compared with SiC fiber, the FeCo/SiCf composites exhibit excellent microwave-absorbing properties in the microwave range, with enhancements in the optimal reflectivity loss from −5.03 to −25.51dB. This excellent performance may be because of the magnetic loss due to ferromagnetic resonance and interfacial polarization, thus inducing dielectric relaxation. In addition, the magnetic properties of FeCo/SiCf composites are significantly improved: the value of saturation magnetization reaches up to 41.45emu/g and the coercivity is 116.27Oe. In addition, the strength of SiC fiber remains at 99.17% after the fabrication process. The method provided in this study for enhancing the microwave-absorbing properties of FeCo/SiCf composites will pave a new way for the development of SiC microwave-absorbing materials.

A study of Al:ZnO based MSM UV sensors with Ni metal electrodes

This work reports, preparation and characterization of Al doped ZnO (Al:ZnO) based metal–semiconductor–metal (MSM) UV sensors with nickel (Ni) metal electrodes. Radio-frequency magnetron sputtering method was used for depositing Al:ZnO thin films on p-type Si substrates. The structural and elemental composition of the Al:ZnO thin films were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD spectra indicated that the Al:ZnO thin films had good crystalline quality. The XPS results confirmed the presence of Zn, Al and O elements, in the Al:ZnO thin films. Finally MSM devices were created with metal electrodes of Ni and an active layer of Al:ZnO thin-films. The interdigitated finger contacts of Ni were patterned on Al:ZnO/Si by optical lithography. Two MSM devices with same finger-spacing and width of 15μm and 30μm were fabricated in the experiment. The electrical measurements were done for examining the UV-sensing of these devices. These low-voltage MSM UV sensors could be liable for practical applications.

Synthesis and characterization of CdTe nanostructures grown by RF magnetron sputtering method

In this paper, we synthesize Cadmium Telluride nanostructures by radio frequency (RF) magnetron sputtering system on soda lime glass at various thicknesses. The effect of CdTe nanostructures thickness on crystalline, optical and morphological properties has been studied by means of X-ray diffraction (XRD), UV-VIS-NIR spectrophotometry, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), respectively. The XRD parameters of CdTe nanostructures such as microstrain, dislocation density, and crystal size have been examined. From XRD analysis, it could be assumed that increasing deposition time caused the formation of the wurtzite hexagonal structure of the sputtered films. Optical properties of the grown nanostructures as a function of film thickness have been observed. All the films indicate more than 60% transmission over a wide range of wavelengths. The optical band gap values of the films have obtained in the range of 1.62–1.45 eV. The results indicate that an RF sputtering method succeeded in depositing of CdTe nanostructures with high purity and controllable physical properties, which is appropriate for photovoltaic and nuclear detector applications.

Passively Q-Switched Nd:YVO4 Laser Using WS2 Saturable Absorber Fabricated by Radio Frequency Magnetron Sputtering Deposition

WS2 layered material offers a great potential for the development of next generation laser photonic devices due to its strong layer absorption compared with graphene. The passively Q-switched Nd:YVO4 laser operating at 1064 nm was first demonstrated by using layered tungsten disulfide WS2 saturable absorber SA, which was fabricated by using radio frequency magnetron sputtering method. The fabrication method is scalable and capable of producing large size sample with high uniformity. Besides, the thickness of produced sample can be well-controlled by adjusting sputtering time. A stable Q-switched laser operation is achieved by using this home made few layers WS2-SA within a diode-pumped Nd:YVO4 laser cavity. The maximum average output power obtained is 19.6 mW corresponding to a repetition rate of 135 kHz, a pulse duration of 2.3 μs and single pulse energy of 145 nJ. This result proves the promising Q-switching performance of the fabricated WS2-SA.

Optical band gap shift in thin LiNbO3 films grown by radio-frequency magnetron sputtering

Abstract Thin polycrystalline LiNbO3 films were deposited by the radio-frequency magnetron sputtering (RFMS) method and ion-beam sputtering (IBS) method under different conditions. Study of the adsorption band edge of fabricated films reveals direct and indirect optical transition. Depending on the particular technological sputtering RFMS regime, the direct energy gap varies from 3.8 to 4.4 eV. Band tails induced by the defects formation due to the reactive plasma effect on the film structure are responsible for indirect optical transitions in the studied films. Thermal annealing has a prominent effect on trap concentration and strain in as-grown films leading to rise in direct band energy up to 4.4 eV which is close to the value for bulk LiNbO3.

The Structural and Electrical Properties of Nanostructures ZnO Thin Films on Flexible Substrate

Zinc oxide (ZnO) thin films were deposited on Teflon substrates by radio frequency (RF) magnetron sputtering method at different substrate temperature. The dependence of residual stress on the substrate temperature was investigated in this work due to the growth process, the bombardment of energetic particles and process heating to the deposited thin films. From field emission scanning electron microscope (FESEM) images, samples that deposited at various substrate temperatures consists nano-sized particles. The obtained X-ray diffraction (XRD) results, it suggested that ZnO thin film deposited at 40 o C with highly c-axis oriented shows unstressed film compared to other thin films. Besides that, the ZnO thin films deposited at 40 o C shows improved electrical properties.

Effect of oxygen partial pressure and transparent substrates on the structural and optical properties of ZnO thin films and their performance in energy harvesters

Zinc oxide (ZnO) thin films were deposited onto different substrates — tin-doped indium oxide (ITO)/glass, ITO/polyethylene naphthalate (PEN), ITO/polyethylene terephthalate (PET) — by the radio-frequency (RF) magnetron sputtering method. The effect of various O2/(Ar+O2) gas flow ratios (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) was studied in detail. ZnO layers deposited onto ITO/PEN and ITO/PET substrates exhibited a stronger c-axis preferred orientation along the (0002) direction compared to ZnO deposited onto ITO/glass. The transmittance spectra of ZnO films showed that the maximum transmittances of ZnO films deposited onto ITO/glass, ITO/PEN, and ITO/PET substrates were 89.2%, 65.0%, and 77.8%, respectively. Scanning electron microscopy (SEM) images of the film surfaces indicated that the grain was uniform. The cross-sectional SEM images showed that the ZnO films were columnar structures whose c-axis was perpendicular to the film surface. The test results for a fabricated ZnO thin film based energy harvester showed that its output voltage increased with increasing acceleration of external vibration.

Preparation and characterization of nanostructured Ni2N thin film as electrode for lithium ion storage

The hierarchical Ni2N thin films were fabricated by a method of reactive radio-frequency magnetron sputtering, operating at ambient temperature. The phase composition and microstructure of the Ni2N thin films were analyzed by using X-ray diffractometer, scanning electron microscopy and transmission electron microscopy (TEM). The Ni2N thin films were applied as electrodes for lithium ion storage with the metallic lithium as counter and reference electrode, and the related electrochemical characteristics were investigated. The binder-free Ni2N thin film electrodes show a reversible specific capacity of around 450mAhg−1 at a current density of 120mAg−1, and exhibit a superior rate performance with a specific capacity of 191.7mAhg−1 at a current density of 2240mAg−1. TEM analysis on the phase evolution of the Ni2N thin film electrodes induced at various discharge/charge statuses revealed that the lithiation process has a stepwise mechanisms consisting of the Li+-intercalation reaction and a subsequent conversion reaction, while the delithiation process is mainly composed of a typical conversion reaction.

Effect of In3+ doping on electroluminescence from MgZnO:In3+/ZnO:Er3+/n-Si LEDs

Rare earth (RE)-related electroluminescence (EL) devices have a wide range of applications in full-color display due to its spectrally pure emissions and insensitivity to the surrounding environment. Here we report a set of MgZnO:In3+/ZnO:Er3+/n-Si light-emitting diodes with different In concentrations prepared by a radio frequency magnetron sputtering method. The current–voltage characteristics and EL spectra are presented. With an increase in the In dopant concentration, the forward threshold voltage of the devices drops significantly. Moreover, we find that EL intensity can be tuned effectively at the same time, and the highest luminous efficiency can be achieved at an appropriate In concentration. These results suggest that an In-doping method can improve performance effectively in RE-related light-emitting devices for full-color display.

The Evolution Behavior of Defects in the Nanofilms of W/Cu and W Probed by Doppler Broadening Positron Annihilation Spectroscopy

W/Cu multilayer nanofilms and pure W nanofilms were prepared in pure Ar and He/Ar mixing atmosphere by radio frequency magnetron sputtering method. The defect evolution of the samples was characterized by Doppler broadening positron annihilation spectroscopy (DB-PAS).The results show that plenty of defects can be produced by introducing helium (He) into W/Cu multilayer nanofilms. With the natural storage time increasing, the helium located in the near surface of W/Cu multilayer nanofilm would be released gradually and induce the coalescence of the helium related defects due to the diffusion of the helium and defects. In addition, the pure W nanofilms were irradiated by 30 keV helium ions and 40 keV hydrogen (H) ions in sequence at room temperature. From the DB-PAS analysis, it can be shown that a large number of vacancy-type defects are produced due to the He and/or H irradiation. H ions would be trapped by He related defects and produced He-H-V complexes.

Polarization-dependent photovoltaic effect in ferroelectric-semiconductor system

Radio-frequency (RF) magnetron sputtering method was used to fabricate ferroelectric films of hafnium oxide doped with 6 mol. % silicon. The effect of polarization of the Si doped HfO2 layer on photovoltaic properties of this ferroelectric-semiconductor system was investigated. Piezoresponse force microscopy method provided clear evidence for ferroelectric properties of HfO2 films with 10 nm thickness. Kelvin probe force microscopy showed that change in the surface potential of the negatively poled sample due to illumination is opposite to the response from unpoled and positively poled samples. Transport measurements also revealed a significant difference between photo-responses of the ferroelectric films that were polarized in opposite directions.

Temperature transition of p- to n- type conduction in the LiNbO3/Nb2O5 polycrystalline films

Thin polycrystalline films (∼300 nm) with arbitrary grain orientation consisting of two phases, LiNbO3 and Nb2O5, were fabricated by using the Radio-Frequency Magnetron Sputtering (RFMS) method under a controlled Ar/O2 environment. The amount of non-textured Nb2O5 phase is decreased by 20% in the LiNbO3/Nb2O5 films with reducing the oxygen content from 40 to 20% in the reactive gas mixture. The fabricated ferroelectric films exhibited the “local domain texture,” i.e., the area of grains with the identical direction of the polar axis. Hall measurements suggest that two types of carries (holes and electrons) are present in the fabricated LiNbO3/Nb2O5 films and the type of majority charge carriers is changed from holes at low temperatures (∼50 K) to electrons with increasing temperature. At low temperatures charge transport is affected by the properties of the bulk grains with holes concentration of Np = 6.5·1015 cm−3 at temperatures T > 200 K conductivity is limited by the inter-granular barrier φb = 0.13 eV regardless of the applied magnetic field. The presence of Nb2O5 phase is responsible for temperature transition of p- to n-type conduction in the studied films.

Structural and photoelectrical properties of AZO thin films improved by Ag buffer layers

In order to obtain more excellent photoelectric properties of transparent conductive film, a series of high-quality AZO thin films and AZO/Ag/AZO thin films with various thickness values of Ag buffer layers are prepared on glass substrates by the radio frequency magnetron sputtering method at room temperature. The phase and surface morphologies of films are characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. The technology of Hall effect measurement and ultraviolet, visible spectrophotometer are employed to investigate the photoelectric properties of films. The electrical properties (including sheet resistance, sheet concentration and mobility) of films are also determined by using non isothermal technique to explore their thermal stability performances. The results indicate that the thickness values of Ag buffer layers have a large influence on the crystalline structures and photoelectric properties of AZO thin films. The XRD results show that with the increase of the thickness of Ag, the diffraction peak of Ag (111) is gradually enhanced, the ZnO (002) diffraction peak is gradually weakened, and the preferred orientation of ZnO (002) crystal plane is weakened. AFM test indicates that the change of Ag layer thickness has a great influence on the surface growth mode of the upper layer AZO thin film. When the Ag layer thickness is less than 5 nm, AZO thin film surface is rough and the grain size is smaller. When the Ag layer thickness is larger than 10 nm, the continuous surfaces of multilayer films begin to be shaped, directly affecte the photoelectric properties of the films. Hall effect measurement and transmittance test show that with the increase of Ag layer thickness, the transmission of AZO/Ag/AZO multilayer film gradually decreases, and also the resistance gradually decreases. When the thickness of Ag layer is 10 nm, AZO(30 nm)/Ag(10 nm)/AZO(30 nm) thin film gains a best figure of merit of 1.5910-1 -1 an average transmittance of 84.2% and a sheet resistance of 0.75 /sq. Hall effect measurement versus temperature indicates that AZO film without an Ag layer proves to be subjecte to the regular change of semiconductor resistance with temperature. When adding an Ag layer, the trend of the relationship of resistance with temperature presentes the characteristic of that metal resistance relating to temperature. Moreover, the sheet concentration of AZO with Ag layer is higher than that of AZO. The highest sheet concentration and the excellent thermal stability are obtained on AZO/Ag (10 nm)/AZO. The changes of the mobility of AZO under different temperatures turn out to be poorly stable. However, when adding an Ag layer, the better stability of AZO/Ag/AZO can be obtained. In conclusion, the photoelectric properties of films own excellent thermal stabilities with optimum thickness of Ag layer.

Effects of Mg doping content and annealing temperature on the structural properties of Zn1-x Mg x O thin films prepared by radio-frequency magnetron sputtering

The doping content of Mg plays an important role in the crystalline structure and morphology properties of Zn1-x Mg x O thin films. Here, using radio-frequency magnetron sputtering method, we prepared Zn1-x Mg x O thin films on single crystalline Si(100) substrates with a series of x values. By means of X-ray diffraction (XRD) and scanning electron microscope (SEM), the crystalline structure and morphology of Zn1-x Mg x O thin films with different x values are investigated. The crystalline structure of Zn1-x Mg x O thin film is single phase with x 0.3, and hexagonal and cubic structures will coexist in Zn1-x Mg x O thin films with higher x values. Especially with lower x values, a shoulder peak of 35.1° appearing in the XRD pattern indicates a double-crystalline structure of Zn1-x Mg x O thin film. The crystalline quality has been improved and the inner stress has been released, after the Zn1-x Mg x O thin films were annealed at 600 °C in vacuum condition.

Piezoelectric Response Evaluation of ZnO Thin Film Prepared by RF Magnetron Sputtering

The most important parameter of piezoelectric materials is piezoelectric coefficient (d33). In this study, the piezoelectric ZnO thin films were deposited on the SiNx/Si substrate. The 4 inches substrate is diced into 8 cm× 8 cm piece. During the deposition process, a zinc target (99.999 wt%) of 2 inches diameter was used. The vertical distance between the target and the substrate holder was fixed at 5 cm. The piezoelectric response of zinc oxide (ZnO) thin films were obtained by using a direct measurement system. The system adopts a mini impact tip to generate an impulsive force and read out the piezoelectric signals immediately. Experimentally, a servo motor is used to produce a fixed quantity of force, for giving an impact against to the piezoelectric film. The ZnO thin films were deposited using the reactive radio frequency (RF) magnetron sputtering method. The electric charges should be generated because of the material’s extrusion. This phenomenon was investigated through the oscilloscope by one shot trigger. It was apparent that all ZnO films exhibit piezoelectric responses evaluated by our measurement system, however, its exhibit a significant discrepancy. The piezoelectric responses of ZnO thin film at various deposition positions were measured and the crystal structures of the sputtering pressure were also discussed. The crystalline characteristics of ZnO thin films are investigated through the XRD and SEM. The results show the ZnO thin film exhibits good crystalline pattern and surface morphology with controlled sputtering condition. The ZnO thin films sputtered using 2 inches target present various piezoelectric responses. With the exactly related position, a best piezoelectric response of ZnO thin film can be achieved.