Influence Of O2 Flow Rate Research Articles

Influence of O2 Flow Rate on the Properties of Ga2O3 Growth by RF Magnetron Sputtering

The influence of the O2 flow rate on the properties of gallium oxide (Ga2O3) by RF magnetron sputtering was studied. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmittance spectra, and photoluminescence (PL) spectra have been employed to study the Ga2O3 thin films. With the increase in oxygen flow rate, both the crystal quality and luminescence intensity of the Ga2O3 samples first decrease and then enhance. All these observations suggested that the reduction in the oxygen defect density is responsible for the improvement in the crystal quality and emission intensity of the material. Our results demonstrated that high-quality Ga2O3 materials could be obtained by adjusting the oxygen flow rate.

Influence of O2 flow rate on the characteristics of TiO2 thin films deposited by RF reactive sputtering

Titanium dioxide (TiO2) thin films were prepared by radio-frequency (13.56 MHz) reactive sputtering onto glass substrate with different oxygen flow rates while maintaining a constant Ar flow rate. The structural and optical properties of these films were studied with variation in O2 flow rate. X-ray diffraction (XRD) analysis of these films reveals the presence of anatase and rutile phases. The lattice parameters and crystallite size were evaluated from XRD patterns. The optical properties of these films were correlated with their morphological nature. Field emission scanning electron microscopy (FESEM) results show a dense granular morphology and the particle size is found to decrease with increase in oxygen flow rate. The average optical transmittance was observed to be 96% for all the films. The room temperature photoluminescence (PL) spectroscopy revealed a blue shift of the near band edge emission as the oxygen flow rate is increased and defect related emissions is shifted towards red region.

Compositional, Optical and Electrical Characteristics of SiOx Thin Films Deposited by Reactive Pulsed DC Magnetron Sputtering

The influence of O2 flow rate on the compositional, optical and electrical characteristics of silicon oxide (SiOx) thin films (x < 2) were studied in this work. The SiOx thin films were obtained by pulsed direct current (DC) magnetron sputtering (PMS) onto n-type Si wafers (and also on glass substrates) at a vacuum of 3 × 10−3 Pa. Rutherford backscattering spectrometry (RBS) was used to check the compositional elements of deposited films and its oxidized states were analysed via Fourier-transform infrared (FTIR) spectroscopy. The optical properties of as-deposited SiOx thin films were investigated from transmittance measurements at room temperature in the wavelength range of 250–800 nm. The obtained data reveal that the Urbach energy (a measure of the band tail extension, Eu) decreased from about 523 to 172 meV as the rate of oxygen gas flow increased. On the contrary, the optical energy band-gap (Eg) increased from 3.9 to 4.2 eV. Conduction and valance band positions (relative to the normal hydrogen electrode) were also evaluated. The observed behavior is probably associated with the degree of disorder and defects presented in the as-deposited SiOx thin films, probably due to the presence of newly inserted oxidized OnSiHy species resulting from some contamination with water vapor desorbed from the walls of the deposition vacuum chamber. After deposition of a gold top electrode, the electrical characteristics of the fabricated Au/SiOx/n-Si system (i.e., a metal/insulator/semiconductor structure—MIS) were studied via characteristic I-V curves and their dependence upon the O2 flow rate are reported. It was observed that the Au/SiOx/n-Si structure behaves like a Schottky-diode exhibiting a very good diode rectifying performance with a rectification ratio of at least 300 and up to 104, which refers to the samples produced with the lower and higher O2 flow rates, respectively. It was also found that the O2 flow rate influences the rectifying performance of the SiOx/n-structures since both the diode ideality factor, n, and the diode series-resistance, RS decreases with the increase of O2 content, possibly reflecting a closer approximation to a full stoichiometric condition.

Nonhomogeneous surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air

Surface properties of parylene-C film etched by an atmospheric pressure He/O2 micro-plasma jet in ambient air were investigated. The morphologies and chemical compositions of the etched surface were analyzed by optical microscopy, SEM, EDS, XPS and ATR-FTIR. The microscopy and SEM images showed the etched surface was nonhomogeneous with six discernable ring patterns from the center to the outside domain, which were composed of (I) a central region; (II) an effective etching region, where almost all of the parylene-C film was removed by the plasma jet with only a little residual parylene-C being functionalized with carboxyl groups (CO, OCO−); (III) an inner etching boundary; (IV) a middle etching region, where the film surface was smooth and partially removed; (V) an outer etching boundary, where the surface was decorated with clusters of debris, and (VI) a pristine parylene-C film region. The analysis of the different morphologies and chemical compositions illustrated the different localized etching process in the distinct regions. Besides, the influence of O2 flow rate on the surface properties of the etched parylene-C film was also investigated. Higher volume of O2 tended to weaken the nonhomogeneous characteristics of the etched surface and improve the etched surface quality.

Influence of O2 flow rate on HfO2 gate dielectrics for back-gated graphene transistors

HfO2 thin films deposited on Si substrate using electron beam evaporation, are evaluated for back-gated graphene transistors. The amount of O2 flow rate, during evaporation is optimized for 35 nm thick HfO2 films, to achieve the best optical, chemical and electrical properties. It has been observed that with increasing oxygen flow rate, thickness of the films increased and refractive index decreased due to increase in porosity resulting from the scattering of the evaporant. The films deposited at low O2 flow rates (1 and 3 SCCM) show better optical and compositional properties. The effects of post-deposition annealing and post-metallization annealing in forming gas ambience (FGA) on the optical and electrical properties of the films have been analyzed. The film deposited at 3 SCCM O2 flow rate shows the best properties as measured on MOS capacitors. To evaluate the performance of device properties, back-gated bilayer graphene transistors on HfO2 films deposited at two O2 flow rates of 3 and 20 SCCM have been fabricated and characterized. The transistor with HfO2 film deposited at 3 SCCM O2 flow rate shows better electrical properties consistent with the observations on MOS capacitor structures. This suggests that an optimum oxygen pressure is necessary to get good quality films for high performance devices.

Electrochromic Property Dependent on Oxygen Gas Flow Rate and Films Thickness of Sputtered WO3 Films

Tungsten oxide films (WO3) were deposited on ITO/glass substrates with tungsten target in UHV by d.c. reactive magnetron sputtering. The WO3 films were deposited at various O2 flow rates from 5 to 20sccm and various film thicknesses from 50 to 500nm at 10 mTorr operating pressure as controlled by pressure control gate valve. The influence of O2 flow rate on structural, optical and electrochromic properties of WO3 films were investigated. All the WO3 films were found amorphous which were indicated by X-ray diffraction (XRD). The deposition rate of WO3 films was decreased with increasing oxygen flow rate. The optical constants and transmission spectra of WO3 films were determined by spectroscopic ellipsometry (SE) and UV-Vis spectrophotometry, respectively. The electrochromic property of WO3 films was performed by cyclic voltametry measurement. The transmission change between colored and bleached states of WO3 films for oxygen flow rate of 5sccm showed excellent electrochromic property which was strongly dependent on the film thickness.

Composition and crystal structure of N doped TiO2 film deposited with different O2 flow rates

N doped TiO2 films were deposited in direct current pulsed magnetron sputtering system at room temperature. We have studied the influence of O2 flow rate on the crystal structure of deposited films by using stylus profilometer, X-ray photoelectron spectroscope, X-ray diffractometer, and ultraviolet-visible spectrophotometer. The results indicate that the growth behavior and crystal structure of N doped TiO2 film is dominated by the O2 flow rate. It was found that the chemical stiochiometry is close to TiO1.68±0.06N0.11±0.01 for all film samples, in which the N mainly exists in substitutional doped state. When O2 flow rate is 2 sccm (1 sccm=1 mL/min), N doped TiO2 film has amorphous structure with high growth rate, which contains both anatase phase and rutile phase crystal nucleuses. In this case, the film displays the mix-phase of anatase and rutile and the band gap is 2.86eV after annealing treatment. The film growth rate decreases with increasing O2 flow rate. After annealing treatment, the band gap of N doped TiO2 films decreases with increasing O2 flow rate. While N doped TiO2 film is anatase phase when O2 flow rate is 12sccm. In this case, the band gap is 3.2eV after annealing treatment. It should be noticed that no TiN phase appears for all samples before and after annealing treatment.