Low Sputtering Pressure Research Articles

The effect of sputtering pressure on structural, optical and electrical properties of indium tin oxide nanocolumns prepared by radio frequency (RF) magnetron sputtering

In the present study, transparent conductive indium tin oxide (ITO) nanocolumns are successfully deposited on glass and silicon substrates by radio frequency (RF) magnetron sputtering system. The effects of sputtering pressure on the morphological, structural, electrical and optical properties of the ITO nanocolumns were investigated. Dense nanocolumns array are obtained at low sputtering pressure. The (400) peaks become more intense at low sputtering pressure, which indicates the improvement in the crystallinity of the ITO nanocolumns. The lowest resistivity of 9.36×10−5Ωcm was obtained for the ITO nanocolumns deposited at sputtering pressure of 3mTorr. The average of optical transparency greater than 80% in the visible range of 470nm was obtained from all samples investigated, give a good potential for blue light emitting diode (LED) applications. The low resistivity and high transparencies give a superior properties as a transparent conducting layer in various optoelectronic devices comparable with that conventional ITO conducting layer.

Tuning the Magnetization Dynamics in Sputtered ${\hbox{Co}}_{2}{\hbox{FeAl}}_{0.5}{\hbox{Si}}_{0.5}$ Heusler Alloy Thin Film by Gas Pressure

The influences of sputtering gas pressure on the high frequency magnetization dynamics properties of sputtered Co2FeAl0.5Si0.5 (CFAS) Heusler alloy thin films have been systematic studied. Results show that the surface roughness, grain size, anisotropy field and dynamic magnetic properties can be tailored by changing sputtering gas pressures. The inhomogeneous linewidth broadening of the sputtered CFAS Heusler thin films is monotonously enhanced with the pressure increasing, similar as with the anisotropy field. A low value intrinsic damping parameter is extracted as 0.0073 with a low sputtering pressure, 1.58 ×10-4 mbar. The intrinsic damping parameter increases monotonously up to 0.0122 with the pressure increasing. The high tunability of the damping constant indicates that controlling the sputtering gas pressure could be an effective method to tune the magnetization dynamics in sputtered CFAS thin film.

Structure and composition of Ba0.5Sr0.5TiO3 films deposited on (001) MgO substrates and the influence of sputtering pressure

The structure and composition of Ba0.5Sr0.5TiO3 thin films, sputter deposited on (001) MgO substrates, have been characterized by transmission electron microscopy. Deviations in film stoichiometry are seen to strongly correlate with the structural and dielectric properties of these films, with the films deposited at the lower sputtering pressures either Ti-deficient or capped with a titanium oxide layer similar to the rutile TiO2 phase. Preferential sputtering of cations is found to be an important factor governing film stoichiometry. The Ti-deficient films deposited at a lower sputtering pressure contain Ruddlesden–Popper faults that increase the average lattice constant of the film and result in compressive strain and low dielectric tunability.

Effect of Sputtering Conditions on the Microstructures of YNiBi Thin Film

Half-Heusler compound YNiBi thin films have been prepared by direct current (DC) magnetron sputtering from an YNiBi target. The film structure and surface morphology of YNiBi thin films were analyzed with X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrical properties of the films were studied by Hall measurements. XRD patterns show that the films prepared at lower sputtering pressure and higher growth temperature exhibit minimum full width at half maximum (FWHM) and maximum diffraction peaks which belong to the same family of crystal planes. Results of AFM reveal that the surface of a variety of fabricated YNiBi films is smooth and keeps good adhesion to the substrate. The increasing of substrate temperature and slightly lowering of sputtering pressure are in favor of reducing the root mean square roughness during magnetron sputtering process. The film with high crystallinity has an electrical conductivity of 938 S/cm and carrier concentration of 2.15×1021 cm-3.

Surface morphology evolution of CeO2/YSZ (001) buffer layers fabricated via magnetron sputtering

Cerium dioxide (CeO2)/yttria-stabilized zirconia (YSZ) has long been proven to be an effective buffer layer architecture for high-temperature superconducting coated conductors. In this study, CeO2 films were deposited on YSZ (001) single crystal substrates via reactive unbalanced magnetron sputtering with varying substrate temperature, sputtering pressure, radio frequency sputtering power, and film thickness. High-quality texture was achieved even at ambient temperature, and deposition parameters were optimized to achieve the best degree of in-plane alignment with (111) ϕ scan full width at half maximum around 1.3°. Atomic force microscopy was utilized to investigate film surface morphology and roughness. At a low sputtering pressure, a flat and uniform film surface comprising nano-sized isotropic islands was observed. The surface islands transited to an anisotropic spindle-like shape at pressure higher than 1.0Pa. The spindle-shaped islands elongated along the CeO2 [110] or [11¯0] directions, constructing an interwoven surface morphology. The distinct surface morphology evolution was correlated with the change in the film strain state attributed to varying sputtering pressure. A possible mechanism for this morphology evolution was discussed.

Structural and electrical properties of CuAlMo thin films prepared by magnetron sputtering

The structural and electrical properties of a low resistivity CuAlMo thin film resistor material were investigated. The thin films were grown on Al2O3 and glass substrates by direct current (dc) magnetron sputtering. The key electrical properties of sheet resistance, temperature coefficient of resistance (TCR) and resistance stability were investigated as a function of sputtering pressure and post-deposition heat treatment time and temperature. A low sputtering pressure range of 0.13 to 0.40Pa produced CuAlMo films with sheet resistance in the range 0.1 to 0.2Ω/□ and resistance stability of 0.45 to 0.65% with a TCR of −90ppm/°C which could be shifted to zero following annealing in air at 425°C. Films grown at higher sputtering pressures of 0.53 to 0.80Pa had increased sheet resistance in the range 0.4 to 0.6Ω/□ and inferior stability of 0.8 to 1.7% with a more negative TCR of −110 to −180ppm/°C which could not be shifted to zero following annealing. The stability of the films grown at 0.13 and 0.40Pa could be further improved to <0.25% with heat treatment, due to the formation of a protective aluminium oxide layer. A minimum dwell time of 3h at 425°C was required to stabilise the films and set the electrical properties.

Mechanical properties and corrosion behaviour of freestanding, precipitate-free magnesium WE43 thin films

Abstract Magnetron sputtered freestanding thin films of two modified WE43 alloys (Mg4Y3Nd and Mg4Y3Gd) consist of a supersaturated single phase microstructure with a strong texture in [0001] direction for a wide range of deposition conditions. While the deposition conditions have no significant influence on the corrosion behaviour of these samples, they strongly influence the mechanical properties, which can be tuned between extremely brittle behaviour for high sputtering pressures (2.0 × 10−2 mbar) and ductile behaviour with a maximum strain of about 18 % at room temperature for low sputtering pressures (8.0 × 10−4 mbar) for both investigated alloys.

RF 마그네트론 스퍼터링에 의해 제조된 AlN 박막의 증착 특성

AlN thin films were deposited on p-type Si(100) substrates by RF magnetron sputtering method. This study showed the change of the preferential orientation of AlN thin films deposition with the change of the deposition conditions such as sputtering pressure and Ar/N2 gas ratio in chamber. It was identified by X-ray diffraction patterns that AlN thin film deposited at low sputtering pressure has a (002) orientation, however its preferred orientation was changed from the (002) to the (100) orientation with increasing sputtering pressure. Also, it was observed that the properties of AlN thin films such as thickness, grain size and surface roughness were largely dependent on Ar/<TEX>$N_2$</TEX> gas ratio and a high quality thin film could be prepared at lower nitrogen concentration. AlN thin films were investigated relationship between preferential orientation and deposition condition by using XRD, FE-SEM and PFM.

Effects of sputtering pressure on properties of Al doped ZnO thin films dynamically deposited by rf magnetron sputtering

Aluminium doped zinc oxide (AZO) films were dynamically deposited by rf magnetron sputtering under various sputtering pressures in the range of 0·3–2·0 Pa. The effect of the Ar sputtering pressure on the structural, electrical and optical properties of the AZO films was systematically investigated by X-ray diffractometry, scanning electron microscope, four-point probe measurement and UV–vis spectrophotometer. As the sputtering pressures decrease, the crystallite sizes of the films became larger, while their deposition rate turns higher. Under the condition of lower sputtering pressures, a decrease in the resistivity was observed due to an increase in carrier concentration. The AZO film deposited at 0·5 Pa in the dynamic mode has shown the lowest resistivity of 9·5×10−4 Ω cm. This work was performed in a dynamic deposition system in order to produce a large area of AZO films, which is more important in practical fields to improve productivity.

Sputtering-Pressure Dependent Optical and Microstructural Properties Variations in DC Reactive Magnetron Sputtered Titanium Nitride Thin Films

Titanium nitride thin films were prepared using DC reactive magnetron sputtering process in a 99.998% reactive nitrogen atmosphere. The sputtering pressure was varied to study its influence on the as-deposited films, using low (0.80 Pa), intermediate (3.40-5.33 Pa) and high (11.33 Pa) sputtering pressures. The deposited films possessed colour that ranged from dark blue, characteristic of oxygen-rich titanium nitride films, to reflective golden yellow, reminiscent of stoichiometric TiNx films. Studies on the optical and microstructural properties were carried out using UV-visible spectrophotometry, scanning electron microscopy (SEM) and X-ray diffractometry. Characterization results showed variation in the optical and structural properties of the film depending on the deposition sputtering pressure with relatively higher enhancement in the optical transmittance of up to 97.52% in the visible region for films deposited under high and intermediate sputtering pressure conditions. The deposition rate of the films was found to decrease with sputtering pressure. In the same vein, the optical transmittance of the films reduced from 97.52 to 10.05% and the transmission band shifted towards higher wavelength with the decrease of the sputtering pressure.

AlN films prepared on 6H–SiC substrates under various sputtering pressures by RF reactive magnetron sputtering

In this paper, we studied the growth of AlN films on 6H–SiC substrates under various sputtering pressures by RF reactive magnetron sputtering at low deposition temperature (300°C). The composition, chemical structure and oxygen impurity of the deposited films were investigated by X-ray photoelectron spectroscopy (XPS). It is suggested that the Al/N ratio of the high purity film is 1.13:1 which is very close to the stoichiometric value (1:1), and a few oxygen impurities exist in the grain boundaries in the form of AlO bonding. The two-dimensional X-ray diffraction (2D-XRD) was used to study the crystal structure of the deposited films. 2D-XRD patterns indicate that a low sputtering pressure favor the growth of AlN film with c-axis oriented, and a highly c-axis oriented AlN film resemble single crystal structure was prepared at the sputtering pressure of 0.3Pa. Surface morphology of the deposited films were investigated by SEM and AFM. The images show that the surface morphology of the films with (0002) preferred orientation present a pebble-like structure, and the grain size and surface roughness of the films decrease with increasing the sputtering pressure.

Deposition of c-axis orientation aluminum nitride films on flexible polymer substrates by reactive direct-current magnetron sputtering

Aluminum nitride (AlN) piezoelectric thin films with c-axis crystal orientation on polymer substrates can potentially be used for development of flexible electronics and lab-on-chip systems. In this study, we investigated the effects of deposition parameters on the crystal structure of AlN thin films on polymer substrates deposited by reactive direct-current magnetron sputtering. The results show that low sputtering pressure as well as optimized N2/Ar flow ratio and sputtering power is beneficial for AlN (002) orientation and can produce a highly (002) oriented columnar structure on polymer substrates. High sputtering power and low N2/Ar flow ratio increase the deposition rate. In addition, the thickness of Al underlayer also has a strong influence on the film crystallography. The optimal deposition parameters in our experiments are: deposition pressure 0.38Pa, N2/Ar flow ratio 2:3, sputtering power 414W, and thickness of Al underlayer less than 100nm.

Improvement of electrical and optical properties of molybdenum oxide thin films by ultralow pressure sputtering method

In this work, we investigated the structural, electrical and optical properties of molybdenum oxide thin films deposited by the reactive dc magnetron sputtering method. The molybdenum oxide films were prepared at sputtering pressures ranging from 6.7 × 10−1 to 6.7 × 10−2 Pa. In order to promote their electrical conductivity, all the deposited MoOx films were annealed in Ar ambient at 450 °C for 8 h. The resistivity of the MoOx films varied from 10−4 to 10−2 Ω cm depending on the O2 content in the sputtering ambient. The lowering of the resistivity of the MoO2 films was mainly attributed to the formation of a monoclinic MoO2 polycrystalline phase. As the sputtering pressure decreased, the content of monoclinic polycrystalline MoO2 phase increased, resulting in low resistivity films. The formation of the dominant MoO2 phase at lower sputtering pressures was attributed to the stress induced crystallization. The post-deposition annealed (PDA) MoOx film, deposited at an ultralow sputtering pressure (6.7 × 10−2 Pa) and O2 content of 40%, had an atomic ratio of O to Mo ≈ 2.85 and was highly transparent and conductive: the transmittance in the visible wavelength range of 400–500 nm was about 73% and the resistivity was 1.05 × 10−3 Ω cm. This result is superior to those of MoOx films epitaxially grown by the pulse laser deposition method.

The effect of argon pressure, residual oxygen and exposure to air on the electrical and microstructural properties of sputtered chromium thin films

Chromium thin films were deposited on SiO 2/Si wafers using two sputtering systems with different levels of cleanliness, and at argon sputtering pressures varying between 0.13 and 0.93 Pa. Films from the two systems grown under identical sputtering conditions had significantly different resistivity values that are shown to be due to differences in residual oxygen in the chambers. Electrical transport measurements were conducted on the series of grown films to investigate the influence of argon pressure on film electrical resistivity. The films morphology, microstructure and composition were characterized using scanning electron microscopy and X-ray photoelectron spectroscopy. Significant differences were found in Cr thin films sputtered at different sputtering pressures; differences in resistivity performance and microstructure were noted. This change was shown to be due to the transition from porous structure to a denser microstructure. The Cr films sputtered at high pressure contained large quantities of oxygen when exposed to air. Some of the oxygen is added to the film during the deposition depending on the deposition rate and the base pressure of the sputtering system. The rest is incorporated into the film once it is exposed to air. The amount of oxygen added at this stage depends on the structure of the film and would be minimal for the films deposited at low sputtering pressures.

Effect of RF power and sputtering pressure on the structural and optical properties of TiO 2 thin films prepared by RF magnetron sputtering

TiO 2 thin films were deposited onto quartz substrates by RF magnetron sputtering. The samples deposited at various RF powers and sputtering pressures and post annealed at 873 K, were characterized using X-ray diffraction (XRD), micro Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectrum indicates that the films are amorphous-like in nature. But micro-Raman analysis shows the presence of anatase phase in all the samples. At low sputtering pressure, increase in RF power favors the formation of rutile phase. Presence of oxygen defects, which can contribute to PL emission is evident in the XPS studies. Surface morphology is much affected by changes in sputtering pressure which is evident in the SEM images. A decrease in optical band gap from 3.65 to 3.58 eV is observed with increase in RF power whereas increase in sputtering pressure results in an increase in optical band gap from 3.58 to 3.75 eV. The blue shift of absorption edge in all the samples compared to that of solid anatase is attributed to quantum size effect. The very low value of extinction coefficient in the range 0.0544–0.1049 indicates the excellent optical quality of the samples. PL spectra of the films showed emissions in the UV and visible regions.

Fabrication of Multiferroic Co-Substituted BiFeO₃ Epitaxial Films on SrTiO₃ (100) Substrates by Radio Frequency Magnetron Sputtering.

The 10 at.% Co-substituted BiFeO3 films (of thickness 50 nm) were successfully prepared by radio frequency (r.f.) magnetron sputtering on SrTiO3 (100) substrates with epitaxial relationships of [001](001)Co-BiFeO3//[001](001)SrTiO3. In this study, a single phase Co-substituted BiFeO3 epitaxial film was fabricated by r.f. magnetron sputtering. Sputtering conditions such as Ar, O2 gas pressure, annealing temperature, annealing atmosphere, and sputtering power were systematically changed. It was observed that a low Ar gas pressure and low sputtering power is necessary to suppress the formation of the secondary phases of BiOx. The Co-substituted BiFeO3 films were crystalized with post-annealing at 600 °C in air. The process window for single phase films is narrower than that for pure BiFeO3 epitaxial films. By substituting Fe with Co in BiFeO3, the magnetization at room temperature increased to 20 emu/cm3. This result suggests that Co-substituted BiFeO3 films can be used in spin-filter devices.

Thermal and stress studies of normal incidence Mo/B_4C multilayers for a 67 nm wavelength

Wavelength, reflectance, and stress stability of Mo/B(4)C multilayers were studied as a function of postdeposition annealing up to 900 °C. These multilayers are of interest as normal incidence coatings for wavelengths above the boron K-absorption edge. Mo/B(4)C multilayers deposited at low sputtering pressure have high compressive stress. Zero stress can be achieved at 360 °C-370 °C, but annealing at <200 °C is sufficient to reduce stress by ∼40%. This stress relaxation is accompanied with a multilayer period expansion of ∼0.02 nm and a <0.5% decrease in normal incidence reflectivity. The multilayer period remains stable up to ∼600 °C, while intrinsic stress changes from compressive to tensile. A four-layer model with amorphous molybdenum and boron carbide layers separated by amorphous layers of molybdenum borides (Mo(x)B(y)) is presented. These interlayers are present already in the as-deposited state and continue to grow with increasing temperature. Their presence lowers the optical contrast and the achievable reflectivity. However, they also increase multilayer thermal stability. At temperatures >600 °C, a noticeable decrease in reflectivity associated with the phase transition from amorphous to crystalline molybdenum boride is observed. This is accompanied with an increase in interface and surface roughness and a change in stress as a function of temperature.

Reversal of patterned Co/Pd multilayers with graded magnetic anisotropy

Magnetization reversal and the effect of patterning have been investigated in full-film and dot arrays of Co/Pd multilayers, using the first-order reversal curve and scanning electron microscopy with polarization analysis techniques. The effect of patterning is most pronounced in low sputtering pressure films, where the size of contiguous domains is larger than the dot size. Upon patterning, each dot must have its own domain nucleation site and domain propagation is limited within the dot. In graded anisotropy samples, the magnetically soft layer facilitates the magnetization reversal, once the reverse domains have nucleated.

Properties of polyimide/Al 2O 3 and Si 3N 4 deposited thin films

Polyimide (PI) nanocomposites with different proportions of Al 2O 3 were prepared via two-step reaction. Silicon nitride (Si 3N 4) was deposited on PI composite films by a RF magnetron sputtering system and used as a gas barrier to investigate the water vapor transmission rate (WVTR). The thermal stability and mechanical properties of a pure PI film can be improved obviously by adding adequate content of Al 2O 3. At lower sputtering pressure (4 mTorr), the PI/Al 2O 3 hybrid film deposited with Si 3N 4 barrier film exhibits denser structure and lower root mean square (RMS) surface roughness (0.494 nm) as well as performs better in preventing the transmission of water vapor. The lowest WVTR value was obtained from the sample, 4 wt.%Al 2O 3–PI hybrid film deposited with Si 3N 4 barrier film with the thickness of 100 nm, before and after bending test. The interface bonding, Al–N and Al–O–Si, was confirmed with the XPS composition-depth profile.

Microstructure and variable emittance property of annealed La-Sr-Mn-O films

The La-Sr-Mn-O films were deposited on Si(100) substrates by DC magnetron sputtering and followed by air annealing at 973 K for 1 h. The microstructure and temperature dependence of total hemispherical emittance (ɛ H) of the annealed La-Sr-Mn-O films prepared at various processing parameters were investigated. The results indicated the films deposited at lower sputtering pressure and lower O 2/(O 2+Ar) volume proportion ( R O) were present in rhombohedral perovskite structure and the length of Mn-O bond was shorter. The metal-insulator transition temperature ( T MI) was higher. All of the annealed films showed the unique feature of variable emittance based on metal-insulator transition. The films showed low emittance at low temperature but high emittance at high temperature. Moreover, the ɛ H significantly changed in the vicinity of T MI. The variability of total hemispherical emittance (Δɛ) and the temperature range with obvious emittance change could be adjusted by changing the processing parameters. The Δɛ could be 0.45 and Δɛ/ɛ 355 (ɛ 355 is the ɛ H at 355K) exceeded 50% for the annealed La-Sr-Mn-O films. Therefore, the annealed La-Sr-Mn-O films showed much potential for thermal control applications as smart thermochromic variable emittance materials.