Off-axis Magnetron Sputtering Research Articles

유연성 기판 위에 증착된 ITO 박막의 공정 온도에 따른 전기적·광학적 특성 평가

In this study, off-axis magnetron sputtering was used for the crystallized ITO thin films at a low temperature of about instead of the conventional RF sputtering because the off-axis sputtering can avoid the damage for the plasma as well as fabrication of thin films with a high quality. The ITO thin films grown on PET substrate at were crystallized with a (222) preferred orientation. 58-nm thick ITO films showed a resistivity of about and a transmittance of about 75% at a wavelength of 550 nm. The transmittance of the ITO thin films by an insertion of SiO2 thin films on ITO films was improved.

Electronic and magnetic tunability of Sr2CrReO6 films by growth-mediated oxygen modulation

Highly ordered epitaxial films of ferrimagnetic semiconductor Sr2CrReO6 (SCRO) have been fabricated by off-axis magnetron sputtering, and characterized as a function of the oxygen partial pressure. In this Letter, we report 18 000% modulation in electrical resistivity at T = 7K (60% at room temperature) from a 1% modulation in the oxygen partial pressure during film growth. The growth window was centered at peak saturation magnetization, which drops due to both increasing and decreasing oxygen growth pressure. The results suggest that n-type doping due to oxygen vacancies plays a dominant role in the electrical properties and modulation of Sr2CrReO6 thin films.

Structural and electrical properties of transparent conducting Al2O3-doped ZnO thin films using off-axis DC magnetron sputtering

Structural and electrical properties of off-axis DC magnetron sputtered Al2O3-doped ZnO (AZO) films were systematically investigated as a function of deposition distance from the center. With increasing distance, the AZO films showed an enhanced crystallinity and a denser microstructure with a smooth surface. The AZO film sputtered at the edge of the deposition stage (∼6cm away from the center) showed the highest mobility (∼10.1cm2/Vs) and the lowest resistivity (∼2×10−3Ωcm) due to the high plasma and thermal power density, which was suitable for transparent conducting oxide applications.

The mechanisms of negative oxygen ion formation from Al-doped ZnO target and the improvements in electrical and optical properties of thin films using off-axis dc magnetron sputtering at low temperature

Transparent conducting aluminum-doped zinc oxide (AZO) films have been prepared on glass substrates by dc magnetron sputtering using ceramic ZnO with 2 wt% Al2O3 target. The mechanism of negative oxygen ion generation on an AZO target surface and its influence on the conductivity of films were discussed. The negative ion generation on an AZO target was contributed by the surface ionization leading to the spot emission from Al atoms adsorbed on the AZO target surface. The contribution of negative ions' current was mainly from the erosion area of the target due to its higher temperature. To reduce the damage caused by negative ion bombardment to film growth, an off-axis sputtering system was proposed, where the substrates were placed perpendicular to the target. The effects of distance (d) on the electrical properties of films were experimentally verified in detail. A low resistivity of 3.7 × 10−4 Ω cm, an average transmittance above 85% in the visible range (300–800 nm) and reflectance higher than 85% in the infrared range (2500–4000 nm) were obtained for the films deposited at d = 2.5 cm. The overall analysis revealed that the generation of negative ions on the AZO target has a great influence on film growth, especially in the ultra-low pressure deposition process. Our work demonstrates the feasibility of reducing the negative effects of ion bombardment on the quality of films, which would be of great merit for industrial applications.

Structural characterization of La 0.9Ba 0.1MnO 3/Y-ZrO 2 film by X-ray diffraction

Perovskite manganite La 0.9Ba 0.1MnO 3(LBMO) films were deposited on (0 0 1)-oriented single crystal yttria-stabilized zirconia (YSZ) substrate by 90° off-axis radio frequency magnetron sputtering. The film thickness ranged from 10 nm to 100 nm. Grazing incidence X-ray diffraction technique and high resolution X-ray diffraction were applied to characterize the structure of LBMO films. The LBMO film mainly consisted of (0 0 1)-orientated grain as well as weakly textured (1 1 0)-orientated grain. The results indicated that an amorphous layer with thickness of about 4 nm was formed at the LBMO/YSZ interface. The strain in LBMO film was small and averaged to be about –0.14%. The strain in the film was not lattice mismatch-induced strain but residual strain due to the difference in thermal expansion coefficient between film and substrate.

Dielectric properties of composition spread SiO 2–Al 2O 3 mixed phase thin films deposited at room temperature by off-axis RF magnetron sputtering

The dielectric properties of composition spread SiO 2–Al 2O 3 thin films deposited by off-axis radio-frequency magnetron sputtering at room temperature were explored to obtain optimized compositions, which have low dielectric constants and losses. The specific points (compositions) showing superior dielectric properties of low dielectric constants (8.13 and 9.12) and losses (tanδ ∼0.02) at 1 MHz were found in area of the distance of 25.0 mm (Al 2Si 3O 8) and 42 mm (Al 2.4Si 3O 8) apart from SiO 2 target side in 75 mm × 25 mm sized Pt/Ti/SiO 2/Si(1 0 0) substrates, respectively. The specific thin films were amorphous phase and the compositions were Al 2Si 3O 8 ( k ∼8.13) and Al 2.4Si 3O 8 ( k ∼9.12).

Epitaxial growth and piezoelectric characterization of the (1−x)BiScO3−(x)PbTiO3 ultrathin film

We studied ferroelectric properties of morphotropic phase boundary (1−x)BiScO3−(x)PbTiO3 (BSPT, x = 0.64) epitaxial thin films on SrTiO3 (001) and Nb:SrTiO3 (001). BSPT thin films with various thicknesses were deposited using off-axis radio frequency magnetron sputtering. By analyzing x-ray data of BSPT thin films with various thicknesses, we confirmed that films thinner than ∼22 nm were in a strained state. Films thicker than ∼22 nm were in a relaxed state because of the strain relaxation mechanism caused by misfit dislocation formation. Clear piezoresponses and polarization reversal phenomena can be observed in the ultrathin limit down to 8 nm through Piezo Force Microscope experiments. The piezoresponse data as a function of thickness correlates with the structural modification of thin films.

A single target RF magnetron co-sputtered iron doped tin oxide films with pillars

The SnO 2 gas sensors and catalytic surfaces are produced by different techniques with a wide range of dopants improving their selectivity and sensitivities. The surface topology is important because the active surface area can be enlarged dramatically by employing nanostructures. Many reported techniques for the tin oxide nanostructures preparation require fine powders or liquid precursors together with high temperatures above 500 °C. But the nanostructures can be formed by the RF off-axis magnetron sputtering technique at room temperature from a bulk target. The single target co-sputtering of SnO 2 target with Fe inset was used to deposit SnO 2 film doped by iron. The 400 nm diameter pillars were successfully deposited in controllable density on polished Si substrates at low pressure 0.3 Pa of argon and oxygen gas mixture. The pillars were not formatted at the beginning of deposition process but certain SnO 2 film was required. The surface around the pillars was flat without any significant texture. The iron in form of the iron oxide was found to be the doping in deposited coatings when the stannic oxide was sub-stoichiometry with oxygen vacancies.

ZnO as a buffer layer for growth of BiFeO3 thin films

Multiferroic BiFeO3 thin film was grown on the ZnO-buffered Pt/TiO2/SiO2/Si(100) substrate by off-axis radio frequency magnetron sputtering, where the ZnO buffer layer gave rise to a strong (110) texture for the BiFeO3 thin film. The resulting BiFeO3/ZnO thin film exhibits diode-like and resistive hysteresis behavior, in which the resistive hysteresis and rectifying ratio are dependent on the applied voltage and temperature. The resistive switching behavior of the BiFeO3/ZnO thin film is shown to relate to the trap-controlled space charge limited conduction and interface-limited Fowler–Nordheim tunneling, while the polarization reversal takes place in the BiFeO3 layer of the heterostructure. The BiFeO3/ZnO thin film is also demonstrated with a higher remanent polarization (2Pr∼153.6 μC/cm2), a much lower dielectric loss (tan δ∼0.012), and a better fatigue endurance as compared to those of the BiFeO3 thin film without a ZnO buffer layer, where the much reduced leakage is largely responsible for the enhanced ferroelectric behavior. The ZnO as a buffer layer for BiFeO3 significantly changes the dielectric relaxation and conduction mechanisms, when the dielectric relaxation and electrical conduction are governed by the thermal excitation of carriers from the second-ionization and short-range motion of oxygen vacancies, respectively, while the relaxation process remains the same over the entire temperature range of 20 to 200 °C investigated in the present study.

Magnetron sputtering of polycrystalline LSMO/YBCO structures on sapphire substrates

La0.7Sr0.3MnO3 (LSMO) films with different thickness were deposited directly on r-cut sapphire substrates by RF off-axis single magnetron sputtering with a view to produce a suitable buffer for growing HTS YBa2Cu3O7-δ (YBCO) films on top. These LSMO layers were polycrystalline and showed a ferromagnetic behavior at room temperatures. The top YBCO films were sputtered in a DC off-axis double magnetron system. The polycrystalline structures thus produced were characterized and discussed.

Temperature Dependence of Magnetization Reversal of Thin Manganite Film

The magnetic domain structure, its transformation with temperature, and the magnetization reversal in 20 nm La0.7Sr0.3MnO3 film grown on LaAlO3 substrate by off-axis magnetron sputtering at 700 ◦C and post-annealed at 600 ◦C were studied in a wide temperature range. The magnetic domains with either in-planeor out-of-plane-orientation of the vector of spontaneous magnetization were observed in the same film depending on the prehistory. The domains with the in-plane magnetization were found to be more stable. Magnetization reversal of the film was shown to occur via the nucleation and motion of 180-degree head-to-head domain walls, the number and the type of which were found to be dependent on temperature. Moreover, the transition between two magnetization reversal regimes was found at 30 K.

Resistive Hysteresis and Diodelike Behavior of BiFeO[sub 3]/ZnO Heterostructure

Bilayered BiFeO 3 /ZnO thin films, which were grown on the SrRuO 3 -buffered MgO(100) substrate by off-axis radio frequency magnetron sputtering, are investigated for their current―voltage relationships at varying voltages and temperatures. A resistive hysteresis and a diodelike behavior are observed for the bilayered BiFeO 3 /ZnO thin films. The resistive hysteresis and the rectification ratio are enhanced with increasing electrical field and temperature. The observed behavior arises from the interfacial depletion layer and ferroelectric switching, where the charge coupling between the semiconducting ZnO and the ferroelectric BiFeO 3 layers occurs.

Characterization of La-doped YBCO superconducting films deposited by DC magnetron sputtering at various off-axis geometries

La-doped YBCO (Y0.9La0.2Ba1.9Cu3Oy) superconducting films were deposited by an off-axis DC magnetron sputtering method. We investigated the relationship between the film characteristics and the deposition conditions, and drew systematical maps in terms of composition, surface morphology, crystal structure and superconducting properties for the films deposited at various spatial geometries of a substrate and a target. Correspondence between the Cu content and the surface morphology was clearly observed. Cu-rich films had precipitates on the surface. Slightly Cu-poor films exhibited c-axis orientation and a high Tc of 87 K. Among them, the film deposited at a rather fast deposition rate exhibited a flat surface with an average surface roughness Ra less than 1 nm for an area of 10 micron square. Considerably Cu-poor films contained a-axis oriented grains or exhibited very rough surfaces. The cationic ratio of Y:La:Ba did not change significantly.

BiFeO 3 thin films of (1 1 1)-orientation deposited on SrRuO 3 buffered Pt/TiO 2/SiO 2/Si(1 0 0) substrates

BiFeO 3 (BFO) thin films of varying degrees of (1 1 1) orientation were successfully grown on SrRuO 3-buffered Pt/TiO 2/SiO 2/Si(1 0 0) substrates by off-axis radio-frequency magnetron sputtering. They demonstrate much enhanced ferroelectric behavior, including a much enhanced remnant polarization (2 P r ∼ 197.1 μC cm −2 at 1 kHz) measured by positive-up negative-down (PUND), at an optimized deposition temperature of 590 °C. The effects of film deposition temperature on the degree of (1 1 1) orientation, film texture, ferroelectric behavior, leakage current and fatigue endurance of the BFO thin films were systematically investigated. While the degree of (1 1 1) orientation is optimized at 590 °C, the defect concentration in the film increases steadily with increasing deposition temperature, as demonstrated by the dependence of leakage behavior on the deposition temperature. The polarization behavior is shown to strongly depend on the degree of (1 1 1) orientation for the BFO thin film. Oxygen vacancies are shown to involve in the conduction and dielectric relaxation of the BFO thin films deposited at different temperatures, as demonstrated by their dielectric and conduction behavior as a function of both temperature (in the range 294–514 K) and frequency (in the range 10 −1–10 6 Hz).

Studies on strain relaxation and in-plane orientation of La0.7Ca0.3MnO3 film by grazing incidence X-ray diffraction

Abstract Perovskite manganite La 0.7 Ca 0.3 MnO 3 (LCMO) films were deposited on (0 0 1)-oriented single crystal MgO and SrTiO 3 (STO) substrates by 90° off-axis radio frequency magnetron sputtering. The thickness of LCMO/STO film was 50 nm. The thickness of LCMO/MgO films ranged from 5 nm to 200 nm. LCMO films were well (0 0 1)-oriented grown with high crystalline quality. Grazing incidence X-ray diffraction technique and normal X-ray diffraction were applied to characterize the in-plane and out-of-plane lattice strains and strain relaxation. The in-plane growth orientations of LCMO films with respect to substrate surface were also studied. The results indicated that the lattice strain of LCMO films began to relax when the film thickness is less than 5 nm. The mechanism for strain relaxation in LCMO films is perhaps different from that for tetragonal distortion. The in-plane growth orientation of LCMO/MgO film studied by grazing incidence X-ray diffraction technique is consistent with that from transmission electron microscopy.

Multiferroic behaviour and orientation dependence of lead-free (1 − x)BiFeO3–x(Bi0.50Na0.50)TiO3 thin films

Lead-free multiferroic (1 − x)BiFeO3–x(Bi0.50Na0.50)TiO3 (BFOBNTx) thin films were deposited by off-axis radio frequency magnetron sputtering on SrRuO3 buffered SrTiO3 (1 1 1), SrTiO3 (1 0 1), SrTiO3 (1 0 0) and LaAlO3 (0 0 1) substrates. Their ferroelectric behaviour is strongly dependent on the film composition and orientation. 0.95BiFeO3–0.05(Bi0.50Na0.50) TiO3 (BFOBNT5) exhibits notably better ferroelectric behaviour and fatigue endurance than the films of other compositions. The largest spontaneous polarization occurs in its (1 1 1) direction, where a remanent polarization of 2Pr ∼ 198.3 µC cm−2 is measured, while the polarizations in other directions are consistent with the projections from the (1 1 1) direction.

Phase transitions and electrical behavior of lead-free (K0.50Na0.50)NbO3 thin film

Lead-free (K0.50Na0.50)NbO3 (KNN) thin films with a high degree of (100) preferred orientation were deposited on the SrRuO3-buffered SrTiO3(100) substrate by off-axis radio frequency magnetron sputtering. They possess lower phase transition temperatures (To-t∼120 °C and Tc∼310 °C), as compared to those of KNN bulk ceramic (To-t∼190 °C and Tc∼400 °C). They also demonstrate enhanced ferroelectric behavior (e.g., 2Pr=24.1 μc/cm2) and fatigue endurance, together with a lower dielectric loss (tan δ∼0.017) and a lower leakage current, as compared to the bulk ceramic counterpart. Oxygen vacancies are shown to be involved in the conduction of the KNN thin film.

The fabrication and characterization ofPbTiO3 nanomesas realizedon nanostructured SrRuO3/SrTiO3 templates

We report the fabrication of PbTiO3 nanomesas down to 30 nm lateral size and 4 nm high on nanostructuredSrRuO3/SrTiO3 templates by off-axis radio frequency magnetron sputtering. The templates were prepared using atop-down lithography approach based on scanning tunneling microscopy. The growth rate of thePbTiO3 nanomesas was found to decrease with increasing growth temperature as well as withshrinking template size. Piezoresponse force microscopy measurements for thePbTiO3 nanomesas showed a strong increase in response with decreasing lateral size. A decrease ofthe coercive voltage was also observed for the same lateral size range. This laterallysize-dependent behavior is attributed to reduction of in-plane strain, when shrinking thenanomesa lateral dimensions.

Ferroelectric stripe domains in PbTiO3 thin films: Depolarization field and domain randomness

Observation of stripe domains in PbTiO3 thin films using standard x-ray diffraction analysis at room temperature is discussed. High-quality c-axis oriented thin films of varying thickness, from 6 to 210 unit cells, were grown on buffered NH4–HF etched SrTiO3(001) and Nb:SrTiO3(001) substrates using off-axis radio frequency magnetron sputtering. High-resolution linear Qx scans reveal a superstructure around the specular Bragg peaks, consistent with the presence of ferroelectric stripe domains. For thin samples, the stripe width is found to be proportional to the square root of the film thickness, with random in-plane orientation of domains. For films with a thickness of more than ∼100 unit cells, both monodomain samples and stripe domains were observed. We present evidence for the presence of a threshold depolarization field, above which there is a monotonically decreasing relationship between the domain width and the depolarization field. Furthermore, simulations show that random variations in size of the domains affect the separation of the diffuse scattering peaks from that of the specular reflection.

Preparation of multilayer films for integrated high- Tc SQUIDs with ramp-edge Josephson junctions

We proposed a novel multilayer structure having a new combination of oxides for integrated high- T c SQUID with ramp-edge Josephson junctions. La 0.1Er 0.95Ba 1.95Cu 3O y (L1ErBCO) and SmBa 2Cu 3O y (SmBCO) were used as counter- and base-electrodes, respectively. An SrSnO 3 (SSO) layer was deposited as an insulating layer. Prior to deposition of SmBCO, Pr 1.4Ba 1.6Cu 2.6Ga 0.4O y (P4G4) and SSO were deposited on MgO (100) substrate in order to improve film quality of L1ErBCO/SSO/SmBCO layers. The black-colored P4G4 layer was expected to work as a temperature homogenizer over a whole substrate area during deposition of the upper layers. All the layers except L1ErBCO were deposited by an off-axis magnetron sputtering. An L1ErBCO layer was deposited by a pulsed laser deposition method. A thin Cu-poor L1ErBCO layer was initially deposited to form an adequate barrier on the ramp-edge of SmBCO. Gradiometer arrays having multilayered feedback coils and pickup loops were made in a chip and their proper operation at 77 K was confirmed. The present multilayer structure is promising for application to SQUIDs with more complicated designs.