DC Facing-target Sputtering System Research Articles

Amorphous indium tin oxide films deposited on flexible substrates by facing target sputtering at room temperature

Indium tin oxide (ITO) thin films were deposited on polyethylene terephthalate substrates using a DC facing target sputtering (DC-FTS) system at room temperature. The sputtering conditions including oxygen partial pressure and discharge current were varied from 0% to 4% and 0.5A to 1.3A, respectively. X-ray diffraction and scanning electron microscopy were used to study the structure and surface morphology of as-prepared films. All the films exhibited amorphous structures and smooth surfaces. The dependence of electrical and optical properties on various deposition parameters was investigated by a linear array four-point probe, Hall-effect measurements, and ultraviolet/visible spectrophotometry. A lowest sheet resistance of 17.4Ω/square, a lowest resistivity of 3.61×10−4Ωcm, and an average relative transmittance over 88% in the visible range were obtained under the optimal deposition conditions. The relationship between the Hall mobility (μ) and carrier concentration (n) was interpreted by a functional relation of μ~n−0.127, which indicated that ionized donor scattering was the dominant electron scattering mechanism. It is also confirmed that the carrier concentration in ITO films prepared by the DC-FTS system is mainly controlled by the number of activated Sn donors rather than oxygen vacancies.

Effects of CH4 gas and substrate temperature on hydrogenated amorphous carbon (a-C:H) films fabricated using DC facing target sputtering

Hydrogenated amorphous carbon (a-C:H) films were deposited on soda-lime glass substrates by using a DC facing target sputtering system. The effects of the CH4 gas and the substrate temperature on the deposition rate and the properties of the film were investigated. We found that the deposition rate of the film grown under an Ar-CH4 plasma was about three times larger than that of the film grown under an Ar plasma. The CH4 gas played a role as an additional carbon precursor to increase the deposition rate, which could be seen as a CH* peak at 431 nm in the optical emission spectra of the Ar-CH4 plasma. The sp 3 fraction in the film increased gradually from 32 to 37% as the substrate temperature was increased from 100 °C to 400 °C. The optical band-gap energy of the a-C:H films varied from 3.9 to 3.98 eV, and this variation was closely related to changes in the sp3 fraction. Overall, these results indicate that the addition of CH4 gas to a-C:H film deposition enhanced the deposition rate by changing the deposition mechanism from physical to reactive.

Annealing effects on the structure and magnetic properties of Fe–C granular films

Fe–C granular films with different Fe volume fractionxv were fabricated using a DC facing-target sputtering system at room temperature andsubsequently annealed at different temperatures. X-ray diffraction and selected areaelectron diffraction analyses indicate that as-deposited and low-temperature annealed () samples are composed of amorphous Fe and C, and highertemperature annealing makes the amorphous Fe transform toα-Fe, which is also confirmed by high-resolution transmission electron microscopy.Magnetic measurements indicate that at room temperature the as-depositedFe–C (xv = 58)granular films are superparamagnetic and annealed ones are ferromagnetic. The coercivity of 100 nm thickFe–C (xv = 58) granular films increases with annealing temperature (for 1 h) and time (at450 °C). The coercivity ofthe 100 nm thick Fe–C (xv = 58) samples annealed at temperatures ranging from 400 to500 °C decreases linearly with measuring temperatureT, signalling a domain wall motion mechanism. For the samples annealed at550 °C, the change of in-planecoercivity with T satisfies the relation , reflecting that this system behaves better as a set of Stoner–Wohlfarth particles. It wasalso found that there exists a critical thickness ( nm) for the 450 °C annealed(for 1 h) Fe–C (xv = 58) granular films with thickness in the range 100–200 nm, below and above which themagnetization reversal is dominated by domain wall motion and by Stoner–Wohlfarthrotation, respectively.

Diamond-like carbon films deposited without deposition particles of large incidence angles by sputtering

Deposition of diamond-like carbon (DLC) films at liquid nitrogen temperature (77 K) under the control of the angular distribution of depositing particles was attempted using a DC facing target sputtering system. The film deposited at 77 K, the liquid-nitrogen temperature, has a much higher density and higher hardness than the film deposited at room temperature. Removal of the depositing particles having high incidence angles was found to be effective for increasing the hardness of the film.

Preparation of c-axis-oriented barium ferrite thin films with small crystallite size

BaM thin films were deposited on thermally oxidized silicon wafer substrates at temperatures near 580 °C by using a dc facing-target sputtering system. The crystallite size of films 200 nm thick was greater than 200 nm, and it decreased monotonically with decreasing film thickness, reaching a value below 30 nm in films 30 nm thick. Further decreases in film thickness led to a degradation of the crystallinity of the film, causing the saturation magnetization and coercive force of the film to decrease significantly. Growth of BaM crystallites in films deposited on a SiO2/Si substrate was significantly suppressed when the films were deposited on a thin initial layer deposited beforehand under a substrate bias of −50 V.