Radio Frequency Magnetron Cosputtering System Research Articles

Electrical and Optical Properties of Al-Doped ZnO Transparent Conductive Oxide Films Prepared via Radio Frequency Magnetron Co-Sputtering System.

In this study, the optical and electrical properties of a transparent conductive oxide (TCO) film synthesized via the radio frequency (RF) magnetron co-sputtering of Al-doped ZnO (AZO) and ZnO targets on a glass substrate were investigated. In the visible region, the resistivity, transmittance, and carrier concentration of the TCO film are influenced by the ratio of Al doping. The samples were prepared using two targets with the same deposition condition, except several different power levels on an AZO target to obtain different Al compositions in the film. The power range was 100-160 W in 20 W steps on the AZO target with a constant 50 W power level on the ZnO target. The electrical and optical characteristics of the film were measured using several apparatuses. The cross-section of the films was measured with via field emission scanning electron microscopy (FESEM) to determine the thickness of the film. The electrical and optical properties of the AZO films were measured via Hall measurement and UV-visible spectroscopy. The structural characteristics of the AZO films were confirmed by Raman spectroscopy.

Electrical and optical properties of annealed AlSnZnO films deposited using radio frequency magnetron cosputtering system

Abstract Using a dual aluminum zinc oxide (AZO) target and tin dioxide (SnO2) target, 200-nm-thick aluminum-tin-zinc-oxide (ATZO) films were deposited onto quartz substrates by a radio frequency magnetron cosputtering system. After measuring X-ray diffraction patterns, carrier concentration, carrier mobility, room-temperature photoluminescence spectra, and ultraviolet–visible–near infrared spectra of the ATZO films without and with thermal annealing treatment in an oxygen ambience for 10 min at various temperatures, the annealing effects were demonstrated. Correlations among crystalline structures, electrical properties, optical properties, and annealing temperatures were observed. As the annealing temperature increased from 200 °C to 300 °C, the atoms of ATZO films gained more kinetic energy and more surface mobility to occupy stable positions. However, by further increasing the annealing temperature to 400 °C, the bonds in ATZO films became broken rather than enabling the atoms to remain in their corresponding stable positions. Consequently, the best properties were obtained for ATZO films annealed at 300 °C.

Performance improvement of Y-doped VOx microbolometers with nanomesh antireflection layer.

In the study, the yttrium (Y)-doped vanadium oxide (VOx:Y) films used as the sensitive layers of microbolometers were deposited using a radio frequency magnetron co-sputtering system. The temperature coefficient of resistance (TCR) of the VOx:Y films was enhanced from -1.88%/°C to -2.85%/°C in comparison with that of the VOx films. To further improve the performance of microbolometers, the nanomesh antireflection layer was placed on the top surface of the microbolometers to reduce the infrared reflection. The responsivity, thermal time constant, thermal conductivity, absorptance, and detectivity of the VOx:Y microbolometers with nanomesh antireflection layer were 931.89 ± 48 kV/W, 4.48 ms, 6.19×10-8 W/K, 74.41% and 2.20×108 cmHz0.5W-1, respectively.

Temperature–Power Simultaneous Effect on Physical Properties of BaxSr1−x TiO3 Thin Films Deposited by RF–Magnetron Cosputtering for 0 ≤ x ≤1

The combined effect on the variation of the in-situ deposition temperature and the variation of the applied power on the deposition rate (DR), gap energy (Eg), and resistivity (ρ) in barium strontium titanate thin films, deposited into RF (radio frequency)–magnetron cosputtering equipment, are presented in this research. The simultaneous action of two magnetrons (BaTiO3 and SrTiO3) is explained using the first and second derivative of Boltzmann’s sigmoidal equation. This found that a deposition gradient is a very novel analysis. Using the color-code lines built through MATLAB® and analyzing the trend information, taking into account the influence of the calculated “x” parameter, by means of the Boltzmann’s sigmoidal equation fit, we propose a method to set up an RF–magnetron cosputtering system to predict the DR(x,T), Eg(x,T), and ρ(x,T) values of BaxSr1−xTiO3 solid solutions with 0 ≤ x ≤ 1 for amorphous and crystalline phases. This method can be a versatile tool to optimize the deposition process with, or without, in situ deposition temperature.

Effect of Silver Dopants on the ZnO Thin Films Prepared by a Radio Frequency Magnetron Co-Sputtering System.

Ag-ZnO co-sputtered films at various atomic ratios of Ag (Ag/(Ag + Zn) at.%) were prepared by a radio frequency magnetron cosputtering system, using the co-sputtered targets of Ag and ZnO. The activation of the Ag acceptors (AgZn) and the formation of the Ag aggregations (Ag0) in the ZnO matrix were investigated from XRD, Raman scattering, and XPS measurements. The Ag-ZnO co-sputtered film behaving like a p-type conduction was achievable after annealing at 350 °C under air ambient for 1 h.

High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance gm change, threshold voltage VT change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

Characterization of 12CaO·7Al<SUB>2</SUB>O<SUB>3</SUB> Doped Indium Tin Oxide Films for Transparent Cathode in Top-Emission Organic Light-Emitting Diodes

12CaO x 7Al2O3, insulator (C12A7) doped indium tin oxide (ITO) (ITO:C12A7) films were fabricated using a radio frequency magnetron co-sputtering system with ITO and C12A7 targets. The qualitative and quantitative properties of ITO:C12A7 films, as a function of C12A7 concentration, were examined via X-ray photoemission spectroscopy and synchrotron X-ray scattering as well as by conducting atomic force microscopy. The work function of ITO:C12A7 (1.3%) films of approximately 2.8 eV obtained by high resolution photoemission spectroscopy measurements make them a reasonable cathode for top-emission organic light-emitting diodes.

Characteristics of Y2O3-doped indium zinc oxide films grown by radio frequency magnetron co-sputtering system

We investigate the effect of Ar/O2 gas ratio on optical, structural and electrical properties of thin yttrium-doped In–Zn–O (YIZO) film. Thin YIZO films were deposited at room temperature on glass substrates by radio frequency magnetron co-sputtering system using IZO target composed of (In2O3)1−x(ZnO)x (x=50 wt.%) and Y2O3. The measured average optical transmittance of as-grown YIZO films is over 84% in visible range. Structural analysis reveals that amorphous phase of YIZO is observed only in pure Ar gas flow condition, while crystalline peaks are found as the oxygen content in gas flow increases. Electrical resistivity of the films sharply increases with increasing Ar:O2 ratio, however its carrier concentration and mobility decreases as the O2 ratio increases. The drain-source on/off modulation from the fabricated YIZO Thin Film Transistors is over 106.

Study on the structural and optical properties of Cd1−x Zn x O layers enhanced by rapid thermal annealing

Cd1-xZnxO alloy layers were grown by a radio-frequency magnetron co-sputtering system. By X-ray diffraction measurement, the Cd1-xZnxO layers were observed to have a single-phase cubic structure at x ≤ 0.21. However, polycrystalline having mixed phases was observed at x = 0.29. It seems that the high miscibility of Zn flux in CdO leads to a large fluctuation in phase segregation caused by the hexagonal ZnO and cubic CdO structure within CdZnO. Therefore, the maximum Zn-composition ratio without phase segregation was found to be x = 0.21. The bandgap energies of the Cd1−xZnxO layers between x = 0 and x = 0.21 were distributed from 2.574 eV to 2.892 eV, respectively, while the bandgap energy of x = 0.29 was a slightly smaller value of 2.834 eV. After rapid-thermal-annealing (RTA) treatment at 600°C, the bandgap energies of each x component decreased, especially the x = 0.29 layer, which converted into the double phase of a cubic-and-hexagonal structure existing in the cubic CdO (111) and hexagonal ZnO (0001) phases. Consequently, reliable formation and crystallinity improvement of the Cd1−xZnxO layers were achieved through an x composition ratio below x = 0.29 and an RTA method of short-time thermal-annealing below 600°C.

Formation and Characterization of Co-sputtered CdZnO Layers for Ozone Sensing

Cd1−xZnxO alloy layers were grown by using a radio-frequency magnetron co-sputtering system. From the X-ray diffraction measurement, the Cd1−xZnxO layers were observed to have a cubic structure until a single phase for x ≤ 0.21. However, a polycrystalline form having mixed phases was observed at x = 0.29. It seems that the high miscibility of Zn in CdO leads to a large fluctuation in phase segregation caused by the hexagonal ZnO and cubic CdO structures within CdZnO. The band gap energies of the Cd1−xZnxO layers for values of x between x = 0 and x = 0.21 were distributed from 2.574 to 2.892 eV, respectively, while the band gap energy for x = 0.29 was a value of 2.834 eV due to the polycrystallinity. From the ozone sensing measurement, the working temperature of the Cd1−xZnxO layers was found to be 200 ◦C. Thus, a sensor with x = 0.21 showed a sensitivity of S = 1.31 at 100 ppb. Furthermore, the response and the reduction times of the sensor were found to be 184 and 210 sec, respectively. From these results, we found that the Cd1−xZnxO layer has a capability for use as a new material for ozone sensing.

Effect of rapid thermal annealing on Zn1‐xCdxO layers grown by radio‐frequency magnetron co‐sputtering

AbstractZn1‐xCdxO layers were deposited on the sapphire substrate using the radio‐frequency magnetron co‐sputtering system. The grown Zn1‐xCdxO layers were carried out in the post‐annealing treatment for 1 min at the 800 °C oxygen‐ambient by the rapid thermal annealing (RTA) method. X‐ray diffraction (XRD) experiment shows that the Zn1‐xCdxO layers are changed from the single phase of the hexagonal structure at 0≤x ≤0.08 to the double phase of hexagonal‐and‐cubic structure at x =0.13. Thus, the maximum Cd‐composition ratio with the hexagonal structure was found out to be x =0.08. Also, the crystallinity of Zn1‐xCdxO layers at x =0.13 was remarkably improved by the RTA annealing treatment. This crystal quality improvement was thought to be associated with the relaxation of the compressive strain remaining in the Zn1‐xCdxO layers. Therefore, the results of XRD and transmittance lead that the crystal quality of the Zn1‐xCdxO layers forming the hexagonal ZnO phase is better than that forming the cubic CdO phase. Consequently, the reliable formation and the crystallinity of the Zn1‐xCdxO layers were achieved by using the RTA method of short‐time thermal‐annealing at the high temperature. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Properties of Zinc Oxide Films Cosputtered with Aluminum at Room Temperature

The electrical, structural, and optical properties of ZnO films cosputtered with Al at room temperature using a radio frequency magnetron cosputtering system were systematically investigated. The increase in carrier concentration was initially drastic with increasing cosputtered Al content and gradually alleviative for the cosputtered films behaving as an n-type degenerated semiconductor. The Hall mobility of these degenerated samples was deeply affected by both the crystal grain size and the degree of the growth orientation, becoming a dominant factor for obtaining the film with the lowest resistivity. The shifts of the ZnO(002) diffraction peak of these cosputtered films were affected by the Al3+ substitute for the lattice Zn2+ sites as well as the excess Al content existing in the interstitials. In terms of the associated optical properties, all these cosputtered films exhibited excellent transmittance around visible wavelengths. In the ultraviolet wavelengths, an apparent blue-shift at the absorption edge due to the increase in carrier concentration correlated to the Burstein–Moss shift was also observed from these degenerated cosputtered Al–ZnO films. The depth distribution of the Al impurities was more uniform than a conventional sputtered Al-doped ZnO film at a similar Al doping level. The carrier concentration and Hall mobility of the cosputtered Al–ZnO film were found to be apparently increased due to the more effective activation of the Al–O chemical bonds and less metallic Al and Zn atoms existed in the interstitials analyzed from X-ray photoelectron spectroscopy (XPS) investigations.

Crystalline Ag Nanocluster-Incorporated RuO[sub 2] as an Electrode Material for Thin-Film Micropseudocapacitors

We prepared crystalline Ag nanocluster-incorporated RuO 2 electrodes using a radio frequency magnetron cosputtering system for use in thin-film micropseudocapacitors and investigated their structural and electrochemical properties. High-resolution electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy results show that crystalline Ag nanoclusters are well dispersed within an amorphous RuO 2 . The Ag nanocluster-incorporated RuO 2 electrodes show much higher capacitance of ∼ 1306.0 F/cm 3 at 200 mV/s with superb high-rate performance compared to RuO 2 -only electrodes. The improved capacitance is explained in terms of the presence of dispersed Ag nanoclusters embedded within the amorphous RuO 2 matrix having good electrical conductivity.

Aluminum-nitride codoped zinc oxide films prepared using a radio-frequency magnetron cosputtering system

Al–N codoped zinc oxide films were prepared using a radio-frequency magnetron cosputtering system at room temperature. AlN and ZnO materials were employed as the cosputtered targets. The as-deposited cosputtered films at various theoretical atomic ratios [Al∕(Al+Zn)at.%] showed n-type conductive behavior in spite of the N atoms exceeding that of the Al dopants, indicating that the N-related acceptors were still inactive. The crystalline structure was obviously correlated with the cosputtered AlN contents and eventually evolved into an amorphous structure for the Al–N codoped ZnO film at a theoretical Al doping level reaching 60%. With an adequate postannealing treatment, the N-related acceptors were effectively activated and the p-type ZnO conductive behavior achieved. The appearance of the Zn3N2 phase in the x-ray diffraction pattern of the annealed Al–N codoped ZnO film provided evidence of the nitrification of zinc ions. The redshift of the shallow level transition and the apparent suppression of the oxygen-related deep level emission investigated from the photoluminescence spectrum measured at room temperature were concluded to be influenced by the activated N-related acceptors. In addition, the activation of the N acceptors denoted as N–Zn bond and the chemical bond related to the Zn3N2 crystalline structure were also observed from the associated x-ray photoelectron spectroscopy spectra.

Electrical, Optical and Material Properties of ZnO-Doped Indium–Tin Oxide Films Prepared Using Radio Frequency Magnetron Cosputtering System at Room Temperature

The relationship between the electrical, optical and material properties of transparent and conductive oxide films prepared by rf cosputtering indium–tin oxide (ITO) and zinc oxide (ZnO) targets has been investigated. The evolution from polycrystalline structure of an undoped ITO film to an amorphous-like ZnkIn2O3+k structure obtained from ZnO-doped ITO films is found to be responsible for the marked improvement in the electrical properties. A low surface roughness is also achieved from this amorphous structure. However, both electrical property and surface uniformity begin to degrade with increasing rf cosputtering power on the ZnO target that corresponds to a high atomic ratio of Zn/(Zn + In). The degradation mechanism is attributed to the appearance of a microcrystalline ZnO structure that is detrimental to the film resistivity. Furthermore, optical band gap calculated from the absorption edge of such cosputtered films also decreases with increasing ZnO impurities.