Oxygen Gas Flow Ratio Research Articles

Electrical and Optical Studies of Reactively Sputtered Indium Oxide Thin Films

Electrical and optical properties of transparent conducting Indium Oxide (In2O3) thin films were studied. These films were deposited by reactive RF sputtering process using Indium target in the presence of oxygen as reactive gas with argon. The pressure and the oxygen gas flow ratios during sputtering were varied to investigate their effect on the resistivity, optical transmission, refractive index, and optical bandgap of In2O3 thin films. The lowest reported resistivity in this study is 2 × 10−3 Ω-cm. The optical transmission was more than 80% in the wavelength range of 400 nm to 800 nm. The optical study revealed the wide optical bandgap of 3.712 eV and 3.875 eV of the deposited In2O3 films. The films showed refractive indices in the range of 1.99 to 2.22. The elemental composition of In2O3 films has been studied through X-ray Photoelectron Spectroscopy (XPS).

Investigation of Electrical and Optical Properties of Low Resistivity Indium Oxide Thin Films

Indium oxide (In2O3) films were deposited by reactive sputtering using an indium target in the presence of oxygen and argon as sputtering gases. The electrical and optical properties of In2O3 films specifically sheet resistance, resistivity, optical transparency, refractive index, and optical bandgap were investigated as a function of oxygen gas flow ratio, keeping the substrate at room temperature. The lowest reported resistivity in this study is 2 x 10-3 Ω-cm. The optical transmission was more than 80% in the wavelengths of 400 nm to 800 nm. The optical study revealed the wide optical bandgap of 3.875 eV of the deposited In2O3 films. The films showed refractive indices in the range of 1.99 to 2.22. The elemental composition of In2O3 films has been studied through X-ray Photoelectron Spectroscopy (XPS).

Characterization of zinc oxide films deposited in helium–oxygen and argon–helium–oxygen atmospheres by sputtering

Zinc oxide (ZnO) thin films were deposited onto glass substrates by radio frequency (RF) magnetron sputtering using a metallic zinc target. Zinc oxide films were prepared in two different gas atmospheres; in the first set, helium and oxygen gas flow ratio (He:O2) was varied from 87.5% to 37.5%. In the second set of experiment, oxygen flow rate was kept constant at 2.5 sccm while argon and helium gas flow ratio (Ar:He) was varied from 9.0% to 87.5%. The structural, wettability, and optical properties of ZnO films were investigated by X-ray diffractometry (XRD), contact angle measuring system, and UV–vis–NIR spectrophotometer. The XRD results show increased preferred orientation along (002) plane for deposited ZnO films in both cases. The average crystallite size of ZnO films increases with increase in gas ratio for both set of experiments. The deposited films are hydrophobic by nature for water and ethylene glycol. Optical transmittances greater than 60% were observed in the wavelength interval from 450nm to 650nm for both cases.

Effects of oxygen partial pressure, deposition temperature, and annealing on the optical response of CdS:O thin films as studied by spectroscopic ellipsometry

Ex-situ spectroscopic ellipsometry measurements are made on radio frequency magnetron sputtered oxygenated cadmium sulfide (CdS:O) thin films. Films are deposited onto glass substrates at room temperature and at 270 °C with varying oxygen to total gas flow ratios in the sputtering ambient. Ellipsometric spectra from 0.74 to 5.89 eV are collected before and after annealing at 607 °C to simulate the thermal processes during close-space sublimation of overlying cadmium telluride in that solar cell configuration. Complex dielectric function (ε = ε1 + iε2) spectra are extracted for films as a function of oxygen gas flow ratio, deposition temperature, and post-deposition annealing using a parametric model accounting for critical point transitions and an Urbach tail for sub-band gap absorption. The results suggest an inverse relationship between degree of crystallinity and oxygen gas flow ratio, whereas annealing is shown to increase crystallinity in all samples. Direct band gap energies are determined from the parametric modeling of ε and linear extrapolations of the square of the absorption coefficient. As-deposited samples feature a range of band gap energies whereas annealing is shown to result in gap energies ranging only from 2.40 to 2.45 eV, which is close to typical band gaps for pure cadmium sulfide.

DC sputtered amorphous In–Sn–Zn–O thin-film transistors: Electrical properties and stability

In this study, we investigated the electrical properties of DC sputtered amorphous In–Sn–Zn–O (a-ITZO) thin-film transistors (TFTs) fabricated under various process conditions. Fabricated a-ITZO TFTs achieved a threshold voltage (VT) of 1.0V, subthreshold swing (SS) of 0.38V/dec and field-effect mobility (μeff) of around 30cm2/Vs. An analytical field-effect mobility model is proposed for a-ITZO TFTs with key parameters extracted using different methods. The impacts of a-ITZO channel thickness and oxygen gas flow ratio on device performance were evaluated. Finally, the a-ITZO TFT bias-temperature stress (BTS) induced electrical instability was studied. In comparison to amorphous In–Ga–Zn–O (a-IGZO) TFTs, improved electrical stability was observed for a-ITZO TFTs using exactly the same BTS conditions.

Eco-Friendly Glass Color Coating Process Using RF Magnetron Sputtering

Color glasses are fabricated with Titanium target by RF magnetron sputtering. The physical properties of the Ti thin films are investigated according to preparation conditions, such as argon and oxygen gas flow ratio, RF power and Working pressure. The results indicate that it is possible to deposits various Ti thin film’s of different colors on glass substrate, such as yellow, orange, brown, purple. The thickness according to the color was analyzed using Veeco's Stylus profiler (model: dektak 6M).

Preparation of a heteroepitaxial LaxSryMnzO3/BiFeO3 bilayer by r.f. magnetron sputtering with various oxygen gas flow ratios

BiFeO3 (BFO) and LaxSryMnzO3 (LSMO) films were epitaxially grown on SrTiO3 (100) substrates by r.f. magnetron sputtering with various oxygen gas flow ratios (FO2). Compositional ratios of each atom in both of BFO and LSMO could be controlled kept to around 10 at.% by changing FO2. Adjusting the compositional ratio to La0.35Sr0.15Mn0.5O3 not only increase Tc of LSMO but also produces sufficient oxygen to form a perovskite lattice. For an LSMO/BFO heterostructure, detailed observation by cross sectional transmission electron microscopy (TEM) revealed that the lattice of rhombohedral (SG: R-3c) LSMO was shrank by a clamping effect from the SrTiO3 substrates, and then the BFO was grown in two layers: (i) an interfacial BFO layer (7 nm thick) with evenly shrunk a-axis and c-axis, and (ii) an upper BFO layer (25 nm thick) expanded along the c-axis. Neither misfit strain nor dislocations appeared at the interface between the shrunken BFO and LSMO layers, and these heterostructures did not show exchange bias. These results suggest that BFO is suitable for a tunneling barrier combine with LSMO electrode.

The electrical, optical, and structural properties of amorphous indium gallium zinc oxide films and channel thin-film transistors

The electrical, optical, and structural properties of amorphous indium gallium zinc oxide (a-IGZO) films deposited at room temperature (RT) examined before and after annealing using a radio frequency (RF) magnetron sputtering system with different hydrogen and oxygen gas flow ratios. The carrier concentration and resistivity of the a-IGZO films fabricated under O2/Ar+O2 and O2/Ar–4%H2+O2 atmospheres were greatly dependent on the addition of hydrogen and heat treatment. Thin-film transistors (TFTs) with an a-IGZO channel layer deposited under O2/Ar–4%H2+O2=1.6% exhibited good subthreshold gate voltage swing (S), on/off ratio, threshold voltage and μFE of 0.4Vdecade−1, 108, 0.3V and 4.8cm2V−1s−1, respectively. From analysis of the interfacial structure in TFTs before and after annealing, the electrical conductivity of the a-IGZO channel layer was greatly affected in regard to TFT performance due to the amorphous a-IGZO channel layer and SiO2 gate insulator.

Magnetic Properties of Oxygen-doping Fe-Co-based Nanocrystalline Alloy Films for High Frequency Application

The effects of the introduction of oxygen were studied on the Fe62Co32Cr6–O alloy films synthesized by magnetron co-sputtering. The as-deposited films exhibited a high saturation magnetization and a suitable in-plane uniaxial anisotropy field at an optimized condition of an oxygen gas flow ratio of 1.3%. Also, a high real permeability of ∼200 at frequency up to 3.3GHz was obtained from the microwave permeability measurement at the optimized condition above. The combination of high saturation magnetization, adjustable in-plane uniaxial magnetic anisotropy field, and high resistivity makes the Fe62Co32Cr6–O films become a promising candidate for the high-frequency applications.

Crystal growth of MgO thin films deposited on ZnO underlayers by magnetron sputtering

The effect of ZnO underlayers on the crystal growth of MgO thin films was investigated. MgO single layers and double-layered coatings consisting of ZnO/MgO were deposited on unheated soda-lime silicate glass substrates by magnetron sputtering. X-ray diffraction measurement revealed that the MgO single layers were poorly crystallized even if the MgO thin films were deposited at various oxygen gas flow ratios and at various gas pressures. Moreover, it was observed that the ZnO/MgO coatings exhibited a preferred orientation along MgO(200) and that well-crystallized MgO thin films with very small thickness (10 nm) could be obtained using ZnO underlayers. This improvement in MgO thin films should be caused by heteroepitaxial-like growth of MgO{100} on ZnO{001} crystal lattice planes. In addition, the possible mismatch between MgO and ZnO atomic arrangements was estimated to be 8.2%.

Optimum packing density and crystal structure of tin-doped indium oxide thin films for high-temperature annealing processes

The influence of high-temperature annealing on the electrical properties and microstructure of tin-doped indium oxide (ITO) thin films was investigated as a function of oxygen gas flow ratio to argon gas during the sputtering deposition. The ITO thin films were annealed at 500 °C in air after the deposition. It was found that the ITO thin films, which were deposited in relatively low oxygen gas flow ratio, exhibited high Hall mobility and low-resistivity after the annealing. Furthermore, the X-ray reflectivity and diffraction measurement revealed that the ITO thin film with low-resistivity after annealing exhibited high packing density, smooth surface and low crystallization degree. It can be considered that the carrier electron scattering was suppressed with increasing in the packing density of the ITO thin film; as a result, the Hall mobility and resistivity were improved.

Ge 기판 위에 HfO2게이트 산화물의 원자층 증착 중 In Situ 질소 혼입에 의한 전기적 특성 변화

Ge은 Si에 비하여 높은 이동도를 갖기 때문에 차세대 고속 metal oxide semiconductor field effect transistors (MOSFETs) 소자를 위한 channel 물질로서 각광받고 있다. 그러나 화학적으로 안정한 게이트 산화막의 부재는 MOS 소자에 Ge channel의 사용에 주요한 장애가 되어왔다. 특히, Ge 기판 위에 고품질의 계면 특성을 갖는 게이트 절연막의 제조는 필수 요구사항이다. 본 연구에서, <TEX>$HfO_xN_y$</TEX> 박막은 Ge 기판 위에 플라즈마 원자층 증착법(plasma-enhanced atomic layer deposition, PEALD)을 이용하여 증착되었다. 플라즈마 원자층 증착공정 동안에 질소는 질소, 산소 혼합 플라즈마를 이용한 in situ 질화법에 의하여 첨가되었다. 산소 플라즈마에 대한 질소 플라즈마의 첨가로 성분비를 조절함으로써 전기적 특성과 계면 성질을 향상시키는데 초점을 맞추어서 연구를 진행하였다. 질소 산소의 비가 1：1이었을 때, EOT의 값의 10% 감소를 갖는 고품질의 소자특성을 보여주었다. X-ray photoemission spectroscopy (XPS)와 high resolution transmission electron microscopy (HR-TEM)를 사용하여 박막의 화학적 결합 구조와 미세구조를 분석하였다. Ge is one of the attractive channel materials for the next generation high speed metal oxide semiconductor field effect transistors (MOSFETs) due to its higher carrier mobility than Si. But the absence of a chemically stable thermal oxide has been the main obstacle hindering the use of Ge channels in MOS devices. Especially, the fabrication of gate oxide on Ge with high quality interface is essential requirement. In this study, <TEX>$HfO_xN_y$</TEX> thin films were prepared by plasma-enhanced atomic layer deposition on Ge substrate. The nitrogen was incorporated in situ during PE-ALD by using the mixture of nitrogen and oxygen plasma as a reactant. The effects of nitrogen to oxygen gas ratio were studied focusing on the improvements on the electrical and interface properties. When the nitrogen to oxygen gas flow ratio was 1, we obtained good quality with 10% EOT reduction. Additional analysis techniques including X-ray photoemission spectroscopy and high resolution transmission electron microscopy were used for chemical and microstructural analysis.

Characterization of sub-stoichiometric rhodium oxide deposited by magnetron sputtering

The preparation and detailed characterization of sub-stoichiometric rhodium oxide films prepared by magnetron sputtering at room temperature have been carried out on silicon substrates. Effects of the oxygen gas flow ratio on chemical bonding state, optical reflectivity and crystallinity were investigated using XPS, reflectivity measurements, XRD and SEM. For oxygen flow ratios higher than 2%, the films become amorphous with high resistivity (1.5 × 10 −5 Ω m) indicating semiconducting properties. The same experiments were performed at 300 °C and even with high oxygen gas flow ratio the films always have a metallic component. Moreover, for high fractions of oxygen in the plasma, films are always sub-stoichiometric.

Growth of c-axis orientation ZnO films on polymer substrates by radio-frequency magnetron sputtering

ZnO films with c-axis orientation were deposited successfully on benzocyclobutene (BCB) and highly fluorinated polyether (HFP) substrates by radio-frequency magnetron sputtering. The effects of the sputtering parameters (argon−oxygen gas flow ratio, sputtering power, and sputtering pressure) on the crystalline quality of the ZnO films were investigated by X-ray diffractometry, atomic force microscopy, and scanning electron microscopy. By using optimized sputtering conditions, uniform ZnO films with good c-axis orientation were formed on hard BCB substrates to a thickness as large as 3.0 μm. The ZnO films formed on soft HFP substrates, however, were always thinner than 1 μm. In addition, a ZnO/BCB channel optical waveguide was fabricated, which had a propagation loss of 7.3 dB/cm at the wavelength 1550 nm.

산소 가스 유량비 변화에 따른 ITO 박막의 전기적 특성에 관한 연구

To prepare the transparent electrode for electronic devices such as flat panel or flexible displays, solar cells, and touch panels; tin doped <TEX>$In_2O_3$</TEX> (ITO) films with low resistivity and a high transparency were fabricated using a facing target sputtering (FTS) system at the various oxygen gas flow rate. The carrier concentration and mobility of ITO films were measured by Hall Effect measurement. And the transmittance was measured using the UV-VIS spectrometer. As a result, we can obtain the ITO thin films prepared at 10% oxygen gas flow ratio, thickness 150 nm with transmittance 85% and resistivity <TEX>$8.1{\times}10^{-4}{\Omega}cm$</TEX> and surface roughness 5.01 nm.

Thermally-induced optical property changes of sputtered PdO x films

Optical property changes of reactively sputtered palladium oxide (PdO x ) thin films during heating have been investigated by light transmission measurements and in situ Raman spectroscopy, combined with X-ray fluorescence and thermogravimetry analysis (TGA). The composition ratio and refractive index of as-deposited PdO x films varies depending on the oxygen gas-flow ratio during sputtering deposition. The transmitted light intensity at wavelengths of 405 and 635 nm measured during heating up to 1000 °C in air exhibits a sharp leap at 832 °C due to the thermal decomposition of PdO, and shows a gradual increase around 200–300 °C. The decomposition process of PdO is also measured by TGA as a significant weight loss of the sample. In situ Raman spectra of sputtered PdO x film obtained during heating up to 600 °C in air demonstrate that the crystallization of PdO starts above 200 °C and progresses during the whole annealing process.

AZO Films Prepared by Facing Target Sputtering System

Al oped zinc oxide (AZO) films were prepared by Facing Targets Sputtering (FTS) system for TCO applications. The electrical, optical and structural properties of AZO thin films have been investigated with input current, oxygen gas flow ratio and substrate temperature. Deposition was carried out at room temperature and . Working gas pressures were fixed at 1mTorr. As a result, AZO thin film deposited with an optical transmittance over 80 % and a resistivity about .

An investigation of preferred orientation of doped ZnO films on the 36° YX-LiTaO 3 substrates and fabrications of Love-mode devices

Love-mode surface acoustic wave (SAW) devices are very promising for liquid and gas media sensing applications because of high sensitivity. In this paper, an experimental study of the structures based on zinc oxide (ZnO) guiding layer and 36° YX-lithium tantalate (LiTaO 3) substrate with different sputtering conditions to deposit ZnO films is presented. Poly-crystal ZnO films with c-axis (002) orientation have been successfully grown on the 36° YX-LiTaO 3 substrate by RF magnetron sputtering technique. The deposited films were characterized as a function of argon–oxygen gas flow ratio, RF power, deposition pressure, and annealing temperature. Crystalline structures, stress, and surface roughness characteristics of the films were investigated by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements. Highly orientated (002) films were obtained under a base pressure of 10 mTorr, containing 40% oxygen and 60% argon at RF power of 60 W and a substrate temperature around 120 °C. The films were then annealed at 600 °C. Love-mode devices based on this structure (ZnO/IDT/36° YX-LiTaO 3) are presented.

FTS법으로 제작한 ZnO/AZO 박막의 결정학적 특성

The ZnO thin films were prepared by the FTS (facing target sputtering) system, which enables to provide high density plasma and a high deposition rate at a low working gas pressure. We introduced the AZO thin film in order to improve the crystallographic properties of ZnO thin film because of the AZO(ZnO:Al) thin film has an equal crystal structure to the ZnO thin film. ZnO/AZO thin films were deposited at a different oxygen gas flow ratio, R.T. 2mTorr working pressure and a 0.8A sputtering current. The film thickness and c-axis preferred orientation of ZnO/AZO/glass thin films were measured by <TEX>${\alpha}$</TEX>-step and an x-ray diffraction (XRD) instrument. In the results, we could prepare the ZnO thin film with c-axis preferred orientation of about 6<TEX>$^{\circ}$</TEX> on substrate temperature R.T. at O<TEX>$_2$</TEX> gas flo rate 0.5.

대향타겟스퍼터링법에 의한 FBAR용 AZO(ZnO:Al) 박막의 제작

In this study, the AZO thin films were prepared as a function of oxygen gas flow ratio at room temperature by FTS(Facing Targets Sputtering) apparatus using Zn:Al(metal)-Zn:Al(metal) or Zn(metal)-ZnO:Al(ceramic). The film thickness, crystalline and electric properties of AZO thin film was evaluated by <TEX>$\alpha$</TEX>-step, XRD and 4-point probe. In the results, the resistivity of AZO thin film was shown the lowest value about 8<TEX>${\times}$</TEX>10<TEX>$^{-2}$</TEX> <TEX>$\Omega$</TEX>-cm(Zn:Al-Zn:Al), 3<TEX>${\times}$</TEX>10<TEX>$^{-1}$</TEX> <TEX>$\Omega$</TEX>-cm(Zn-ZnO:Al) at the oxygen gas flow ratio 0.3. And the AZO thin film has good crystalline at oxygen gas flow ration 0.4, using Zn:Al-Zn:Al targets.