Pure Argon Ambient Research Articles

Microstructural evolution of oxygen incorporated CdTe thin films deposited by close-spaced sublimation

In this work, cadmium telluride (CdTe) thin film was deposited in vacuum (pure argon ambient) as well as different argon (Ar) and oxygen (O2) ambient conditions using close-spaced sublimation (CSS) method at the deposition pressure of 1 Torr. The deposited films were characterized via X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), UV–Vis spectrophotometer and Hall Effect measurement for the analysis of structural properties, morphology, optical properties and electrical properties, respectively. XRD patterns exhibited almost similar preferential orientation plane at (111) irrespective of the O2 concentration. SEM surface morphology microstructure revealed that O2 presence had a substantial effect on grain size reaching up to 7.19 µm. Optical properties also demonstrated insignificant changes in the direct band gap values of around 1.48 eV. Carrier concentration showed an upward trend in the order of 1013 cm−3, whereby resistivity and mobility did not change substantially either in vacuum (pure Ar ambient) or in Ar/O2 ambient.

Thermal transition behaviors of vanadium pentoxide film during post-deposition annealing

Vanadium pentoxide (V2O5) films were deposited on sapphire substrates by radio frequency (R.F.) magnetron sputtering at 450 °C and annealed in various ambient atmospheres. The influence of ambient atmospheres on the structure, optical properties, and morphology of the thin films after annealing were characterized, and the transition behaviors in the annealing process were investigated by DSC, temperature-dependent Raman and FTIR. The results demonstrated that V2O5 films underwent four different transition behaviors during post-deposition annealing due to the different oxygen proportion of ambient. Different products (VO2(B), VO2(R)) in the transition process were the main reason for the evolution of optical properties. No transition behaviors occurred because of the oxygen-rich ambient when annealed in air, and no significant change in infrared transmittance was observed. When annealed in 0.1% O2/Ar, the film was converted to VO2(B) with the decrease of infrared transmittance. In the case of 0.01% O2/Ar, metastable VO2(B) and VO2(R) were observed as intermediate crystalline phases before V2O5 finally transformed to VO2(M), and the changes in the three stages of two drops and one rise were shown in infrared transmittance. While annealed in pure argon ambient, V2O5 was turned into VO2 (R) and VO2 (M) without VO2 (B) phase production, accompanied by a single change of infrared transmittance reduction and recovery. This provides a more detailed vanadium oxide thermal transition process and shows data reference for the preparation technology and application of vanadium oxide materials.

Characteristics of transparent indium zinc oxide electrode prepared on poly(ethylene naphthalate) by radio frequency magnetron sputtering for flexible dye-sensitized solar cells

In this study, for the use as a transparent electrode in flexible dye-sensitized solar cells (DSSCs), the indium zinc oxide (IZO) thin films on unheated poly(ethylene naphthalate) (PEN) substrate in pure argon ambient by radio frequency (RF) magnetron sputtering method have been prepared, and their characteristics with respect to RF power were investigated. It has been found that the IZO films on PEN show a dense amorphous structure and the surface microstructure of the films is hardly sensitive to the RF power. The electrical and optical properties of RF magnetron sputtered IZO thin films on PEN are strongly influenced by RF power. At a RF power of 60 W, it is obtained the IZO thin film with the sheet resistance of about 7.65 Ω/sq. and optical transmittance of about 80% at 550 nm wavelength, resulting in the highest value for figure of merit. The flexible DSSC device embedded with the transparent IZO electrode deposited at 60 W shows the high power conversion efficiency, which is the value of 4.7% under simulated air mass 1.5 irradiation.

Radio Frequency (RF) Magnetron Sputtered Barium Strontium Titanate (BST) Thin Film

Barium strontium titanate (BST) thin films with excellent dielectric properties are deposited by on-axis RF magnetron sputtering system. The effects of composition of the target and oxygen partial pressure on the microstructure of BST thin film have been investigated. The dielectric properties of the thin films are investigated. The results show that composition of BST thin film deposited with pure argon ambient by the target with 30atm% excess of Ba and Sr is stoichiometric. Perovskite phase can be observed in the thin film annealed in oxygen at 750 °C for 30 min. A metal-insulator-metal (MIM) capacitor is fabricated by microfabrication technique. The capacitance value at 2 GHz is 0.417 pF and 1.42 pF for 50 nm and 90 nm BST thin film respectively, and the leakage current density is 6×10-6 A/cm2 and 5.35×10-8 A/cm2 respectively.

The dependence of electromagnetic noise suppress characteristics on magnetic and high-frequency properties of FeCoSiO thin films

A series of soft magnetic granular FeCoSiO films is fabricated using radio frequency magnetron sputtering under pure argon ambient conditions. The magnetic, high-frequency, and microwave noise suppression characteristics of these thin films are studied in detail. By using microwave probe station, integrated-type electromagnetic noise suppressors based on a coplanar waveguide transmission line and incorporated with a SiO2 dielectric and a granular FeCoSiO magnetic thin film with excellent high frequency and soft magnetic properties are investigated. The relationship between transmission properties of electromagnetic noise suppressors and magnetic characteristics of FeCoSiO magnetic thin films were studied. The experimental values of the loss peak frequencies agree well with the calculated ferromagnetic resonant frequency, which considers the demagnetizing field. The results indicate that the main loss mechanism of the integrated devices is the ferromagnetic resonance, but not the L–C resonance. The FeCoSiO magnetic films are considered to be promising as ideal candidate materials for electromagnetic noise suppressor.

Ionizing radiation effects on electrical and reliability characteristics of sputtered Ta2O5/Si interface

This paper describes the effect of ionizing radiation on the interface properties of Al/Ta2O5/Si metal oxide semiconductor (MOS) capacitors using capacitance–voltage (C–V) and current–voltage (I–V) characteristics. The devices were irradiated with X-rays at different doses ranging from 100 rad to 1 Mrad. The leakage behavior, which is an important parameter for memory applications of Al/Ta2O5/Si MOS capacitors, along with interface properties such as effective oxide charges and interface trap density with and without irradiation has been investigated. Lower accumulation capacitance and shift in flat band voltage toward negative value were observed in annealed devices after exposure to radiation. The increase in interfacial oxide layer thickness after irradiation was confirmed by Rutherford Back Scattering measurement. The effect of post-deposition annealing on the electrical behavior of Ta2O5 MOS capacitors was also investigated. Improved electrical and interface properties were obtained for samples deposited in N2 ambient. The density of interface trap states (Dit) at Ta2O5/Si interface sputtered in pure argon ambient was higher compared to samples reactively sputtered in nitrogen-containing plasma. Our results show that reactive sputtering in nitrogen-containing plasma is a promising approach to improve the radiation hardness of Ta2O5/Si MOS devices.

Conduction and field induced degradation in thin ZrO2 films sputtered in nitrogen containing plasma on silicon

This paper deals with the electrical and stress induced degradation of reactively sputtered ZrO2/Si interface deposited in N2 containing plasma and pure argon ambient. MOS C–V and I–V techniques were used for interface characterization. Leakage current and flat band shifts were compared for ZrO2 films deposited with and without N2 containing plasma. The effect of current stress and post deposition annealing carried out on the samples deposited in different ambient was investigated. The annealed devices showed better electrical and reliability characteristics. The flat band voltage shifts towards negative value in annealed devices on being stressed, indicating positive charge trapping in the high-k dielectric layer. The flat band voltage saturates faster when stressed with higher current density. The oxide charge density increases from 4.5 × 1012 cm−2 for as deposited samples to 5.6 × 1012 cm−2 on application of stress. The samples grown in pure argon ambient showed enhanced leakage when compared with samples grown in nitrogen ambient on application of stress .

Modulation of Interface and Bulk States in Amorphous InGaZnO Thin-Film Transistors with Double Stacked Channel Layers

A high-performance amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) was achieved using a double stacked channel layer (DSCL). An oxygen-poor IGZO film was deposited in pure argon ambient as a buffer layer to prevent oxygen plasma bombardment and improve device performance. An oxygen-rich IGZO film was then deposited on top of that buffer layer to modulate device stability. With this structure, an interface with low oxygen-plasma-induced damage and few oxygen vacancies in the bulk was achieved using DSCL, leading to a higher stability of the threshold voltage.

Effect of RF Power on the Structural Properties of Magnetron Sputtered ZnO Thin Films Deposited at Room Temperature

Zinc oxide thin films were prepared at room temperature in pure argon ambient on glass substrates by RF magnetron sputtering. The effect of sputtering power (50~250 Watt) on the structural properties of the film were investigated. The thickness of ZnO thin films was measured using surface profiler (Dektak 150+). Atomic force microscopy machine (AFM-Park system XE-100) was used to characterize the morphology while the crystalinity have been characterized using XRD (Rigaku Ultima IV). It was found that the thickness, growth rate and RMS roughness increases with increasing RF power. All films exhibit the (002) plane which correspond to hexagonal wurtzite structure with the highest peak at 150 Watt.

Preparation of highly transparent conductive Al-doped ZnO thin films and annealing effects on properties

Aluminum-doped ZnO (ZAO) thin films were deposited on fused quartz substrates by radio frequency sputtering in pure argon ambient at 450 °C. Effects of in situ annealing temperature and annealing atmosphere on microstructure, electrical and optical properties of ZAO films have been investigated. Results showed that as-grown film without annealing treatments attained lowest resistivity of 1.1 × 10−4Ω cm. And all films performed high average transmittance greater than 90% in visible region. X-Ray diffraction (XRD), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) were utilized to characterize the microstructure properties of films. XRD results indicated that as-grown film had higher crystalline quality and larger grain size than annealed films. Al atoms replaced Zn efficiently to provide electrons stable in all samples. PL spectra revealed that high annealing temperature and oxygen atmosphere would generate more Zn vacancy (VZn) and oxide antisite defect (OZn), respectively and composition content results from XPS provided supports to this.

Atomically Flattening Technology at 850ºC for Si(100) Surface

We demonstrate a low temperature flattening method for the 200-mm-diameter (100) orientation silicon wafers. By annealing in ultra pure argon ambient at 850ºC or above, atomically flat surfaces composed of atomic terraces and steps appear uniformly in the whole 200mm wafer. The width of atomic terrace changes with the off angle of wafer surface. It is found that with the off angle of 0.50º or below, only mono-atomic steps appear on the atomically flat surface, and the terrace widths are almost equal to the calculation values. Moreover, we have found using the vertical furnace the whole 200mm wafer surface can be atomically flattened in shorter time by increasing the argon gas flow rate or the annealing temperature. Furthermore, after annealing at 900ºC or below, there is no slip-line defect in the whole wafer. This low temperature flattening method is very suitable to be applied in the LSI manufacturing.

Electrical characterization of a‐C:H as a dielectric material in metal/insulator/metal structures

AbstractThe fabrication and electrical characterization of Metal‐Insulator‐Metal (MIM) structures, using a‐C:H films as the insulating material, are presented in this work. These PECVD carbon films show a very low dielectric constant and a very high resistivity. The current conduction mechanisms were analyzed before and after the post deposition annealing in pure argon ambient at 400°C. For as‐deposited films, the experimental J ‐U curves showed that under low biasing regime (|U | < 8 V) the space charge limited current conduction is the main transport mechanism, whereas under higher biasing regime (|U | > 8 V)) the current transport is dominated by the Schottky mechanism. For annealed structures, under low and high biasing the ohmic and Schottky mechanisms were identified as the main processes for the electrical transport. Finally, we found that both parameters, the dielectric constant and resistivity, decrease slightly after the thermal annealing. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of ZnO buffer layer on AZO film properties and photovoltaic applications

Aluminum-doped ZnO (AZO) transparent conducting films were deposited on glass substrates with and without intrinsic ZnO (i-ZnO) buffer layers by a home made and low cost radio-frequency (RF) magnetron sputtering system at room temperature in pure argon ambient and under a low vacuum level. The films were examined and characterized for electrical, optical, and structural properties for the application of CIGS solar cells. The influence of sputter power, deposition pressure, film thickness and residual pressure on electrical and optical properties of layered films of AZO, i-ZnO and AZO/i-ZnO was investigated. The optimization of coating process parameters (RF power, sputtering pressure, thickness) was carried out. The effects of i-ZnO buffer layer on AZO films were investigated. By inserting thin i-ZnO layers with a thickness not greater than 125 nm under the AZO layers, both the carrier concentration and Hall mobility were increased. The resistivity of these layered films was lower than that of single layered AZO films. The related mechanisms and plasma physics were discussed. Copper indium gallium selenide (CIGS) thin film solar cells were fabricated by incorporating bi-layer ZnO films on CdS/CIGS/Mo/glass substrates. Efficiencies of the order of 7–8% were achieved for the manufactured CIGS solar cells (4–5 cm2 in size) without antireflective films. The results demonstrated that RF sputtered layered AZO/i-ZnO films are suitable for application in low cost CIGS solar cells as transparent conductive electrodes.

Growth of ZnO:Al films by RF sputtering at room temperature for solar cell applications

Aluminum-doped ZnO (ZnO:Al) films were prepared at room temperature in pure argon ambient on glass substrates by RF magnetron sputtering. The influence of sputtering power, deposition pressure and film thickness on the film properties was investigated. The deposited ZnO:Al films were characterized to examine the electrical, optical, and structural properties for the application of thin copper indium gallium selenide (CIGS) solar cells. The deposition parameters of ZnO:Al films were optimized. The optimized ZnO:Al films showed a strong and sharp (0 0 2) X-ray diffraction peak. The 600–800 nm thick ZnO–Al films showed a high transparency above 85% in the visible range and a sheet resistance low to 10 Ω/□. CIGS solar cells with 1.2 μm thick absorbers were fabricated using bi-layer ZnO films (low resistive and thick ZnO:Al/high resistive and transparent thin i-ZnO) as front contacts. The thin absorber layers were prepared by the low cost technique involving co-sputtering of Cu–Ga alloy and In targets and selenization with Se powders. Efficiencies of the order of 6–7% were achieved for the manufactured thin CIGS solar cells without antireflective films. The results demonstrated that RF sputtered ZnO:Al films are suitable for application in low cost and thin CIGS solar cells as transparent conductive electrode layers.

Radio frequency sputtering process of a polytetrafluoroethylene target and characterization of fluorocarbon polymer films

Fluorocarbon polymer films have been deposited on glass, silicon, and carbon substrates by radio frequency (rf) sputtering of a polytetrafluoroethylene (PTFE) target in pure argon and Ar–C3F8 mixtures using either a conventional sputtering mode or a self-sustaining glow discharge mode. The substrates could be isolated from the plasma region by a grounded grid electrode. The deposition rate of films produced on glass and silicon substrates was measured as a function of the gas composition and total pressure. The grounded grid electrode effect on the deposition rate of films was also investigated. The polymer films were characterized by x-ray diffraction, infrared spectroscopy, and Rutherford backscattering spectroscopy. The morphology of films was examined before and after annealing at 450 °C in pure argon ambient for 4–24 h. The optimum deposition conditions to produce (CFx)n polymer films with high fluorine contents and high deposition rates by rf sputtering of a PTFE target are reported and discussed in the article.