DC Reactive Sputtering Research Articles

CHARACTERISTICS AND OPTICAL PROPERTIES OF NITROGEN IONS IMPLANTED TiO2 THIN FILM PREPARED BY REACTIVE DC SPUTTERING TECHNIQUE

This study reports on the properties of Titanium Dioxide (TiO2) thin films fabricated by Reactive DC sputtering technique on glass substrate. TiO2 thin films were implanted with several doses of N+ ions namely; (2×1015, 1×1016 and 1×1017 ions/cm2 ) using homemade implantation equipment. The optical properties of N+ ions implanted TiO2 thin films examined by UV-Vis spectrophotometry. The transparency of the N+ ion implanted TiO2 decreased with increasing of N+ ion dosage while the absorption spectrum was shifted toward visible region. The band-gap energy of N+ ion implanted TiO2 exhibited a decrease with various doses from 3.15 eV to 2.52 eV. The intensity of diffraction peak A(101) and R(110) decreased specially at the dose (1×1017 ions/cm2 ). XRD and SEM analyses indicated a degeneration of the crystal quality.

Thermal annealing of AlN films for piezoelectric applications

Aluminum nitride is an excellent electrical insulator and important piezoelectric material making it suitable for a wide range of applications in electronics and optoelectronics. However, to exhibit and preserve those piezoelectric properties, care has to be taken during manufacturing process. Indeed, the c-axis crystalline orientation of AlN is a necessary condition for piezoelectricity. Therefore, the goal of this paper is to compare AlN films grown on (100) silicon substrate by pulsed reactive DC sputtering at 400 °C on top of three different metallic underlayer electrodes (Ti/Pt, Cr/Pt, and AlN/Cr/Pt) by preserving the crystalline properties not only at room temperature but also at high temperatures. Among all deposited AlN films on top of the metallic underlayer electrode, only AlN/Cr/Pt has kept its crystallinity up to 950 °C.

Highly photoresponsive VO2(M1) thin films synthesized by DC reactive sputtering

We report synthesis, characterization and IR photoresponse properties of 150 ± 10 nm thick high quality VO2(M1) thin films synthesized by DC reactive sputtering. Phase formation was confirmed by X-ray diffraction and Raman spectroscopic measurements. Morphology and microstructure were analysed by atomic force microscope, scanning electron microscope and transmission electron microscope which revealed polycrystalline nature of nanosized films with root mean square (rms) roughness value of 8 ± 0.7 nm. Electrical measurements revealed 1st order transition of thin films with a change in resistance of more than two orders of magnitude and temperature coefficient of resistance, TCR of − 1.24% K−1 at 30 °C. The fabricated VO2(M1) IR photodetector exhibited excellent reproducible photoresponse properties when subjected to a 1064 nm laser under 250 mW cm−2 power density with a bias voltage of 5 V at the ambient conditions of temperature and pressure. The sensitivity, responsivity, external quantum efficiency and specific detectivity were observed to be 1775%, 40.09 mA W−1, 4.67% and 7.07 × 1011 Jones, respectively.

Sensing Performance of Stable TiN Extended-Gate Field-Effect Transistor pH Sensors in a Wide Short Annealing Temperature Range

In this letter, the structural properties and sensing performances of TiN sensing films deposited on a n+-type Si through the reactive DC sputtering method with rapid thermal annealing at a wide temperature range of 200 °C to 800 °C were investigated for extended-gate field-effect transistor (EGFET) pH sensors. We used X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy to study the structural characteristics of these films. These TiN EGFET sensors exhibited almost the same sensing performances, such as pH sensitivity ~58 mV/pH), hysteresis voltage ~2 mV), and drift rate (~0.45 mV/h), indicating that they contained similar or identical in the film composition and surface roughness.

Study of morphological and electrical properties of the ZnO/p-Si hetero-junction: Application to sensing efficiency of low concentration of ethanol vapor at room temperature

In this work, thin films of ZnO were deposited by DC reactive sputtering of zinc target under (Ar and O2) gas atmosphere, at a deposition temperature of 100 °C. A series of samples were prepared on both corning glass and p-doped crystalline silicon substrates, at different Ar flow rates (FAr) ranging from 0.5 and 2.5 sccm. The films properties were investigated by atomic force microscopy (AFM), Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD). The results showed thin films with rough surfaces and polycrystalline structure. The electrical study (current-voltage characteristics) of ZnO/p-Si hetero-junctions revealed a rectification behavior. The highest forward current was obtained for FAr = 1.5sccm. The exposure at room temperature of ZnO/p-Si hetero-structures to ethanol vapors showed a high gas sensing response for ZnO/p-Si hetero-junctions with rough surface and high forward current, corresponding to FAr = 1.5 sccm. For a low concentration of ethanol vapor (10 ppm), the dynamic response at room temperature of ZnO/p-Si hetero-junctions revealed a sensitivity ranging from 40 to 80% with response and recovery times of 5 and 3 s respectively. Comparing these characteristics to those already obtained by other teams showed that the elaborated devices in this work are good candidates for fast sensors of low concentrations of ethanol vapors at room temperature.

Electrical conductivity enhancement of indium tin oxide (ITO) thin films reactively sputtered in a hydrogen plasma

Transparent conducting oxides are materials characterized by the simultaneous occurrence of high optical transparency and electrical conductivity. Among them, tin-doped indium oxide (ITO) has been established as the best material with these criteria. This work focused on the enhancement of the electrical conductivity of ITO thin films through reactive DC sputtering under a hydrogen plasma. The films were deposited on heated substrates (350 °C) with the hydrogen concentration varying from 0 to 20% of the flow rate of argon. The structural properties (crystalline orientation and surface roughness) varied as functions of the hydrogen concentration. The electrical resistivity reached a minimum value of 2.0 × 10−4 Ω cm for a hydrogen concentration of 15%, corresponding to a reduction by a factor of 4 compared to the films deposited without hydrogen. The optical band gap of the films was 4 eV, and was not affected by the hydrogen concentration. The average visible transmittance decreased as the hydrogen concentration increased but maintained a value above 80%. The infrared reflectance increased upon hydrogenation, shifting the plasmon frequency into the near-infrared spectral range.

Influence of Si on the Structural, Electrical, and Optical Properties of (Al, Ti, Si)N Films Deposited Via Reactive DC Sputtering

Abstract The physical and chemical properties of multifunctional materials have been extensively studied in the last few years especially the mechanical and tribological applications and less attention has taken the electrical and optical properties. Therefore, in this work presents the growth of (Al, Ti, Si)N films deposited on common glass substrates with a maximum thickness of 1024 nm, via reactive DC magnetron sputtering, to analyze the influence of the silicon content on their crystallographic structure, optic and electric behavior. The microstructure of the films was characterized by X-ray diffraction (XRD). The films morphology was evaluated through scanning electronic microscopy (SEM). The optical measurements were carried out by means UV-vis spectroscopy, and the electrical properties were analyzed using a four-point probe. XRD analysis indicated that the films changed from a crystalline phase to an amorphous phase, and the electrical and optical response indicated that the films with higher Si content have l223.6 Ω.cm of resistivity with an energy gap of approximately 1.0 eV and an optical energy gap of 1.5 eV. This electrical property has not been previously reported in these films.

Guidelines for fabrication of high quality BiFeO3 based multiferroic thin films in pulsed DC reactive sputtering method

Guidelines for fabrication of high quality BiFeO₃ based multiferroic thin films in pulsed DC reactive sputtering method

Coating of Al-Cu Alloy with Ti-N Graded Film by Reactive DC Sputtering

Coating of Al-Cu Alloy with Ti-N Graded Film by Reactive DC Sputtering

EFECTO DE LA TEMPERATURA DE SUSTRATO SOBRE LA ESTRUCTURA Y RESISTIVIDAD ELÉCTRICA DE PELÍCULAS DELGADAS DE NITRURO DE MOLIBDENO

Películas delgadas de nitruro de molibdeno fueron depositadas sobre obleas de silicio (111) mediante la técnica de la pulverización catódica magnética reactiva DC, a la temperatura de sustrato de 100, 200, 300 y 400 °C, en la mezcla de gases (Ar+N2 ) a la presión de trabajo de 4,3x-3 torr. La composición de las películas ha sido definida con espectroscopia Auger (AES). La difracción de rayos X muestra que tales películas presentan una orientación cristalográfica preferencial a lo largo del plano (112) y el tamaño de grano se incrementa desde 8,21 a 13,16 nm en el rango de 100 a 400 °C de la temperatura de sustrato. La resistividad de las películas disminuye con el aumento de la temperatura de sustrato desde 74,20 a 2,45 μΩ.cm mostrando características óhmicas. El valor más bajo de la resistividad eléctrica fue de 2,45 μΩ.cm a la temperatura de sustrato de 400 °C.

Ultra-sensitive H2S sensing at ppb concentrations by barely crystalline WOx/W thin film

This work describes the preparation of thin films of tungsten oxide (WO3) and a semiconducting composite of tungsten-containing tungsten oxide (WOx/W), for sensing hydrogen sulfide. These thin films were prepared on oxidized Si substrates, respectively by RF magnetron sputtering and DC reactive sputtering. DC reactive sputtering was used to optimize the stoichiometry of thin films to achieve tungsten-containing tungsten oxide films for sensing hydrogen sulfide. Scanning electron microscopy (SEM), x-ray diffractometry (XRD), and x-ray photoelectron microscopy (XPS) were employed to analyze the structure and the morphology of the thin films. An inter-digitated platinum electrode structure was patterned using optical lithography to define the sensor device. In sensing hydrogen sulfide, the reactive DC-sputtered WOx/W film sensors exhibit superior response (conductometric response of ∼3100% to 10 ppb concentration, at operating temperature of 250 °C) and a high degree of selectivity. On the other hand, RF-sputtered tungsten oxide thin films show no response when H2S concentration is lower than 500 ppb.

Photocatalytic property of polyester fabrics coated with Ag/TiO2 composite films by magnetron sputtering

The Silver/Titanium dioxide film (Ag/TiO2) composite films prepared by two different magnetron sputtering methods were deposited on textile substrates using the characteristics of nano-Ti films oxidized easily in the air. The microstructures and the photocatalytic property of Ag/TiO2 composite films deposited on textile substrates were analyzed, and compared with that of TiO2/Ag composite films also deposited on textile substrates. The experimental results indicated that the Ag film and the TiO2 film were uniformly distributed in layers on the surface of the fabrics. The surface microstructures of Ag/TiO2 composite films deposited on the surface of fabrics was even and dense and was smoother than that of TiO2/Ag composite films. The photocatalytic activity of fabrics coated with TiO2 film prepared by DC magnetron sputtering method was much lower than that of TiO2 films prepared by DC and RF reactive sputtering method because of the structure of TiO2 films formed by oxidation in the air. Due to the effect of the Ag film, the photocatalytic activity of Ag/TiO2 composite films and TiO2/Ag composite films deposited on the fabrics were all improved, and the photocatalytic activity of Ag/TiO2 composite films was the highest, and that of TiO2 films was the smallest.

Simple fabrication of the Ag-Ag2O-TiO2 photocatalyst thin films on polyester fabrics by magnetron sputtering and its photocatalytic activity

The polyester fabrics were modified with Ag-Ag2O-TiO2 coating. The TiO2 layer was prepared by DC magnetron sputtering and oxidation in air: a method which avoids the problem of Ti target poisoning in reactive sputtering. The Ag2O layer was deposited by DC reactivesputtering. As a contrast, the TiO2 layer of Ag-Ag2O-TiO2 coating was also prepared using radio frequency(RF) reactivesputteringin Ar/O2 gas mixture. The surface photovoltage (SPV) spectrum and the measured work functions of samples indicate that a built-in electric field was formed at the interface between Ag2O layer and TiO2 layer. The photocatalytic efficiency was analyzed through monitoring the degradation of RhodamineB (RB) under UV illumination. Compared to the polyester merely coated with TiO2, the polyester fabrics coated with Ag-Ag2O-TiO2 showed the superior performance of photocatalysis, indicating the Ag2O/TiO2 heterojunction contributes to photocatalytic degradation of RB. Results also show that the TiO2 layer in Ag-Ag2O-TiO2 coating prepared by DC magnetronsputtering and then natural oxidation had comparable photocatalytic activities with that prepared by RF reactive sputtering.

Periodic density fluctuations in sputtered aluminum‐doped silicon oxynitride layers

AbstractMagnetron sputtering is widely used for deposition of silicon oxynitride (SiOxNy) coatings on glass in large‐area applications. Since repeated deposition simulates the factory‐scale in‐line processing, amorphous aluminum‐doped SiOxNy layers with thickness of about 250 nm were deposited by reactive pulsed DC sputtering in a multi‐pass process with repeated linear movement of a glass substrate under an Al‐alloyed Si target. Using specular X‐ray reflectivity we show periodic fluctuations of the material density throughout the entire thickness of the resulting coating. The number of periods corresponds to the number of passes of the substrate through the plasma of the magnetron. Fitting results suggest a model consistent with a periodic alternation of the O/N ratio. These subtle stoichiometric fluctuations in the SiOxNy layer composition were confirmed by scanning transmission electron microscopy analysis with nanoscale resolution, and with detailed elemental maps of characteristic X‐rays of the layered cross‐section. Our study demonstrates the superior sensitivity of the relatively simple nondestructive X‐ray reflectivity method for industrial line‐process inspection compared to ellipsometry.

Transparent and p-type conductive NixO:V thin films obtained by reactive DC sputtering at room temperature

A non-magnetic alloy consisting of Ni(92%):V(8%) was used to obtain NixO:V thin films by reactive DC magnetron sputtering on unheated glass substrates. The oxygen content and the nickel oxidation state were modified by the oxygen partial pressure (Opp) applied for sputtering, while the film thickness (t) was changed through the deposition time. The structural, optical and electrical properties of the samples have been analyzed by x-ray diffraction, Raman spectroscopy, spectrophotometry and Hall-effect measurements. Visible transmittance and sheet resistance have been used to evaluate the quality of the films as transparent electrodes, which is found maximum for the layers prepared at 24% Opp with t ≤ 100 nm. These samples show maximum p-type conductivity σ = 0.78 S cm−1 and optical absorption α = 1.4 × 105 cm−1 at 0.55 μm wavelength, both independent of the layer thickness.

Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings

Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by pulsed DC reactive sputter deposition on Si(100) at a temperature of 550 °C. XRD showed three different crystal structures depending on V-metal fraction in the coating: α-V2O3 rhombohedral structure for 100 at.% V, a defect spinel structure for the intermediate region, 63–42 at.% V. At lower V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed, shifted to larger d-spacing compared to pure γ-Al2O3. The microstructure changes from large columnar faceted grains for α-V2O3 to smaller equiaxed grains when lowering the vanadium content towards pure γ-Al2O3. Annealing in air resulted in formation of V2O5 crystals on the surface of the coating after annealing to 500 °C for 42 at.% V and 700 °C for 18 at.% V metal fraction respectively. The highest thermal stability was shown for pure γ-Al2O3-coating, which transformed to α-Al2O3 after annealing to 1100 °C. Highest hardness was observed for the Al-rich oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7 at.% V metal fraction. The measured hardness after annealing in air decreased in conjunction with the onset of further oxidation of the coatings.

Threshold switching of a NbOx device prepared by DC reactive sputtering

Threshold switching devices based on insulator-metal transition (IMT) are expected to overcome the reduction of sneak current and studies of their use for self-oscillators attract much attention. In this study, we observed threshold switching caused by IMT in a cross-point Pt/Ti/NbOx/Pt/Ti/SiO2 device after annealing at 400 °C, annealing assisted formation of stable stoichiometric NbO. The diffusion of Ti atoms of thetop electrode to the NbOx layer was observed. It is suggested that Ti oxidation caused scavenging of oxygen from NbOx, and valence number of Nb ion is reduced to form stoichiometric metallic NbO. With applying negative voltage to the upper Pt/Ti electrode, a NbO2 layer was formed by diffusion of oxygen ions from the TiOx layer. Then threshold switching has become easy to occur in the succeeding positive voltage sweeping.

Synthesis of AuAg@Ag core/shell bimetallic nanoparticles in titanium nitride thin films by sequential ion implantation

In this study, we demonstrated the formation of a new type of AuAg@Ag nanostructure in titanium nitride (TiN) thin films using sequential implantation of Au and Ag ions. The TiN films deposited by DC reactive sputtering were sequentially implanted with 200 keV gold ions at fluences of 0.5 × 1016 and 1 × 1016 ions/cm2 and 150 keV silver ions at fluences of 1 × 1016, 2 × 1016, 3 × 1016, and 4 × 1016 ions/cm2. Formation of spherical-like particles with dimensions below 10 nm, homogeneously distributed along the ion track of implanted ions is verified by high resolution transmission electron microscopy. Specific nanostructure containing AuAg alloy in the center of the particle and only silver on the periphery was found in the TiN sample sequentially implanted with 1.0 × 1016 ions/cm2 of Au and 4 × 1016 ions/cm2 of Ag using high angle annular dark field scanning electron microscopy together with elemental mapping analysis. On the other hand, for the sample implanted with 0.5 × 1016 ions/cm2 of Au and 4 × 1016 ions/cm2 of Ag only formation of AuAg alloy was observed. A mechanism for the formation of a new type core/shell nanostructure in ion implanted TiN thin films is proposed. By varying the implantation fluence of the gold and silver ions properly, the optimized experimental parameters for creation of a specific AuAg@Ag core/shell nanoparticles were achieved.

Intrinsic and extrinsic doping contributions in SnO2 and SnO2:Sb thin films prepared by reactive sputtering

SnO2 thin films are considered cheap transparent electrodes, interesting for scalable electronic applications, with intrinsic n-type conductivity related to donor defects like tin interstitials and oxygen vacancies. Besides, SnO2 allows n-type extrinsic doping by pentavalent cations such as Ta or Sb. In the present work, SnO2 and SnO2:Sb films were deposited on unheated soda lime glass substrates by reactive DC sputtering from Sn and Sn:Sb(5%) targets. Their structural, optical and electrical properties have been analyzed comparatively for the layers prepared at different oxygen partial pressures in the sputtering atmosphere, as-grown and after heating in air at several temperatures. Sb doping is proven effective to improve the electrical conductivity of sputtered tin dioxide samples. The contribution of oxygen vacancies is found dependent on the reactive deposition environment, in both pure and Sb-doped films, but subsequent heating can change the proportion and nature of the donor defects. For operation at temperatures above 400 °C, SnO2:Sb shows the best electrical performance and good thermal behavior is also achieved with pure SnO2 layers by adjusting the oxygen content in the sputtering atmosphere.

P-type SnO thin films prepared by reactive sputtering at high deposition rates

SnO is an ideally suitable p-type conductive material, with large hole mobility, and has attracted great interest in connection with next-generation electronic applications. In the present work, tin oxide (SnOx) thin films were deposited on unheated soda lime glass substrates by reactive DC sputtering from a pure Sn target. The structural, optical and electrical properties of the films were analysed as a function of the oxygen partial pressure in the sputtering atmosphere and of the post-deposition annealing temperature in air. A structural analysis was carried out using Raman spectroscopy and X-ray diffraction. Optical and electrical characterizations were performed using photo-spectrometry and Hall effect measurements, respectively. The films grown at room temperature and low oxygen pressures reached high deposition rates of above 45 nm/min, showing poorly crystalline SnO and low transparency. Subsequent heating to 350 °C allowed to achieve a more crystalline tetragonal SnO with an average visible transmittance of 65%, a p-type conductivity of 0.8 S/cm, and a hole mobility of 3.5 cm2/(V s).