Co-sputtering Technique Research Articles

GOLD NANOPARTICLES-EMBEDDED TRANSPARENT CONDUCTING OXIDES: PREPARATION, CHARACTERIZATION, AND TUNING OF THE OPTICAL PROPERTIES

Gold nanoparticles ( AuNP )-embedded indium oxide and indium tin oxide thin films were prepared by DC and DC magnetron reactive co-sputtering techniques. The concentration and size distribution of AuNP were changed by deposition conditions. The nanoparticles-embedded films were characterized by X-ray diffraction, transmission electron microscopy, and optical spectrophotometry. The X-ray diffraction data showed the polycrystalline nature of indium oxide and indium tin oxide along with the Au (111) peak confirming the presence of elemental AuNP in the matrices. The transmission electron microscope studies revealed that AuNP are distributed in the matrices in different shapes and sizes with the average sizes as 40 nm and 10 nm, respectively for DC-sputtered and DC magnetron-sputtered films. The optical absorbance measurements showed the SPR peak due to AuNP to be around 600 nm. The position and intensity of the SPR peak could be tuned from 650 to 570 nm by changing the concentration of AuNP and annealing the films in oxygen and Ar for different durations.

The effect of titanium current on structure and hardness of aluminium titanium nitride deposited by reactive unbalanced magnetron co-sputtering

Nanocrystalline aluminium titanium nitride (AlTi 3N) thin films were deposited on Si (100) wafer and grid substrates without external heating and biasing at room temperature by reactive unbalanced magnetron co-sputtering technique using pure individual titanium and aluminium targets. The effects of titanium current (I Ti) on the structure and hardness of these films have been studied. The films were sputtered with Ar and N 2 gases flow rate of 8 and 4 sccm, respectively. The sputtering current of the aluminium current (I Al) was kept at 600 mA and the sputtering current of titanium (I Ti) was varied from 600 to 800 mA. The films were deposited for different deposition times ranging from 15 to 60 min. The deposited films were then characterized and analyzed by X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and nanoindentation measurement. The results indicated that the modification of the crystal structure, surface morphology and microstructure were dependent on the deposition parameters. The XRD patterns show polycrystalline structure with preferred orientations in (112), (004) and (153) planes which agree with the standard structure of aluminium titanium nitride (AlTi 3N) films. In addition, the structure of AlTi 3N was also confirmed by TEM. These results show that the films are composed of high Al content. The root mean square surface roughness and the average thicknesses were strongly influenced by I ti and deposition times. Cross section analysis by SEM showed dense and compact columnar morphology. The typical hardness of the films was approximately 26.24–30.37 GPa.

Surface modification of magnetron-sputtered hydroxyapatite thin films via silicon substitution for orthopaedic and dental applications

There have been a significant advances made in the field of bioceramics, particularly hydroxyapatite (HA) during the past 10years. Emphasis has now shifted towards designing HA with enhanced bioactivity for bone tissue repair. The aim of this study was to assess whether surface wettability can be correlated with cellular interactions with silicon-substituted hydroxyapatite (SiHA)-coated titanium (Ti) substrates. SiHA thin coatings of varying Si compositions were deposited on Ti substrates via a magnetron co-sputtering technique. These coatings were then subjected to an in vitro study using primary human ostoeblast (HOB) cells, to evaluate their biological property. HOB cells showed initial poor adhesion and spreading on hydrophobic Ti surface. The application of HA or SiHA thin coatings on Ti substrates by magnetron co-sputtering technique renders the surface more hydrophilic, with water contact angles between 30 and 40°. HOB cells attached, spread and proliferated well on these coatings. Enhanced calcification (formation of calcium phosphate nodules across the collagenous matrices) was observed on SiHA coatings with increasing Si content. This interdisciplinary paper highlighted that enhanced bioactivity was associated with surface wettability. Producing a nanostructured HA coating on a Ti substrate by magnetron sputtering resulted in the promotion of cell proliferation and calcification, and the latter was further enhanced with Si substitution. Hence, SiHA thin coating holds great potential as an alternative dental material.

Flexible thermoelectric generator for ambient assisted living wearable biometric sensors

In this work we proposed design, fabrication and functional characterization of a very low cost energy autonomous, maintenance free, flexible and wearable micro thermoelectric generator (μTEG), finalized to power very low consumption electronics ambient assisted living (AAL) applications. The prototype, integrating an array of 100 thin films thermocouples of Sb2Te3 and Bi2Te3, generates, at 40°C, an open circuit output voltage of 430mV and an electrical output power up to 32nW with matched load. In real operation conditions of prototype, which are believed to be very close to a thermal gradient of 15°C, the device generates an open circuit output voltage of about 160mV, with an electrical output power up to 4.18nW.In the first part of work, deposition investigation Sb2Te3 and Bi2Te3 thin films alloys on Kapton HN polyimide foil by RF magnetron co-sputtering technique is discussed. Deposition parameters have been optimized to gain perfect stoichiometric ratio and high thermoelectric power factor; fabricated thermogenerator has been tested at low gradient conditioned to evaluate applications like human skin wearable power generator for ambient assisted living applications.

THERMAL STABILITY OF ENERGY-EMISSION FROM CdTe NANOCRYSTALS EMBEDDED IN SiO2 THIN FILMS

CdTe -doped SiO 2 thin films were produced by RF magnetron co-sputtering technique. Presence of CdTe nanocrystals inside the silica matrix was confirmed by Raman spectroscopy and grazing incidence X-ray diffraction. The samples demonstrate size dependent photoluminescence. Temperature dependent photoluminescence measurements were carried out in the temperature range 15–295 K and revealed energy-emission thermal stability. This feature can be usefully applied in a production of light-emitting diodes with wavelength stability in a wide temperature range.

Physical properties of polycrystalline Cr-doped SnO 2 films grown on glasses using reactive dc magnetron co-sputtering technique

Abstract Electrical, optical and magnetic properties of polycrystalline Cr-doped SnO 2 films grown on glasses using reactive dc magnetron co-sputtering technique were investigated. The Cr content was modulated by varying the sputtering power applied on the Cr target. The carrier concentration and conductivity of doped films are reduced with increasing the Cr doping. Moreover, while the Cr content ratio Cr/(Sn + Cr) exceeds 0.9 at.%, the doped SnO 2 films become insulators and the optical transmission is strongly affected. The surface roughness of sputtered films is also increased by Cr doping. The co-sputtered Cr-doped SnO 2 films exhibit paramagnetic characteristics from room temperature down to 25 K.

Ferromagnetism in carbon-doped [formula omitted] thin films

Carbon-doped In 2O 3 thin films exhibiting ferromagnetism at room temperature were prepared on Si (100) substrates by the rf-magnetron co-sputtering technique. The effects of carbon concentration as well as oxygen atmosphere on the ferromagnetic property of the thin films were investigated. The saturated magnetizations of thin films varied from 1.23 to 4.86 emu/cm 3 with different carbon concentrations. The ferromagnetic signal was found stronger in samples with higher oxygen vacancy concentrations. In addition, deposition temperature and different types of substrates also affect the ferromagnetic properties of carbon-doped In 2O 3 thin films. This may be related to the oxygen vacancies in the thin film system. The experiment suggests that oxygen vacancies play an important role in introducing ferromagnetism in thin films.

In situ growth of Cu 2ZnSnS 4 thin films by reactive magnetron co-sputtering

High-quality Cu 2ZnSnS 4 (CZTS) thin films were first in situ grown by a reactive magnetron co-sputtering technique. Raman examination and XRD analysis indicate that the grown film shows a single CZTS phase with good crystallinity and strong preferential orientation along (1 1 2) plane. SEM analysis reveals a homogeneous, compact surface morphology and large columnar grains throughout thickness for the film. The in situ grown CZTS film demonstrates an optical absorption coefficient of higher than 10 4 cm −1 and an optical band gap of 1.52±0.01 eV. The carrier concentration, resistivity and mobility of the CZTS film are 3.9×10 16 cm −3, 5.4 Ω cm and 30 cm 2 V −1 s −1, respectively and the conduction type is p-type. These optical and electrical properties are suitable for a thin film solar cell fabrication.

Highly conductive indium zinc oxide prepared by reactive magnetron cosputtering technique using indium and zinc metallic targets

Zn-doped In2O3 film is frequently deposited from an oxide target; but the use of metallic target is increasingly expected as preparing the film with comparable properties. This work aimed to prepare a highly conductive and transparent Zn-doped In2O3 thin film on Corning Eagle2000 glass substrate by magnetron cosputtering method using indium and zinc targets. Structural characterization was performed using x-ray diffraction and x-ray photoelectron spectroscopy. The film had an amorphous structure when the film was prepared on an unheated substrate, but had an In2O3 polycrystalline structure when the film was deposited on 150 and 300 °C substrates. The electrical properties of the film were greatly affected by annealing; the Zn-doped In2O3 film had a low resistivity of 6.1×10−4 Ω cm and an average transmittance of 81.7% when the film was deposited without substrate heating and followed a 600 °C annealing.

An investigation of the effect of structural order on magnetostriction and magnetic behavior of Fe–Ga alloy thin films

This paper reports results from a comprehensive study of Fe–Ga films fabricated over a wide range of growth conditions. Polycrystalline Fe 100− x Ga x films (14 ⩽ x ⩽ 32) were deposited (using three different combinations of growth parameters) on Si(1 0 0) using a co-sputtering and evaporation technique. The growth parameters (sputter power, Ga evaporation rate and chamber pressure) were used primarily to control the Fe:Ga ratio in the films. X-ray diffraction showed that all films had 〈1 1 0〉 crystallographic texture normal to the film plane. The lattice parameter increased with % Ga up to x = 22 and was independent of growth parameters. Conversion electron Mössbauer spectroscopy studies showed a predominance of the disordered A2 phase in all films. It appears that the use of vacuum deposition with appropriate parameters can effectively suppress the D0 3 ordered phase. Systematic studies of the effective magnetostriction constant as a function of composition support this conclusion. It was found that films of high effective saturation magnetostriction constant and low stress could be fabricated using low Ar pressure, irrespective of sputter power or evaporation rate, giving properties useful for application in microelectromechanical systems.

The Role of High-κ TiHfO Gate Dielectric in Sputtered ZnO Thin-Film Transistors

In this study, we demonstrate the role of a titanium hafnium oxide (TiHfO) gate dielectric in improving the overall electronic performance of a ZnO thin-film transistor (TFT). TixHf1-xO (x = 0.63) was fabricated by the rf co-sputtering technique. Using TiHfO as the gate dielectric, the device fabricated in this study exhibits a threshold voltage of 0.34 V, a subthreshold swing of 0.23 V/dec, a field-effect mobility of 2.1 cm2 V-1 s-1, and an ON/OFF current ratio of 105. The small subthreshold swing and low positive threshold voltage are attributed to the higher value of κ of 40 for the dielectric. This result enables device operation below 2 V, allowing its use in low-power driving circuits in display applications.

Combinatorial investigation of Hf–Ta thin films and their anodic oxides

A co-sputtering technique was used for the fabrication of a thin film combinatorial library (Hf–21 at.% Ta to 91 at.% Ta) based on alloying of Hf and Ta. The microstructure and crystallography of individual metallic alloy compositions were analyzed using SEM and XRD mapping, respectively. Three different zones of microstructure were identified within the range of alloys, going from hexagonal to tetragonal through an intermediate amorphous region. The local oxidation of Hf–Ta parent metal alloys at different compositions was investigated in steps of 1 at.% using an automated scanning droplet cell in the confined droplet mode. Potentiodynamic anodisation cycles combined with in situ impedance spectroscopy provide basic knowledge regarding the oxide formation and corresponding electrical properties. Dielectric constants were mapped for the entire composition range and XPS depth profiles allowed investigation of the oxide compositions.

Magnetic Properties and Magnetoresistance in Fe-ITO Granular Films

Fe-ITO granular films with various volume fractions of Fe were prepared using the radio frequency (RF) co-sputtering technique. The magnetic and magnetoresistance properties were investigated. A transition from superparamagnetic granular films to ferromagnetic multidomain granular films with increasing the volume fraction of Fe is observed. The magnetoresistance of sample with low volume fraction of Fe follows (M/MS)2, while the magnetoresistance of samples with high volume fraction of Fe is composed of a ferromagnetic and a superparamagnetic contribution that is likely caused by the presence of small isolated superparamagnetic granules and interconnected or larger granules of ferromagnetic Fe. Further morphological and crystallographic analysis is required to fully establish the explanation.

Label-free detection of serum uric acid using novel high- k Sm 2TiO 5 membrane-based electrolyte–insulator–semiconductor

In this study, we constructed a highly pH sensitive electrolyte–insulator–semiconductor (EIS) sensor with a layer of novel rare-earth metal-oxide, Sm 2TiO 5. This high- k membrane with a thickness of 40 nm was deposited on the Si substrate by using reactive cosputtering technique. The effect of annealing temperature on the structural properties and surface roughness of Sm 2TiO 5 membrane was investigated. Based on X-ray diffraction and atomic force microscopy data, it was found that high temperature annealing (900 °C) leads to the formation of crystalline oxide thin film with a rough surface. The pH sensing experiments of EIS with Sm 2TiO 5 membrane annealed at 900 °C shows that reference voltage is linearly dependent on solution pH and an average sensitivity of 60.5 mV/pH. This outstanding pH sensitivity may be attributed to the high surface roughness of oxide membrane. Furthermore, the EIS sensor with Sm 2TiO 5 membrane showed the great stability and no sign of sensitivity degradation within an operation time of 140 days. Finally, we successfully demonstrated the first example of the use of EIS with uricase-immobilized alginate film for the detection of uric acid in serum. The concentration of serum uric acid measured by EIS biosensor is comparable to that determined by commercial assay kit. This sensitive EIS based biosensor can potentially be served as the diagnosis tool for general clinical examinations.

HREM characterization of nano‐composite Au/SiO2 layers

Nano-composite layers of Au nano-crystallites embedded in amorphous silica matrix were obtained by a radio-frequency co-sputtering technique. Glass or single crystal silicon wafers were chosen as substrates. After deposition, the layers were heat treated at 900 degrees C for 60 min. Microstructure of the layers was investigated using a TECNAI G(2) FEG SuperTwin (200 kV) transmission electron microscope. Thin foils were cut using a focused ion beam Quanta 3D. The investigations confirmed that the applied process allowed obtaining nano-composite layers containing spherical Au crystallites of average size of approximately 3 nm embedded in an amorphous silica matrix. Some of the nano-crystallites were twinned. The layers were heat treated in subsequent step and rise of the crystallite average size up to 5.5 nm confirming activation of diffusion processes was seen. Presence of irregularly shaped Au crystallites in the latter layers indicates incomplete sintering due to short annealing time.

Amorphous In–Sn–Si–O Thin-Film Transistors Having Various Si Compositional Ratios

We investigate the possibility of utilizing a new material, amorphous indium-tin-silicon oxide In10Sn1SixO2x+17 (a-ITSO), for the active layer in oxide-semiconductor TFTs, using a co-sputtering technique with ITO and Si targets. A Si compositional ratio x=1.88 yielded the TFT performance with a field-effect mobility of approximately 5 cm2 V-1 s-1. Spectroscopic investigations confirmed that the diversity of the Si compositional ratio in the a-ITSO films results in significant changes in chemistry and electronic structure, leading to considerable variations in the characteristics of the a-ITSO TFTs.

Methanol oxidation enhanced by the presence of O2 at novel Pt–C co-sputtered electrode

In this paper, we describe a novel electrode that exhibits sensitized methanol electrooxidation in an oxygen atmosphere. A binary Pt-C electrode has been developed for use as the anode catalyst of a direct methanol fuel cell using a co-sputtering technique. Characterizations of the electrodes revealed that the sputtered Pt-C forms nanosize and phase-separated Pt and C domains, in which the Pt particle size decreases and its crystallinity gradually becomes amorphous with increasing C content. The current density of methanol oxidation in deaerated conditions exhibited a maximum value at a C content of 23 at%. The result can be well explained from the viewpoints of the morphology and binding energy of Pt. The methanol oxidation current is sensitized by O(2) when the Pt-C electrode contains >23 at% C, and the extent of sensitization increases monotonically with C content. This phenomenon is not observed at a Pt electrode. The sensitization mechanism was investigated by considering the reduction reaction of O(2); it was clarified that the amount of adsorbed species created by O(2) reduction increases with increasing C content. It was deduced that the Pt-OH produced by O(2) reduction participates in oxidation of Pt-CO, which is believed to be the rate-determining step of the methanol electrooxidation.

Mechanism Investigation of p-i-n ZnO-Based Light-Emitting Diodes

Using a cosputtering technique to deposit P-ZnO : AlN film and using a vapor cooling condensation system to deposit n-ZnO : In and i-ZnO films on sapphire substrates, thin-film-type ZnO-based light-emitting diodes (LEDs) were fabricated. A Nd : YAG laser with a wavelength of 413 nm is utilized to identify the defect-related emissions of p-ZnO, i-ZnO, and n-ZnO films. The characteristics of i-ZnO layer of ultraviolet (UV) emissions were analyzed using temperature-dependent photoluminescence. The mechanism of the UV electroluminescence emission peak at 3.20 eV observed from the p-i-n ZnO-based LEDs were attributed to the low deep-level defects and the radiative recombination occurred in the i-ZnO layer.

Characterization of Aluminium Titanium Nitride Thin Films Deposited by Reactive Magnetron Co-Sputtering

Nanocrystalline aluminium titanium nitride (AlTi3N) thin films were deposited on Si (100) wafers and grids by reactive magnetron co-sputtering technique using titanium and aluminium targets. The films were sputtered in Ar and N2 mixture at a constant flow rate under different conditions of deposition time ranging from 15 to 60 minutes. The crystal structure was characterized by X-Ray diffraction (XRD) and microstructure was analyzed by transmission electron microscopy (TEM). The results indicated that the formation of polycrystalline AlTi3N with the orthorhombic structure and the development of crystal structure was observed by varied the deposition time. The microstructure of films was good according to the XRD results. On the other hand, after annealed the films at 500OC in the air for 1 hour, the crystal structure did not change that exposed the stable structure of AlTi3N films.

Study on microstructure and soft magnetism of (Fe 65Co 35) x(SiO 2) 1−x nano-granular films with very high ferromagnetic resonance frequency

A series of (Fe 65Co 35) x (SiO 2) (1− x ) nano-granular films with different volume fraction x are fabricated by magnetron co-sputtering technique. The structure, magnetic and high frequency properties are investigated systematically by using X-ray diffraction, transmission electronic microscopy, vibrating sample magnetometer, resistivity and complex permeability measurements. Study results indicate that the films consist of Fe 65Co 35 magnetic metal particles uniformly embedded in an insulating SiO 2 matrix. (Fe 65Co 35) x (SiO 2) (1− x ) films exhibit large magnetic anisotropy field H k and excellent soft magnetic properties in a wide x range from 0.80 to 0.52 with coercivity H c smaller than 18 Oe. A minimum H c value of 7.8 Oe is obtained for the sample with x=0.60 whose electrical resistivity ρ reaches 2220 μ Ω cm and the magnetic anisotropy field H k is as high as 185 Oe. Especially, for the result of complex permeability measurement of the samples, very high ferromagnetic resonance (FMR) frequency is obtained. For the typical sample with x=0.60, the FMR frequency reaches 4.9 GHz, implying a very high cut-off frequency for high frequency applications, and the real part μ′ of its complex permeability exceeds 60 below 3.8 GHz while the imaginary part μ″ is very small until f>2.0 GHz. These good high frequency properties imply that (Fe 65Co 35) x (SiO 2) (1− x ) granular films are promising for applications in high frequency range. The good soft magnetic properties are ascribed to the exchange coupling among magnetic particles, which is discussed in this paper.