Co-sputtering Technique Research Articles

Effect of Doping Concentration on the Proton Conductivity of Y-doped BaZrO3 Thin Films

Y-doped BaZrO3 (BYZ) pellets and thin films were fabricated by solid state reaction and co-sputtering technique, respectively. The conductivity of BYZ samples was measured using electrochemical impedance spectroscopy technique in the atmospheres of air, dry H2, and wet H2. As Y content increases from 6 at.% to 20 at.%, the increase of bulk and grain boundary conductivity is observed, while at 30 at.%, the conductivity starts to degrade. The activation energies in bulk and grain boundary are in the range of 0.28-0.40 eV and 0.91-0.96 eV, respectively. BYZ pellets have the highest proton conductivity at the Y doping concentration of 20 at.%. Furthermore, the dense and uniform BYZ thin films of 130-140 nm in thickness were obtained by co-sputtering technique. The conductivities of the BYZ thin films are about 10^3 - 10^4 times those of the pellet samples. The reason of the observed high conductivity is still under further investigation.

Development of a low temperature amorphous Si/Ti for integrated MEMS/NEMS

Co-sputtering techniques are used to deposit amorphous Si/Ti (a-Si/Ti) composite materials at room temperature with a view to enabling post-CMOS fabrication of MEMS/NEMS. Electrical and mechanical properties of a-Si/Ti are characterised and analysed, benchmarking those of polycrystalline Si (poly-Si) commonly used for MEMS/NEMS. The surface micromachining feasibility of a-Si/Ti is preliminarily investigated using a commonly available Si dry etching process. The promising material and process development suggests that a-Si/Ti composites can potentially be exploited as MEMS/NEMS structural materials with desirable post-CMOS process compatibility, leading to monolithic integration of MEMS/NEMS and ICs.

Effects of Si-rich oxide layer stoichiometry on the structural and optical properties of SiQD/SiO2 multilayer films

The effects of the stoichiometry of the Si-rich oxide (SRO) layer,O/Si ratio, on the structural and optical properties ofSRO/SiO2 multilayer films were investigated in this work.SRO/SiO2 multilayer filmswith different O/Si ratios were grown by a co-sputtering technique, and Si quantum dots (QDs) were formed withpost-deposition annealing. By transmission electron microscopy (TEM) and glancing incidencex-ray diffraction (GIXRD), it was found that the Si QD size decreases with increases inO/Si ratio. The photoluminescence (PL) spectrum varies with theO/Si ratio in band position, shape and intensity. In addition, it wasobserved that the absorption edge blue-shifts with increases in theO/Si ratio. The change in the absorption edge is consistent with strengthening quantumconfinement effects in Si QDs, as indicated by TEM and GIXRD. The optical propertieswere also investigated by 2D photoluminescence excitation (2D-PLE) and lifetimemeasurements. The origin of emission and absorption is discussed based on the absorption,PL, 2D-PLE and decay time measurements.

Superhydrophilic stability enhancement of RF co-sputtered Ti xSi 1− xO 2 thin films in dark

Ti x Si 1− x O 2 compound thin-film systems were deposited by reactive RF magnetron co-sputtering technique. The effect of Ti concentration on the hydrophilicity of Ti x Si 1− x O 2 compound thin films was studied and it was shown that the films with Ti 0.6Si 0.4O 2 composition possess the best hydrophilic property among all the grown samples. Surface ratio and average roughness of the thin films were measured by atomic force microscopy (AFM). Surface chemical states and stoichiometry of the films were determined by X-ray photoelectron spectroscopy (XPS). In addition, XPS revealed that the amount of Ti–O–Si bonds in nanometer depth from the surface of the Ti 0.6Si 0.4O 2 films was the maximum, which resulted in the most stable superhydrophilic property. According to XRD data analysis for the pure TiO 2 films, the polycrystalline anatase phase was formed with an average grain size of about 15 nm. Moreover, amorphous phase was also formed for the Ti x Si 1− x O 2 compound systems due to presence of silicon in the films. Finally, optical properties of the films such as transmission, reflection and band gap energy were investigated using UV–vis spectrophotometry. It was found that the transmittance of the films was decreased with increasing Ti concentration in the films.

Magnetic Properties, Microwave Characteristics, and Thermal Stability of the FeCoAlN Films

FeCoAlN films were prepared by reactive radio frequency magnetron co-sputtering technique in an argon and nitrogen mixture atmosphere. The soft magnetic properties, GHz dynamic properties, and magnetic thermal stability of the FeCoAlN films were investigated. The FeCoAlN films deposited at N2/(Ar + N2) gas flux percentages larger than 8% have amorphous structure. The (Fe64.8Co35.2)96.3Al3.7N film as-deposited at the N2/(Ar + N2) gas flux percentage of 9% has good magnetic softness and uniaxial in-plane anisotropy, as demonstrated by the typical hysteresis loops along easy and hard axis. The magnetic thermal stability of the FeCoN films can be obviously improved by introduction of a high Al content. The (Fe64.8Co35.2)86.5Al13.5N films annealed at 400 °C for 1 h exhibit good magnetic softness and GHz dynamic properties with a saturation magnetization (μ0Ms) of 1.21 T, an easy axis coercive field (Hce) of 8.5 Oe, an anisotropy field (Hk) of 35 Oe, a ferromagnetic resonance frequency (fr) of 1.89 GHz, and a real part of permeability (μ′) of 380. The dynamic characteristics can be described by the theoretical model based on Landau-Lifshitz-Gilbert (L-L-G) equation and eddy current dynamics.

Innovative Platform for Transmission Localized Surface Plasmon Transducers and Its Application in Detecting Heavy Metal Pd(II)

Transmission localized surface plasmon resonance (T-LSPR) transducers based on the characteristic surface plasmon absorption band of Au island films have become increasingly attractive. The first and main bottleneck hampering the development of T-LSPR sensors is instability, manifested as change in the surface plasmon absorbance band following immersion in organic solvents and aqueous solutions. In this paper, we innovate the platform for T-LSPR transducer by using remarkably stable and highly adhesive Au/Al(2)O(3) nanocomposite film. Isolated Au nanoparticles embedded in dielectric matrix Al(2)O(3) were prepared by a simple one-step radio frequency magnetron cosputtering technique. The obtained nanocomposite film is exceedingly stable during immersion in solvents, drying, and binding of different molecules; it successfully passes the adhesive tape test and sonication treatment. The superior stability and adhesion, obtained without the use of any intermediate adhesion layer or protective overlayer, is attributed to (1) the Au nanoparticles embedment and Al(2)O(3) rim formation during the sputtering process and (2) the resistance of element Al in matrix to the nucleophilic attack by the solvent molecules. Given this success, we believe that the Au/Al(2)O(3) nanocomposite film holds promise as an innovative sensing platform in T-LSPR detection technology, as demonstrated here for the Pd(II) sensing process with excellent sensitivity and low detection limit.

Morphology and structural studies of Ag photo-diffused Ge ySe 1−y thin films prepared by RF-sputtering

Thin films of Ag photo-doped-Ge y Se 1− y films were prepared by RF co-sputtering technique. A systematic study of the relation existing between the host layer composition and the saturation rate in silver was carried out. Morphology and composition studies before and after chemical etchings were performed by scanning electron microscopy and electron probe micro-analyses, respectively. Raman spectroscopy studies showed the presence of corner-sharing and edge-sharing Ge(Se 1/2) 4 tetrahedra in all thin films. The vibration mode corresponding to Se n -chains is observed for the Ge-poor host layer and on the contrary, Ge-rich thin films exhibited some tendency to form homopolar Ge–Ge bonds as a part of ethane-like Ge 2Se 6 units. These investigations revealed the amount of Ag that could be incorporated in the host layer. Such an amount strongly depends on the relative ratio Ge/Se in the Ge y Se 1− y thin film. For the Ge-poor host layer, an incorporation of Ag (54 at.%) was observed but also a drastic increase in the film heterogeneity. On the other hand, the host layers with higher Ge content showed homogeneous surfaces and a saturation level of ∼32–41 at.% Ag.

Formation of Al–N co-doped p-ZnO/n-Si (1 0 0) heterojunction structure by RF co-sputtering technique

Al–N co-doped ZnO (ZnO:Al–N) thin films were grown on n-Si (1 0 0) substrate by RF co-sputtering technique. As-grown ZnO:Al–N film exhibited n-type conductivity whereas on annealing in Ar ambient the conduction of ZnO:Al–N film changes to p-type, typically at 600 °C the high hole concentration of ZnO:Al–N co-doped film was found to be 2.86 × 10 19 cm −3 and a low resistivity of 1.85 × 10 −2 Ω-cm. The current–voltage characteristics of the obtained p-ZnO:Al–N/n-Si heterojunction showed good diode like rectifying behavior. Room temperature photoluminescence spectra of annealed co-doped films revealed a dominant peak at 3.24 eV.

Characteristics of cubic MgZnO thin films grown by radio frequency reaction magnetron co-sputtering

Cubic MgZnO thin films were prepared on fused quartz substrate by radio frequency (rf) reaction magnetron co-sputtering technique, and composition modulation of cubic MgZnO films could be accomplished by changing rf power on Zn metal target. During growth process crystal quality of our MgZnO films can be improved by increasing the ratio of O 2/Ar. Unlike reported growth of (1 1 1) plane cubic MgZnO films, our cubic MgZnO films show (2 0 0) plane growth properties. This phenomenon was assigned to a preferred selection growth characteristic of MgZnO on non-crystalline quartz substrate. Band gaps of cubic MgZnO films calculated by empirical formula are different from that obtained in the absorption spectrum. It is suggested that parts of Mg do not contribute to the band gaps of Mg x Zn 1− x O thin films.

Characterization of reactively sputtered c-axis orientation (Al, B)N films on diamond

In this research, we demonstrated the viability of oriented AlN layer that incorporated BN to enhance the texturing. Wurtzite (Al, B)N films were deposited on a diamond wafer (diamond film on Si wafer) by a co-sputtering technique. The preferred orientation structure is sensitive to sputtering control factors. The relationship between the microstructures and process conditions were examined with XRD, TEM and AFM analysis. The cross-section TEM images showed that amorphous and randomly aligned structures were produced in the initial sputtering period, but the higher c-axis orientation structure formed as the sputtering time increased. The thickness of the amorphous and randomly aligned layer decreased with increasing sputtering power, nitrogen concentration, substrate temperature and bias voltage. As the thickness of the amorphous and the randomly aligned layer decreased, an (Al,B)N film with higher film quality than AlN was observed.

Effect of rapid thermal annealing on Si rich SiO 2 films prepared using atom beam sputtering technique

We report here the synthesis of silicon-nanoclusters embedded in SiO 2 by atom beam co-sputtering technique. A sputtering target consisted of 40% and 60% area of Si pieces glued on a fused silica plate. A co-sputtered film containing Si embedded in SiO 2 having different compositional fractions of Si was deposited on fused silica and c-Si substrates. Annealing was done in N 2 atmosphere for 1 min at temperatures ranging from 700–900 °C to precipitate silicon nanoclusters. Samples were characterized using Raman and FTIR spectroscopy. In IR absorption spectra, the blue shift of the Si–O–Si asymmetric stretching band, from 1017 cm − 1 for as-deposited samples, to 1070 cm − 1 for samples annealed at 900 °C, indicates that phase separation of Si and SiO 2 has been completed and films consist of Si particles embedded in an SiO 2 matrix. Raman spectrum showed the emergence of 513 cm − 1 due to nanocrystalline silicon after RTA at 900 °C.

Structural, optical and magnetic properties of Fe-doped ZnO

Zn1-xFexO (x =0.011, 0.029, 0.048, 0.10, 0.20) thin films have been grown on Al2O3 (0001) substrates by magnetron co-sputtering technique. X-ray diffraction analysis revealed that Fe atoms were successfully incorporated into ZnO host matrix, and the films exhibited wurzite structure up to x = 0.20 with reduced c-axis lattice constant compared to that of pure ZnO. There are not any secondary phases, and Fe2+ as well as Fe3+ substitutes for Zn2+ of ZnO host. With increasing x, the optical band gap is found to shift slightly to lower energies (66 meV for x = 0.20) than that of the pure ZnO. Magnetization measurement indicated that all samples were ferromagnetic at room temperature. An explanation for the dependence of the optical and magnetic properties of the samples on the value of x is also given.

Shape deformation of embedded metal nanoparticles by swift heavy ion irradiation

Swift heavy ions (SHI) induce high densities of electronic excitations in narrow cylindrical volumes around their path. These excitations have been used to manipulate the size and shape of noble metal nanoparticles embedded in silica matrix. Films containing noble metal nanoparticles were prepared by magnetron co-sputtering techniques. SHI irradiation of films resulted in the formation of prolate Ag nanoparticles with major axis along the ion beam direction. It has been observed that the nanoparticles smaller than the track size dissolve and other grow at their expense, while the nanoparticles larger than track size show deformation with major axis along the ion beam direction. The aspect ratio of elongated nanoparticles is found to be the function of electronic energy loss and ion fluence. Present report will focus on the role of size and volume fraction on the shape deformation of noble metal nanoparticles by electronic excitation induced by SHI irradiation. The detailed results concerning irradiation effects in silica–metal composites for dissolution, growth and shape deformation will be discussed in the framework of thermal spike model.

A combinatorial approach of developing alloy thin films using co-sputtering technique for displays

In this study we have used a combinatorial approach for producing binary and ternary alloy thin film libraries using a lab-scale RF co-sputtering system. Initially we used two elemental sputtering targets, i.e. aluminum (Al) target and neodymium (Nd) target, to produce a film library of varying composition and successfully identified a suitable composition range (1.95–2.38 at% Nd) in which resistance to hillock formation and resistivity of the film spots were found to be satisfactory in annealed state (350°C, 30 min). In another case, in order to form ternary alloy composition library we have used two sputtering targets, i.e. an Al-0.5 at% Nd alloy target and an elemental Ni target. Though, co-sputtered Al-0.6 at% Nd-0.9 at% Ni alloy films showed satisfactory resistance to hillock formation and low resistivity after annealing, film deposited from a ternary alloy target with the same composition failed to show satisfactory resistance to hillock formation during annealing. In case of Al-0.6 at% Nd-0.9 at% Ni alloy target, 250 nm thick film showed poor resistance to hillock formation than the 500 nm thick film. This clearly showed thickness-dependent hillock performance of Al-0.6 at% Nd-0.9 at% Ni alloy. In this study it was found that, in addition to the process variables, metallurgical microstructure of the alloy sputtering targets had significant effect on the film properties which was not obvious from the results of films deposited using co-sputtering of the individual elemental targets.

Synthesis and characterization of boron-doped Si quantum dots for all-Si quantum dot tandem solar cells

Multiple layers of Si quantum dots (QDs) in SiO 2 with a narrow size distribution were synthesized by a co-sputtering technique. Structural, electrical and optical properties of Si QD/SiO 2 multilayer films with various boron (B) concentrations introduced during the sputtering process were studied. X-ray photoelectron spectroscopy (XPS) revealed B–B/B–Si bonding, which suggests possible boron inclusion in the nanocrystals. The addition of boron was observed to suppress Si crystallization, though the boron concentration was found to have little effect on the QD size. Reductions in film resistivity were observed with the increase in boron concentration, which is believed to be a consequence of an increase in carrier concentration. This is supported by a large decrease in the activation energy accompanying the drop in resistivity, consistent with the Fermi energy moving towards the valence bands. The photoluminescence (PL) intensity was found to decrease with increase in boron concentration.

Post growing annealing effect on the optical, electrical and structural properties of CdSe nanocrystals embedded in silica thin films

In this work post-growth annealing effect on CdSe/SiO 2 thin films grown by rf-magnetron co-sputtering technique was investigated. Annealed samples were characterised by Raman scattering, grazing incidence X-ray diffraction and room temperature photoluminescence. The nanocrystals (NCs) size changed from 1.5 to 5 nm by varying the annealing temperature from 550 to 400 °C. Evaporation of Se at high temperatures was invoked to explain this phenomenon. Fowler–Nordheim tunnelling mechanism was found to be responsible for carrier transport for samples with bigger CdSe NCs sizes, and which showed better photovoltaic properties.

Annealing Induced Aggregations and Sign Alterations of Nonlinear Absorption and Refraction of Dense Au Nanoparticles in TiO2 Films

Au-TiO2 dis-conductive composite films with Au atom concentrate as high as 82% are prepared by using reactive co-sputtering technique. The annealing effect on the nanostructures and optical nonlinearities of the composite films are investigated. Au nanoparticles aggregated to semi-continuum network structures during the annealing processes. As the annealing temperature increases from 25° C to 400° C, the surface plasmon absorption band is shifted and its strength is increased, consequently, the nonlinear absorption coefficient β decreases from 5.6 × 104 cm/GW to −1.7 × 104 cm/GW, while the nonlinear refractive index γ increases from —0.95 cm2/GW to 1.3 cm2/GW.

Magnetic behavior of cosputtered Fe-Zr amorphous thin films exhibiting perpendicular magnetic anisotropy

Excellent mechanical properties of amorphous or glassy metals along with the capability to fabricate sub-50-nm patterns promise their application as a futuristic material for production of various nano- or microelectromechanical systems. In addition to their applications, these materials pose a lot of challenges in understanding their fundamental properties because of their random structure and involvement of three or more different kinds of atoms. The amorphous Fe-Zr system which is reported to exhibit superconductivity, ferromagnetism, spin glass, and antiferromagnetism is an ideal system to understand. The controversial magnetic properties of this system are still a subject of debate. In the present paper we revisited Fe-Zr system and studied their detailed magnetic properties in the temperature range of 5--330 K. ${\text{Fe}}_{x}{\text{Zr}}_{100\ensuremath{-}x}$ ($x=63$, 68, 76, 86, 92, and $93\text{ }\text{at}\text{.}\text{ }%$) thin films were deposited on silicon (100) substrate by a cosputtering technique. The Curie temperature $({T}_{c})$ is shown to increase almost linearly with an increase in Fe concentration, but it decreases rapidly for the Fe-rich films. The films with $x$ up to $\ensuremath{\sim}86\text{ }\text{at}.\text{ }%$ have a strange shape of the hysteresis loop and are shown to exhibit perpendicular magnetic anisotropy with a stripe domain structure. Hysteresis loop shapes are correlated with the magnetic structure of the films, and provide an easy understanding of magnetic properties. It has been shown that the Fe-rich films are composed of antiferromagnetic Fe clusters which are embedded in the ferromagnetic amorphous FeZr.

Charging effects in CdSe nanocrystals embedded in SiO 2 matrix produced by rf magnetron sputtering

Charging effects in CdSe nanocrystals embedded in SiO 2 matrix fabricated by rf magnetron co-sputtering technique were electrically characterized by means of capacitance–voltage ( C– V) combined with current–voltage ( I– V). The presence of CdSe nanocrystals was demonstrated by X-ray diffraction technique. The average size of nanocrystals was found to be approximately 3 nm. The carriers transport in the CdSe/SiO 2 structure was shown to be a combination of Fowler–Nordheim tunnelling and Poole–Frenkel mechanisms. A memory effect was demonstrated and a retention time was measured.

Nanostructured hydroxyapatite/TiO2 composite coating applied to commercially pure titanium by a co-sputtering technique

We demonstrate an approach for the coating of nanostructuredhydroxyapatite(HAP)/TiO2 composite on commercially pure Ti (CP-Ti) by a co-sputtering process.HAP/TiO2 composite film was obtained by controlling the processing pressure. It wasobserved that decomposition of HAP into CaO was easily induced duringsputtering at 0.53 Pa, a typical sputtering condition for film deposition. However,HAP/TiO2 composite film was obtained with the sputtering pressure of 2.67 Pa. TheCa/P ratio was nearly maintained at 1.66 by sputter deposition at 2.67 Pa. We further confirmedby analysis of plasma spectral emission that the variation of the hydroxyl (OH) radicalpresent was due to the Ar pressure during sputtering. It has been shown that HAP coatingsare dependent on the processing pressure, which the hydroxyl radical requires in order tocreate HAP.