Showing papers on "Sputtering published in 2012"

High power impulse magnetron sputtering discharge

Abstract: The high power impulse magnetron sputtering (HiPIMS) discharge is a recent addition to plasma based sputtering technology. In HiPIMS, high power is applied to the magnetron target in unipolar pulse ...

Gas sensors based on one dimensional nanostructured metal-oxides: a review.

Abstract: Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

An introduction to thin film processing using high-power impulse magnetron sputtering

Abstract: High-power impulse magnetron sputtering (HiPIMS) is a promising sputtering-based ionized physical vapor deposition technique and is already making its way to industrial applications. The major difference between HiPIMS and conventional magnetron sputtering processes is the mode of operation. In HiPIMS the power is applied to the magnetron (target) in unipolar pulses at a low duty factor (<10%) and low frequency (<10 kHz) leading to peak target power densities of the order of several kilowatts per square centimeter while keeping the average target power density low enough to avoid magnetron overheating and target melting. These conditions result in the generation of a highly dense plasma discharge, where a large fraction of the sputtered material is ionized and thereby providing new and added means for the synthesis of tailor-made thin films. In this review, the features distinguishing HiPIMS from other deposition methods will be addressed in detail along with how they influence the deposition conditions, such as the plasma parameters and the sputtered material, as well as the resulting thin film properties, such as microstructure, phase formation, and chemical composition. General trends will be established in conjunction to industrially relevant material systems to present this emerging technology to the interested reader.

Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties

Abstract: Thin film capacitors were fabricated by sputtering TiN-Y doped HfO2-TiN stacks on silicon substrates. Yttrium was incorporated into the HfO2 layers by simultaneously sputtering from Y2O3 and HfO2 sources. Electric polarization and relative permittivity measurements yield distinct ferroelectric properties as a result of low yttrium dopant concentrations in the range of 0.9-1.9 mol. %. Grazing incidence x-ray diffraction measurements show the formation of an orthorhombic phase in this range. Compared to atomic layer deposition films, the highest remanent polarization and the highest relative permittivity were obtained at significantly lower doping concentrations in these sputtered films.

Nanometric transformation of the matter by short and intense electronic excitation: Experimental data versus inelastic thermal spike model

Abstract: Experimental investigations of ion tracks and sputtering phenomena with energetic heavy projectiles in the electronic energy loss regime are re-examined in metallic and insulating materials. An overview of track data such as the velocity dependence of the track size and the critical electronic energy loss for track formation is presented. Different physical characterizations of the material transformation are listed in order to deduce a track size which is independent of the observations. It will point out the differences of damage creation by electronic energy loss compared to nuclear energy loss. In the second part, we present a theoretical description of track formation based on the inelastic thermal spike model. This thermodynamic approach combines the initial size of the energy deposition with the subsequent diffusion process in the electronic and lattice subsystems of the target. The track size, resulting from the quench of a molten phase, is determined by the energy density deposited on the atoms around the ion path governed by the electron–phonon strength. Finally, we discuss the general validity of this model in metallic materials and its suitability to describe track formation in amorphizable and non-amorphizable insulators.

Correlation between Surface Chemistry, Density, and Band Gap in Nanocrystalline WO3 Thin Films

Abstract: Nanocrystalline WO3 thin films were produced by sputter-deposition by varying the ratio of argon to oxygen in the reactive gas mixture during deposition. The surface chemistry, physical characteris...

High power impulse magnetron sputtering discharges: Instabilities and plasma self-organization

Abstract: We report on instabilities in high power impulse magnetron sputtering plasmas which are likely to be of the generalized drift wave type. They are characterized by well defined regions of high and low plasma emissivity along the racetrack of the magnetron and cause periodic shifts in floating potential. The azimuthal mode number m depends on plasma current, plasma density, and gas pressure. The structures rotate in E→×B→ direction at velocities of ∼10 km s−1 and frequencies up to 200 kHz. Collisions with residual gas atoms slow down the rotating wave, whereas increasing ionization degree of the gas and plasma conductivity speeds it up.

Argon Cluster Ion Beams for Organic Depth Profiling: Results from a VAMAS Interlaboratory Study

Abstract: The depth profiling of organic materials with argon cluster ion sputtering has recently become widely available with several manufacturers of surface analytical instrumentation producing sources suitable for surface analysis. In this work, we assess the performance of argon cluster sources in an interlaboratory study under the auspices of VAMAS (Versailles Project on Advanced Materials and Standards). The results are compared to a previous study that focused on C(60)(q+) cluster sources using similar reference materials. Four laboratories participated using time-of-flight secondary-ion mass spectrometry for analysis, three of them using argon cluster sputtering sources and one using a C(60)(+) cluster source. The samples used for the study were organic multilayer reference materials consisting of a ∼400-nm-thick Irganox 1010 matrix with ∼1 nm marker layers of Irganox 3114 at depths of ∼50, 100, 200, and 300 nm. In accordance with a previous report, argon cluster sputtering is shown to provide effectively constant sputtering yields through these reference materials. The work additionally demonstrates that molecular secondary ions may be used to monitor the depth profile and depth resolutions approaching a full width at half maximum (fwhm) of 5 nm can be achieved. The participants employed energies of 2.5 and 5 keV for the argon clusters, and both the sputtering yields and depth resolutions are similar to those extrapolated from C(60)(+) cluster sputtering data. In contrast to C(60)(+) cluster sputtering, however, a negligible variation in sputtering yield with depth was observed and the repeatability of the sputtering yields obtained by two participants was better than 1%. We observe that, with argon cluster sputtering, the position of the marker layers may change by up to 3 nm, depending on which secondary ion is used to monitor the material in these layers, which is an effect not previously visible with C(60)(+) cluster sputtering. We also note that electron irradiation, used for charge compensation, can induce molecular damage to areas of the reference samples well beyond the analyzed region that significantly affects molecular secondary-ion intensities in the initial stages of a depth profile in these materials.

Afm studies on surface morphology, topography and texture of nanostructured zinc aluminum oxide thin films

Abstract: Zinc Aluminum Oxide (ZAO) thin films were deposited on glass substrates by DC reactive magnetron sputtering technique with high purity Zn and Al targets. After the deposition, the films were annealed in vacuum from 200 to 500 o C. Surface roughness measurement of ZAO thin films in the nanometer scale can be accurately determined using the atomic force microscopy. Surface roughness and grain size for all the samples shows a direct relation between each other where the surface roughness increases as the grain size increases with increase of annealing temperature. The average roughness, maximum peak to valley height, root mean square (RMS) roughness, ten-point mean height roughness, surface skewness and surface kurtosis parameters are used to analyze the surface morphology of ZAO films.

Reactive magnetron sputtering of transparent conductive oxide thin films: Role of energetic particle (ion) bombardment

Abstract: Transparent conductive oxides (TCOs) are degenerately doped compound semiconductors with wide band gaps (Eg > 3 eV), which are used as transparent electrodes in optoelectronic devices. Reports on the influence of negative ions on the electrical properties of TCO films are reviewed and compared with our results. It was reported that the radial resistivity distributions depend (i) on the excitation mode of the magnetron (direct current or radio frequency), (ii) on the erosion state of the sputtering target, and (iii) on the density of the ceramic targets. This can be explained by the fact that the negative ions in magnetron discharges (in our case O−) are generated at the target surface and accelerated toward the growing films. Their energy and their radial distribution depend on the discharge voltage and the shape of the emitting surface, i.e., of the erosion groove. Ways for reducing the effect of negative ion bombardment are discussed.

Role of Tin+ and Aln+ ion irradiation (n = 1, 2) during Ti1-xAlxN alloy film growth in a hybrid HIPIMS/magnetron mode

Abstract: Metastable Ti1-xAlxN (0.4 less than= x less than= 0.76) films are grown using a hybrid approach in which high-power pulsed magnetron sputtering (HIPIMS) is combined with dc magnetron sputtering (DC ...

Growth of silver nanoparticles by DC magnetron sputtering

Abstract: Silver (Ag) nanoparticles are of great interest for many applications. However, their fabrications have been limited by the synthesis methods in which size, shape, and aggregation are still difficult to control. Here, we reported on using direct current (DC) magnetron sputtering for growing Ag nanoparticles on unheated substrates. Effects of sputtering condition on grain size of Ag nanoparticle were discussed. At constant sputtering current and deposition time, the average sizes of Ag nanoparticles were 5.9 ± 1.8, 5.4 ± 1.3, and 3.8 ± 0.7 nm for the target-substrate distances of 10, 15, and 20 cm, respectively. The morphology evolution from nanoparticles to wormlike networks was also reported. High-resolution transmission electron microscopy image represented clear lattice fringes of Ag nanoparticles with a d-spacing of 0.203 nm, corresponding to the (200) plane. The technique could be applied for growth of nanoparticles that were previously difficult to control over size and size uniformity.

Thin Film Growth Through Sputtering Technique and Its Applications

Abstract: During the last decade the dc and rf sputtering techniques have been used extensively in their two configurations — balanced and unbalanced magnetron. The main applications have been in the fields of industry and research. Examples of industrial applications are: decorative thin films (Raymond & Baham, 1999), hard wear-resistant thin films (Rodil & Olaya, 2006), low-friction thin films (Heimberg et al., 2001) corrosion-resistant thin films (Flores et al., 2006), and thin films used as a protective optical system (Stefan et al., 2008), as well as maybe the most interesting applications, thin films used in the electronic industry (Monroy et al., 2011). In the research field, the investigation has been oriented toward understanding the main physical mechanisms, such as: interaction between charged particles and the surface of the target material, adherence between the substrate and the deposited material, and chemical reactions near the substrate, as well as the influence of the deposit parameters (substrate temperature, working pressure, density power applied to the target). This research has produced thin films with a high degree of crystallinity and with the possibility of various industrial applications.

Characterization of nanoporous gold electrodes for bioelectrochemical applications.

Abstract: The high surface areas of nanostructured electrodes can provide for significantly enhanced surface loadings of electroactive materials. The fabrication and characterization of nanoporous gold (np-Au) substrates as electrodes for bioelectrochemical applications is described. Robust np-Au electrodes were prepared by sputtering a gold–silver alloy onto a glass support and subsequent dealloying of the silver component. Alloy layers were prepared with either a uniform or nonuniform distribution of silver and, post dealloying, showed clear differences in morphology on characterization with scanning electron microscopy. Redox reactions under kinetic control, in particular measurement of the charge required to strip a gold oxide layer, provided the most accurate measurements of the total electrochemically addressable electrode surface area, Areal. Values of Areal up to 28 times that of the geometric electrode surface area, Ageo, were obtained. For diffusion-controlled reactions, overlapping diffusion zones betwee...

Metal versus rare-gas ion irradiation during Ti1−xAlxN film growth by hybrid high power pulsed magnetron/dc magnetron co-sputtering using synchronized pulsed substrate bias

Abstract: Metastable NaCl-structure Ti1-xAlxN is employed as a model system to probe the effects of metal versus rare-gas ion irradiation during film growth using reactive high-power pulsed magnetron sputter ...

Plasma generation source including belt-type magnet and thin film deposition system using this

Abstract: The present invention is a plasma generation source and a thing that is in its application and it is for getting high quality thin film by generating even high density plasma in high vacuum and like this plasma generation source applying like this plasma generation source to sputtering system, neutral particle beam source, thin film deposition system combining sputtering system and neutral particle beam source. According to the present invention, it generates plasma by using microwave through the microwave irradiating equipment and magnetic field by more than one pair of the belt type magnets and above goal can be accomplished maximizing plasma confinement effect by inducing electron returning trajectory in accordance with above continuous structure on belt type magnet.

Thermal conductivity of aluminium nitride thin films prepared by reactive magnetron sputtering

Abstract: The relationship between thermal conductivity and microstructures of aluminium nitride films is reported Films were deposited on silicon substrates by magnetron sputtering of a pure Al target in nitrogen argon plasma at low temperatures (<300 °C) with thickness ranging from 150 to 3500 nm Balanced and unbalanced magnetron configurations were used for different nitrogen contents in the gas phase Various microstructures were thus created and their thermal conductivity was measured with the transient hot strip technique Depending on the crystalline structure of the films, the bulk thermal conductivity of the AlN films at room temperature varied between 2 and 170 W m−1 K−1 Unbalanced magnetron allowed achieving highly dense (0 0 2) oriented AlN films with a grain size in the 100 nm range, a low oxygen content close to 05 at% and a resulting bulk thermal conductivity as high as 170 W m−1 K−1 Such a crystalline quality resulted from the ion energy involved in the growth process In contrast, balanced magnetron led to weakly textured AlN films containing 5 at% oxygen with a grain size in the 30 nm range and a resulting thermal conductivity ranging from 2 to 100 W m−1 K−1 depending on the microstructure Otherwise, the thermal boundary resistance between AlN films deposited by unbalanced magnetron and the silicon substrate was found to be as low as 10 × 10−8 K m2 W−1 Such a value was in good agreement with the thickness of the interfacial amorphous layer determined in the 2 nm range by high resolution transmission electron microscopy

Exploring the potential of high power impulse magnetron sputtering for growth of diamond-like carbon films

Abstract: Amorphous carbon films are deposited employing high power impulse magnetron sputtering (HiPIMS) at pulsing frequencies of 250 Hz and 1 kHz. Films are also deposited by direct current magnetron sputtering (dcMS), for reference. In both HiPIMS and dcMS cases, unipolar pulsed negative bias voltages up to 150 V are applied to the substrate to tune the energy of the positively charged ions that bombard the growing film. Plasma analysis reveals that HiPIMS leads to generation of a larger number of ions with larger average energies, as compared to dcMS. At the same time, the plasma composition is not affected, with Ar + ions being the dominant ionized species at all deposition conditions. Analysis of the film properties shows that HiPIMS allows for growth of amorphous carbon films with sp 3 bond fraction up to 45% and density up to 2.2 g cm − 3 . The corresponding values achieved by dcMS are 30% and 2.05 g cm − 3 , respectively. The larger fraction of sp 3 bonds and mass density found in films grown by HiPIMS are explained in light of the more intense ion irradiation provided by the HiPIMS discharge as compared to the dcMS one.

Plasma potential mapping of high power impulse magnetron sputtering discharges

Abstract: Pulsed emissive probe techniques have been used to determine the plasma potential distribution of high power impulse magnetron sputtering (HiPIMS) discharges. An unbalanced magnetron with a niobium target in argon was investigated for a pulse length of 100 μs at a pulse repetition rate of 100 Hz, giving a peak current of 170 A. The probe data were recorded with a time resolution of 20 ns and a spatial resolution of 1 mm. It is shown that the local plasma potential varies greatly in space and time. The lowest potential was found over the target’s racetrack, gradually reaching anode potential (ground) several centimeters away from the target. The magnetic presheath exhibits a funnel-shaped plasma potential resulting in an electric field which accelerates ions toward the racetrack. In certain regions and times, the potential exhibits weak local maxima which allow for ion acceleration to the substrate. Knowledge of the local E and static B fields lets us derive the electrons’ E×B drift velocity, which is abou...

Hysteresis-free deposition of niobium oxide films by HiPIMS using different pulse management strategies

Abstract: We systematically investigate the reactive behaviour of two types of high-power pulsed magnetron discharges above a Nb target using either square voltage pulses (denoted as HiPIMS) or custom-shaped pulses (denoted as MPPMS), and compare it with that of a dc magnetron sputtering (DCMS) discharge. We demonstrate that the surface metal oxides can be effectively sputter-eroded from the target during both HiPIMS and MPPMS pulses operated in reactive O2/Ar gas mixtures, and that sputtering from a partially oxide-free target is possible even at high oxygen concentrations. This results in a hysteresis-free deposition process which allows one to prepare optically transparent high refractive index Nb2O5 coatings exhibiting an elevated deposition rate without the need for feedback control commonly used in reactive DCMS. The cathode voltage was identified as the principal parameter that affects the reactive discharge behaviour.

Photovoltaic properties of the p-CuO/n-Si heterojunction prepared through reactive magnetron sputtering

Abstract: Films of p-CuO were deposited on glass and n-Si substrates through reactive magnetron sputtering. The influence of flow rate ratio of O2 to Ar on the structural and electrical properties of the CuO films was studied. By increasing the flow rate ratio, the hole concentration of the CuO films decreased while the mobility and resistivity increase. At a flow rate ratio of 0.5, the average crystal size, hole concentration, mobility, resistivity, and optical bandgap of the deposited p-CuO films are ∼8 nm, 2.76×1015 cm−3, 0.134 cm2/Vs, 0.217 Ωcm, and 1.07 eV, respectively. A p-CuO film/n-Si substrate heterojunction cell has been fabricated and has an open-circuit voltage of 0.33 V and short-circuit current density of 6.27 mA/cm2 under AM 1.5D illumination. The fill factor and energy conversion efficiency are 0.2 and 0.41%, respectively.

Thin-Film Piezoelectric Materials For a Better Energy Harvesting MEMS

Abstract: Ferroelectric PZT-based perovskite thin films are widely studied for fabrication of compact piezoelectric energy harvesting (EH) power microelectromechanical systems (MEMS) due to their large piezoelectric coefficients. Output energy of the piezoelectric EH power MEMS is chiefly governed by their energy conversion rate, κ2 and/or (e2/e), where e and e denote their piezoelectric coefficient and dielectric constant. The values of (e2/e) are considered as figures of merit (FOM) for the piezoelectric EH power MEMS. At present nonferroelectric AlN thin films are considered as a candidate for a better piezoelectric EH power MEMS due to their high FOM values. These PZT-based thin films are mostly polycrystalline thin films of binary perovskite compounds, Pb(Zr, Ti)O3 (PZT). We have proposed single crystal thin films of PZT-based ternary perovskite compounds, Pb(Mn,Nb)O3-PZT (PMnN-PZT), instead of the binary perovskite PZT. The single crystal PMnN-PZT thin films have been successively fabricated by rf-magnetron sputtering. It is found that the FOM values of single c-domain/single crystal PMnN-PZT thin films are one order of magnitude higher than those of AlN thin films. This suggests output powers of the PMnN-PZT thin-film EH power MEMS are one order of magnitude higher than those of the AlN thin-film EH power MEMS.