Sputtering Of Silicon Research Articles

Synergistic Effect of He for the Fabrication of Ne and Ar Gas-Charged Silicon Thin Films as Solid Targets for Spectroscopic Studies.

Sputtering of silicon in a He magnetron discharge (MS) has been reported as a bottom-up procedure to obtain He-charged silicon films (i.e., He nanobubbles encapsulated in a silicon matrix). The incorporation of heavier noble gases is demonstrated in this work with a synergistic effect, producing increased Ne and Ar incorporations when using He-Ne and He-Ar gas mixtures in the MS process. Microstructural and chemical characterizations are reported using ion beam analysis (IBA) and scanning and transmission electron microscopies (SEM and TEM). In addition to gas incorporation, He promotes the formation of larger nanobubbles. In the case of Ne, high-resolution X-ray photoelectron and absorption spectroscopies (XPS and XAS) are reported, with remarkable dependence of the Ne 1s photoemission and the Ne K-edge absorption on the nanobubble's size and composition. The gas (He, Ne and Ar)-charged thin films are proposed as "solid" targets for the characterization of spectroscopic properties of noble gases in a confined state without the need for cryogenics or high-pressure anvils devices. Also, their use as targets for nuclear reaction studies is foreseen.

Surface composition driven rippling of oblique Ar+ irradiated SiC/Si(111) thin films

Oblique ion beam patterned and structured thin films hold promise as an advanced material for applications to photonics, micro- to nano-electronics, electro-optical and electrochemical devices fabrication. Herein, for the first time, we report the fabrication of patterned and structured SiC thin films over Si(111) by obliquely incident Ar+ beam. We show that at a short time scale, carbon clusters possessing nano-dimensional size evolve while ripple structures with direction parallel to the ion beam projection emerge at later time scales. The roughness evolution plot follows exponential and power law scaling at low and high bombarding time (in terms of ion fluence). The underlying mechanism is the altered surface layer composition due to the non-stoichiometric sputtering of silicon and carbon. The optical bands corresponding to silicon carbide (3.27–4.23 eV) & silicon (1.15–1.45 eV) co-exist for lower argon ion fluences while optical bands of silicon (1.15- 1.45 eV) remains and silicon carbide vanishes for higher argon ion fluences. Our experimental findings demonstrated the fabrication of ripple patterns over radiation tolerant, thermally and physically stable SiC by large area irradiation and capability to tailor the temporal characteristics of these evolved structures.

Direct Current Sputtering Deposition of the Metallic Ceramic Ti3SiC2 Thin Film with Improved Hydrophobicity and Reduced Surface Energy

Metallic ceramic compounds, such as Ti3SiC2, are innovative materials that combine the properties of metals and ceramics. However, most methods used in synthesizing these materials employ high deposition temperatures. Hence, in this work, Ti3SiC2 thin film was prepared and deposited on a steel sample without heating or biasing using a magnetized sheet plasma source. The synthesis was carried out by sputtering titanium, silicon, and graphite targets with Ar plasma at different deposition times of 60, 90, and 120 minutes. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) scans of the samples confirmed the synthesis of the desired compound. Moreover, the wettability and surface energy properties of the coated substrate were calculated by contact angle measurements. Results showed that as the deposition time increased, the coated substrate became more hydrophobic. Indeed, these findings show that Ti3SiC2 deposited steel substrate, with its increased hydrophobicity, is a potential self-cleaning coating for industrial tools.

Microstructural characterization and thermal stability of He charged amorphous silicon films prepared by magnetron sputtering in helium

Sputtering of silicon in a Helium magnetron discharge has been reported as a bottom-up procedure to obtain amorphous Si films containing high amounts of gas-filled nanopores. Here we compare the microstructure and composition of Si–He nanocomposite films deposited by magnetron sputtering (MS) with 4He in DC or RF and 3He in RF operation modes. Electron microscopy (SEM and TEM), X-ray diffraction (XRD) and ion beam analysis (IBA) have been used to analyze the films and to investigate the in-situ and ex-situ thermal evolution. Depending on deposition conditions different in depth compositions, nanopore size and shape distributions, porosity and He content could be obtained. The presence of impurities (i.e. oxygen) has shown to promote He diffusivity reducing He accumulation. The start temperature of He-release varied in the range 473–723 K without films crystallization. Films grown in RF mode reached contents of 32 and 29 at% of 4He and 3He and were respectively stable up to 573 and 723 K both in vacuum and under inert gas flow. In-situ p-EBS (proton Elastic Back Scattering) allowed monitoring the He release accompanied by blistering/delamination effects visualized by SEM. These results show the potentiality of annealing to hold nano-porous structures after liberation of trapped gas.

Ripple pattern formation on silicon carbide surfaces by low-energy ion-beam erosion

A versatile experimental facility air insulated high current medium energy 200 kV Ion Accelerator, with the terminal voltage in the range of 30-200 kV has been running successfully at Ion Beam Centre, KUK for carry out multifarious experiments in material science and surface physics. This system offers single charge state, switching magnet with five exit ports and large area irradiation/implantation using hollow cathode ion source. Ion beam induced structures on the surfaces of semiconductors have potential applications in photonics, magnetic devices, photovoltaics, and surface-wetting tailoring etc. In this regard, silicon carbide (SiC) is a fascinating wide-band gap semiconductor for high-temperature, high-power and high-frequency applications. In this work, fabrication of ripple patterns is carried out on the SiC surfaces using 80 keV Ar+ ion beam for different fluences at oblique incidence of 500. AFM study demonstrates that ripple wavelength and amplitude, ordering and homogeneity of these patterns vary linearly with argon ion fluence. The formation of such surface structures is attributed to the preferential sputtering of silicon in comparison to carbon. The evolution of high degrees of order is explained with the help of existing formalisms of coupling between surface topography and preferential sputtering.

Influence of water contamination on the sputtering of silicon with low-energy argon ions investigated by molecular dynamics simulations.

Focused ion beams (FIB) are a common tool in nanotechnology for surface analysis, sample preparation for electron microscopy and atom probe tomography, surface patterning, nanolithography, nanomachining, and nanoprinting. For many of these applications, a precise control of ion-beam-induced processes is essential. The effect of contaminations on these processes has not been thoroughly explored but can often be substantial, especially for ultralow impact energies in the sub-keV range. In this paper we investigate by molecular dynamics (MD) simulations how one of the most commonly found residual contaminations in vacuum chambers (i.e., water adsorbed on a silicon surface) influences sputtering by 100 eV argon ions. The incidence angle was changed from normal incidence to close to grazing incidence. For the simulation conditions used in this work, the adsorption of water favours the formation of defects in silicon by mixing hydrogen and oxygen atoms into the substrate. The sputtering yield of silicon is not significantly changed by the contamination, but the fraction of hydrogen and oxygen atoms that is sputtered largely depends on the incidence angle. This fraction is the largest for incidence angles between 70 and 80° defined with respect to the sample surface. Overall, it changes from 25% to 65%.

Study of the topography of silicon surface evolution under irradiation by a gallium ion beam

The silicon surface was irradiated with 30 keV gallium ion beam at incidence angles from 0 to 50° and fluences from 6·1016 to 5·1018 cm−2. Surface topography was investigated by scanning electron microscopy. It was found that one of four types of a relief can be formed on the silicon surface depending on the ion beam incidence angle and these fluences. Pattern formation starts with fluences of ∼2·1017 cm−2. The peculiarities of a relief evolution can be explained by the angular dependences of silicon sputtering with gallium ion beam and the possible existence of implanted gallium in the near-surface layer in the form of precipitates.

Study of silicon dioxide focused ion beam sputtering using electron microscopy imaging and level set simulation

Sputtering silicon dioxide by the ion beam of gallium ions was studied to obtain the angular dependence of the sputtering yield and estimate the secondary sputtering yield of the redeposited material. For this purpose, rectangular boxes were formed in the SiO2 layer at different incidence angles of the ion beam. The box depths and the distributions of gallium atoms were estimated using the cross-sectional specimens examined by scanning and transmission electron microscopy techniques. The found depth values enabled calculating the sputtering yield angular dependence which was approximated using well-known fitting formulas. It was also demonstrated that for an incidence angle varied from approximately 40°–70° ripple topography is formed on the ion bombarded silicon dioxide. To validate the obtained data characterizing SiO2 sputtering, test symmetrical and asymmetric structures with different aspect ratios were experimentally prepared and simulated using the level set method taking into account the redeposition effect and reflection of incident ions from the sputtered surface. It was established that the performed simulation provides sufficient accuracy in predicting the shape of the focused ion beam fabricated structures in silicon dioxide.

Nonlinear effects in the sputtering of gallium arsenide and silicon by bismuth cluster ions

An experimental study on the influence of the energy and the number of atoms in the bombarding ions Bin+ (n=1-4) on the sputter yield of GaAs was carried out. It was shown that the specific sputter yield Ysp non-additively increases with increasing n and specific kinetic energy Esp per an atom in the bombarding ion, and the efficiency of energy transfer from bombarding ions to target atoms also increases with increasing n. A comparison was made with the previously obtained results for Si targets. Keywords: ion sputtering, non-additivity factor, cluster ions, bismuth.

Electrical and Optical Characterization of Non-Hydrogenated a-Si/c-Si Heterojunction Solar Cells

This work deals with the performance of a heterojunction with intrinsic thin layer solar cell by sputtering silicon on p-type crystalline silicon substrate in argon ambient without hydrogen addition. This first effort was an attempt to use cost-effective means to convert light into electricity and to find fabrication processes which use fewer and cheaper materials for the fabrication of solar cells. Since transport mechanisms of amorphous silicon/crystalline silicon heterojunctions are still under investigation, the aim is to examine the behavior of the fabricated samples under electrical and optical constraints. Initial cell characterization includes electrical behavior via current-voltage characteristics and optical investigation via reflectance and absorptance measurements. Results are analyzed in a tentative to follow the absorption, generation and collection processes in the fabricated cell. The heterojunction interface is found to be a limiting factor in the cell performance. Under sun illumination, the open circuit voltage was 140 mV, the short circuit current was of 6 µA and the fill factor was of 42.56 %. Dark current-voltage characteristics indicated a tunneling and/or recombination carrier transport mechanism, while aborptance/reflectance measurements showed a generation process occurring in most in the crystalline silicon-side of the amorphous/crystalline silicon heterojunction. A carrier collection limitation is a very probable origin of the decreased cell generated current.

Ripple patterns over oblique Ar+ sputtered SiC/Si(1 1 1) surfaces: Role of preferential sputtering

Controlled surface structuring of amorphous silicon carbide (a-SiC) thin films as grown on silicon substrates Si(111) by Radio Frequency (RF) sputtering and irradiation of obliquely incident 80 keV Ar+ ion beam has been investigated. Sub-wavelength ripple patterns with wave-vector parallel to the ion beam projection are found to evolve on argon sputtered surfaces. Studies reveal that the temporal parameters such as ripple wavelength and amplitude, ordering and homogeneity of these patterns vary non-linearly with argon ion fluence. The formation of such surface structures is attributed to the preferential sputtering of silicon in comparison to carbon. Our results reveal that ion irradiation can be exploited to fabricate controlled surface nanostructures by optimizing the irradiation parameters.

Photoluminescence and Stability of Sputtered SiOx Layers

SiOx layers with thicknesses of about 300–1000 nm are produced by sputtering silicon onto glass and quartz substrates. Silicon is oxidized during deposition, and the refractive index of the sputtered layers vary from 1.63 to 1.86. Oxygen atomic concentration in SiOx is in the range of . Photoluminescence of SiOx layers is observed and assumed to originate from silicon nanocrystals embedded in a SiOx matrix that is formed after thermal treatment by a Xe flash‐lamp. A layer on quartz substrate exhibits the strongest emission and shows Raman spectral peak at 507 , which is smaller than the value of 521 of bulk silicon crystal. Based on this difference, the size of silicon nanocrystals is estimated to be equal to 1.2 nm. The photoluminescence spectrum consists of overlapping Gaussian functions indicating the size distribution of the silicon nanocrystals. Mean silicon nanocrystals size in the layer on a quartz substrate is estimated at 1.4 nm from the photoluminescence peak datasets reported in previous researches. Thus, sputtering of silicon in a low‐pressure air and subsequent flash‐heating seems to be a convenient method to produce silicon nanocrystals in SiOx layers. These could be useful to realize Si‐LEDs or even silicon lasers. In addition, the aging of SiOx layers during 6 months is evaluated.

6-Phenylhexyl silane derivatized, sputtered silicon solid phase microextraction fiber for the parts-per-trillion detection of polyaromatic hydrocarbons in water and baby formula.

We report the fabrication of 6-phenylhexylsilane derivatized, sputtered silicon, solid phase microextraction fibers that show parts per trillion detection limits for polyaromatic hydrocarbons, and negligible carry over and phase bleed. Their fabrication involves sputtering silicon on silica fibers under various conditions. Six different fibers were evaluated by generating three different thicknesses of sputtered silicon at two different throw distances, which altered the morphologies of the silicon surfaces. All of the fibers were coated with similar thicknesses of 6-phenylhexylsilane (ca. 2nm). These fibers were characterized with multiple analytical techniques. The optimum fiber configuration was then used to analyze polyaromatic hydrocarbons via direct immersion, gas chromatography mass spectrometry. Our best fiber for the extraction of low molecular weight polyaromatic hydrocarbons in water had similar performance to that of a commercial fiber. However, our fiber demonstrated ca. 3 times the extraction efficiency for higher molecular weight polyaromatic hydrocarbons. In addition, it outperformed the commercial fiber by showing better linearity, repeatability, and detection limits. A method for analyzing polyaromatic hydrocarbons in baby formula was developed, which showed very good linearity (0.5-125 ppb), repeatability (2-26%), detection limits (0.12-0.81 ppb), and recoveries (103-135%). In addition, our fiber showed much less (negligible) carry over and phase bleed than the commercially available fibers.

Effects of silica sputtering on adhesion between zirconia and composite resin cores.

Radiofrequency magnetron sputtering of silicon was applied onto zirconia surfaces by use of a non-doped Si wafer at 2%, 5%, 8%, and 10% oxygen volumes. Immediately after sputtering, the contact angle was practically 0 for all oxygen volume specimens. In terms of sustainability of the hydrophilicity, however, 5% oxygen volume was found to be optimal. Scanning electron microscopy and energy dispersive X-ray spectroscopy clearly suggested the presence of silica layer on zirconia surfaces. The shear bond strength of the pre-treated zirconia and resin was 35.03±4.97 MPa, which was approximately 3.5 times higher than that of zirconia without any sputtering treatment (9.26±1.21 MPa). The failure mode of the pre-treated zirconia specimen was cohesive failure, whereas that of the control specimen was observed to be interface failure.

Sputtering of silicon by atomic and cluster bismuth ions: An influence of projectile nuclearity and specific kinetic energy on the sputter yield

An influence of the specific kinetic energy Esp and nuclearity n of Bin+ (n = 1–4) projectiles on the sputter yield of Si was studied by means of the volume loss method. It was found that the specific sputter yield Ysp exhibited non-additive increase with an increasing of n and Esp values. As a non-additivity k-factor, the slope of the straight line approximating Ysp(n) dependences at the same specific energy was proposed to use. For Bin+ (n = 1–4) projectiles at Esp = 10 keV at−1 the k-factor was equal to 0.41 ± 0.08. In addition, it was ascertained that the efficiency of energy transfer from projectiles to target atoms increased with an increase in the projectile nuclearity, e.g., it was 2.8 times greater for Bi3+ bombarding ions as compared with Bi+ ones.

ВПЛИВ ЛОКАЛЬНИХ МЕХАНІЧНИХ НАПРУЖЕНЬ НА КОЕФІЦІЄНТ РОЗПИЛЕННЯ КРЕМНІЮ ІОННИМ ПУЧКОМ

A review of scientific publications and modeling of the effect of mechanical stresses on the sputtering yield of silicon by an ion beam is carried out. It is shown that the flux of atoms (from the depth to the surface) through interstitial or vacancy mechanisms due to the stress gradient caused by the limiting bending of the plate is insufficient to explain the increase in the sputtering coefficient. Calculations show that even the limiting elastic deformations do not significantly change the energy of atom detachment from the site, and an increase in the drift velocity of atoms due to the enrichment of the near-surface region with vacancies is insufficient to increase the sputtering rate. Consequently, it is necessary that the elastic deformation is transformed into plastic with the formation of mobile weakly bound atoms. The calculated stress distribution in a loaded silicon wafer using the COMSOL Multiphysics software package showed that the key driving force behind the increase in the silicon sputtering coefficient is the concentration of compressive and tensile stresses in the vicinity of the simulated crater during sputtering. The created crater is a stress concentrator, the gradients of which significantly exceed the values obtained by bending a plate without a crater. It is demonstrated that the generated stresses exceed the ultimate strength of the material in the vicinity of the crater, which begins to relax due to the expulsion of "excess" atoms in the tension region. The appearance of additional deformation-stimulated fluxes of weakly bound surface atoms at the bottom and walls of the crater provides an increase in the concentration of knocked-out atoms in the process of ion sputtering. Simulations predict an increase in sputtering yield of up to 40%. It is also shown that closely spaced craters, due to elastic interaction with each other, compensate each other's elastic fields, which has an effect on the value of the sputtering coefficient.

Influence of Surface Curvature on Silicon Sputtering by Low-Energy Ar Ions

Molecular dynamics (MD) method was used to study 200 eV Ar ion impact on silicon nanoparticles of various sizes . Based on the MD simulations, the analysis of sputtering mechanisms and differences in the ion energy deposition which are determined by the curvature of the target surface, is performed in the paper.

Angular Dependences of Silicon Sputtering by Gallium Focused Ion Beam

Angular dependences of the surface layer composition and the sputtering yield of silicon upon irradiation of the surface with a focused beam of gallium ions with an energy of 30 keV are obtained. The surface composition is analyzed by scanning Auger electron spectroscopy (SAES) and secondary ion mass spectrometry (SIMS). The sputtering yields are determined by measuring the volume of sputtering craters and irradiation doses. It is found that the content of gallium in the surface layer is about 30 at % with incidence angles close to the normal. With incidence angles greater than 30°, the concentration of gallium decreases quite sharply. The angular dependence of the sputtering yield of silicon does not correlate with the content of gallium in the surface layer and is rather well described by the cascade sputtering mechanism proposed by P. Sigmund.

Magnetron Sputtered Silicon Coatings as Oxidation Protection for Mo‐Based Alloys

Mo‐based alloys with solidus temperatures around and above 2000 °C are attractive high‐temperature structural materials for future applications in the hot section of gas turbines. However, their oxidation behavior is poor due to pesting starting at 600 °C and nonprotective oxide growth at temperatures above 1000 °C. To ensure a sufficient oxidation resistance over a wide temperature range, protective coatings become inevitable. Herein, silicon coatings have been applied by magnetron sputtering on Mo‐9Si‐8B and on titan–zirconium–molybdenum alloy (TZM). The coating architecture is designed to minimize the intercolumnar gaps and porosity, thereby increasing the density. Specimens are tested at 800 and 1200 °C in air isothermally for up to 300 h. The focus is put on the chemical reactions at the coating–substrate interface, the phase formation, and the evolution of the thermally grown oxide. An initially globular SiO2 evolves into a uniform SiO2 layer providing excellent oxidation protection. The investigations reveal a rather slow interdiffusion between the coating and the alloys when tested in air. At the coating–substrate interface exclusively, the Mo3Si phase develops. Finally, the phase formation at the coating–substrate interface is studied in detail for various heat treatments in air and vacuum.

Properties of secondary particles for ion beam sputtering of silicon using low-energy oxygen ions

The properties of secondary particles for sputtering silicon with primary low-energy oxygen ions were investigated with dependence on the primary ion energy Eion and geometric parameters (ion incidence angle, polar emission angle, and scattering angle). The mass and energy distributions of the secondary particles were measured by energy-selective mass spectrometry. The experimental results were compared with simulations using the Monte Carlo code sdtrimsp and with calculations based on a simple elastic binary collision model. The main secondary ion species were found to be O+, O2+, Si+, and SiO+. Their energy distribution functions depend on the primary ion energy Eion and the scattering angle γ. For O+, Si+, and SiO+ ions, a decreasing scattering angle γ or an increasing primary ion energy Eion leads to a pronounced feature in the high-energy part of the distributions. The energy distributions of the secondary O2+ ions show hardly any changes with regard to the primary ion energy or the scattering angle γ. In the case of the O+ ions, the energy distribution appears to reflect several direct scattering channels, which could be associated with the primary ion energy Eion, and half of the ion energy Eion/2. The present experimental results are compared with previous investigations for the sputtering of Si with the noble gas ions, such as Ne+, Ar+, and Xe+.