Silicon Carbide Thin Films Research Articles

Tailoring of magnetic phase: Co-doped SiC thin films grown by RF sputtering

In the present work, we investigate the influence of cobalt (Co) doping on the structural and magnetic properties of cobalt-doped silicon carbide (Co-SiC) thin films. The films were fabricated using DC/RF magnetron sputtering technique on Si (100) substrates at a temperature of 1200°C, with varying Co concentrations ranging from 5 to 16 at. (at%. X-ray diffraction (XRD) analysis unveiled the co-existence of CoSi2 and SiC phases in all the thin films. Surface morphological study through atomic force microscopy (AFM) revealed the densely packed nature of the films. Field emission scanning electron microscopy (FE-SEM) study showed that particles are uniformly distributed at the surface of the substrate. According to UV measurements, the films have high transmittance in the visible range, and as Co concentration rises, transmittance decreases. A magnetic phase transition from superparamagnetic to ferromagnetic behavior occurred with Co content surpassing 8 at% in the SiC thin films. Moreover, an increase in coercivity was observed from 38 Oe to 316 Oe as the doping concentration increased from 10 to 16 at%. This study represents an exploration into the induction of ferromagnetism through moderate Co doping in SiC thin films.

Investigation of amorphous-SiC thin film deposition by RF magnetron sputtering for optical applications

Silicon carbide (SiC) is a rapidly emerging material for photonic applications, thanks to its exceptional optical properties. To be used as a waveguide, SiC thin films must be deposited directly on silica at low temperature. Amorphous SiC films were deposited by RF magnetron sputtering using a single source of high-purity polycrystalline SiC. A systematic study of the chemical, structural and optical properties of the films was carried out, using a combination of XRD, XPS, SIMS, spectroscopic ellipsometry, Raman spectroscopy and UV–Vis absorption spectroscopy. The aim was to link deposition conditions to film properties. By exploring a three-parameter space (RF power, substrate temperature, pressure), we have demonstrated that RF power is the main parameter which controls the entire deposition process and film properties. By simply adjusting the RF plasma power between 150 and 450 W, it is possible to adjust the refractive index at a wavelength of 1.5 μm in the range 2.50–2.75 and vary the bandgap from 2.5 to 1.7 eV. This is attributed to a slight variation in film composition, particularly in terms of Si/C ratio and C–C bond concentration.

Synthesis of silicon carbide thin film as a source for white light emission

Synthesis of doped silicon carbide (SiC) thin film on silicon (111) wafer was carried out employing chemical vapour deposition (CVD) technique using boron-doped liquid polycarbosilane (LPCS) as polymer precursor under inert atmosphere of argon and nitrogen gas. The present study investigated the physical and optical properties of fabricated SiC thin films by varying doping concentrations. Subsequent analysis of bonds and phases by Fourier transform infrared (FTIR) spectroscopy, micro-Raman spectroscopy and X-ray diffraction (XRD) affirm the formation of Si–C, Si–N and unique silicon carbonitride (SiC–N). Stable photoluminescence has been observed across the entire visible spectra with enhanced quantum efficiency and lifetime, which ensures its application in opto-electronic devices such as LED.

Investigations of In2O3 Added SiC Semiconductive Thin Films and Manufacture of a Heterojunction Diode

This study involved direct doping of In2O3 into silicon carbide (SiC) powder, resulting in 8.0 at% In-doped SiC powder. Subsequently, heating at 500 °C was performed to form a target, followed by the utilization of electron beam (e-beam) technology to deposit the In-doped SiC thin films with the thickness of approximately 189.8 nm. The first breakthrough of this research was the successful deposition of using e-beam technology. The second breakthrough involved utilizing various tools to analyze the physical and electrical properties of In-doped SiC thin films. Hall effect measurement was used to measure the resistivity, mobility, and carrier concentration and confirm its n-type semiconductor nature. The uniform dispersion of In ions in SiC was as confirmed by electron microscopy energy-dispersive spectroscopy and secondary ion mass spectrometry analyses. The Tauc Plot method was employed to determine the Eg values of pure SiC and In-doped SiC thin films. Semiconductor parameter analyzer was used to measure the conductivity and the I-V characteristics of devices in In-doped SiC thin films. Furthermore, the third finding demonstrated that In2O3-doped SiC thin films exhibited remarkable current density. X-ray photoelectron spectroscopy and Gaussian-resolved spectra further confirmed a significant relationship between conductivity and oxygen vacancy concentration. Lastly, depositing these In-doped SiC thin films onto p-type silicon substrates etched with buffered oxide etchant resulted in the formation of heterojunction p-n junction. This junction exhibited the rectifying characteristics of a diode, with sample current values in the vicinity of 102 mA, breakdown voltage at approximately −5.23 V, and open-circuit voltage around 1.56 V. This underscores the potential of In-doped SiC thin films for various semiconductor devices.

High-performance self-biased Cu/SiC/Si photo-sensor with swift response for NIR/Vis photodetection

Silicon Carbide (SiC) shows great potential for use in high temperatures and harsh environments due to its promising physical properties. This report introduces a novel double depletion functional heterointerface comprising a multilayer structure of Cu/SiC/Si. High-quality nanocrystalline SiC thin films are fabricated on p-type Silicon (Si) by RF magnetron sputtering at a relatively low temperature of 900 °C as compared to conventional methods. A multilayer photo-sensor device, comprising Cu/SiC/Si layers, is fabricated through the thermal evaporation of Cu metal using a shadow mask. The device exhibits good photo-response at both 750 nm and 440 nm wavelengths. Both the junctions Cu/SiC and SiC/Si play role in generating electron-hole pairs along the depth of the device. The device exhibits a very high responsivity of 1.26 A/W and a rapid response of 94/137 ms at a wavelength of 750 nm at self-bias conditions. It also demonstrates a high responsivity of 0.46 A/W and a very fast response time of 66.8/66.4 ms for 440 nm wavelength. Owing to its impressive performance, this device distinguishes itself as a superior choice among state-of-the-art SiC-based photodetectors. Its significance lies in the robust stability of the SiC/Si junction in high-temperature settings, surpassing low bandgap materials for NIR/vis photodetectors.

Influence of the substrate conductivity type on the electroluminescence properties of PP+IN and PIN+N diodes based on amorphous silicon carbide (a-Si1-xCx:H) / crystalline silicon (c-Si) heterostructures

The study of the conduction and light emission mechanisms of PIN diodes based on amorphous silicon-carbide (a-Si1-xCx:H) thin film and crystalline silicon (c-Si) substrates is reported in this work. Using the same low-temperature process (200 °C), PP+IN and PIN+N structures were fabricated on p-type and n-type silicon (Si) substrates, respectively. The plasma enhanced chemical vapor deposition (PECVD) technique was employed for the active layers deposition where two different CH4/SiH4 flow rates ratios of 30 sccm/6 sccm and 30 sccm/1 sccm were used. All structures show red-orange light emission in forward bias (FB). The structures with the active layer deposited with a lower SiH4 flow rate, display light emission with a higher intensity at a lower voltage bias.In addition, we related the current-voltage measurements with different conduction models and the dominant charge transport mechanisms in the PIN structures were proposed. The highest Si content structures were related to Fowler-Nordheim (F-N) tunneling, because of its active layer with lower barrier height. On the other hand, the lowest Si content structures were associated with the Poole-Frenkel (P-F) emission, due to a higher density of defects in localized tail states. The results showed the same conduction and emission mechanisms for the PP+IN and PIN+N diodes with the same active layer, regardless of the conduction type of substrate, proving that it is feasible to use the same process for developing light emission devices on p-type and n-type Si substrates.

Fabrication of highly conductive phosphorous-doped nc-SiCx:H thin film on PET

Plasma enhanced chemical vapor deposition (PECVD) method has been utilized to fabricate phosphorous-doped hydrogenated nanocrystalline silicon carbide (P-doped nc-SiCx:H) thin films on polyethylene terephthalate (PET) substrate. With the aim at obtaining highly conductive thin films, H2/Ar mixed dilution has been applied for creating plasma during deposition, and the variation of structural, electrical and optical properties with H2/Ar flow ratio RH have been systemically investigated through a series of characterizations. Results show that the highly crystallized P-doped nc-SiCx:H thin film can be prepared while the properties are controllable through adjusting RH. In the case of RH = 0.75, the maximum dark conductivity (6.42 S cm−1) and a wide optical bandgap (1.93 eV) are attained. Finally, detail discussion has been made to illustrate the growth mechanism of the flexible P-doped nc-SiCx:H thin films.

Effect of surface morphology on optical properties of two multilayer structures CuO/ZnO/SiC and Al2O3/ZnO/SiC

Zinc oxide (ZnO) and Silicon carbide (SiC) thin films demonstrate unique properties such as high electron mobility, thermal stability, good chemical resistance, and low cost made them good candidates for optical applications. Moreover, semiconductors absorb short wavelengths of light due to the presence of a band gap. This work’s purpose is to study the effect of deposited ZnO and SiC thin films by physical vapor deposition (PVD) above two different oxides and substrates. Copper (Cu) with copper oxide (CuO) and aluminum (Al) with aluminum oxide (Al2O3) were the used substrates and oxides. After deposition of thin films, two different multilayer structures were resulted, which are CuO/ZnO/SiC and Al2O3/ZnO/SiC. Microstructure and morphology were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). Structure and phases identification were examined by X-ray diffraction (XRD). Optical properties (absorbance and emittance) before and after depositions of thin films were measured by spectrophotometer and Fourier transform infrared spectroscopy (FTIR). The results showed that the CuO/ZnO/SiC structure (85%) had higher absorbance than Al2O3/ZnO/SiC structure, however Al2O3/ZnO/SiC showed higher selectivity (absorbance/emittance (α/ε)) of about 0.65/0.15, compared to 0.85/0.5 for CuO/ZnO/SiC multilayer structure. The effect of surface topography and roughness on the efficiency of each multilayer structure has been studied.

Evaluation of equi‐biaxial strength of thin sic coatings using ring‐on‐ring testing and digital image correlation

AbstractTo assess the strength of coatings under multi‐axial stress conditions, a method was developed to evaluate the biaxial strength of thin silicon carbide (SiC) coatings using a ring‐on‐ring test. A graphite substrate was used as an intermediary to transmit stress from the load ring to the coated specimen, and the thin coating was subjected to a uniform equi‐biaxial stress. The strain in the thin film was continuously monitored using digital image correlation, allowing the identification of the time at which and when the initial crack occurred; the stress applied to the loading area at time was determined to be the fracture strength of the thin SiC films. The obtained fracture strength ranged from 209 to 1014 MPa and was dependent on specimen volume. Notably, the thinnest specimen exhibited the highest strength, whereas the strengths of thicker specimens approached previously reported bulk strengths.

Study of optical and passivation properties of hydrogenated silicon carbide thin films deposited by reactive magnetron sputtering for c-Si solar cell application

In this paper, optical and passivating properties of hydrogenated silicon carbide synthesized by reactive magnetron sputtering for c-Si solar cell application were studied. SiC:H films were synthesized by sputtering a SiC target in an argon-hydrogen ambient at a Radio Frequency (RF) power of 100–250 W. The thickness, density, and roughness of the films were measured by X-ray reflectometry. The optical properties of the films were studied by UV–visible spectroscopy. It is shown that with an increase in RF power, the refractive index increases from 1.53 to 2.32 (at λ = 633 nm), and the extinction coefficient does not exceed 0.009 in most of the visible and near-IR spectrum. Based on the measured optical constants using computer simulation the optimal thicknesses were calculated to maximize antireflection effect. IR spectroscopy showed correlation between the structure and physical properties of the films. It has been established that, at a lower RF power (100–150 W), particles are deposited instead of atoms. This leads to the formation of voids at the particle boundaries, which are subsequently filled with oxygen. Using the non-contact microwave photoconductance decay method, it was shown that the maximum effective lifetime (τeff) is achieved at RF power of 250 W. In addition, influence of preliminary surface cleaning procedure and post-annealing in vacuum on the τeff was considered.

Mesoporous SiC-Based Photocatalytic Membranes and Coatings for Water Treatment.

Photocatalytically active silicon carbide (SiC)-based mesoporous layers (pore sizes between 5 and 30 nm) were synthesized from preceramic polymers (polymer-derived ceramic route) on the surface and inside the pores of conventional macroporous α-alumina supports. The hybrid membrane system obtained, coupling the separation and photocatalytical properties of SiC thin films, was characterized by different static and dynamic techniques, including gas and liquid permeation measurements. The photocatalytic activity was evaluated by considering the degradation efficiency of a model organic pollutant (methylene blue, MB) under UV light irradiation in both diffusion and permeation modes using SiC-coated macroporous supports. Specific degradation rates of 1.58 × 10-8 mol s-1 m-2 and 7.5 × 10-9 mol s-1 m-2 were obtained in diffusion and permeation modes, respectively. The performance of the new SiC/α-Al2O3 materials compares favorably to conventional TiO2-based photocatalytic membranes, taking advantage of the attractive physicochemical properties of SiC. The developed synthesis strategy yielded original photocatalytic SiC/α-Al2O3 composites with the possibility to couple the ultrafiltration SiC membrane top-layer with the SiC-functionalized (photocatalytic) macroporous support. Such SiC-based materials and their rational associations on porous supports offer promising potential for the development of efficient photocatalytic membrane reactors and contactors for the continuous treatment of polluted waters.

Study of the annealing effect in optical properties for phosphorus-doped a-Si x C1− x :H films deposited by PECVD

The optical properties of phosphorus-doped hydrogenated amorphous silicon carbide (P-doped a-Si x C1−x :H) thin films are studied. Films were deposited by plasma-enhanced chemical vapor deposition at 110 kHz of frequency and pressure of 1.5 Torr, with silane (SiH4) and methane (CH4) as precursor gases. Hydrogen (H2) and phosphine (PH3) were used as diluent and dopant gases, respectively. The impact of the gases flow rate and thermal annealing on the optical properties is evaluated. A concordance is observed between the atomic content of Si, C, and P in films, determined by Energy Dispersive X-ray Spectroscopy, as gases flow rate increases. The composition of the films is established by identifying the vibrational bonding modes using Fourier transform infrared spectroscopy measurements. Si−H, Si−C, and C−H bonds were identified and their density was obtained. Characterization with UV–Vis spectroscopy shows that the optical band gap (E gopt), oscillation energy (Eo ), Urbach energy (EU ), and iso-absorption energy (E 04) increase with the doping level but decrease with the annealing treatment. However, values of dispersion energy (Ed ), dielectric constant (ϵ) and the refractive index (n) generally become smaller as the phosphorus and carbon content grows, but with a tendency to fall during the annealing. The refractive index by UV–Vis is compared with measurements made with ellipsometry, resulting in a similarity between both techniques. High values of E gopt obtained in P-doped a-Si x C1−x :H films can be related to better values of the temperature coefficient of resistance for flow sensor applications.

Opto-electrical properties of amorphous silicon carbide thin films adjustably prepared by magnetron sputtering at room temperature

The application of silicon carbide (SiC) thin films is extensive, and they can be prepared at room temperature using magnetron sputtering. In this study, a wide range of deposition pressures (0.5–5.5 Pa) was utilized for the sputtering of amorphous SiC thin films. With an increase in deposition pressure, not only does the oxygen content increase, but also the carbon phase changes. The oxygen ratio increases from approximately 6.8% to 20.0% as the deposition pressure rises from 0.5 Pa to 1.5 Pa, and it gradually increases further to around 25.0% as the deposition pressure rises to 5.5 Pa. When the deposition pressure is>3.0 Pa, the amorphous carbon phase transforms into diamond-like and graphite-like carbons. As a result, the optical bandgap varies from about 1.7 eV to 3.6 eV with the change in deposition pressure, while the conductivity reduces from 2.5 × 10-4 S/cm to 1.3 × 10-8 S/cm. This study provides insights into the significant impact of high deposition pressure on the material properties of sputtered SiC thin films. It demonstrates that the chemical bonding, composition, and opto-electrical properties of SiC thin films can be effectively tailored for application in optoelectronic devices.

Structural properties and optical modeling of thermally annealed silicon carbide thin films

Non–hydrogenated amorphous silicon carbide films were processed by electron beam-physical vapour deposition on c-Si (100) and glass substrates. The films were isochronally annealed at varying temperatures. FTIR and Raman spectroscopies as well as XRD studies were used for structural investigation. For the pristine sample, it is found that the film is Si rich in an amorphous SiC matrix and that the observed graphitization is exclusively described by a single broad D-band in Raman. During the annealing process, a start of rearrangement of the network is observed at low temperatures of annealing but the amorphous phase still dominates in the microstructure. Still at low temperatures, the graphitization band broadens and expands to the G-bands region while at higher temperatures, an improved stochiometric crystalline SiC phase is achieved and distinct graphitic D and G bands are resolved. The induced crystalline network through annealing is prone to oxidation both in Si-O, bridged oxygen Si-O-Si and/or to silicon oxycarbide SiCx -O groups. An optical model based on effective medium approximation (EMA) theory is proposed in order to extract the optical properties of the material. It is established, from the evolution of the bandgap, that the films become transparent over a wider region of the visible spectrum as the temperature of annealing is increased to high values.

Molecular Dynamics Simulation of Thin Silicon Carbide Films Formation by the Electrolytic Method.

Silicon carbide is successfully implemented in semiconductor technology; it is also used in systems operating under aggressive environmental conditions, including high temperatures and radiation exposure. In the present work, molecular dynamics modeling of the electrolytic deposition of silicon carbide films on copper, nickel, and graphite substrates in a fluoride melt is carried out. Various mechanisms of SiC film growth on graphite and metal substrates were observed. Two types of potentials (Tersoff and Morse) are used to describe the interaction between the film and the graphite substrate. In the case of the Morse potential, a 1.5 times higher adhesion energy of the SiC film to graphite and a higher crystallinity of the film was observed than is the case of the Tersoff potential. The growth rate of clusters on metal substrates has been determined. The detailed structure of the films was studied by the method of statistical geometry based on the construction of Voronoi polyhedra. The film growth based on the use of the Morse potential is compared with a heteroepitaxial electrodeposition model. The results of this work are important for the development of a technology for obtaining thin films of silicon carbide with stable chemical properties, high thermal conductivity, low thermal expansion coefficient, and good wear resistance.

In-situ growth mechanism and structural evolution of silicon quantum dots embedded in Si-rich silicon carbide matrix prepared by RF-PECVD

Amorphous silicon-rich silicon carbide (a-SixC1-x) thin films that contain Si quantum dots (QDs) were prepared using radio-frequency plasma-assisted chemical vapor deposition (RF-PECVD) from reactive silane and methane precursor gases at a substrate temperature of 300 °C. The effect of the silane-to-methane flow ratio on the structural properties of the Si QDs/a-SixC1-x nanocomposite films, is systematically studied by means of high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The obtained results confirm the in-situ formation of Si QDs within the amorphous SiC matrix. Moreover, it is found that the Si crystalline fraction increases from 60.7 to 78.5% with increasing the gas flow ratio. Photoluminescence analyses reveal broader emission spectra which are explained in terms of quantum confinement-related emission corresponding to different QD sizes. Based on the obtained results, the growth mechanisms of Si QDs during the deposition of the a-SixC1-x film and the amorphous-to-crystalline transition are discussed.

CFD simulation of CVD reactors in the CH3SiCl3(MTS)/H2 system using a two-step MTS decomposition and one-step SiC growth models

In this study, we report on a computational fluid dynamics (CFD) simulation of the chemical vapor deposition reactor of silicon carbide (SiC) in the methyltrichlorosilane (MTS, CH3SiCl3)/H2 system. The formation of SiC thin film is controlled by various process parameters, such as temperature and pressure. In this study, we propose a reaction mechanism of MTS decomposition to SiC growth on a substrate surface for CVD reactors in the CH3SiCl3(MTS)/H2 system. The reaction mechanism has two gas-phase pyrolysis reactions and one SiC film formation reaction. However, we individually build and validate MTS decomposition and SiC growth models to reduce uncertainty. An in-house version of reactingFoam, a reactive flow solver within OpenFOAM v2006, was used as the simulation tool. Our model accurately reproduced MTS decomposition for T = 1100–1350 K and [H2]/[MTS] = 2.65–14 at p = 101,325 Pa. Then, the MTS decomposition model was coupled with the SiC growth model, and the coupled model was applied to the SiC deposition data. The model could reproduce multiple datasets through validation studies.

Effect of substrate temperature and annealing on the structure and opto-electrical properties of silicon carbide thin films prepared by e-beam evaporation

The silicon carbide (SiC) thin films prepared by e-beam evaporation show tunable optical and electrical properties. In this work the structure and opto-electrical properties of SiC films were studied by varying the substrate temperature (TS = 25–400 °C) within two series of e-beam current Ie = 38 mA or 71 mA. It was found that the oxygen or carbon ratio were strongly affected by the temperatures of the evaporant and the substrate. For SiC samples with Ie = 38 mA, the silicon oxide ratio decreases with increasing TS leading to the deteriorated transparency. While at Ie = 71 mA, the samples show less silicon oxide and more ordered SiC phases instead when TS = 400 °C. Given the Raman spectra of SiC samples, the carbon phase appears in all samples and tend to reduce under high TS conditions. The existence of carbon phase was further evidenced by the diamond and graphite like carbon Raman signals after annealing at 1100 °C. Overall, the optical band gap and conductivity of SiC thin films prepared by e-beam evaporation can be tailored within a range of 1.4–2.6 eV and 10−8 to 10−3 S/cm, respectively.

High thermo-optic tunability in PECVD silicon-rich amorphous silicon carbide.

In this work, the thermo-optic coefficient (TOC) of the silicon-rich amorphous silicon carbide (a-SiC) thin film deposited by plasma-enhanced chemical vapor deposition (PECVD) was characterized. We found that the TOC of the film increases as its silicon content increases. A more than threefold improvement in the TOC was measured, reaching a TOC as high as 1.88×10-4 ∘C-1, which is comparable to that of crystalline silicon. An efficient thermo-optic phase shifter has also been demonstrated by integrating the silicon-rich a-SiC micro-ring structure with a NiCr heater. Tunability of 0.117 nm/mW was demonstrated, and a corresponding tuning efficiency P π as low as 4.2 mW has been measured at an optical wavelength of 1550 nm. These findings make silicon-rich a-SiC a good candidate material for thermo-optic applications in photonic integrated circuits.

Effects of different incidence rates of carbon and silicon clusters on the surface properties of SiC films

The crystal quality of silicon-carbide (SiC) films plays a very important role in experimental and device production, but there is little research on the deposition and annealing process at the atomic scale. Using molecular dynamics, we simulated the deposition of crystalline Si, C clusters on a rough-surfaced Si substrate followed by annealing and investigated the effect of incidence rate on film surface morphology, crystallization rate, surface roughness, incident atom distribution, density, and vacancies. The results showed that the surfaces became smoother with increasing incidence rate both before and after deposition, but the difference in surface roughness between film groups with different incidence rates decreased after annealing. After annealing, the film density increased with increasing cluster incidence rate, while the volume fraction of the vacancies and cavities simultaneously increased. The higher the cluster incidence rate during deposition, the deeper the distribution of incident atoms, and the more the mixing with substrate atoms. An interesting phenomenon was observed during the high-temperature relaxation phase of the annealing, when the crystallization rate increased, stabilized, and then decreased as the relaxation proceeded. This study is of great significance to better understanding the nanoscale annealing of thin film deposits and guiding SiC thin film generation experiments.