Growth Rate Of Thin Films Research Articles

Free‐Radical Polymerization of Liquid Hydroxyethyl Methacrylate Layers Using Nanosecond Plasma Pulses

ABSTRACTPromoting both high functional group preservation and high deposition rates is a major challenge in plasma deposition. This study explores a dynamic method using nanosecond pulsed plasma discharges to polymerize thin liquid layers of 2‐hydroxyethyl methacrylate (HEMA). The influence of plasma pulse frequency (200 ns) and liquid layer thickness on chemical structure retention, polymeric growth, and thin film growth rate is examined. High‐resolution mass spectrometry (HRMS) highlights that plasma curing of liquid monomer layers achieves significantly better chemical structure preservation and polymeric growth, along with deposition rates an order of magnitude higher than traditional vapour‐phase methods. This work provides valuable insights and guidelines for plasma‐induced free‐radical polymerization of liquid layers into functional thin solid films.

Influence of porous media and substrate rotation on AlN growth in MNVPE reactors based on CFD simulations

AlN is an important III-V wide-bandwidth semiconductor material. Its maximum (ultra-wide) direct bandgap of up to 6.2 eV at room temperature and excellent physical properties make it have great application prospects in the fields of high-power high-frequency electronics and high-efficiency optoelectronic devices. In this paper, based on Computational Fluid Dynamics (CFD), the finite volume method was employed to investigate the process of growing AlN thin films by MNVPE using CFD simulation software for three-dimensional numerical simulation. By optimizing the chamber structure, it was devoted to improving the growth rate and uniformity of AlN thin films. Different thicknesses of porous media were placed in front of the substrate respectively, and the flow field analysis showed that the presence of eddy currents can be effectively suppressed to reduce the pre-reaction, and the best growth effect was achieved when the thickness reached 7 cm. With the increasing of porosity, more gas reached the substrate surface and improved the growth rate of AlN films. Secondly, for the 90° substrate, substrate rotation created a pumping effect and the growth rate was higher with the increase of the rotation speed. At 160 rpm, the growth rate reached 11.29 μm/h and the coefficient of variation decreased to less than 5 %.

Growth rate of AL2O3 Thin Film by Liquid Phase Deposition as an Anti-reflection Coating Layer on Crystalline Silicon for Solar Cell Applications

The fabrication of photovoltaic (PV) device requires that surface reflectance of solar cells has to be minimized to achieve higher photo-conversion efficiency (PCE). Antireflection coating layer is deposited on the surface of a p-type crystalline silicon material to reduce the surface reflections of solar radiation and increase its absorption for efficient solar cell application. In this work, aluminum oxide thin film by liquid phase deposition (LPD-Al2O­3) is synthesized from combined solution of aluminum sulfate octadecahydrate (Al2(SO4)3·18H2­O) and sodium carbonate (NaHCO3) with pH of 3.1. Some samples of p-type (100) crystalline silicon (c-Si) wafers of resistivity 1 – 10 mΩ were immersed inside the growth liquid of LPD-Al2O­3 thin film for 1hr – 2.5 hours. This is followed by annealing the samples at a temperature of 450oC, the deposition rate is faster in the range 1 – 1.5 hours is about 35nm/hr. As the growth time increases, the growth rate of the film decreases and remains nearly constant at about 10 nm/hour at 1 – 2 hours. When the growth time exceeds 2 hours, the film thickness remains unchanged showing that the liquid has lost in growth ability. The weighted average reflection (%) of planar c-Si is reduced from 44.9 % to 29.6 % after deposition of the LPD-Al2O­3 for 2.5 hours growth time, indicating a 34.1 % reduction in reflection within wavelength region of 300–1100 nm. While the root means square (RMS) surface roughness of 36.5 nm was also recorded at the highest growth time of 2.5 hours. This shows the effect of thicker LPD-Al2O­3 thin film layer increases the anti-reflecting coating property of the material.

Growth rate of AL2O3 Thin Film by Liquid Phase Deposition as an Anti-reflection Coating Layer on Crystalline Silicon for Solar Cell Applications

The fabrication of photovoltaic (PV) device requires that surface reflectance of solar cells has to be minimized to achieve higher photo-conversion efficiency (PCE). Antireflection coating layer is deposited on the surface of a p-type crystalline silicon material to reduce the surface reflections of solar radiation and increase its absorption for efficient solar cell application. In this work, aluminum oxide thin film by liquid phase deposition (LPD-Al2O­3) is synthesized from combined solution of aluminum sulfate octadecahydrate (Al2(SO4)3·18H2­O) and sodium carbonate (NaHCO3) with pH of 3.1. Some samples of p-type (100) crystalline silicon (c-Si) wafers of resistivity 1 – 10 mΩ were immersed inside the growth liquid of LPD-Al2O­3 thin film for 1hr – 2.5 hours. This is followed by annealing the samples at a temperature of 450oC, the deposition rate is faster in the range 1 – 1.5 hours is about 35nm/hr. As the growth time increases, the growth rate of the film decreases and remains nearly constant at about 10 nm/hour at 1 – 2 hours. When the growth time exceeds 2 hours, the film thickness remains unchanged showing that the liquid has lost in growth ability. The weighted average reflection (%) of planar c-Si is reduced from 44.9 % to 29.6 % after deposition of the LPD-Al2O­3 for 2.5 hours growth time, indicating a 34.1 % reduction in reflection within wavelength region of 300–1100 nm. While the root means square (RMS) surface roughness of 36.5 nm was also recorded at the highest growth time of 2.5 hours. This shows the effect of thicker LPD-Al2O­3 thin film layer increases the anti-reflecting coating property of the material.

Remote plasma chemical vapor deposition of silicon oxycarbide film with a styrene-containing precursor and in situ O2 plasma treatment

In this paper, a study was conducted on silicon oxycarbide thin-film deposition using remote plasma chemical vapor deposition. A di-methyldimethoxysilane)2styrene (MDMS)2styrene precursor and CH4 plasma were used in the deposition process, and in situ oxygen plasma treatment was performed to control the carbon content and properties of the thin film. During the deposition process, the thin-film growth rate was found to be almost constant regardless of in situ plasma treatment. This means that in situ oxygen plasma treatment had no significant effect on thin-film growth itself. Auger electron spectroscopy analysis revealed that the carbon content of the deposited thin film was 43 % when only deposition was performed, but could be lowered to 3 % by in situ oxygen plasma treatment, which demonstrated that the carbon content can be controlled in a relatively wide range. X-ray photoelectron spectroscopy showed that it was possible to preserve SiC bonds even as the oxygen content increased with the number of in situ plasma treatments. The refractive index increased from 1.33 to 1.49, indicating a decrease in the number of pores and an increase in density. Meanwhile, the dielectric constant increased with the oxygen content, but did not exceed 3.9 due to the SiC bond structure. As the pore size decreased, the leakage current tended to decrease to 9.51 × 10−9 A/cm2 in an electric field of 1 MV/cm, and the breakdown voltage increased. Finally, it was possible to improve the etching characteristic through plasma treatment by lowering the wet etch rate from 78 to 19 Å/min.

Physics based optical modeling of iron disulfide thin films

In this work, physics based optical modeling is carried out using iron disulfide thin films deposited by using a plasma-assisted, radio frequency-powered technique. Iron disulfide is a transition metal dichalcogenide material, exhibiting a variety of unique and excellent characteristics. Various characterization techniques are employed to examine the growth rate, film thickness, and behavior of as-grown iron disulfide thin films. Furthermore, the physics based optical modeling was performed using a combination of experimental techniques and computer modeling approaches. The analyzed thin films exhibit a bandgap of around 1.16 eV. The theoretically calculated values of absorbance, transmission, and reflectance show a good match with the experimental measurements. Moreover, a physics based optical model is developed based on the experimental data and is used to calculate the external quantum efficiency and the optically generated current density of the iron disulfide films to provide insight into its use as an absorber layer.

Controlled ultrasonic nebulization: A physical vapor deposition variant for low temperature and low growth rate of small molecule thin films

Controlled ultrasonic nebulization: A physical vapor deposition variant for low temperature and low growth rate of small molecule thin films

Growth rate control and phase diagram of wafer-scale Ga2O3 films by MOCVD

The potential of gallium oxide (Ga2O3) as a promising semiconductor for advanced electronics and optoelectronics has been propelled by its wide bandgap, high breakdown voltage tolerance, and excellent chemical and thermal stability. To develop it into an industrial-level application, extensive research needs to be conducted to advance wafer-scale and high-quality epitaxy growth techniques. In this work, a close-coupled showerhead (CCS) metal-organic chemical vapor deposition (MOCVD) system was used to grow wafer-scale Ga2O3 films. Through a detailed examination of growth parameters including substrate temperature, oxygen flow rate, precursor proportion, and chamber pressure, as well as their effect on film crystallinity, surface morphology, and optical properties, a comprehensive growth phase diagram and control over the growth rate of 2-inch Ga2O3 thin films were obtained at a wafer-scale. These findings suggest that the CCS-MOCVD system presents a competitive avenue for future industrial high-speed fabrication of single-phase Ga2O3 films.

Optical Properties of Sputtered Iron Sulfide for Photonic Device Applications

In the current study, two-dimensional pyrite thin films were produced on various substrates using a plasma-assisted, radio frequency (RF)-powered sputtering process. The photosensitivity of pyrite thin films with varying thicknesses was investigated. The sputtering process was carried out at room temperature under argon gas flow. The pressure was maintained at 3 mTorrs, and the RF power was held at 70 watts. The thickness was adjusted by changing the sputtering time from 20 to 90 minutes. The purpose of this work was to investigate the suitability of these films for use in photovoltaic applications. The growth rate, film thickness, and behaviour of as-grown pyrite thin films were analyzed using various characterization techniques. These films displayed favourable absorption in the UV/Vis range.

High-rate growth of gallium oxide films by plasma-enhanced thermal oxidation for solar-blind photodetectors

Almost all reported high-performance β-Ga2O3 thin films are grown by molecular beam epitaxy, metal–organic chemical vapor deposition, and pulsed laser deposition at a very high cost and low throughput. To explore the fast growth method for β-Ga2O3 with high quality and low cost, a custom-made plasma-enhanced chemical vapor deposition is designed for innovative thermal oxidation of gallium nitride. It is shown that the growth rate of gallium oxide thin films prepared by the plasma-enhanced thermal oxidation (PETO) is 2 to 5 times higher than that of thermal oxidation process under similar growth conditions. For β-Ga2O3 thin films prepared by the PETO, the high-rate growth, low root-mean-square roughness, and growth with the orientation along (2¯ 01) lattice plane are achieved. The developed growth mechanism elucidates the role of the O2 and Ar + O2 plasma-surface interactions in the β-Ga2O3 growth process. Solar-blind photodetectors based on the β-Ga2O3 films grown by the PETO with a high solar blind-to-UV rejection ratio (R245 nm/R360 nm = 10.2), a low rise time of 0.17 s, and a low fall time of 0.2 s are demonstrated. The plasma-surface interaction effects are generic and are applicable to a broader range of materials systems and devices for diverse applications.

Numerical Modelling on the Effect of Temperature on MOCVD Growth of ZnO Using Diethylzinc and Tertiarybutanol

The dynamic growth of MOCVD-grown ZnO thin films under temperature effect was systematically investigated by a numerical approach using computational fluid dynamics (CFD) technique. A three-dimensional (3D) reactor-scale model was developed to determine the growth rate and uniformity of ZnO thin film in the temperature range of 593 K to 713 K. The mixed-convection flow and heat transfer inside the reactor chamber were assessed. The results showed that as the temperature increased, ZnO thickness increased initially before decreasing. At 673 K, the highest deposition rate with acceptable uniformity was achieved. The admixture of transverse and longitudinal rolls was observed for the flow conditions. Temperature variations were found to directly affect the axial and lateral uniformity of deposition, but had a minor impact on the size and position of transverse rolls. Experimental verification studies were conducted, and high-quality ZnO films were successfully fabricated by using diethylzinc (DEZn) and tertiarybutanol (t-BuOH) as precursors; it was found that the comprehensive thickness and structural properties of ZnO deposited at temperature of 673 K are preferred. Experimental results and numerical simulations exhibited good agreement.

Electrochemical properties and morphology of boron-doped diamond thin films

A boron-doped diamond (BDD) thin film was synthesized using the hot filament chemical vapor deposition (HFCVD) method. The surface shape, growth rate, bonding structure, and electrochemical properties of the BDD thin films were estimated through scanning electron microscopy (SEM), Raman spectroscopy, and cyclic voltammetry. As the boron doping concentration increased, the growth rate and crystal size of the diamond thin film decreased. Through Raman analysis, it was confirmed that the 1332 cm[Formula: see text] peak of diamond gradually became less intense, and peaks were generated at 480 cm[Formula: see text] and 1220 cm[Formula: see text] due to the bonding of boron to carbon. Cyclic voltammetry analysis of the BDD thin film showed a large potential window with a width of approximately 2.8 V. The highest applied voltage (2 V) versus response current (0.02 A) was obtained at a B/C ratio of 2000 ppm.

Vapor-solid interfacial reaction and polymerization for wafer-scale uniform and ultrathin two-dimensional organic films

Chemical vapor deposition is a conventional synthesis method for growing large-scale and high-quality two-dimensional materials, such as graphene, hexagonal boron nitride, and transition-metal dichalcogenides. For organic films, solution-based methods, such as inkjet printing, spin coating, and drop and micro-contact printing, are commonly used. Herein, we demonstrate a general method for growing wafer-scale continuous, uniform, and ultrathin (2–5 nm) organic films. This method is based on a copper (Cu) surface-mediated reaction and polymerization of several equivalent bromine (Br)-containing π-conjugated small molecules (C12S3Br6, C24H4O2Br2, and C24H12Br2N4), in which local surface-mediated polymerization and internal π-π interactions among organic molecules are responsible for the dimension and uniformity control of the thin films. Specifically, the growth rate and morphology of thin films were found to be Cu-facet-dependent, and single-crystal Cu(111) surfaces could improve the uniformity of thin films. In addition, the number of Br groups and size of organic molecules were critical for crystallinity and thin-film formation. This method can be used to fabricate heterostructures, such as organic film/graphene, giving room for various functional materials and device applications.

Transparent SiOxCyHz Barrier Film Prepared by Roll to Roll PECVD

This paper uses plasma-enhanced chemical vapor deposition (PECVD) to successfully fabricate silicon oxide films on silicon dioxide substrates for supporting layers of uncooled infrared focal plane array microbridge structures. In this paper, the thickness, refractive index, growth rate, and other parameters of the films were measured using the XP-2 step meter and ellipsometer. At the same time, atomic force microscopy (AFM) was used to study the surface morphology of the films. The experimental results show that deposition temperature and ICP power are the main factors affecting the growth rate of thin films. Deposition temperature is a crucial factor affecting the surface morphology of thin films.

In2O3 film prepared by a PEALD process with balanced oxygen radical supply and ion bombardment damage

The growth rate of In2O3 thin film prepared by atomic layer deposition (ALD) is usually low when using conventional oxidants, such as water vapor and oxygen gas, due to the low reactivity and thermal stability of most available In-precursors. In this work, In2O3 film was prepared by a remote O2 plasma enhanced ALD process with reasonable growth rate. The O2 plasma duration was tuned taking not only the oxidizing effects but also the ion bombardment effects that have received little attention into consideration. The results show that the film growth was dominated by the oxidizing process manifested by the increase of film growth rate with increasing plasma duration in the early stage of the O2 plasma pulse. In this stage, the optical properties were rarely influenced by the plasma duration, whereas the carrier mobility significantly increased with increasing plasma duration. However, the ion bombardment effects became dominant in the later stage of the O2 plasma pulse symbolized by the saturation of the growth rate. Accordingly, more oxygen vacancy defects were created in the film by ion bombardment, leading to the increase of carrier concentration and decrease of refractive index, optical band gap and carrier mobility.

Influence of oxygen partial pressure on properties of monoclinic Ga2O3 deposited on sapphire substrates

Thin monoclinic Ga2O3 films were deposited on c-plane sapphire substrates by low pressure chemical vapor deposition. The thin films were synthesized using high purity metallic gallium (Ga) and oxygen gas (O2) as precursors. The effect of oxygen volume percentage on the growth rate of thin films was observed at two growth temperatures. Within the investigated growth window, a maximum growth rate of ∼2.9 μm/h was obtained for an oxygen volume percentage of 4.8% with a growth temperature at 800 °C. The film growth rate decreased as growth temperature increased when other growth parameters were kept the same. X-ray diffraction indicates that all films have the β-Ga2O3 structure with (−201) orientation, and those deposited with higher oxygen partial pressure are thicker and have improved crystalline quality. Polarized micro-Raman scattering is consistent with small grains of (−201) β-Ga2O3 having random in-plane orientations. The large variation of the relative intensities of overlapping emission bands contributing to the broad luminescence emission extending between 1.5 and 4.5 eV (∼825 and 275 nm) suggest that deposition conditions strongly affect different defect concentrations. Films deposited at 800 °C with a higher oxygen partial pressure yielded higher resistance, which may result from the incorporation of gallium vacancies, identified as a compensating point defect affecting the electrical conductivity of bulk monoclinic Ga2O3.

Effects of growth pressure on the characteristics of the β-Ga2O3 thin films deposited on (0001) sapphire substrates

β-Ga2O3 films were grown on (0001) sapphire substrates by low-pressure MOCVD. The effects of growth pressure on the growth rate, surface morphology and optical properties of β-Ga2O3 thin films were investigated. XRD showed that the β-Ga2O3 films grown preferentially along the (-201) crystal plane family were obtained, and the increase in growth pressure led to a decrease in growth rate, consistent with the SEM results. AFM measurements indicated that the increase in growth pressure reduced the grain size and RMS roughness. Optical transmission spectroscopy demonstrated that the average transmittance of all films in the visible range exceeded 75%, and the optical bandgap at 20, 30 and 40 Torr were 4.95, 4.93 and 4.91 eV, respectively. XPS revealed that the Ga 2p peak and O 1s peak blue shift as the growth pressure. Through RT-Raman spectroscopy, the low-frequency and high-frequency Raman vibration modes of β-Ga2O3 were detected.

Growth and vacuum post-annealing effect on the structural, electrical and optical properties of Sn-doped In2O3 thin films

Nowadays, the fabrication of cheaper, thermodynamically stable and durable transparent semiconducting oxide-based thin films are on high demand to enhance the properties of optoelectronic, sensing and energy harvesting devices. It is well known that Sn-doped In2O3 (ITO) thin films are difficult to grow by direct current sputtering. However, in this work cost-effective Sn-doped In2O3 films are deposited onto borosilicate glass substrates using a direct current sputtering of metallic In/Sn-target. The film thickness was controlled by the deposition time. A post-deposition annealing of the films in a vacuum atmosphere was performed in order to control the structural, optical and electrical properties. The phase formation, crystallite grain sizes (D) and lattice parameters have been assessed from the X-ray diffraction data analysis. Cross-section Scanning electron microscope image analyses were performed in order to estimate the growth rate of thin films. A band gap energy closing was observed associated with relaxation process of the unit cell suggested by the monotonic reduction of the lattice constant. Besides, a low sheet resistance (44 Ohm/square) was obtained, which is comparable to the commercially available ITO films. Furthermore, a inverse-square dependence between the sheet resistance and the grain size was determined (Rsq ∼ 1/D2). The last was used to estimate the carrier concentration of the thicker film ∼ 1020cm−3, which is in agreement with the value obtained from the Hall measurement.

High-purity core / shell structured nanoparticles synthesis using high-frequency plasma technology and atomic layer deposition

In this study, an equipment for synthesizing high purity core/shell nanoparticles was developed using high frequency plasma technology and atomic layer deposition method. The plasma chamber was designed so that the gas phase precursor could stabilize the flow in the plasma, and a holder capable of adjusting the rotation and the height of substrate was constructed to enable the uniform deposition of nanoparticle on the substrate surface regardless of the precursor species. ALD (atomic layer deposition) deposition technique was used for the shell coating of the deposited nanoparticles. MTL (main transfer line) equipment was constructed to move the substrate from the plasma chamber to the ALD chamber without external exposure. By constructing a pneumatic gate, the contamination of ALD chamber by the plasma process can be prevented and the vacuum state can be maintained. By means of the SEM and TEM analysis, the growth rate of the core-TiO2 thin film and the growth thickness of the shell-Al2O3 were controlled at a growth rate of 0.05 μm/s and 1 Ẳ/cycle, respectively. In addition, it was confirmed that the weight fraction and the particle size can be controlled through the X-ray diffraction analysis and the dynamic light scattering analysis.

Influence of precursor dose and residence time on the growth rate and uniformity of vanadium dioxide thin films by atomic layer deposition

The growth of vanadium dioxide (VO2) thin films using tetrakis (ethyl-methyl) amino vanadium (TEMAV) and H2O by atomic layer deposition (ALD) has been investigated as a function of the exposure dose and residence time. A novel multiple pulse mode has been employed to mitigate the small deposition rate brought about by the low vapor pressure of TEMAV. Compared to the conventional ALD cycle with a single pulse of precursor, the use of multiple pulsing with very short pulse time allows lower consumption of precursor, but larger exposure dose and longer residence time on the growth surface, resulting in a higher growth rate for a low volatility precursor, while maintaining a good film uniformity across 4-in. wafers. The Raman analysis and the electrical resistivity modulation of the VO2 thin films show that the films synthesized by the multiple pulse mode is comparable to the films synthesized by the conventional single pulse mode.