Plasma-enhanced Chemical Vapor Deposition Method Research Articles

Interfacial Si–O coordination for inhibiting the graphite phase enables superior SiC/Nb heterostructure joining by AuNi

The reaction between SiC and Ni-based brazing alloy is extremely intense, where the brittle Ni–Si compound and accompanied dissociate graphite phase as the interfacial reaction product in the joint damage the mechanical properties. In this study, the design of "graphite-controlled" heterogeneous integration component structure on SiC surface is developed to weaken the intense reaction of Ni and SiC. The high-quality surface Si–O coordination was successfully achieved by plasma-enhanced chemical vapor deposition (PECVD) method at relatively low temperature on SiC, which increases the Si bond strength due to that the higher binding energy of Si–O (451 kJ/mol) than that of Si–C (347 kJ/mol). SiO2 films enhance the mechanical properties of the joint through macro-weak side interface interlocking and micro-stress mismatch regulation. The shear strength of SiC/Nb heterostructure joints by AuNi alloy was increased by 44 %, which paves an inspiring way for boosting heterogeneous integration of SiC ceramic components.

Tailored multi-layer graphene arrays for precision detection of neurotransmitter

The development of sensitive dopamine (DA) sensors has significantly contributed to our understanding of DA-related disorders and has enabled advancements in medical diagnostics and neuroscience research. Therefore, in the present work, a novel electrochemical sensing platform was developed using multi-layer graphene arrays (MGA) modified electrodes for the selective detection of DA. The preparation of high-quality MGA was achieved using the plasma-enhanced chemical vapor deposition (PCVD) method and was confirmed using various physiochemical techniques such as transmission electron microscopy and Raman spectroscopy. The modified electrode, made of MGA, was utilized for the electrochemical detection of DA using cyclic voltammetry and amperometry i-t methods. DA’s electrochemical oxidation response and sensitivity at the MGA electrode were ≈9 and 3 times higher than observed with unmodified and commercially available multi-layer graphene-modified electrodes. The MGA sensor exhibited excellent analytical parameters for DA detection, including a wide linear range of up to 172.1 μM and a low detection limit of 1.3 nM. The sensor also demonstrated remarkable sensitivity, storage stability, and selectivity for DA detection, making it highly suitable for accurately detecting DA in medical diagnostics and neuroscience research. Furthermore, the practical application of the MGA sensor for DA detection was demonstrated in various real samples.

Effects of the In Situ Growth of CNTs on Ti-Coated Diamond Surfaces on the Mechanical Properties of Diamond/Aluminum Composites.

Diamond/aluminum composites have attracted significant attention as novel thermal management materials, with their interfacial bonding state and configuration playing a crucial role in determining their thermal conductivity and mechanical properties. The present work aims to evaluate the bending strength and thermal conductivity of CNT-modified Ti-coated diamond/aluminum composites with multi-scale structures. The Fe catalyst was encapsulated on the surface of Ti-coated diamond particles using the solution impregnation method, and CNTs were grown in situ on the surface of Ti-coated diamond particles using the plasma-enhanced chemical vapor deposition (PECVD) method. We investigated the influence of interface structure on the thermal conductivity and mechanical properties of diamond/aluminum composites. The results show that the CNT-modified Ti-coated diamond/aluminum composite exhibits excellent bending strength, reaching up to 281 MPa, compared to uncoated diamond/aluminum composites and Ti-coated diamond/aluminum composites. The selective bonding between diamond and aluminum was improved by the interfacial reaction between Ti and diamond particles, as well as between CNT and Al. This led to the enhanced mechanical properties of Ti-coated diamond/aluminum composites while maintaining acceptable thermal conductivity. This work provides insights into the interface's configuration design and the performance optimization of diamond/metal composites for thermal management.

Fabrication of pH-Responsive PDPAEMA Thin Film Using a One-Step Environmentally Friendly Plasma Enhanced Chemical Vapor Deposition

In recent years, there has been growing interest in pH-responsive polymers. Polymers with ionizable tertiary amine groups, which have the potential to be used in many critical application areas due to their pKa values, have an important place in pH-responsive polymers. In this study, poly(2-Diisopropyl aminoethyl methacrylate) (PDPAEMA) thin films were coated on various substrates such as glass, fabric, and silicon wafer using a one-step environmentally friendly plasma enhanced chemical vapor deposition (PECVD) method. The effects of typical PECVD plasma processing parameters such as substrate temperature, plasma power, and reactor pressure on the deposition rate were studied. The highest deposition rate was obtained at a substrate temperature of 40 °C, a reactor pressure of 300 mtorr, and a plasma power of 60 W. The apparent activation energy was found to be 17.56 kJ/mol. Based on the results of this study, uniform film thickness and surface roughness were observed in a large area. The PDPAEMA thin film was exposed to successive acid/base cycles. The results showed that the pH sensitivity of the thin film produced by the PECVD method is permanent and reversible.

Diamond-like carbon (DLC) coating on graphite: Investigating the achievement of maximum wear properties using the PECVD method

Considering the potential for morphological changes and the adjustment of the sp3/sp2 ratio in diamond-like carbon (DLC) coatings, and consequently the possibility of adjusting the properties of self-lubricating, hardness, and wear of these coatings, the present study investigates the effect of varying the power applied during the deposition of coatings using plasma-enhanced chemical vapor deposition (PECVD) method. Raman spectroscopy, Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), nanoindentation, wear, and wear depth tests were employed for this purpose. The results obtained from the Raman spectroscopy indicated that the percentage of sp3 hybridization, as well as the amount of internal stress, increased with the higher applied power of the coating. AFM results also reveal an increase in surface roughness with increasing applied power, and FESEM results indicate a reduction in the diameter of DLC grains with increasing applied power. Moreover, the alternating increase in hardness and modulus of elasticity, along with a decrease in friction coefficient and wear depth, are among the other effects of increasing the applied power. Therefore, the results of this research suggest an enhancement in the tribological properties of the applied coating at higher powers (up to 250 W).

All-Nitrogen Energetic Material Cubic Gauche Polynitrogen: Plasma Synthesis and Thermal Performance.

Numerous theoretical calculations have demonstrated that polynitrogen with an extending polymeric network is an ultrahigh-energy all-nitrogen material. Typical samples, such as cubic gauche polynitrogen (cg-N), have been synthesized, but the thermal performance of polynitrogen has not been unambiguously determined. Herein, macroscopic samples of polynitrogen were synthesized utilizing a coated substrate, and their thermal decomposition behavior was investigated. Polynitrogen with carbon nanotubes was produced using a plasma-enhanced chemical vapor deposition method and characterized using infrared, Raman, X-ray diffraction X-ray photoelectron spectroscopy and transmission electron microscope. The results showed that the structure of the deposited polynitrogen was consistent with that of cg-N and the amount of deposition product obtained with coated substrates increased significantly. Differential scanning calorimetry (DSC) at various heating rates and TG-DSC-FTIR-MS analyses were performed. The thermal decomposition temperature of cg-N was determined to be 429 °C. The apparent activation energy (Ea) of cg-N calculated by the Kissinger and Ozawa equations was 84.7 kJ/mol and 91.9 kJ/mol, respectively, with a pre-exponential constant (lnAk) of 12.8 min-1. In this study, cg-N was demonstrated to be an all-nitrogen material with good thermal stability and application potential to high-energy-density materials.

Targeting Biomechanical Endurance of Dental-Implant Abutments Using a Diamond-Like Carbon Coating.

Abutment components (i.e., fixtures associated with oral implants) are essentially made of titanium (Ti), which is continuously exposed to the hash oral environment, resulting in scratching. Thus, such components need to be protected, and surface treatments are viable methods for overcoming long-term damage. Diamond-like carbon (DLC), an excellent protective material, is an alternative surface-treatment material for Ti abutments. Here, we demonstrate that a silicon interlayer for DLC film growth and the pulsed-direct current plasma-enhanced chemical vapor deposition (DC-PECVD) method enables the deposition of an enhanced protective DLC film. As a result, the DLC film demonstrated a smooth topography with a compact surface. Furthermore, the DLC film enhanced the mechanical (load-displacement, hardness, and elastic modulus) and tribological properties of Ti as well as increased its corrosion resistance (16-fold), which surpassed that of a bare Ti substrate. The biofilm formed (Streptococcus sanguinis) after 24 h exhibited an equal bacterial load (∼7 Log colony-forming units) for both the groups (Ti and DLC). In addition, the DLC film exhibited good cytocompatibility, owing to its noncytotoxicity toward human gingival fibroblast cells. Therefore, DLC deposition via DC-PECVD can be considered to be a promising protective and cytocompatible alternative for developing implant abutments with enhanced mechanical, tribological, and electrochemical properties.

Hydrogen peroxide sensing with nitrogen-doped carbon nanowalls

The fabrication of miniaturized, low-cost, enzyme-free sensors based on nanomaterials via high-performance techniques is expected to provide important benefits for applications in biological detection. In this work, nitrogen-doped carbon nanowalls (CNWs) were synthesized and used to fabricate electrochemical sensor for hydrogen peroxide (H2O2) sensing. The CNWs were grown on Ti\\SiO2\\Si substrates by radical-injection plasma-enhanced chemical vapor deposition (RI-PECVD) method with different nitrogen concentration. Structural and morphological properties of the obtained CNWs were analyzed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron microscopy. Cyclic voltammetry and chronoamperometry were used to analyze the electrochemical properties of N-doped CNWs. This study demonstrates the effectiveness of CNWs doping with nitrogen during the synthesis process to improve the electrochemical characteristics of the sensor. It was shown that CNWs doped at high nitrogen flow rate (N2: 20 sccm) exhibited the highest amperometric response. Cyclic voltammetry results indicate that the CNWs doped at high nitrogen flow rate demonstrate excellent electrochemical activity for the reduction of H2O2. These results could pave the way for the development of easy-to-manufacture and highly efficient metal-free biosensors for H2O2 detection.

Evaluating the Ge: C ratio on the bonding structure, hardness, and residual stress of Ge1-x-Cx coatings fabricated by the PE-CVD method

In the present research, the effect of the Ge: C ratio was evaluated and explained on the bonding structure, the hardness, and residual stress of germanium-carbon (Ge1-x-Cx) coatings fabricated by plasma-enhanced chemical vapor deposition (PECVD) method. For characterizing the coatings, a field emission scanning electron microscope (FE-SEM) equipped with an energy dispersive spectrometer (EDS), transmission electron microscope (TEM), Raman spectrometer, Rutherford backscattering spectrometer (RBS), elastic recoil detection (ERD) analysis, X-ray photoelectron spectrometer (XPS), nanoindentation test, and cohesion test were used. by increasing the flow rate ratio of CH4:GeH4 and as a result of decreasing the ratio of Ge: C, the fraction of sp2 C-C and sp3 Ge-C bonds were increased and the fraction of Ge-Ge bonds was decreased. The hardness of the Ge1-x-Cx coatings was heavily reliant on changes in the Ge: C ratio and, consequently, the fraction of the bonds incorporated within the coating structure. To achieve a hard coating, the selection of a moderate carbon content is very important such that it would lead to the formation of maximum sp3 Ge-C bonds alongside slight amounts of sp2 C-C and hydrogen bonds. For very low carbon concentrations, the existence of dominant Ge-Ge bonds would create the coating structure as germanium-like; the excessive rise of the carbon concentration promotes the undesirable graphite-like structures. In the optimum conditions, the hardness of the coating was obtained at 10.1 GPa. The coatings presented a very low residual stress (∼98-240 MPa) despite having suitable hardness.

Structural, Optical, Electrical, and Thermoelectric Properties of Bi2Se3 Films Deposited at a High Se/Bi Flow Rate.

Low-temperature synthesis of Bi2Se3 thin film semiconductor thermoelectric materials is prepared by the plasma-enhanced chemical vapor deposition method. The Bi2Se3 film demonstrated excellent crystallinity due to the Se-rich environment. Experimental results show that the prepared Bi2Se3 film exhibited 90% higher transparency in the mid-IR region, demonstrating its potential as a functional material in the atmospheric window. Excellent mobility of 2094 cm2/V·s at room temperature is attributed to the n-type conductive properties of the film. Thermoelectrical properties indicate that with the increase in Se vapor, a slight decrease in conductivity of the film is observed at room temperature with an obvious increase in the Seebeck coefficient. In addition, Bi2Se3 thin film showed an enhanced power factor of as high as 3.41 μW/cmK2. Therefore, plasma-enhanced chemical vapor deposition (PECVD)-grown Bi2Se3 films on Al2O3 (001) substrates demonstrated promising thermoelectric properties.

Preparation of pure hydrogenated amorphous silicon film via PECVD method as anode materials for high-performance lithium-ion batteries

In this paper, plasma-enhanced chemical vapor deposition (PECVD) is used to prepare a nano-scale pure hydrogenated amorphous silicon thin film anode, which improves the problem of large volume effect of traditional silicon-based anode materials during the charge and discharge process of lithium-ion batteries. Among them, the thinnest 120 nm pure silicon film still has a high specific capacity of 1254.6 mAh g−1 after 200 cycles at 0.5C (1C = 4.2 A g−1), and also has an excellent performance of 848.2 mAh g−1 after a large rate of charge and discharge of 5C. To give consideration to the performance and obtain a certain mass load at the same time, 170 nm pure silicon film was selected for vacuum annealing treatment at different temperatures to release the non-uniform compression stress during the deposition of hydrogenated amorphous silicon, and a more stable film structure was constructed, which further improved the performance of silicon film. Among them, the best performance is held at 100 °C for 5 h, and the reversible specific capacity of 1172.7 mAh g−1 is still maintained at 200 cycles at 0.5C, and the reversible specific capacity of 1131.6 mAh g−1 is also available at a super high rate of 10C.

Electronic structure of P-type amorphous silicon nanowires

Silicon nanowires can improve broadband optical absorption and reduce the radial carrier collection distance in solar cell devices. The disordered nanowire arrays grown by the Plasma-Enhanced Chemical Vapor Deposition method are attractive because they can be embedded on low-cost substrates such as glass, and are compatible with large areas. Here, we experimentally demonstrate that reactive Hydrogen ions with increasing concentrations are doped to construct nanowire architectures in amorphous silicon solar cells. Similar to our investigated planar a-Si: H layers, the amorphous silicon nanowires exhibit a loss function coefficient of about 105/cm. From the reflectivity function, it can be shown that the nanostructures can offer a reliable carrier pool. Our results show that the addition of nanowires can increase the efficiency of a-Si solar cells from 1.11% to 1.57%. The input-photon-to-current conversion efficiency spectrum shows effective carrier collection from 1.2 to 2.2 eV of incident light and the nanowire devices show an increase in short-circuit current of 15% with amorphous Si and 26% with nanocrystalline Si compared to planar devices appropriate.

Application of NiO deposited by atomic layer deposition for carbon nanotubes catalytic growth

Carbon nanotubes (CNTs) are a unique object for various kinds of electronic devices. At the same time, an important task remains the development of catalytic structure synthesis methods for repeatability and uniform growth of CNTs. One of such methods is atomic layer deposition (ALD). The article considers the effect of the initial NiO layer thickness obtained by the ALD method on the growth of carbon nanotubes array. Deposition of the CNTs was carried out by the direct current plasma-enhanced chemical vapor deposition method using a direct current discharge in an acetylene and ammonia at 680 °C. Before CNT deposition, the NiO film was reduced to metallic nickel in an ammonia atmosphere at 680 °C. Samples were studied by scanning and transmission electron microscopy. As a result, the thickness of the initial NiO film for intensive CNT growth was in the range of 3.5 to 3.9 nm. CNTs had a “multi-walled” structure and consisted of 15 ± 5 graphene layers. The density of the tubes was about 7.5 ± 0.2 × 1010 cm−2, and the length was 6–7.5 µm.

Controllable Fabrication of Vertical Graphene with Tunable Growth Nature by Remote Plasma-Enhanced Chemical Vapor Deposition.

As an important member of the graphene family, vertical graphene (VG) has broad applications like field emission, energy storage, and sensors owing to its fascinating physical and chemical properties. Among various fabrication methods for VG, plasma enhanced chemical vapor deposition (PECVD) is most employed because of the fast growth rate at relatively low temperature for the high-quality VG. However, to date, relations between growth manner of VG and growth parameters such as growth temperature, dosage of gaseous carbon source, and electric power to generate plasma are still less known, which in turn hinder the massive production of VG for further applications. In this study, the growth behavior of VG was studied as functions of temperature, plasma power, and gas composition (or chamber pressure). It was found that the growth behavior of VG is sensitive to the growth conditions mentioned above. Although conditions with high growth temperature, large flow rate of mixed gas of methane and carrier gases, and high plasma power may be helpful for the fast growth of VG, brunching of VG is simultaneously enhanced, which in turn decreases the vertical growth nature of VG. High-quality VG can be achieved by optimizing the growth parameters. It was revealed that the vertical growth nature of VG is governed by the electric field at the interfacial layer between VG and the substrate, for which its strength is influenced by the density of plasma. These findings are important for the general understanding of the VG growth and provided a feasible way for the controllable fabrication of VG using the remote PECVD method which is usually believed to be unsuitable for the fabrication of VG.

Evolution of Cu-In Catalyst Nanoparticles under Hydrogen Plasma Treatment and Silicon Nanowire Growth Conditions.

We report silicon nanowire (SiNW) growth with a novel Cu-In bimetallic catalyst using a plasma-enhanced chemical vapor deposition (PECVD) method. We study the structure of the catalyst nanoparticles (NPs) throughout a two-step process that includes a hydrogen plasma pre-treatment at 200 °C and the SiNW growth itself in a hydrogen-silane plasma at 420 °C. We show that the H2-plasma induces a coalescence of the Cu-rich cores of as-deposited thermally evaporated NPs that does not occur when the same annealing is applied without plasma. The SiNW growth process at 420 °C induces a phase transformation of the catalyst cores to Cu7In3; while a hydrogen plasma treatment at 420 °C without silane can lead to the formation of the Cu11In9 phase. In situ transmission electron microscopy experiments show that the SiNWs synthesis with Cu-In bimetallic catalyst NPs follows an essentially vapor-solid-solid process. By adjusting the catalyst composition, we manage to obtain small-diameter SiNWs-below 10 nm-among which we observe the metastable hexagonal diamond phase of Si, which is predicted to have a direct bandgap.

Epitaxial growth of trilayer graphene moiré superlattice

The graphene-based moiré superlattice has been demonstrated as an exciting system for investigating strong correlation phenomenon. However, the fabrication of such moiré superlattice mainly relies on transfer technology. Here, we report the epitaxial growth of trilayer graphene (TLG) moiré superlattice on hexagonal boron nitride (hBN) by a remote plasma-enhanced chemical vapor deposition method. The as-grown TLG/hBN shows a uniform moiré pattern with a period of ∼ 15 nm by atomic force microscopy (AFM) imaging, which agrees with the lattice mismatch between graphene and hBN. By fabricating the device with both top and bottom gates, we observed a gate-tunable bandgap at charge neutral point (CNP) and displacement field tunable satellite resistance peaks at half and full fillings. The resistance peak at half-filling indicates a strong electron–electron correlation in our grown TLG/hBN superlattice. In addition, we observed quantum Hall states at Landau level filling factors ν = 6, 10, 14, …, indicating that our grown trilayer graphene has the ABC stacking order. Our work suggests that epitaxy provides an easy way to fabricate stable and reproducible two-dimensional strongly correlated electronic materials.

Boron Carbonitride Films with Tunable Composition: LPCVD and PECVD Synthesis Using Trimethylamine Borane and Nitrogen Mixture and Characterization

This study reports the chemical vapor deposition of amorphous boron carbonitride films on Si(100) and SiO2 substrates using a trimethylamine borane and nitrogen mixture. BCxNy films with different compositions were produced via variations in substrate temperature and type of gas-phase activation. The low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) methods were used. The “elemental composition—chemical bonding state—properties” relationship of synthesized BCxNy was systematically studied. The hydrophilicity, mechanical, and optical properties of the films are discussed in detail. The composition of films deposited by the LPCVD method at temperatures ranging from 673 to 973 K was close to that of boron carbide with a low nitrogen content (BCxNy). The refractive index of these films changed in the range from 2.43 to 2.56 and increased with temperature. The transparency of these films achieved 85%. LPCVD films were hydrophilic and the water contact angles varied between 53 and 63°; the surface free energy was 42–48 mN/m. The microhardness, Young’s modulus and elastic recovery of LPCVD films ranged within 24–28 GPa, 220–247 GPa, and 70–74%, respectively. The structure of the PECVD films was close to that of hexagonal boron nitride, and their composition can be described by the BCxNyOz:H formula. In case of the PECVD process, the smooth films were only produced at low deposition temperatures (373–523 K). The refractive index of these films ranged from 1.51 to 1.67. The transparency of these films achieved 95%; the optical band gap was evaluated as 4.92–5.28 eV. Unlike LPCVD films, they were very soft, and their microhardness, Young’s modulus and elastic recovery were 0.8–1.4 GPa, 25–26 GPa, and 19–28%, respectively. A set of optimized process parameters to fabricate LPCVD BCxNy films with improved mechanical and PECVD films with high transparency is suggested.

A Review of Vertical Graphene and Its Biomedical Applications

This paper explores the synthesis methods and properties of vertically aligned graphene nanosheets (VG) and their applications. VG is obtained using the plasma-enhanced chemical vapor deposition (PECVD) method, and different VG types with other properties can be obtained by changing the process parameters. VG is part of the graphene family; properties such as excellent electrical conductivity, thermal conductivity, chemical stability, and a large, specific surface area make it suitable for biomedical applications. Examples of biomedical applications in which VG is used are biosensors, electrochemical sensors, modified surfaces for bone growth, regeneration, and for antimicrobial effects. First, VG’s properties are reviewed in this review article, and then the most recent progress in its applications and related sciences and technologies are discussed.

Effect of the energy of hydrocarbon ions on diamond-like carbon films deposited on alumina microparticles through repeated pulsed discharge in hollow cathode with methane gas

Diamond-like carbon (DLC)-modified alumina microparticles are expected to be an ideal filler that can greatly improve the thermal conductivity of epoxy-alumina composites with a high fill factor, while the composites can still maintain high dielectric properties. Plasma-enhanced chemical vapor deposition (PECVD) has been mostly used to prepare DLC film on bulk material, and the ion energy in the plasma shows a crucial influence on the properties of the DLC. However, the properties of the DLC on solid microparticles prepared through the PECVD method as well as the effect of the ion energy are still unclear. In this paper, DLC on alumina microparticles has been prepared through a highly efficient method of repeated pulsed hollow cathode discharge in methane gas, and the characteristics of the DLC on the alumina particles have been studied and analyzed. The morphology and bond composition of DLC on particles have been studied through electron microscopy, Raman spectrometer and x-ray photoelectron spectroscopy. The ion energy distribution in the discharge plasma was diagnosed and used to analyze its effect on the hybrid bond content of the DLC through correlation analysis. The correlation of the ion energies and the hybrid bond content of the DLC shows that hydrocarbon ions in the discharge plasma with an energy of 100–200 eV present the most benefit to the formation of the sp3 hybrid bond content of DLC film on alumina microparticles. In addition, hydrogen ions with an energy of 700–1000 eV are also beneficial to improve the sp3 hybrid bond content of the DLC film.

Bayesian optimization of hydrogen plasma treatment in silicon quantum dot multilayer and application to solar cells

Silicon quantum dot multilayer (Si-QDML) is a promising material for a light absorber of all silicon tandem solar cells due to tunable bandgap energy in a wide range depending on the silicon quantum dot (Si-QD) size, which is possible to overcome the Shockley–Queisser limit. Since solar cell performance is degenerated by carrier recombination through dangling bonds (DBs) in Si-QDML, hydrogen termination of DBs is crucial. Hydrogen plasma treatment (HPT) is one of the methods to introduce hydrogen into Si-QDML. However, HPT has a large number of process parameters. In this study, we employed Bayesian optimization (BO) for the efficient survey of HPT process parameters. Photosensitivity (PS) was adopted as the indicator to be maximized in BO. PS (σp/σd) was calculated as the ratio of photoconductivity (σp) and dark conductivity (σd) of Si-QDML, which allowed the evaluation of important electrical characteristics in solar cells easily without fabricating process-intensive devices. 40-period layers for Si-QDML were prepared by plasma-enhanced chemical vapor deposition method and post-annealing onto quartz substrates. Ten samples were prepared by HPT under random conditions as initial data for BO. By repeating calculations and experiments, the PS was successfully improved from 22.7 to 347.2 with a small number of experiments. In addition, Si-QD solar cells were fabricated with optimized HPT process parameters; open-circuit voltage (VOC) and fill factor (FF) values of 689 mV and 0.67, respectively, were achieved. These values are the highest for this type of device, which were achieved through an unprecedented attempt to combine HPT and BO. These results prove that BO is effective in accelerating the optimization of practical process parameters in a multidimensional parameter space, even for novel indicators such as PS.