Effect Of Buffer Layer Research Articles

Effect of P21 buffer layer on interfacial bonding characteristics of high‑carbon tool steel hardfaced through directed energy deposition

The elevated hardness of high‑carbon tool steel (M2) powder makes it an effective material for hardfacing components requiring strong wear resistance. However, if the brittle M2 powder is deposited on a ductile substrate, significant stress occurs during cooling, leading to defects, such as cracks at the interface between the substrate and deposited regions. Therefore, in this study, ductile P21 powder was deposited as a buffer layer between the substrate and the deposited M2 layer to prevent interface defects. To confirm whether this P21 buffer layer effectively prevents interfacial defects, bending, impact, and tensile tests were performed. No interfacial defects were observed in the cross-section of the deposition specimen when a P21 buffer layer was applied. The average hardness of the surface deposited M2 region was 733 HV, similar to that of the carburized substrate. As-built (M2) specimen showed 94% lower in weight reduction than the carburized material after the wear test. The specimen without a buffer layer revealed cracks propagating along the interface between the deposited region and substrate, with the lowest impact energy absorption of 25 J. However, the energy absorption of the specimen with a P21 buffer layer was 60% higher than that without a buffer layer. The tensile test results show 7% increase in tensile strength with the buffer layer and 244% increase in elongation. This study demonstrated that high hardness and wear resistance could be achieved through M2 deposition and confirmed the improved strength and toughness with a P21 buffer layer.

Effect of buffer layer on thermal recovery of superconducting nanowire single-photon detector

Superconducting nanowire single-photon detectors (SNSPDs) wherein ultrathin films are fabricated on Si substrates are greatly affected by lattice mismatch between the thin film and the substrate. A buffer layer can be used to reduce such lattice mismatch or optimize the strain in the film, thereby improving device performance. We prepared and optimized Nb5N6 as a buffer layer and found that it considerably improved the properties of NbN films on Si substrates. The zero-resistance critical temperature (T C0) of a 3 nm thick NbN film with a 20 nm thick buffer layer was 10.3 K. SNSPDs with Nb5N6-buffered NbN films were fabricated and compared with normal devices; the fabricated devices had high hysteresis current and low timing jitter. Furthermore, we investigated the thermal diffusion process of the device based on the hysteresis current and hotspot relaxation time and found that Nb5N6 buffer layers enhance the thermal coupling between the superconducting film and substrates. The relaxation time of buffered SNSPD was 14.2 ps, which was shorter than that of nonbuffered SNSPD by 17.8 ps. These effects explain the performance improvement observed in the case of the buffered devices.

Effect of MoS2 interlayer on performances of copper-barium-tin-sulfur thin film solar cells via theoretical simulation

Cu2BaSn(S,Se)4 (CBTSSe) solar cells are emerging photovoltaic devices due to their high theoretical efficiencies of ~31%, environment-friendly and earth-abundant composition, low density of non-recombination defects, and so on. However, the record efficiency of CBTSSe solar cell is only 5.2%, showing the importance of studying their performance via numerical analysis to further enhance their practical efficiencies. In this paper, the effect of absorber and buffer layers on performances of Cu2BaSnS4 (CBTS) solar cells are firstly systematically studied via the SCAPS-1D software to provide a platform for the study of the effect of MoS2 interlayer on the performances of CBTS solar cells. The highest PCE of CBTS solar cell with a 30 nm CdS buffer layer is 11.87%. The PCE of CBTS solar cell with a 0.8 μm CBTS absorb layer is 12.51%, indicating that the CBTS solar cell is a potential low-cost solar cell due to its large optical absorption coefficient (α > 104 cm−1). The efficiency of CBTS solar cell is improved to 16.47% when the carrier concentration of CBTS is 1016 cm−3. The relationship between the performance of solar cell and the band gap, thickness, donor concentration, acceptor concentration of MoS2 interlayer is systematically investigated on the basis of the optimized efficiency. It is found that MoS2 interlayer plays an important role in the performance of CBTS solar cell. The p-type MoS2 has a beneficial effect on the efficiency improvement while the n-type MoS2 has a negative effect on the efficiency enhancement. The highest PCE of CBTS solar cell is as high as 18.28% when the thickness and the acceptor concentration of MoS2 are 4 nm and 1019 cm−3, respectively. Our simulation result provides a promising research direction to further improve the actual efficiency of the CBTS solar cell.

Numerical simulation of the effect of varied buffer layers on the performance of Cu(In, Ga)Se2 solar cells using Silvaco Tcad 2D

The CIGS thin-film solar cells Solar cells are regarded as one of the most promising photovoltaic technologies. They have the advantage of fast and low-cost manufacturing by depositing several thin layers. In this work, a numerical simulation was made to compare the effect of different buffer layers (CdS, ZnS, ZnSe, and In2S3) on the performance of CIGS solar cells using Silvaco Tcad 2D software. The results show that each buffer layer influences the performance of the cell. Therefore, our results suggest that the ZnS material as a buffer layers has better performance for our cell (Jsc=37.0252mAcm2, Voc=1,281, FF=88,01 , ƞ=20,88).

Advances in the modification and device integration of multiferroic bismuth ferrite

As a single-phase multiferroic oxide, BiFeO3 (BFO) is suitable for applications such as magnetoelectric memories, sensors and actuators. However, BFO suffers from high leakage current density and small magnetization. And the BFO in film form is apt to react with Pt bottom electrode during the thermal treatment. In addition, its required high processing temperatures can not be compatible well with the interconnect technologies for semiconductor. In this review, we summarize both the improvement in leakage characteristics and enhancement of magnetic properties of BFO. The effects of buffer layers on properties and device integration of BFO thin films are also introduced.

Laser-patterned Si/TiN/Ge anode for stable Si based Li-ion microbatteries

Progress in micro/nano-electro-mechanical system (M/NEMS) and microelectronics technologies urgently require the synchronous development of the micro/nano energy storage systems. Herein, a novel patterned Si/TiN/Ge electrode is fabricated on the Si substrate surface by the facile femtosecond-laser direct writing and the microelectronic thin film deposition techniques. The surface-engraved Si/TiN/Ge electrode displays superior cyclability and rate capability when evaluated as anode for lithium ion microbatteries (LIMBs). The patterned TiN interlayer can act as an effective buffer layer to optimize the Li ions storage in the Si substrate, and the introduction of the Ge nanocomposites would further enhance the areal capacity, thus eventually bring the improved electrochemical performance. Moreover, the Li ions storage behaviours are experimentally investigated from the post morphologies of all the cycled electrodes, and theoretically studied by the COMSOL Multiphysics simulations and the first principles calculations. These results would shed light on the new strategy to design and exploit other high-performance Si based LIMBs.

Enhanced interface properties of solution-processed antimony sulfide planar solar cells with n-type indium sulfide buffer layer

Although antimony sulfide (Sb2S3) has become a promising photovoltaic material, the performance of Sb2S3 planar solar cells is pinned by the charge recombination and interface defects of Sb2S3 thin film . Herein, n-type indium sulfide (In2S3) serving as the buffer layer between TiO2 and the Sb2S3 layers was prepared by chemical bath deposition (CBD) method. Sb2S3 thin films were in situ prepared with a solution-processed construction strategy. The characteristics of the obtained thin films were studied in more detail by electron microscopy, X-ray technique, optical and electrochemical performance measurements. Results show that the In2S3 buffer layer prepared by the optimized CBD time improves the compactness and crystallinity, prevents Sb3+ from being oxidized, and boosts the light absorption ability for the Sb2S3 films. The fabricated FTO/TiO2/In2S3/Sb2S3/P3HT/Au planar cell device exhibits the higher open-circuit voltage (Voc) of 0.59 V, short-circuit current density (Jsc) of 8.90 mA cm−2, and power conversion efficiency (PCE) of 2.41%, respectively, compared to the FTO/TiO2/Sb2S3/P3HT/Au cell device. The superior photoelectric conversion performance is attributed to the promoting effects of the In2S3 buffer layer at the interface between TiO2 and the Sb2S3 layers, which reduce the charge recombination, facilitate the electron transfer, and enhance the electron lifetime. This work proposes an original insight towards non-toxic In2S3 as a buffer layer in Sb2S3 planar solar cells.

Elucidating the Effect of the Different Buffer Layers on the Thermal Stability of CIGSe Solar Cells

In this contribution, the impact of thermal stress on Cu(In,Ga)Se $_{2}$ (CIGSe) thin film photovoltaic devices is investigated. The tolerance of such devices to high temperatures is of particular interest for processing transparent conductive oxides (TCOs) in order to further close the gap to the theoretical efficiency limit and for their potential use as bottom devices in tandem applications in order to overcome the theoretical efficiency limit of single junction solar cells. When CdS-buffered CIGSe high efficiency solar cells are subjected to thermal stress, elemental interdiffusion of Na and Cd between the absorber and the window layers as well as chemical reactions at the CIGSe/CdS interface result in a degraded power conversion efficiency (PCE). Here, we compare the degradation mechanisms of CdS and GaO $_{x}$ buffered CIGSe solar cells under thermal stress. A model explaining the observed degradation behaviors is proposed.

Combined Effects of Buffer Layers and Electrode Contacts on the Performance of Organic Solar Cells

This study investigates the effects of buffer layer and electrode contact on various structures of an organic solar cell (OSC), including the effect of the thickness of the active layer and the band gap, simultaneously. This study analyzes different structures of OSCs based on materials that are commonly used for organic cells improvement. The organic solar cell with the blend poly(3-hexylthiophene-2,5-diyl) (P3HT):phenyl-C61-butyric-acid-methyl ester (PCBM) has been used for the proposed model, yielding the following results: power conversion efficiency (PCE) = 4.20%, open circuit voltage (Voc) = 0.60 V, short circuit current density (Jsc) = 10.86 mA/cm2, fill factor = 64.68%. The effect of changing the electrode contact has given PCE from 1.18% to 11.54%, whereas PCE of the effect of changing the buffer layer was from 1.43% to 13.17%. The characteristics of the current density–voltage (J–V) for all structures were comparatively analyzed, and the proposed model has been approved by comparing the results achieved with experimental data of real devices. This analysis helps to adjust the appropriate structures with the optimizing parameters for enhancing the performance of OSCs.

High-Temperature Atomic Layer Deposition of GaN on 1D Nanostructures.

Silica nanosprings (NS) were coated with gallium nitride (GaN) by high-temperature atomic layer deposition. The deposition temperature was 800 °C using trimethylgallium (TMG) as the Ga source and ammonia (NH3) as the reactive nitrogen source. The growth of GaN on silica nanosprings was compared with deposition of GaN thin films to elucidate the growth properties. The effects of buffer layers of aluminum nitride (AlN) and aluminum oxide (Al2O3) on the stoichiometry, chemical bonding, and morphology of GaN thin films were determined with X-ray photoelectron spectroscopy (XPS), high-resolution x-ray diffraction (HRXRD), and atomic force microscopy (AFM). Scanning and transmission electron microscopy of coated silica nanosprings were compared with corresponding data for the GaN thin films. As grown, GaN on NS is conformal and amorphous. Upon introducing buffer layers of Al2O3 or AlN or combinations thereof, GaN is nanocrystalline with an average crystallite size of 11.5 ± 0.5 nm. The electrical properties of the GaN coated NS depends on whether or not a buffer layer is present and the choice of the buffer layer. In addition, the IV curves of GaN coated NS and the thin films (TF) with corresponding buffer layers, or lack thereof, show similar characteristic features, which supports the conclusion that atomic layer deposition (ALD) of GaN thin films with and without buffer layers translates to 1D nanostructures.

TEM investigation of microstructure of semipolar GaN layers grown on nano-patterned Si(001) substrates

The synthesis of III-nitride binary compounds on commercial standard (001) silicon wafers by vapour-phase epitaxy is one of the promising directions for III-nitride technology development. However, the difference between crystal symmetry of Si(001) and wurzite (0001) surface structures is challenge that hinders the development. A use of silicon substrates with nano-patterned surface is one of the solutions to the problem. In this paper we present a transmission electron microscopy study of polar and semipolar GaN layers grown by halide vapour-phase epitaxy and metalorganic vapour-phase epitaxy on nano-patterned silicon (001) substrate. Crystallographic orientation relationships between the silicon substrate and GaN layers is identified. For GaN layers grown by metalorganic vapour-phase epitaxy an effect of SiC buffer layer synthesized by original growth method on their microstructure and surface morphology is under consideration.

Effective buffer layer thickness of La-doped CeO2 for high durability and performance on La0.9Sr0.1Ga0.8Mg0.2O3-δ electrolyte supported type solid oxide fuel cells

Solid oxide fuel cells (SOFCs) have been gaining increased attention in the energy sector. Commonly, yttria-stabilized zirconia is widely employed as commercial electrolyte, however, resulted in drawbacks such as high-temperature operating and low conductivity which negatively affect the durability and efficiency. Thus there are many efforts to find high-ionic conductors. From the point of manufacturing, the major difficulty of LaGaO3-based electrolyte as a high-ionic conductor is its incompatibility with commercial Ni-based anodes during high-temperature processes as well as operating. Several interlayers have been introduced to prevent the reaction between LaGaO3-based electrolyte and Ni-based anode. In this study, we investigate the optimal thickness of the La-doped CeO2 (LDC) interlayer by the screen-printing method using La0.9Sr0.1Ga0.8Mg0.2O3-δ for the commercial electrolyte supported SOFCs. As a result, the superior power performance of 2.2 W·cm−2 at 1123 K is achieved through the optimized LDC thickness of 20 μm through not lab-scaled but commercial ceramic manufacturing processing.

Electron-phonon coupling behavior in MgB2 films with various thicknesses of ZnO buffer layer on metallic substrates

In order to investigate the effect of buffer layer on the superconducting properties of MgB2, behaviors of electron-phonon coupling (EPC) in MgB2 thin films with various thicknesses of ZnO buffer layer on two different substrates Al2O3 and Hastelloy were studied. As the ZnO thickness increases, the values of Tc of MgB2 films on two substrates show opposite behaviors. Sharply decreased and then saturated Tc of ~38K is observed on Al2O3 substrates while an abrupt increase of Tc with no tendency of decrease is obtained on Hastelloy substrates. These Tc behaviors are closely related to the E2g phonon hardening/softening inside MgB2 which may be induced from a lattice distortion caused by an introduction of ZnO buffer layer. The electron-E2g coupling provides a dominant contribution to EPC from all phonon modes, however, it shows a very weak dependence on ZnO thickness to explain the Tc behavior of our samples. Therefore, in order to establish a mechanism of ZnO buffer layer influencing Tc of MgB2 films, contribution from other phonon modes needs to be considered. Understanding the effect of ZnO buffer layer on the EPC and the Tc behavior opens a possibility to obtain an optimal condition for ZnO buffer layer of MgB2 for the field of application.

Influence of buffer layer on surface and tribomechanical properties of laser cladded Stellite 6

Wear resistance coatings of Stellite 6 were deposited on SS316 substrate by blending a buffer layer of Inconel 625 with varying Linear Heat Inputs (LHI). The mechanical and microstructural properties of Stellite 6 coatings are investigated to evaluate the effect of buffer layer. The surface flaws, microstructure, micro-hardness and wear resistance of Stellite 6 clads with buffer layer are studied and compared with direct deposited Stellite 6. The results show an increment in clad height by 30% and 9% at lower and higher LHIs, respectively as compared to pre-deposited Stellite 6 clads. The deposition pattern (with and without buffer) are free from surface and internal cracks. The dilution is reduced by 25% and 10% whereas the microhardness shown an improvement by 12% and 5% with addition of buffer layer. Further, a fine-grain microstructure is observed in buffer layer clads at the interface zone. Moreover, the studies on wear rate have shown improvement of 14% and 3%, respectively with low coefficient of friction (COF) in buffer layer deposition because of high microhardness and fine grain microstructure. Thus, laser cladding of Stellite 6 at lower LHI with buffer layer has shown excellent mechanical and microstructural properties.

Manipulating the structural and magnetic properties of double perovskite Y2NiMnO6 thin films by oxygen pressure and buffer layer

Replicating the properties of a bulk oxide in its film counterpart is critical for device applications. In this work, the effects of oxygen pressure and buffer layer on double perovskite Y2NiMnO6 (YNMO) thin films have been studied carefully. The increase in oxygen pressure is found to contribute to the lattice relaxation, reduction of Mn3+ ions, and enhancement of magnetization of YNMO films. The out-of-plane lattice constant of the YNMO film at high oxygen pressure can be tuned to nearly match that of the bulk. Moreover, the insertion of a CaTiO3 buffer layer is beneficial for the oxidization of Mn4+ ions. It affects the spin state of YNMO films significantly, while it has little influence on the lattice structure. With co-action of oxygen pressure and the CaTiO3 buffer layer, the lattice structure, element composition, and magnetization of the obtained YNMO films are almost comparable to those of the bulk.

Effect of InAs buffer layer thickness on physical properties of InAsBi heterostructures grown by MOCVD

Different InAsBi/buffer-InAs/GaAs(100) and InAs/GaAs(100) heterostructures have been grown by metal-organic chemical vapor deposition at 375°C. The epitaxy was monitored, in the visible – near-infrared domain, by employing the reflectance spectroscopy (RS) technique. Bismuth (Bi) incorporation has been quantitatively and qualitatively discussed in the light of optical measurement performed by ex situ spectroscopic ellipsometry and in situ RS measurements; It induced a narrowing of the E1 and E1+Δ1 critical points in comparison to those of InAs. The shrinkage-rate was of 4.5meV/%Bi and 7.8meV/%Bi, respectively for E1 and E1+Δ1. The effect of various buffer layer thicknesses on physical, epitaxial, structural, and morphological modifications of InAs1-xBix layers have been explored using high-resolution X-ray diffraction and atomic force microscopy. We found that the InAs buffer layer surface structure and thickness dominate the structural features and the uniformity of the InAsBi films. The optical parametric quantities such as the refractive index and the extinction coefficient are determined in comparison with available experimental and theoretical data. The value of the bismuth composition obtained from the analysis of in situ reflectance data agrees very well with that given by HRXRD analysis. The presented results contribute to a better understanding of Bi-containing III–V alloys growth mechanisms.

The buffer layer effect of the exchange stiffness constants on Co thin film

The exchange stiffness of Cobalt thin films with various buffer layers (Pd, Pt, Ta, and no buffer) has been studied by Brillouin scattering in the applied magnetic field of up to 175 mT. We found that Pd and Pt buffer layers led to higher exchange stiffness constants more than 12% compared to the Ta buffer layer, whereas, it was difficult to determine the exchange stiffness constant with no buffer layer due to broad spinwave spectra with poor signal-to-noise ratios. The determined exchange stiffness constant value is 25.7 ± 0.1, 25.6 ± 0.2, and 22.7 ± 0.1 pJ/m for Pd, Pt, and Ta buffer layers. We also observed that the Pd-underlayered sample gives us the largest saturation magnetization and in contrast the Ta underlayer shows the relatively smaller values. This observation indicates that the exchange stiffness constant and the saturation magnetization exhibit the same trend on various buffer layers.

Strain-induced local structural change and its effect on the superconducting properties of GdBa2Cu3O7-x /La0.7Sr0.3MnO3 heterostructure

The effect of ferromagnetic buffer layer on the superconducting properties of relatively thick, high temperature superconductors is investigated. Elaborately designed heterostructure films consisting of epitaxial GdBa2Cu3O7-x (GdBCO) on top of two types of La0.7Sr0.3MnO3 (LSMO) layer and particles, were fabricated by pulsed laser deposition. Unlike a typical superconducting/ferromagnetic system where the superconducting properties are degraded, the superconducting properties of our GdBCO/LSMO system are enhanced depending on the local structural details of the GdBCO and LSMO layers. The strain state of GdBCO characterized from the bond length of the Cu-O and the Mn-O bonds lengths is observed to vary depending on the formation of LSMO. The phase diagram of Tc for the GdBCO/LSMO system established by the micro-strain of the Cu-O bond-length shows that Tc reaches its maximum at the critical micro-strain. This result suggests the importance of strain state in improving the superconducting properties of thick-GdBCO/LSMO films.

Effect of Ba(Mg1/3Nb2/3)O3 buffer layer on electrical properties of PZT-based films

Pb[Nbx(Zr0.52Ti0.48)1−x]O3 (PNZT) thin films were deposited on Pt/Ti/SiO2/Si(100) by the sol–gel method using Ba(Mg1/3Nb2/3)O3 (BMN) buffer layer. The effects of Nb doping and BMN buffer layer on fatigue endurance and ferroelectric properties of PZT thin film were investigated. The optimum ferroelectric properties of PNZT film: Pr = 43.4 µC/cm2, Ec = 29.3 kV/cm and J = 2.73 × 10− 6 A/cm2 were obtained by doping 3 mol% Nb in PZT film. After 1010 cycles, the Pr of PZT film reduces by 50%. After 1012 cycles, the Pr of PNZT film only reduces by 20%. The reason for enhanced ferroelectric properties and fatigue endurance of PNZT thin film is that Nb doping effectively prevents the generation of oxygen vacancies. The Pr of the PNZT/BMN film remains 85% after 1010 cycles, and it remains stable even till to 1012 cycles. Moreover, the leakage current of PNZT/BMN film is 5.40 × 10− 7 A/cm² under 100 kV/cm electric field, which is about one order of magnitude lower than that of PNZT (2.73 × 10− 6 A/cm²). The effect of BMN on improving the fatigue endurance and ferroelectric properties of PNZT thin film could be ascribed to blocking of Pt diffusion at the PNZT–Pt interface. Moreover, PNZT/BMN film with excellent ferroelectric and fatigue endurance shows the promising application in FeRAM.

Simultaneous realization of infrared-light switching and high visible-light transmittance in extremely thin VO2 films grown on ZnO-nanorods buffered glasses

The authors demonstrate a significant effect of ZnO-nanorod buffer layers on the growth of extremely thin VO2 films. Highly c-axis oriented ZnO-nanorods were grown on glasses with sputtered ZnO-seed layers by using the chemical bath deposition method. Introducing an organic compound, (CN2)6N4 (hexamethylenetetramine), together with a Zn source, Zn(NO3)2, achieved highly c-axis oriented ZnO-nanorods with an average diameter of around 150 nm. Due to such a superior template, b-axis oriented VO2 films were grown on the ZnO-nanorod buffered glasses even with the film thickness lower than several tens of nanometers. The thinnest VO2 film emerged in insulator-metal transition, achieving high visible-light transmittance and clear infrared-light switching, which are characterized by luminous transmittance (Tlum) of 56% even at metallic state and solar modulation ability (ΔTsol) of 6.0%. The results obtained in this study propose a way to achieve practical smart windows that enable not only infrared-light switching but also maintaining high visible-light transmittance without any optical design.