Sulfurized Layer Research Articles

Utilizing H2S to sulfurize transition metal and oxide barriers for suppressing resistivity scaling of ruthenium metallization

Ruthenium is of great potential for use as next-generation interconnect metallization but still suffers from resistivity scaling at nanoscale linewidths due to the severe interface scattering of electrons. In this study, a thin sulfurized layer was hence formed on titanium-tantalum and titanium-tantalum oxide barriers by utilizing hydrogen sulfide gas for interface modification. The microstructure, chemical composition, bonding configuration and interfacial adhesion of the sulfurized barriers and ruthenium films were investigated, and the resistivity scaling of the ruthenium films on the barriers was evaluated. Experimental results indicate that an amorphous sulfide layer of only several nanometers thick was uniformly formed on the top surface of the barriers and changed the resistivity and binding state of the metal and oxide barriers. Attributed to the formation of the sulfide layer, the specular scattering of electrons at the ruthenium/barrier interface was enhanced, effectively suppressing the resistivity scaling of the ruthenium films, and the interfacial adhesion strength was also markedly improved.

Toward improving the performance of Cu2ZnSnS4-based solar cells with Zr, W or sulfurized layers at the SnO2:F/Cu2ZnSnS4 rear interface

The photovoltaic performance of Cu2ZnSnS4 (CZTS)-based thin film solar cells with transparent back contacts is mainly constrained by the ohmic loss due to degradation of the back contacts at high temperatures required for the growth of the CZTS absorbers. This work has attempted to use ultrathin Zr and W interlayers at the SnO2:F (FTO)/CZTS interface with the purpose of improving the ohmic properties of FTO and hence the performance of solar cells. 20 nm thick Zr and W layers were coated on FTO using direct current magnetron sputtering, followed by heating at 550 °C in a sulfur atmosphere for some of the samples. Inclusion of Zr and W interlayers compromised the transmittance of the FTO back contact, however heating of the samples in a sulfur atmosphere improved the transmittance to values comparable to or better than those of un-heated FTO. Furthermore, heated W/FTO showed a significant improvement in electrical conductivity as observed from Hall effect measurements. To make complete solar cells, CZTS absorber, buffer (CdS) and window (i-ZnO/ZnO:Al) layers were sequentially deposited on the un-heated FTO, Zr/FTO, W/FTO and Mo back contacts. Glow discharge optical emmision spectroscopy confirmed that Zr and W did not diffuse into the absorber and also prevented Na diffusion into the absorber. From the scanning electron microscopy cross sectional analysis, an impovement in the absober grain size and a clear junction between the absorber and FTO with W interlayer were observed. Grazing incident X-ray diffractometry confirmed the polycrystalline nature of the CZTS thin films and indicated the presence of other phases, particularly SnS2. On the resulting solar cell parameters, the inclusion of a W interlayer reduced the series resistance from 4.5 Ωcm to 3.7 Ωcm2. An improvement in short circuit current density (JSC) is also observed, enhancing the efficiency of the solar cells with CZTS/W/FTO to 3.1 % compared to that with CZTS/Mo at 2.7 % and CZTS/FTO at 3.0 %. W was found to improve the external quantum efficiency response and JSC of the solar cells for both backside and frontside light illumination. On the other hand, inclusion of a Zr interlayer (Zr/FTO) only slighlty improved the open circuit voltage, but compromised the JSC compared to FTO and W/FTO back contacts. Thus, the findings of this study demonstrate the prospect for improving the performance of the CZTS-based thin film solar cells through the inclusion of ultrathin Zr and W interlayers between the FTO back contact and CZTS absorber.

Synthesis of WS2 Ultrathin Films by Magnetron Sputtering Followed by Sulfurization in a Confined Space

In the quest for advanced materials suitable for next-generation electronic and optoelectronic applications, tungsten disulfide (WS2) ultrathin films have emerged as promising candidates due to their unique properties. However, obtaining WS2 directly on the desired substrate, eliminating the need for transfer, which produces additional defects, poses many challenges. This paper aims to explore the synthesis of WS2 ultrathin films via physical vapor deposition (PVD) followed by sulfurization in a confined space, addressing the challenge of film formation for practical applications. Precursor layers of tungsten and WS2 were deposited by RF magnetron sputtering. Subsequent sulfurization treatments were conducted in a small, closed, graphite box to produce WS2 films. The physical and chemical properties of these precursor and sulfurized layers were thoroughly characterized using techniques such as X-ray reflectometry (XRR), X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The findings reveal notable distinctions in film thickness, structural orientation, and chemical composition, attributable to the different precursor used. Particularly, the sulfurized layers from the tungsten precursor exhibited a preferred orientation of WS2 crystallites with their (00L) planes parallel to the substrate surface, along with a deviation from parallelism in a small angular range. This study highlights the necessity of precise control over deposition and sulfurization parameters to tailor the properties of WS2 films for specific technological applications.

Reduction of Friction and Wear for AISI321 Stainless Steel through Surface Modification Using Nanocrystallization.

Through surface nanocrystallization and low-temperature ion sulfurization, the nanocrystalline/FeS thin film with excellent friction-reduction and antiwear properties was fabricated on the surface of AISI321 stainless steel. The nanocrystallization treatment formed the high hardness and active nanocrystalline structure on the surface of AISI321, with the harness increased from 4.6 GPa to 7.56 GPa. Furthermore, the significantly refined nanostructure strongly increased the concentration of S element in comparison with the single-sulfurized layer on the substrate. Tribological tests reveal that both the original AISI321 substrate and the single-sulfurizing-treated samples are subject to severe abrasion. Single nanocrystallization treatment can improve the wear resistance of AISI321, while the compound treatment can obviously improve the comprehensive tribological properties. The compound-modified layer presents excellent tribological properties with the lowest coefficient of friction (COF) of 0.33, which is related to the increased hardness of the substrate and increased thickness, density, and homogeneity of the sulfurized layer. Furthermore, a physical model is developed for the vacuum tribological behavior of the samples after different treatments. This model provides a reference for revealing the tribological mechanism of the compound-modified layer treated using surface nanocrystallization-assisted chemical heat treatment.

Ag/Ag2S–TiO2 composite film formed using dual phase Ag/Ag2O layer as a sulfurized layer for enhanced photocatalytic activity

The Ag/Ag2S–TiO2 composite films were synthesized through vulcanizing sputtering Ag/Ag2O dural-phase template capping layer on the TiO2 film. After hydrothermal vulcanization using thiourea as a sulfur precursor, the initially decorated Ag2O layer transformed into the Ag2S. The surface morphology of the continuous block structure of the Ag/Ag2S composite layer gradually shrinks to form irregular island grains dispersed on the surface of the composite film, with vulcanization reaction duration increased from one to 3 h. The light absorption ability of the Ag/Ag2S–TiO2 composite film was enhanced substantially compared to the TiO2 film because of the surface plasmon resonance effect from the Ag particles and the narrow energy band of the Ag2S. Among various surface morphologies of the Ag/Ag2S–TiO2 composite films, the irregular island Ag/Ag2S grains-decorated TiO2 composite film presents superior photoelectrochemical and photocatalytic degradation performances than the composite films consisting of continuous block and spider-web structure of the Ag/Ag2S decorated layers. The synergistic effects of surface plasmon resonance, Ag pathway between the semiconductors, and Z-scheme charge transfer mechanism explain the high-efficiency photocatalytic activity of the Ag/Ag2S–TiO2 composite films.

Tribological performance analysis of nano-FeS films deposited on the surface of bearing steel

The wear and adhesion of bearing surface under boundary lubrication is the key to the development and application of bearing technology. For improving the antifriction and antiadhesion properties of the bearing materials, the sulfur rich nano self-lubricating thin layers were prepared on the bearing surface by low-temperature sulfide permeation technology. The morphology and composition of the sulfurized layer were characterized microscopically, and the tribological properties of the sulfurized layer were analyzed to reveal the anti-friction and anti-adhesion mechanism of the sulfurized layer on the surface of bearing steel. The results show that the sulfurized layer is flatter and does not contain nanostructures when the formulation does not contain thiourea, and the content of element S is lower. After the addition of thiourea, the surface of the sulfurized layer is formed by the accumulation of nanosheet-like structures. The nano sulfurized layer has higher S-element content and better tribological properties. When thiourea and tartaric acid are added to the sulfurizing formula at the same time, the nano-sheet structure of the sulfurized layer is more dense and uniform. Moreover, the number of microcracks in the sulfurized layer is small, and the tribological properties are further improved. At the same time, the sulfide in the self-lubricating thin layer and the lubricating oil stored in the gaps can make the bearing surface have a typical "liquid-solid synergistic lubrication effect". That is conducive to the formation of the self-lubricating film and the transfer to the dual parts. All these factors improve the antifriction and antiadhesion properties of the bearing materials effectively.

Timing of sulfur introduction in the sulfurization of WO3 films dictates WS2 formation

Sulfurization of WO3 films can be an alternative to conventional chemical vapor deposition processes were both WO3 and S must be transported in the gas phase. Nevertheless, W loss and incomplete sulfurization were reported using this approach, constituting experimental hurdles to obtain WS2 layers with a specific thickness. The moment of S introduction in the process showed to play a decisive role, determining the obtention of a completely sulfurized layer or a modified oxide. Results evidenced that during a certain period, while sulfurization conditions are not efficient (S heating zone below 170 °C), WO3 annealing induces morphological and structural modifications (mainly crystallization) which modify oxide’s reactivity towards S. With this knowledge, efficient sulfurization strategies can be designed aiming at obtaining WS2 layers with the desired characteristics.

Feasibility of Using Sequential Sulfurized Nanoscale Zerovalent Iron-Persulfate Process to Degrade Tetrabromobisphenol A

This study proposed a sequential redox process to partially degrade tetrabromobisphenol A (TBBPA) within a reactor to a great extent. After 72 hours in an anoxic environment, 20 ppm of TBBPA could be effectively degraded by sulfurized zerovalent iron nanoparticles (S-nZVI) at concentrations of 2 g L-1 and 4 g L-1. Biphenol A (BPA) together with tri-, di-, and monobromobisphenol A was detected by high-performance liquid chromatography (HPLC) suggesting that TBBPA was debrominated by S-nZVI in a stepwise manner. Following the S-nZVI treatment, a persulfate-advanced oxidation process (PS-AOP) system with persulfate concentrations varied from 5 to 20 mM was incorporated to degrade the final debrominated byproduct, BPA, for 2 hours. The two-stage anoxic/oxic reactions at the same reactor with initial conditions (0.037 mM TBBPA, 4 g L-1 of S-nZVI, pH 6 in anoxic stage, 20 mM of PS in the latter oxic stage) were investigated. The sulfurized layer played an important role in such a system and hypothetically contributes to increasing electron transfer from Fe0 core as well as hydrophobicity of the NP surface. It was demonstrated that the S-nZVI/PS-AOP system could effectively remediate TBBPA and BPA and consequently provide a promising strategy to remedy brominated organic pollutants in the environment.

Effect of Sulfurization Time on the Physical Properties of Tin (II) Monosulfide Thin Films

Tin (II) monosulfide (SnS) films were prepared via sulfurization using sputtered Sn precursors of the tin metal layers in the presence of elemental sulfur vapor as a function of sulfurization time (ts) in the range of 30–180 min while keeping other parameters constant. The properties of these sulfurized layers were examined through suitable characterization techniques. The diffraction patterns exhibited various planes with the orientations (110), (120), (021), (101), (111), (211), (131), (210), (141), (002), (112), (122), and (042) corresponding to orthorhombic SnS at ts ≤ 90 min. However, for ts ≥ 120 min, the diffraction patterns showed a single (111) plane and enhanced the intensity of the peak with the increase of ts up to 150 min; with further increase of time, the peak intensity was found to decrease. The Raman spectra of films sulfurized at various ts showed modes at 95, 162, 189, 219, and 284 cm−1 for times were lower than 120 min and 95, 189, and 219 cm−1 for ts ≥ 120 min, related to SnS. In the transmittance spectra of the sulfurized films, it is clear that the film grown at ts = 30 min had higher transmittance, and with the increase of ts to 120 min, transmittance was decreased. For further extension of ts to 150 min, a sharp falling of the absorption edge was observed.

Tribological Study of Borocarburizing/Sulfurizing Composite Coatings on 2Cr13 Stainless Steel

The aim of this work was to investigate the mechanical properties and wear characteristics of 2Cr13 stainless steel coated with borocarburized and sulfurized layers using pack cementation. The microstructure and phase composition of the composite coatings were analyzed using scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffraction. The tribological properties under dry sliding against a ZrO2 ceramic ball were evaluated using a ball-on-disk friction tester at different loads, and the wear mechanism was proposed. The sulfurized layer mainly consisted of FeS and Fe2S, with the FeS phase acting as a solid lubricant for the coating. The borocarburized layer was mainly composed of FeB, Fe3C, and Fe2B, with a maximum hardness of approximately 1200 HV. The borocarburizing/sulfurizing treatment significantly decreased the friction coefficient and improved the wear resistance of the 2Cr13 steel. In addition, the composite coating exhibited excellent antifriction and wear resistance under slight adhesive and oxidation wear in high-load conditions.

Simultaneous Interphase Optimizations on the Large-Area Anode and Cathode of High-Energy-Density Lithium-Ion Pouch Cells by a Multiple Additives Strategy.

Prior to the maturation of next-generation energy storage devices, the actual lithium-ion batteries for commercial purposes are still expected to fulfill some critical requirements, among which the high energy density, wide operating temperature range, and related long-term cycling stability are the most challenging issues. Herein a multiple additives strategy is employed to simultaneously optimize the solid electrolyte interphase on the large-area anode and cathode in a 2 Ah artificial graphite (AGr)/LiNi0.5Co0.2Mn0.3O2 (NCM523) pouch cell with high gravimetric (>260 Wh kg-1) and volumetric (>630 Wh L-1) energy density. By introducing a rational mixture of electrolyte additives, a highly sulfurized surface layer and a uniform and thin passivation layer are separately formed on the anode and cathode of the AGr/NCM523 pouch cell, exhibiting high storage stability at 60 °C, much improved discharge capacity at -10 and -20 °C, high anodic stability at high voltage of 4.4 V, and stable cyclic performance with a capacity retention of 85.5% after 500 cycles, significantly outperforming the value of 75.7% after only 200 cycles of the cell without additional additives. These results demonstrate the critical effect of simultaneous optimizations of anode and cathode interphase layers to construct stable high-energy-density lithium-ion pouch cells.

Study on microstructural and tribological properties of sulphonitrocarburized layers diffused by hollow cathode discharging

In the present research, sulfurized, nitrided, nitrocarburized, and sulphonitrocarburized layers were diffused on the investigated specimens by hollow cathode diffusion, which was introduced as a new surface treatment method due to its numerous advantages over traditional diffusion methods. The structural morphologies, composition, phase structure, and tribological properties of different diffused layers were analyzed. It was found that both the sulfurized and sulphonitrocarburized layers were relatively porous compared with the other two diffused layers, especially the grain size and the microscopic roughness of the sulphonitrocarburized layer were much smaller than those of the sulfurized layer. The sulphonitrocarburized layer had the highest nano-hardness, the lowest friction coefficient, wear loss, and the smallest wear spot of the counterparts, which is superior over nitrided layer, nitrocarburized layer, and sulfurized layer. It benefited from the synergistic effect of the sulfurized layer and the nitrocarburized layer. This paper is significant for the protection of high-load high-speed friction pair s, exceptionally soft-hard pairs.

Sulfur treated 1D anodic TiO2 nanotube layers for significant photo- and electroactivity enhancement

In this work, we show that sulfur treated 1D anodic TiO2 nanotube layers lead to improved photo-electrochemical and catalytic properties compared to the blank nanotube layers. This treatment was performed in the evacuated quartz ampoules in the temperature range from 250 to 450 °C. Inspection of the sulfurized nanotube layers via scanning electron microscopy (SEM) and X-ray diffraction (XRD) has disclosed a gradual crystal growth within nanotube walls, represented by TiS2 or TiS3 phases. Optimally sulfurized TiO2 nanotube layers exhibit 3 times enhanced photocurrent in the UV spectral region, compared to the blank counterpart, with a shift of the light absorption up to the wavelength of 550 nm. In addition, the photocatalytic decomposition of a methylene blue aqueous solution using a wavelength of 365 nm is gradually improved with increasing sulfurization temperature. The highest photocatalytic decomposition rate is 2.3 times larger compared to the blank TiO2 nanotube layer. The application of sulfurized TiO2 nanotube layers for the electrocatalytic hydrogen evolution is also discussed.

Inhibiting MoS2 formation by introducing a ZnO intermediate layer for Cu2ZnSnS4 solar cells

A 10nm ZnO layer have been employed as an intermediate layer between absorber and back contact in Cu2ZnSnS4 thin film solar cells prepared by sulfurization of the metallic stacking layers. By introducing this layer, the device conversion efficiency increases from 2.1% up to 3.3%, open-circuit voltage increases from 476mV to 657mV while short-circuit current decreases from 14.52mA/cm2 to 10.72mA/cm2. The ZnO layer can significantly suppress the reaction of Mo back contact with S and facilitate the reaction between S and metallic stacking layers. It results in the MoS2 thickness decrease from 300nm to 80nm and less unreacted elemental Sn left in the CZTS absorber after sulfurization annealing as shown in transmission electron microscopy images. However, due to the Sn loss through a path of SnS at high annealing temperature, the reacted and eliminated elemental Sn results in a higher density of voids formed at the bottom of sulfurized stacking layers. The improvement in the cell efficiency and open-circuit voltage could be related to both reduced MoS2 thickness and removal of shunting path generated by elemental Sn. However, the voids formation at back contact deteriorates the carrier transportation and decreases short-circuit current.

Synergistic effects between sulfurized W-DLC coating and MoDTC lubricating additive for improvement of tribological performance

Low temperature ion sulfuration technology was used to obtain sulfurized layer on W doped diamond-like carbon (W-DLC) coating. The tribological behaviors of the pure W-DLC and sulfurized W-DLC coatings were investigated under PAO and MoDTC lubrication conditions. It shows that sulfurized W-DLC coatings can obviously improve their tribological performances under PAO with MoDTC lubrication. The primary reason is due to the formation of WSx on the surface of sulfurized W-DLC coating, the decomposition of additives for formation a higher ratio of Mo sulfide/Mo oxide and the graphitization for a high ratio of sp2/sp3.

The Low-temperature Ion Sulfurizing Technology and its Applications

Abstract A solid lubrication film mainly consists of FeS, which has excellent tribology properties, can be formed on the sulfurized iron or steel surface. The sulfurizing technology has aroused intense attention from the day it appeared. However, the widespread industrial application of sulfurizing technology was promoted by the low-temperature ion sulfurizing (LTIS) process. This paper summarized the phylogeny and sorts of sulfurizing technology firstly; then, the process flow of LTIS technology, the forming mechanism, microstructure and tribological properties of ion sulfurized layer were introduced detailedly; and then, the technological, economic and environmental merits of LTIS technology were generalized; finally, the industrial applications of LTIS technology in various typical rolling, sliding and heavy duty parts were reviewed briefly. LTIS technology, with the advantages of high sulfurizing speed, good performance of sulfurized layer and without sideeffect, has played an important role in the tribology modification of ferrous parts, and the LTIS process will become more green, simple and efficient in the future.

Investigation on Microstructure of CrN-Based Solid Self-Lubricant Composite Coating

The CrN-based solid self-lubricant composite coating was obtained by magnetron sputtering and low-temperature ion sulfuring. The XPS, AES and SEM equipped with EDS were utilized to observe and analyze the microstructure of the composite coating. The results show that there are Cr, Mo, N, S in the composite coating, and the phase structure is CrN, MoS2 and a few oxide. The element S was implanted 500nm in depth. For the sulfurized layer is extremely apt to be oxidized, in this paper, the source of element O is analyzed in detail through comparative studies on different methods for preservation of specimens, and the film-forming mechanism of CrN-based solid self-lubricant composite coating is discussed.

Preparation and Characterization of FeS Film by Low Temperature Ion Sulfurizing Technique

In this article, solid lubrication FeS film was prepared on the surface of AISI 1045 steel by means of low temperature ion sulfurizing process. Scanning electron microscopy (SEM) was utilized to observe the surface and cross-section morphologies of the sulfurized layer. The element distribution of the sulfurized layer surface was analyzed by X-ray energy spectrometer. The crystalline phases were determined by X-ray diffraction (XRD). X-ray stress determinator was utilized to measure the residual stress in the sulfurized layer. The nano-hardness and elastic modulus of the sulfurized layer were surveyed by a nano-indentation tester. The results showed that the surface of the FeS film was composed of many minute spherical particles with homogeneous grain size and distribution. The texture of the film was very loose with lots of micro-pores, and the crystallinity was well. There was compressive stress in the FeS film, and the stress value measured is -150 MPa. The average value of nano-hardness and elastic modulus were 4.02 GPa and 157.36 GPa respectively.

Tribological properties of WS 2 composite film prepared by a two -step method

In order to extend the application range of solid lubricant WS 2, the author adopted a two-step method to prepare WS 2 film; namely, W film was first fabricated on the AISI 1045 steel by magnetron sputtering method, and then treated by low temperature ion sulfuration to obtain WS 2 composite film. XRD was used to analyze the phase structure of the WS 2 composite film; its surface and worn scar morphologies were analyzed with SEM + EDS; X-ray stress determinator was utilized to measure its residual stress; the nano-hardness and elastic modulus of WS 2 composite film were surveyed by a nano-indentation tester. The tribological properties were investigated on a ball-on-disk wear tester under dry condition. The results showed that WS 2 composite film had much better anti-friction and wear-resistance properties than the original 1045 steel and sulfurized layer.

Synthesis of WS 2 nanosheets by a novel mechanical activation method

WS 2 nanosheets were synthesized by a novel mechanical activation method, in which a ball-milled mixture of WO 3 and S was adopted as reagent and then annealed at 600 °C for 2 h in an atmosphere of Ar. The final products were characterized by XRD, SEM and TEM. It was found that the nanosheets were obtained with thickness of only about 10 nm, through the exfoliation from the sulfurized outer layers of tungsten trioxide. The ball milling played a crucial role in the mechanical activation of reagents and promoted direct production of WS 2 without any intermediate products. The effect of temperature was also discussed.