Thermal Vapor Sulfurization Research Articles

Thermal vapor sulfurization of Ti3C2TX MXene to TiS2/carbon nanosheet cathode for long-life and high-loading all-solid-state lithium batteries

Stable and fast operation of all-solid-state lithium batteries (ASSBs) depends on durable and sufficient interfacial contacts between electrode components, especially when the loading and content of electrode active materials are high. Here, we propose promoting ionic/electronic transportations and contacts in sulfide electrolyte-based ASSBs by using TiS2/carbon nanosheets (TiS2/C-s) with large area-to-thickness aspect ratios as the cathode, which are prepared by simple thermal vapor sulfurization of exfoliated Ti3C2Tx MXene. The elastic 2D structure of the TiS2/C-s material can substantially improve interfacial contact with the solid electrolyte, minimize the diffusion distance of lithium ions, and buffer volume/stress changes during cycling, thereby ensuring the electro-chemo-mechanical stability and fast reaction kinetics of electrodes. Consequently, a 50 wt% TiS2/C-s cathode without any conductive carbon additives demonstrates a high discharge capacity (295 mAh g−1), long-term cyclic stability (94.7 and 74.7 % capacity retention after 250 cycles at 0.1 mA cm−2 and after 2300 cycles at 1 mA cm−2, respectively), and decent rate capability (126.0 mAh g−1 at 3 mA cm−2). Moreover, stable cycling with a high areal capacity (5.95 mAh cm−2) can also be achieved.

Thermal vapor sulfurization modified micro-sized red phosphorus/activated carbon composite anode for sodium-ion batteries

High-capacity red phosphorus/activated carbon (P/C) composites are promising anode materials for next-generation sodium-ion batteries. However, the poor conductivity and significant volume effect of red phosphorus inevitably deposited on the outer surface of P/C composites may incur significant capacity decay and structural degradation. This work reports a method for preparing surface-modified micro-sized P/C composites with built-in nanoscale features. Through thermal vapor sulfurization, the obtained micron-sized sulfur-modified P/C (S-P/C) composites not only fulfill the requirements of the battery manufacture but also maintain their nano-in-micro structure. It can eliminate the detrimental red phosphorus on the outer surface of P/C composites and convert it into the ion conductive layer of Na3PS4, limiting its volume effect and significantly promoting ion conduction. As a result, S-P/C composites exhibit excellent cyclic stability in a half cell (610 mAh/g at 0.2 A/g and capacity retention of 94.2 % after 100 cycles) and reach a high areal capacity level (1.99 mAh cm−2) in a full cell.

Epitaxial Growth of SnS2 Ribbons on a Au-Sn Alloy Seed Film Surface.

Two-dimensional metal chalcogenide film has attracted considerable interest for its use as an emerging device material for nanoelectronics. The film has been synthesized by various methods such as chemical vapor deposition, molecular beam epitaxy, and thermal vapor sulfurization. In this study, we took a new approach to synthesize tin disulfide (SnS2) by using Au-Sn alloy film as a metal seed deposited on a sapphire substrate. Multilayer SnS2 films were formed in a ribbon shape on (111)-oriented Au film and were aligned in the directions of threefold rotational symmetry. Furthermore, the SnS2 was found to have an epitaxial relationship relative to the Au film and the sapphire substrate as follows: SnS2[2̅110] || Au[101̅] || Al2O3[011̅0]. The segregation of grains consisting of a Sn-rich phase on the Au film surface and the subsequent sulfurization of these grains can be the key to the epitaxial SnS2 ribbon formation.

Highly Sensitive NO2 Detection by TVS-Grown Multilayer MoS2 Films

Two-dimensional layered materials have been investigated for sensor applications over the last decade due to their very high specific surface area and excellent electrical characteristics. Although grain boundaries are inevitably present in polycrystalline-layered materials used for real applications, few studies have investigated their effects on sensing properties. In this study, we demonstrate the growth of two distinct MoS2 films that differ in grain size by means of chemical vapor deposition (CVD) and thermal vapor sulfurization (TVS) methods. Transistor-based sensors are fabricated using these films, and their NO2 sensing properties are evaluated. The adsorption behavior of NO2 on MoS2 is considered in terms of the Langmuir isotherm, and the experimental results can be well fitted by the equation. The CVD-grown film exhibits electrical properties 1–2 orders of magnitude superior to those of the TVS-grown one, which is attributed to the large grain size of the CVD-grown film. In contrast, the sensitivity to NO2 is unexpectedly found to be higher in the TVS-grown film and is of the same order of a previously reported record value. Transmission electron microscopy observations suggest that the TVS-grown film consists of multiple rotationally oriented grains that are connected by mirror twin grain boundaries. Theoretical calculation results reveal that the adsorption of NO2 on the grain boundary that we modeled is equal to that on the ideal basal plane surface of MoS2. In addition, the porous structure in the TVS-grown film may also contribute to enhancing the sensor response to NO2. This study suggests that a highly sensitive MoS2 sensor can also be fabricated by using a polycrystalline film with small grain size, which can possibly be applied to other two-dimensional materials.

In‐Plane and Out‐of‐Plane Optical Properties of Monolayer, Few‐Layer, and Thin‐Film MoS2 from 190 to 1700 nm and Their Application in Photonic Device Design

Monolayer, few‐layer, and thin‐film MoS2 is synthesized using chemical vapor deposition (CVD) and thermal vapor sulfurization (TVS) methods. The complex refractive index of these samples is assessed using variable angle spectroscopic ellipsometry (VASE) measurements over a broad spectral range between 190 and 1700 nm. The ellipsometry data are sensitive to birefringence effects in the thickest thin‐film sample. These birefringence effects are investigated, and an analysis method is developed to extract the in‐plane and out‐of‐plane optical properties. The complex refractive index is then used to calculate reflectance, transmittance, and absorption of the MoS2 films using the transfer‐matrix method (TMM) and is matched with experimentally measured transmittance of the same samples. The modeled results show that the monolayer, few‐layer, and thin‐film MoS2 absorbs 7.4%, 12.6%, and 32.4% of the incident light, respectively, between 300 and 700 nm. When normalized to per unit‐thickness absorption, they absorb 12.1%, 5.9%, and 1.1% nm−1, respectively, clearly showing superior light–matter interaction in the monolayer and few‐layer films. These new complex refractive index data are further used to design optical coatings for these films to either confine absorption in a narrow bandwidth for photodetector applications or enhance broadband absorption for photovoltaic applications.

Morphological and structural evolutions of α-MoO3 single crystal belts towards MoS2/MoO2 heterostructures upon post-growth thermal vapor sulfurization

We have studied thermal vapor sulfurization (TVS) of α-MoO3 single crystal belts that were grown by chemical vapor deposition and transferred onto sapphire substrates. Micro-Raman scattering spectroscopy reveals an onset of material conversion from α-MoO3 to MoS2/MoO2/α-MoO3 heterostructures at TTVS = 600 °C; the conversion increases with the increase in TTVS, accompanied by monotonically mode hardening of MoO2 phonons up to TTVS = 900 °C; and the α-MoO3 base materials completely disappeared when TTVS is increased to higher than 800 °C, giving rise to thermodynamic stable MoS2/MoO2 heterostructures at TTVS = 900 °C. Layered structures consisted of a network of linear structures with regular in-plane orientation at the bottom and densely packed crystallites on top have also been observed, which is attributable to the effect of the epiready c-plane sapphire substrate. Absorption spectroscopy measurements reveal huge blue shifts in the absorption edge of the MoS2/MoO2 heterostructures when the thickness of the MoO2 layer is reduced, which is attributed to optical interferences at the crystal surfaces.

Thermal vapor sulfurization of molybdenum layers

Sulfurization of molybdenum layers is a promising route for obtaining large-scale and high-quality transition metal dichalcogenides. Here we describe the synthesis of continuous and homogeneous MoS2 in the centimeter scale by the thermal vapor sulfurization of pre-deposited molybdenum precursors on SiO2. Metallic molybdenum as well as MoO3 were used as precursors while the sulfurization was performed by chemical vapor deposition. A multi-technique characterization was employed to fully describe the deposition of molybdenum as well as its sulfurization. Thus, Raman spectroscopy, X-ray and ultra-violet photoelectron spectroscopies as well as scanning electron and atomic force microscopies indicated that the molybdenum layers were completely transformed in MoS2. The samples were homogeneous in the centimeter scale and quite flat with a root mean square roughness of 1.4 Å. Furthermore, its work function was 4.1 eV.

Analysis of photoluminescence behavior of high-quality single-layer MoS2

The ability to tailor and enhance photoluminescence (PL) behavior in two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) is significant for pursuing optoelectronic applications. To achieve this, it has been essential to obtain high-quality single-layer MoS2 and fully explore its intrinsic PL performance. Here, we fabricate single-layer MoS2 by a thermal vapor sulfurization method in which a pre-deposited molybdenum trioxide (MoO3) thin film is sulfurized over a short period (for several minutes) to turn into MoS2. These as-grown MoS2 crystals show quite strong PL, which is about one order of magnitude higher than that of chemical-vapor-deposited MoS2. Temperature- and power-dependent spectroscopy measurements disclose the apparent influence of sulfur (S) vacancies on the PL behavior and the noticeable free-to-bound exciton recombinations in the luminescence process. The fact that PL intensity of the sample in vacuum sharply lowered down relative to in air reveals that the high PL is facilitated by molecular adsorption on S vacancies in air. And multi-channel decay processes coupled with S vacancies are revealed in the time-resolved PL spectroscopy. In our work, single-layer MoS2 with high PL is synthesized and its defect-induced PL features are analyzed, which is of great importance for developing advanced nano-electronics and optoelectronics based on 2D structures.

High-performance FET arrays enabled by improved uniformity of wafer-scale MoS2 synthesized via thermal vapor sulfurization

The fabrication of wafer-scale multilayers molybdenum disulfide (MoS2) induced by sulfurizing molybdenum (Mo) seed layer could compatible with traditional semiconductor process but the random growth orientations especially the vertical aligned structures lead to the unreliability for electronic devices thus hindered their wide application. Here, we utilize multi-step heating (MH) sulfurization method to regulate the sulfurization rate and diffusion rate of thermal sulfur vapor, thus realize the fabrication of MoS2 nanofilms with wafer-level uniformity and based on this, we integrate back-gate field-effect transistor (FET) arrays with an average hole mobility of 0.9cm2 V−1 s−1 and high device yield (~98%) which illustrate the reliable electrical-performance among the device arrays and the high quality of the as-fabricated MoS2 nanofilms. Therefore, we believe our efforts could pave the way for fabricating wafer-scale transition metal dichalcogenides (TMDCs) nanofilms with high uniformity and promoting their application for the integration of electronics/optoelectronics.

A short review on thermal vapor sulfurization of semiconductor thin films for optoelectronic applications

Band-gap and electrical engineering of semiconductor thin films as well as their heterostructural integrations are of increasing interest in optoelectronics for photodiodes and energy harvesting. In this short review, we have presented and discussed how semiconductor thin film materials are processed under vaporized sulfur environment at elevated temperatures, i.e., thermal vapor sulfurization (TVS), for advanced optoelectronic applications. Examples of the uses of TVS over a wide range of materials and length scales are also discussed. We conclude that this relatively simple and low-cost processing method, i.e., TVS, although has some remaining issues for practical industrial applications, can have important consequences in feasible explorations of novel opto-electronic materials.

Wafer-scale synthesis of monolayer and few-layer MoS2 via thermal vapor sulfurization

Monolayer molybdenum disulfide (MoS2) is an atomically thin, direct bandgap semiconductor crystal potentially capable of miniaturizing optoelectronic devices to an atomic scale. However, the development of 2D MoS2-based optoelectronic devices depends upon the existence of a high optical quality and large-area monolayer MoS2 synthesis technique. To address this need, we present a thermal vapor sulfurization (TVS) technique that uses powder MoS2 as a sulfur vapor source. The technique reduces and stabilizes the flow of sulfur vapor, enabling monolayer wafer-scale MoS2 growth. MoS2 thickness is also controlled with great precision; we demonstrate the ability to synthesize MoS2 sheets between 1 and 4 layers thick, while also showing the ability to create films with average thickness intermediate between integer layer numbers. The films exhibit wafer-scale coverage and uniformity, with electrical quality varying depending on the final thickness of the grown MoS2. The direct bandgap of grown monolayer MoS2 is analyzed using internal and external photoluminescence quantum efficiency. The photoluminescence quantum efficiency is shown to be competitive with untreated exfoliated MoS2 monolayer crystals. The ability to consistently grow wafer-scale monolayer MoS2 with high optical quality makes this technique a valuable tool for the development of 2D optoelectronic devices such as photovoltaics, detectors, and light emitters.

Thermal Vapor Sulfurization of Ultrathin GaAs Layers on Sapphire Substrates Prepared by Direct Growth and Lift-Off and Transfer

We have studied the structural, morphological, and lattice vibrational properties of GaAs thin films upon thermal vapor sulfurization (TVS) at elevated temperatures. The GaAs layers, 10∼30 nm in thickness, directly grown on c-plane sapphire substrates by molecular beam epitaxy (MBE) consisted of (111)-oriented crystallites with noncrystal arsenic inclusions. Upon TVS, nucleation of crystalline arsenic occurred and the nucleation developed at consuming GaAs with increasing the temperatures up to 650°C. X-ray photoelectron spectroscopy (XPS) and transmission-electron microscopy (TEM) revealed that the crystalline arsenic was covered by a thin layer of Ga2S3. In comparison, the GaAs layer grown on a GaAs (111) substrate after an AlAs scarification layer consisted of (111)-oriented micron-sized GaAs islands and crystalline arsenic inclusions. This layer, after lift-off and transferred onto sapphire, was converted to Ga2S3 by TVS without crystalline arsenic incorporations. These results shed light on fabricating Ga2S3 and its layered semiconductor/semimetal composites for consequent metamaterial applications in optical and optoelectronic devices.

ChemInform Abstract: CVD Growth of MoS2‐Based Two‐Dimensional Materials

AbstractReview: 80 refs.

CVD Growth of MoS2‐based Two‐dimensional Materials

The ‘self‐limiting’ character of graphene growth on the surface of metals such as Ni and Cu makes CVD the natural choice for growing large‐area and continuous graphene films. Beyond graphene, absence of the self‐limiting property results in a challenge to achieving large‐area, high‐quality two‐dimensional (2D) crystals by CVD. Recent studies of structural, optical, and electrical properties of MoS2‐based atomic layers grown by CVD are reviewed, concluding that thermal vapor deposition will outperform thermal vapor sulfurization in producing the required materials. Whether gaseous sources will replace the now dominant solid sources in direct deposition methods is an open issue. The latest progression in various CVD techniques used in MoS2 growth and their resultant products are discussed and compared.

Anomalous SiO2 layer formed on crystalline MoS2 films grown on Si by thermal vapor sulfurization of molybdenum at elevated temperatures

We have synthesized crystalline MoS2 thin films on Si substrates by thermal processing of molybdenum layers in sulfur vapor environment at elevated temperatures. The molybdenum layers were deposited at room temperature by magnetron sputtering. X-ray diffraction, Raman scattering spectroscopy, and transmission-electron microscopy characterizations revealed that the synthesized MoS2 thin films are of hexagonal crystal with van der Waals layered structures that bended into bell-like domains. Amorphous SiO2 layers have been observed not only at the MoS2/Si interface but also anomalously on top of the MoS2 layer. Secondary ion mass spectroscopy has been employed to investigate the elemental depth profiles, which, together with the structural properties, provides evidence that the surface SiO2 was grown out from its bottom layers rather than deposited from the growth environments. A mechanism based on solid-state reactions and atomic diffusions is introduced to explain the formation of the observed SiO2/MoS2/SiO2 sandwich structures, which may have important consequences when fabricating and/or processing MoS2/Si heterostructures for electrical and optoelectronic applications.

Cobalt sulfide nanoparticles decorated on TiO2 nanotubes via thermal vapor sulfurization of conformal TiO2-coated Co(CO3)0.5(OH)·0.11H2O core–shell nanowires for energy storage applications

TiO2 nanotube W/O cobalt sulfide nanoparticle decorations are obtained by thermal vapor sulfurization of amorphous TiO2 nanotubes W/O Co(CO3)0.5(OH)·0.11H2O cores.

Atomic layer deposition of crystalline Bi2O3thin films and their conversion into Bi2S3by thermal vapor sulfurization

Download options Please wait... Supplementary files Supplementary information PDF (1475K) Article information DOI https://doi.org/10.1039/C4RA09896J Article type Paper Submitted 05 Sep 2014 Accepted 22 Oct 2014 First published 22 Oct 2014 Download Citation RSC Adv., 2014,4, 58724-58731 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Atomic layer deposition of crystalline Bi2O3 thin films and their conversion into Bi2S3 by thermal vapor sulfurization H. F. Liu, K. K. A. Antwi, Y. D. Wang, L. T. Ong, S. J. Chua and D. Z. Chi, RSC Adv., 2014, 4, 58724 DOI: 10.1039/C4RA09896J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author H. F. Liu K. K. Ansah Antwi Y. D. Wang L. T. Ong S. J. Chua D. Z. Chi

Towards large area and continuous MoS2 atomic layers via vapor-phase growth: thermal vapor sulfurization

We report on the effects of substrate, starting material, and temperature on the growth of MoS2 atomic layers by thermal vapor sulfurization in a tube-furnace system. With Mo as the starting material, atomic layers of MoS2 flakes are obtained on sapphire substrates while a bell-shaped MoS2 layer, sandwiched by amorphous SiO2, is obtained on native-SiO2/Si substrates under the same sulfurization conditions. An anomalous thickness-dependent Raman shift (A1g) of the MoS2 atomic layers is observed in Mo-sulfurizations on sapphire substrates, which can be attributed to the competition between the effects of thickness and the surface/interface. Both effects vary with the sulfurizing temperatures for a certain initial Mo thickness. The anomalous frequency trend of A1g is missing when using MoO3 instead of Mo as the starting material. In this case, the lateral growth of MoS2 on sapphire is also largely improved. Furthermore, the area density of the resultant MoS2 atomic layers is significantly increased by increasing the deposition temperature of the starting MoO3 to 700 °C; the adjacent ultrathin MoS2 grains coalesce in one or other direction, forming connected chains in wafer scale. The thickness of the so-obtained MoS2 is generally controlled by the thickness of the starting material; however, the structural and morphological properties of MoS2 grains, towards large area and continuous atomic layers, are strongly dependent on the temperature of the initial material deposition, and on the temperature of sulfurization, because of the competition between surface mobility and atom evaporation.