Low-temperature Deposition Method Research Articles

Enhanced photocatalysis via inverse opal structures: Synthesis and characterization of TiO2/ZnO and ZnO/TiO2 composites using plasma-enhanced ALD

Inverse opals (IO) based functional materials show potential in photocatalysis due to their unique light interaction properties. This study presents a low-temperature plasma-enhanced atomic layer deposition (PEALD) method for synthesizing TiO2, ZnO, and composite IOs using a polystyrene nanoparticle-based opal template. We comprehensively characterized the obtained materials using SEM-EDX, TSEM, TG, FTIR, XRD, Raman, ellipsometry, photoluminescence (PL), and UV–Visible spectroscopy. SEM analysis confirmed the successful formation of PEALD IOs with a periodically ordered structure, enabling conformal coating while preserving their original architecture. XRD and Raman analysis also confirmed that the IOs consisted of anatase for TiO2 and hexagonal wurtzite for ZnO. UV–Vis reflectance spectroscopy revealed strong UV absorption and modified photonic bandgaps (PBGs) for all materials. The bare and composite IOs exhibited PBGs in the visible region, suggesting that the arising “slow photon” effect might enhance photocatalysis. This study explored the photocatalytic degradation of 4-Nitrophenol (4-NP) and Rhodamine 6G (Rh6G) using pristine and composite IO photocatalysts under UV and visible light irradiation. Pristine TiO2 and ZnO IOs demonstrated superior performance for 4-NP degradation under UV light. This can be attributed to two key factors: their highly ordered macroporous structure (with a large surface area for efficient dye adsorption, and their band gaps (3.0 eV for TiO2 and 3.2 eV for ZnO) that enable strong absorption of UV light photons for effective pollutant degradation. Conversely, composite IOs (TiO2/ZnO and ZnO/TiO2) displayed higher activity for both test molecules under visible light due to a synergistic effect between bandgap harmonization and the PBG effect.

Zn-doped V2O5 film electrodes as cathode materials for high-performance thin-film zinc-ion batteries

Zn-doped V2O5 film electrodes were prepared by in-situ growth on indium‑tin oxide (ITO) conductive glass by a low-temperature liquid-phase deposition method and calcined by calcination treatment, and assembled into thin-film zinc-ion batteries (ZIBs). After galvanostatic charge/discharge (GCD) tests with 90 and 200 charge/discharge cycles, the ZIBs system provided specific capacities of 95.7 mAh m−2 and 63.9 mAh m−2 with capacity retention rates of 97.88% and 78.72%, respectively. The electrochemical reaction process of the Zn-doped V2O5 film electrode was analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to understand the insertion/extraction mechanism of Zn2+. The doping of appropriate amount of Zn2+ in the preparation plays the role of “pillar”, which helps to stabilize the structure of V2O5 and improve the cycling stability and lifetime. Therefore, the research may provide a new idea for the assembly and preparation of thin-film ZIBs with improved performance.

PVD decorative coatings on polycarbonate and polyamide substrates for the automotive industry

Utilizing magnetron sputtering to incorporate metal onto polymer surfaces as a substitute for metal parts in the automobile industry offers an eco-friendly alternative. In this work, decorative titanium oxynitride (TiNxOy) coatings were sputter deposited over polycarbonate and polyamide 12 substrates using a low-temperature pulsed deposition method. In order to improve coating adhesion, all substrate surfaces were pre-treated for 30 s by reactive plasma etching. Four different film thicknesses were investigated to achieve various colours. The TiNxOy coatings were quasi-amorphous, and the oxygen content decreased with increasing film thickness. Overall, four distinct colours - green, purple, magenta, and blue - were produced, and all coatings showed excellent adhesion to the polymeric substrates. Colour fastness was assessed using adapted pin-on-disk tests to evaluate the film's applicability as decorative coatings for automotive parts, with all films achieving high ratings for colour fastness. This study provides insights into the deposition of thin films on polymeric substrates, showcasing successful approaches to achieve desired colours while preserving the film's optical properties after color fastness testing.

Sensitive and Low-Noise Perovskite Nanocrystal-Organic Bulk Heterostructure X-ray Detectors Enabled by Sodium Bromide-Assisted In Situ Reparation.

Perovskite nanocrystals (PNCs) offer unique advantages in large-area and thick-film deposition for X-ray detection applications due to the decoupling of the crystallization of perovskite from film formation, as well as their low-temperature and scalable deposition methods. However, the partial detachment of long-chain ligands in PNCs during the purification process would lead to the exposure of surface defects, making it challenging to ensure efficient charge carrier extraction and stable X-ray detection. In this study, we propose a beneficial strategy that involves the in situ reparation of these exposed defects with sodium bromide (NaBr) during the purification process to construct CsPbBr3 PNC-organic bulk heterostructure X-ray detectors. The NaBr-passivated PNCs exhibit stronger photoluminescence intensity and lower trap density in films compared to those of the control samples, confirming the effective passivation of halide vacancy defects. Furthermore, the NiOx hole transport layer with remarkable electron blocking capability is introduced to further suppress the dark current of the devices. Consequently, the optimal devices exhibit a large sensitivity of 4237 μC Gyair-1 cm-2 and a low dark current density of 10 nA cm-2, as well as improved operational stability, which allows for high-contrast and low-dose X-ray imaging applications.

The GeSe/SnSe heterojunction photodetector with self-powered characteristics and high infrared response performance

We present a GeSe/SnSe van der Waals heterojunction fabricated using the wet transfer technique. GeSe and SnSe were synthesized via a low-temperature and atmospheric-pressure chemical vapor deposition method. The GeSe/SnSe heterostructure photodetector demonstrates remarkable rectification characteristics, boasting a rectification ratio of 102, along with an exceptionally low dark current, indicating minimal power consumption. Furthermore, it exhibits a broad optical response, spanning from the visible spectrum (450 nm) to the near-infrared (1064 nm). Under 808 nm laser illumination and reverse bias, the device achieves a responsivity of 19.82 A/W, a detectivity of 4.74 × 109 Jones, and an external quantum efficiency of 3048.32%. Notably, the GeSe/SnSe heterojunction photodetector also exhibits self-powered characteristics, with a responsivity of 0.11 mA/W and a detectivity of 5.44 × 106 Jones at zero bias voltage, accompanied by a fast response time of 23/61 ms (rise/fall). These findings underscore the effectiveness of the GeSe/SnSe heterojunction as a strategy for near-infrared photodetectors to simultaneously achieve low power consumption, high photoresponsivity, and self-powered photodetection, which is promising for optoelectronic device applications.

Flexible, Transparent, and Bifacial Perovskite Solar Cells and Modules Using the Wide-Band Gap FAPbBr3 Perovskite Absorber.

Perovskite solar cells (PSCs) offer impressive performance and flexibility, thanks to their simple, low-temperature deposition methods. Their band gap tunability allows for a wide range of applications, transitioning from opaque to transparent devices. This study introduces the first flexible, bifacial PSCs using the FAPbBr3 perovskite. We investigated the impact of optimizing electron and hole transport layers on the cells' bifaciality, transparency, and stability. PSCs achieved a maximum power conversion efficiency (PCE) of 6.8 and 18.7% under 1 sun and indoor light conditions (1200 lx), respectively, showing up to 98% bifaciality factor and an average visible transmittance (AVT) of 55%. Additionally, a P1-P2-P3 laser ablation scheme has been developed on the flexible poly(ethylene terephthalate) (PET) substrate for perovskite solar modules showing a PCE of 4.8% and high geometrical fill factor (97.8%). These findings highlight the potential of flexible, bifacial PSCs for diverse applications such as building-integrated photovoltaics (BIPV), agrivoltaics, automotive technology, wearable sensors, and Internet of things (IoT).

Completely annealing-free flexible Perovskite quantum dot solar cells employing UV-sintered Ga-doped SnO2 electron transport layers

The electron transport layer (ETL) is a critical component in perovskite quantum dot (PQD) solar cells, significantly impacting their photovoltaic performance and stability. Low-temperature ETL deposition methods are especially desirable for fabricating flexible solar cells on polymer substrates. Herein, we propose a room-temperature-processed tin oxide (SnO2) ETL preparation method for flexible PQD solar cells. The process involves synthesizing highly crystalline SnO2 nanocrystals stabilized with organic ligands, spin-coating their dispersion, followed by UV irradiation. The energy level of SnO2 is controlled by doping gallium ions to reduce the energy level mismatch with the PQD. The proposed ETL-based CsPbI3-PQD solar cell achieves a power conversion efficiency (PCE) of 12.70%, the highest PCE among reported flexible quantum dot solar cells, maintaining 94% of the initial PCE after 500 bending tests. Consequently, we demonstrate that a systemically designed ETL enhances the photovoltaic performance and mechanical stability of flexible optoelectronic devices.

Uniform Synthesis of Bilayer Hydrogen Substituted Graphdiyne for Flexible Piezoresistive Applications.

Graphdiyne (GDY) has garnered significant attention as a cutting-edge 2D material owing to its distinctive electronic, optoelectronic, and mechanical properties, including high mobility, direct bandgap, and remarkable flexibility. One of the key challenges hindering the implementation of this material in flexible applications is its large area and uniform synthesis. The facile growth of centimeter-scale bilayer hydrogen substituted graphdiyne (Bi-HsGDY) on germanium (Ge) substrate is achieved using a low-temperature chemical vapor deposition (CVD) method. This material's field effect transistors (FET) showcase a high carrier mobility of 52.6cm2V-1s-1 and an exceptionally low contact resistance of 10Ωµm. By transferring the as-grown Bi-HsGDY onto a flexible substrate, a long-distance piezoresistive strain sensor is demonstrated, which exhibits a remarkable gauge factor of 43.34 with a fast response time of ≈275ms. As a proof of concept, communication by means of Morse code is implemented using a Bi-HsGDY strain sensor. It is believed that these results are anticipated to open new horizons in realizing Bi-HsGDY for innovative flexible device applications.

Photo-assisted epitaxial growth from nanoparticles to enhance multi-materialization for advanced surface functionalization.

To meet the requirements of freeform objects, a wide range of highly designable resin-based materials has been created, highlighting the need for low-temperature ceramic deposition methods for surface functionalization. Photo-assisted chemical solution deposition (PCSD), an efficient technique for low-temperature ceramic growth, is used to fabricate thin films via photochemical and photothermal effects. The hybrid-solution-incorporated PCSD (HS-PCSD), in which a hybrid-solution comprising metal-organic compounds and nanoparticles is used in PCSD, has attracted considerable interest as it enables deposition at reduced temperatures and accelerated rates. However, the crystal growth processes in the HS-PCSD remain underexplored, which hinders the design of films using this method. In this study, we quantitatively evaluated the photocrystallization of ceramic thin films that were fabricated under various HS-PCSD conditions. We determined that the laser intensity at the reaction interface must exceed a threshold for epitaxial growth through dangling bond photoactivation and photothermal atomic migration to compete with crystal nucleation growth. We also identified that the particle growth during photocrystallization occurred because of amorphous-phase crystallization and not grain boundary migration. Through these quantitative analyses, we obtained insights into ways to achieve true multi-materialization with desirable physical properties in HS-PCSD.

One‐step elaboration of flexible transparent conductive electrodes from silver nanowires/polymer nanocomposites

AbstractA new simplified low temperature deposition method to manufacture flexible transparent conductive electrodes (FTCE) based on conductive polymer composite filled with silver nanowires (AgNWs) was investigated. Polyurethane/AgNWs composite was deposed on a poly(ethylene terephthalate) substrate as a conductive paint in a thin layer lower than 2 μm. The high aspect ratio nanowires influence on the electrical behavior is followed with surface resistivity and optical transparency experiments. The best compromise was obtained with a conductive layer filled with 2.84 vol.% of AgNWs; it exhibits a surface resistivity of 143 Ω/sq with 73% in transmittance. These transparent conductive composites processing in one step with good touching manipulation resistance demonstrate the real interest for this kind of FTCEs technology without indium tin oxide.

Achieving stable Zn metal anode via a hydrophobic and Zn2+-conductive amorphous carbon interface

High security and low cost enable aqueous zinc ion batteries (AZIBs) with huge application potential in large-scale energy storage. Nevertheless, the loathsome dendrite and side reactions of Zn anode are harmful to the cycling lifespan of AZIBs. Here, a new type of thin amorphous carbon (AC) interface layer (∼100 nm in thickness) is in-situ constructed on the Zn foil (Zn@AC) via a facile low-temperature chemical vapor deposition (LTCVD) method, which owns a hydrophobic peculiarity and a high Zn2+ transference rate. Moreover, this AC coating can homogenize the surface electric field and Zn2+ flux to realize the uniform deposition of Zn. Consequently, dendrite growth and side reactions are concurrently mitigated. Symmetrical cell achieves a dendrite-free Zn plating/stripping over 500 h with a low overpotential of 31 mV at 1 mA cm−2/1 mAh cm−2. Of note, the full cell with a MnO2/CNT cathode harvests a capacity retention of 70.0 % after 550 cycles at 1 A/g. In addition, the assembled flexible quasi-solid-state AZIBs display a stable electrochemical performance under deformation conditions and maintain a capacity of 76.5 mAh/g at 5 A/g after 300 cycles. This innovative amorphous carbon layer is expected to provide a new insight into stabilizing Zn anode.

De-Ammonium Ba0.18V2O4.95/NH4V4O10 Film Electrodes as High-Performance Cathode Materials for Magnesium-Ion Batteries.

Magnesium-ion batteries (MIBs) have been pushed into the research boom in the post-lithium-ion batteries era due to their low cost, no dendrite hazard, and high capacity. However, finding suitable cathode materials to improve the slow kinetics of Mg2+ is an ongoing challenge. In this work, Ba0.18V2O4.95/NH4V4O10 film electrodes were grown in one step on indium tin oxide (ITO) conductive glass using a low-temperature liquid-phase deposition method. Temperature was used as the probe condition, and it was concluded that the films annealed at 400 °C had suitable crystallinity and de-ammonium lattice space. At lower current density, with 0.5 M Mg(ClO4)2/PC as the electrolyte, it exhibited an initial discharge capacity of 130.99 mA h m-2 at 210 mA m-2 and 106.52% capacity retention after 100 cycles. In addition, it exhibited excellent electrochemical performance in long-term cycling (92.98% capacity retention after 300 cycles at 600 mA m-2). According to the results of ex situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM), the removal of NH4+ created more lattice space, assisting Ba0.18V2O4.95 to increase the transfer channels of Mg2+, providing more active sites to promote diffusion kinetics (the average DMg2+ was 2.07 × 10-12 cm2 s-1) and specific capacity. Therefore, these film electrodes for scalable Mg2+ storage are promising MIB cathode candidates that exhibit good performance advantages in storage applications.

Estimation of the work of adhesion between ITO and polymer substrates: a surface thermodynamics approach.

Indium tin oxide (ITO) is one of the most widely used semiconductor among transparent conducting oxides (TCOs) due to their electrical conductivity and optical transparency properties. Since the development of low temperature deposition methods, coating of ITO on polymer substrates especially for use in flexible electronics has been a popular topic. The existence of adequate adhesion strength between ITO and polymer is critical in producing a successful film. Nowadays, polycarbonate (PC), poly(methyl methacrylate) (PMMA) and polyethyleneterephtalate (PET) are frequently used as substrates for such coatings. However, there may be other polymeric alternatives that have a potential to be used for this purpose in the future. To evaluate these alternatives, work of adhesion (Wa) knowledge between ITO and polymers is necessary, and it has not been handled systematically previously. In this study, the interphase interaction parameters and Wa values between ITO and various polymers were calculated based on the Dupré, Fowkes and Girifalco-Good equations. PC, PMMA, PET, polystyrene (PS), polyphenylene sulfide (PPS), Nylon 66, polypropylene (PP), polyvinylchloride (PVC), styrene-butadiene rubber (SBR), high density polyethylene (HDPE), low density polyethylene (LDPE), polyvinyl acetate (PVAc), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polytrifluoroethylene (PTrFE) and polyperfluoroalkylethyl acrylate (PPFA) were considered as substrate material. Surface free energy (SFE) components calculated by acid-base, geometric mean and harmonic mean approaches for polymeric substrates were used during the calculations. In the present study, the polymers that can be used as substrates were evaluated in terms of adhesion ability to ITO, the significance of calculation methods on Wa values were also investigated simultaneously. It was determined that the Wa between ITO and polymer substrates was directly related with the total SFE value of the polymers.

Ca-doped NaV6O15 film electrodes as high-performance cathodes for sodium-ion batteries

The Ca-doped NaV6O15 films have been prepared on indium-doped tin oxide (ITO) conductive glasses using a low-temperature liquid-phase deposition method. The crystal structure, morphology, and structural information of the Ca-doped NaV6O15 films were systematically studied by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. X-ray photoelectron spectroscopy revealed that the Ca-doped NaV6O15 had a lower ratio of V5+/V4+, which was the compensation for doped Ca2+. Electrochemical properties of films were measured by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge tests. The results proved the doped Ca2+ obviously improved electrochemical performance, which exhibited quicker diffusion process, higher specific capacity, and longer lifespan. The Ca-doped NaV6O15 films showed a high discharge capacity of 237.476 mA h m−2 at 1C rate, which was larger than 96.719 mA h m−2 of the pure NaV6O15 films. The capacity retention reached to 84.72 % at 0.5C rate after 100 cycles, the excellent cyclic ability was attributed to the doped Ca2+ with strong electronegativity stabilizing the structure. This work presents a great potential approach that explores high-performance cathodes for sodium-ion batteries.

Synthesis and Electrochemical Performance of V6O13 Nanosheets Film Cathodes for LIBs

V6O13 thin films were deposited on indium-doped tin oxide (ITO) conductive glass by a concise low-temperature liquid-phase deposition method and through heat treatment. The obtained films were directly used as electrodes without adding any other media. The results indicate that the film annealed at 400 °C exhibited an excellent cycling performance, which remained at 82.7% of capacity after 100 cycles. The film annealed at 400 °C with diffusion coefficients of 6.08 × 10-12 cm2·s-1 (Li+ insertion) and 5.46 × 10-12 cm2·s-1 (Li+ extraction) in the V6O13 film electrode. The high diffusion coefficients could be ascribed to the porous morphology composed of ultrathin nanosheets. Moreover, the film endured phase transitions during electrochemical cycling, the V6O13 partially transformed to Li0.6V1.67O3.67, Li3VO4, and VO2 with the insertion of Li+ into the lattice, and Li0.6V1.67O3.67, Li3VO4, and VO2 partially reversibly transformed backwards to V6O13 with the extraction of Li+ from the lattice. The phase transition can be attributed to the unique structure and morphology with enough active sites and ions diffusion channels during cycles. Such findings reveal a bright idea to prepare high-performance cathode materials for LIBs.

Bandgap engineering of indium gallium nitride layers grown by plasma-enhanced chemical vapor deposition

This paper reports on the fabrication of InxGa1−xN (InGaN) layers with various compositions ranging from InN to GaN using a cost-effective low-temperature plasma-enhanced chemical vapor deposition (PECVD) method and analyzes the influence of deposition parameters on the resulting films. Single-phase nanocrystalline InGaN films with crystallite size up to 30 nm are produced with deposition temperatures in the range of 180–250 °C using the precursors trimethylgallium, trimethylindium, hydrogen, nitrogen, and ammonia in a parallel-plate type RF-PECVD reactor. It is found that growth rate is a primary determinant of crystallinity, with rates below 6 nm/min producing the most crystalline films across a range of several compositions. Increasing In content leads to a decrease in the optical bandgap, following Vegard’s law, with bowing being more pronounced at higher growth rates. Significant free-carrier absorption is observed in In-rich films, suggesting that the highly measured optical bandgap (about 1.7 eV) is due to the Burstein–Moss shift.

Co-deposition of MoS2 films by reactive sputtering and formation of tree-like structures

Transition metal dichalcogenides are versatile layered materials with potential applications ranging from optoelectronic devices to water splitting. Top-down fabrication methods such as exfoliation are not practical for a large-scale production of high-quality devices: a bottom-up approach such as sputtering, a low-temperature deposition method, is more suitable. However, due to its anisotropic nature, the growth mechanism of molybdenum disulfide (MoS2) via sputtering is complex and remains to be investigated in detail. In this paper, we study the growth of MoS2 films co-deposited by using a sulfur (S) hot-lip cell and a molybdenum (Mo) sputtering target via reactive sputtering. The impact of S partial pressure on the structure and morphology of MoS2 films was systematically characterized, and it was observed that the growth is dominated by vertically-oriented sheets with horizontal branches, resulting in a tree-like structure. The growth front of the structures is ascribed to the anisotropic incorporation of adatoms with regards to the orientation of MoS2.

Industrially Compatible Fabrication Process of Perovskite-Based Mini-Modules Coupling Sequential Slot-Die Coating and Chemical Bath Deposition.

To upscale the emerging perovskite photovoltaic technology to larger-size modules, industrially relevant deposition techniques need to be developed. In this work, the deposition of tin oxide used as an electron extraction layer is established using chemical bath deposition (CBD), a low-cost and solution-based fabrication process. Applying this simple low-temperature deposition method, highly homogeneous SnO2 films are obtained in a reproducible manner. Moreover, the perovskite layer is prepared by sequentially slot-die coating on top of the n-type contact. The symbiosis of these two industrially relevant deposition techniques allows for the growth of high-quality dense perovskite layers with large grains. The uniformity of the perovskite film is further confirmed by scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM) analysis coupled with energy dispersive X-ray spectroscopy (EDX) and cathodoluminescence measurements allowing us to probe the elemental composition at the nanoscale. Perovskite solar cells fabricated from CBD SnO2 and slot-die-coated perovskite show power conversion efficiencies up to 19.2%. Furthermore, mini-modules with an aperture area of 40 cm2 demonstrate efficiencies of 17% (18.1% on active area).

CuPc nanowires PVD preparation and its extra high gas sensitivity to chlorine

Efficient copper phthalocyanine gas sensors capable of sensitive and selective analysis of toxic gases at room temperature have shown their great potential for gas sensing in recent years. In this work, a gas sensor based on phthalocyanine copper (II) (CuPc) was prepared by a one-step low-temperature physical vapor deposition (PVD) method. The uniform cotton-wool nanowires film has high yield, and can also be easily peeled off. PVD preparation temperature had a significant influence on both the recovery and cyclic properties of the gas sensor to chlorine. High-performance CuPc nanowires prepared at 230 °C had the lowest detection limit of 1.5 ppm with a recovery time of 2.74 s (this time is over 100 times faster than previous results 260–600 s). In addition, it showed excellent light-induced gas-sensitive characteristics to Cl2 and at room temperature. This sensor can be potentially useful in photo-gas sensors, photocatalytic devices, or photoelectric devices.

Earth-abundant nickel cobalt disulfide nanoporous networks catalyst for efficient hydrogen evolution

Using transition metal disulfide (TMD) as a substitute for noble-metal-based catalysts is considered a promising strategy for achieving practical hydrogen production from water splitting. Herein, an earth-abundant, highly crystalline, bimetal disulfide nanoporous networks (Ni0.33Co0.67S2) was constructed via dealloying and low-temperature chemical vapor deposition (CVD) methods. As expected, the as-prepared Ni0.33Co0.67S2 can be served as an efficient, and robust electrocatalyst for HER, and exhibiting a lower overpotential (191.2 mV at 10 mA cm−2) and Tafel slope (93.64 mV dec-1) than that of NiS2 and CoS2 synthesized through the similar methods. Moreover, the potential increase is only 50 mV in 12 h of long-term durability test for Ni0.33Co0.67S2 catalyst. Further analysis shows the significantly improved performance of Ni0.33Co0.67S2 should be attributed to the enhanced charge transfer, as well as increased electrochemical active specific surface area. Therefore, the combination of versatile dealloying inheritance effect and CVD modification strategy could provide a promising channel for preparing practical HER catalyst.