Thermal Evaporation Process Research Articles

Comparative analysis of thermally evaporated nanoscale CdS thin film's structural, morphological, optical and nanomechanical properties

CdS nanoscale thin films were deposited on glass substrates at 1, 5 and 10 Å/s deposition rates by thermal evaporation process. The structural, morphological, compositional, optical and nanomechanical properties of CdS thin films were analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), energy dispersive x-ray (EDX), UV-vis spectrophotometer and nanoindentation. XRD diffractogram indicate that the deposited CdS thin films have hexagonal structure with preferred orientation towards (002) plane and nearly stoichiometric composition. Various crystal structure parameters like lattice constant, crystallite size, defect density, dislocation density, lattice strain, number of crystallite per unit surface, stacking fault were determined. From XRD results, the calculated crystal structure parameters such as the crystallite size, microstrain and defect density were in the range of 20.4-14.7 nm, 7.74-10.62 and 2.3-4.52 × 1011 lines/cm2, at 1, 5 and 10 Å/s deposition rates, respectively .The AFM images indicated that the film's rms surface roughnesses were 2.73 nm, 2.94 nm and 3.18 nm at 1, 5 and 10 Å/s, respectively. The SEM images indicated that the films were uniform, continuous and defect free. The EDX examination revealed that at 1 Å/s deposition rate the film was nearly stoichiometic. The optical band gaps were determined to be in the range of 2.37-2.43 eV. Nanoindentation tests evaluated the hardness, Young's modulus, creep behavior and strain rate of CdS films. Hardness evaluated to be 0.14-1.48 GPa, 0.15-2.46 GPa, and 0.21-2.55 GPa at 1,5 and 10 Å/s deposition rate, respectively for 20-50 µN load. The Young's modulus decreases 1-5 Å/s deposition rate and becomes almost constant 5-10 Å/s deposition rate at 70 µN load. The characterization of CdS thin film recommend it as a favorable window layer in applications like photovoltaic, optoelectronic, thermoelectric and solar cells.

Charge transport properties and variable photo-switching of three-terminal Cs2AgBiBr6 device

In this study, we present an in-depth exploration of charge transport phenomena and variable photo-switching characteristics in a novel double-perovskite-based three-terminal device. The Cs2AgBiBr6 thin film (TF) was synthesized through a three-step thermal evaporation process followed by precise open-air annealing, ensuring superior film quality as confirmed by structural and morphological characterizations. Photoluminescence spectroscopy revealed distinct emissions at 2.28 and 2.07 eV, indicative of both direct and indirect electronic transitions. Our device exhibited space-charge limited current (SCLC) behaviour beyond 0.35 V, aligning with the relationship , where the exponent m transitioned from ≤1 to >1. Detailed analysis of Schottky parameters within the trap-filled limit (TFL) regime was conducted, accounting for variations in temperature and optical power. Significantly, the self-powered photodetector demonstrated outstanding performance under illumination. The sensitivity of the device was finely tunable via the applied bias voltages at the third terminal. Notably, an optimal bias voltage of ±100 μV yielded maximum responsivity (R) of 0.48 A/W and an impressive detectivity (D*) of 1.07 × 109 Jones, highlighting the potential of this double-perovskite-based device for advanced optoelectronic applications.

Shadow effect in dual‐source thermally evaporated perovskite patterns

AbstractPerovskite light‐emitting diodes (PeLEDs) have recently emerged as a potential next‐generation display technology due to their wide color gamut, high external quantum efficiency (EQE), and low fabrication cost. The thermal evaporation process with no solvent involvement and offers low substrate selectivity and high compatibility with production lines has attracted significant academic interest. However, in thermal evaporation processes, the shadow effect greatly affects the deposition size and positioning accuracy of the patterns, consequently impacting the effective device area and process repeatability of PeLEDs. In this study, we calculated the shadow distance during the dual‐source thermal evaporation and analyzed the issues of misalignment and size deviation caused by shadow effects. Based on the calculation of shadow distance, we increased the substrate height from 33 to 38 cm to enhance the deposition angle. This adjustment led to an improvement in the characteristic parameter W1/Wdot from 0.178 to 0.365 during perovskite deposition. As a result, we successfully obtained a high‐resolution perovskite array with uniform morphology and photofluorescence (PL) emission at 600 pixels per inch (ppi). This demonstrated the reliable calculation and analysis of shadow distance, which is effective for fine deposition of high‐resolution perovskite patterns and PeLEDs.

Structural and Electrochemical Properties of Binary ZnO:Al Nanocomposites as Anode for Lithium-ion Batteries

In conventional lithium-ion batteries (LIBs), carbon compounds are commonly utilised as the anode owing to their great performance, low cost, and abundance. However, due to the limited storage capability of pure carbon materials that restrict further improvement of LIBs, zinc oxide (ZnO) has been one of the promising anode materials to be used as an alternative to strengthen the electrochemical performance of LIBs due to its high theoretical capacity of 987 mAh g-1. This study aims to synthesise ZnO:Al nanowires using the hot-tube thermal evaporation method. Three types of samples are made using this method by varying the concentration of 0 wt% (S1), 3wt% (S2), and 6 wt% (S3) of aluminium (Al) during the Al deposition process. The EDX findings indicated that the sample has a high proportion of zinc (Zn) and oxygen (O), with the S3 sample having the highest Al concentration after being deposited. The most substantial diffraction peak for XRD of all samples was found at (101), exhibiting a single crystalline hexagonal structure with optimum growth direction on the c-axis. For EIS analysis, the S3 sample has the lowest bulk resistance and maximum ionic conductivity. In conclusion, the ZnO sample with 3 wt% of Al as a dopant was selected as the optimum result to synthesise a homogenous surface of ZnO:Al with good crystallinity by using a hot-tube thermal evaporation process and giving the best conductivity in electrochemical performance.

Enhanced corrosion protection of steel strip through advanced Zn–Mg alloy coatings manufactured by Continuous Physical Vapor Deposition: A review

The growing global consensus on the “carbon peak and neutrality” has focused on high-strength steel, highlighting its critical role in enhancing energy efficiency, reducing emissions in the steel industry, and reducing the weight of automobiles. Traditional Electro-Galvanizing (EG) and Hot-Dip Galvanizing (HDG) technologies face challenges in meeting the surface protection demands of these applications. This limitation is evident with the development of Zn–Mg coated strip steel, which offers high corrosion resistance. Continuous Physical Vapor Deposition (CPVD) effectively addresses these issues in a sealed vacuum environment, drawing significant attention in the strip coating industry owing to its superior surface quality, diverse material options, and environmental advantages. This article reviews the latest advancements and current status of Zn–Mg alloy coatings prepared using the CPVD technology. It discusses the typical thermal evaporation process used in CPVD, traces the development history of CPVD coatings on strip steel, and examines the microstructure, corrosion resistance, and adhesion performance evolution mechanisms of Zn–Mg alloy coatings. By designing multilayer structures, adjusting the Mg composition, and implementing controllable heat treatments, the overall performance of the coatings is enhanced. This study also comprehensively analyzes the feasibility of applying multilayer, highly corrosion-resistant Zn–Mg coatings. Additionally, it identifies the main challenges in applying CPVD technology to Zn–Mg coatings on strip steel, such as the large-scale, stable, and low-cost mass production of typical processes and controlling the void content at multilayer interfaces. Finally, future research directions are anticipated, underscoring the potentially significant impact of further alloying and computer simulations in advancing steel surface treatments.

Orientation optimization for high performance Mg3Sb2 thermoelectric films via thermal evaporation

Low-cost, highly efficient thermoelectric thin-film materials are becoming increasingly popular as miniaturization progresses. Mg3Sb2has great potential due to its low cost and high performance. However, the fabrication of Mg3Sb2thin films with high power factors (PFs) poses a certain challenge. In this work, we propose a general approach to prepare Mg3Sb2thin films with excellent thermoelectric properties. Using a two-step thermal evaporation and rapid annealing process, (001)-oriented Mg3Sb2thin films are fabricated onc-plane-oriented Al2O3substrates. The structure of the film orientation is optimized by controlling the film thickness, which modulates the thermoelectric performance. The PF of the Mg3Sb2at 500 nm (14μW·m-1·K-2) would increase to 169μW·m-1·K-2with Ag doping (Mg3Ag0.02Sb2) at room temperature. This work provides a new strategy for the development of high-performance thermoelectric thin films at room temperature.

High‐Speed Short Infrared Detector Based on Vertical Gr/Se0.2Te0.8/GaAs Heterojunction

AbstractIn the domain of high‐performance short‐wave infrared (SWIR) photodetection and imaging, existing technologies predominantly utilize single‐crystal germanium and III‐V semiconductors. Despite their efficacy, these materials are encumbered by laborious synthesis and complex fabrication demands. In this study, the synthesis of large‐area, high‐crystallinity Se0.2Te0.8 thin films through a CMOS‐compatible vacuum thermal evaporation process is reported. A high‐speed, broad‐spectrum photodetector engineered with an innovative Gr/Se0.2Te0.8/GaAs vertical heterostructure is presented, which capitalizes on the augmented carrier mobility and employs graphene innovatively as both a carrier collection interface and an electrode. This configuration facilitates a remarkably swift response time of 800 ns/1 µs at the crucial 1310 nm wavelength for optical communications. Moreover, the fabrication of a 5 × 5 array device demonstrates substantial SWIR imaging capabilities at ambient conditions, marking a paradigm shift in uncooled infrared imaging and communication technologies. This work not only extends the boundaries of SWIR photodetector performance but also underscores the potential of novel material systems in high‐speed optical applications.

Unveiling photon-driven nonlinear evaporation via liquid drop interferometry.

We investigated photomolecular-induced evaporation, wherein photons cleave off water clusters near water-vapor interfaces, bypassing the typical thermal evaporation process. However, thermal-induced evaporation is the main bottleneck to precisely identify photon-induced evaporation. Liquid drop interferometry (LDI) resolved this bottleneck, utilizing evaporating water drops as an active element. Interestingly, we first observed near-total internal reflection, a nonlinear increase in evaporation attributed to photomolecular-induced evaporation, which had never been studied before, to the best of our knowledge. Furthermore, by generating a standing wave on a partially metallic polished prism, we uncovered an unexpected enhancement in evaporation coinciding with the wave reaching its maxima at the air-water (AW) interface, validating that photomolecular-induced evaporation is a surface phenomenon. Significantly, our noninvasive measurements have identified transient deformation height as a key indicator of photon-induced cluster breaking and increased evaporation, thus significantly advancing our understanding of photomolecular effects on water droplet evaporation.

The Influence of Varying Ar/O2 Gas Ratio with Catalyst-Free Growth by Homemade Thermal Evaporation Technique

A nanostructured zinc oxide (ZnO) with different percentages of argon and oxygen gas flow rate was deposited on a silicon wafer by a simple hot tube thermal evaporation technique. The effect of different percentages of gas flow rate on the crystal structure, surface morphology and optical properties were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and RAMAN spectroscopy, respectively. The changes of morphologies from FESEM were significant where the grown ZnO nanostructures show three different shapes which are nanotripods, nanoclusters and nanorods at 5%, 10% and 25% of oxygen gas, respectively. EDX results revealed that Zn and O elements have a major percentage in the sample indicating a composition has high purity of ZnO. XRD patterns displayed the most intense diffraction peak of ZnO at (101), which exhibited a single crystalline hexagonal structure with preferred growth orientation in the c-axis. RAMAN scattering study found that synthesized ZnO shows the high intensity of E2 mode and low intensity of E1 mode attributed to all the samples having good crystal quality containing fewer structural defects. In conclusion, the E15 sample with a 25% oxygen gas flow rate was selected as an optimum result for synthesizing a homogenous surface and high crystallinity of ZnO by using a hot tube thermal evaporation process. This work can enhance the development of ZnO production in various applications.

Ultra-long Al doped core-shell nanowires: Relationship between structural defect and optical property

The defects in nanomaterials can greatly affect their photoluminescence (PL) properties. To investigate the role of defects in the PL properties of SiCnw and improve their properties, Al doping and core-shell structure design are employed. Based on the above purpose, ultra-long Al-SiCnw@SiO2 with a length of hundreds of micrometers are prepared via one-step thermal evaporation process. The Al exists in the lattice of SiC and SiO2 in the form of substitutional and interstitial atoms, respectively, causing more defects in the nanowires. These defects can enhance the phonon scattering and phonon energy. After doping Al, the PL property of nanowires is improved by 36% and 244%, respectively, compared with SiCnw@SiO2 and SiCnw. The enhanced Fröhlich electron-phonon interaction caused by defects and the decreased band gap accelerating the transition of electrons are the main mechanisms of the property improvement. With the help of phonons, the electrons will be easier excited to conduction band. When they back to the ground state, more energy will be released, thereby improving the PL property. This work is helpful for the design of nanowires by doping elements to improve the PL property, and the preparation of large scale ultra-long doped nanowires applied in the optoelectronics.

Correction: Optimizing the single-source flash thermal evaporation process of Zn-doped CsPbBr3 films for enhanced performance in perovskite LEDs

Correction: Optimizing the single-source flash thermal evaporation process of Zn-doped CsPbBr3 films for enhanced performance in perovskite LEDs

Synergetic impact of binary/ternary zeolitic composites on cellulose acetate membranes for potential CO2 removal and antibacterial attributes

The aim of this research is to synthesize multifunctional mixed matrix cellulose acetate (CA) membranes that can provide better CO2/N2 selectivity and will simultaneously fight against bacteria, to immaculate the indoor environment. For that purpose, two different fillers labelled as binary ZnO@Zeolite (1:10, ZZ) and ternary ZnO–CuO@Zeolite (0.8:0.2:10, ZZC) composites have been synthesized via co-precipitation method to entrench into CA matrix with 8 wt% each. The solution mixing technique assisted by thermal evaporation process (TEAP) has been adopted to formulate the desired membranes. Surface morphology, crystalline structure, thermal decomposition, and mechanical properties of novel composites ZZ and ZZC, along with their respective corresponding membranes CA/ZZ-8 and CA/ZZC-8, have been analyzed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and universal testing machine (UTM). The inclusion of tri-zeolitic composite (ZZC) favors the formation of denser CA membranes, with a smaller crystallite size (10.8 nm), higher thermal stability (%), and a notable increase in mechanical strength (MPa) in contrast to virgin CA as well as bi-zeolitic composite (ZZ) loaded membranes. The selectivity for CO2/N2 separation of tri-zeolitic composite loaded membranes (CA/ZZC-8) is almost six folds higher compared to the pristine CA membrane, whereas it is five folds for bi-zeolitic composite impregnated membrane (CA/ZZ-8). To eradicate bacterial fouling, bi/tri-zeolitic composite loaded membranes are tested against E. coli bacteria by broth culture method and the results validate their antibiotic nature. Synthesized novel CA membranes with hybrid composites provide convenient access towards the development of multipurpose membranes.

Vacuum-Processed Propylene Urea Additive: A Novel Approach for Controlling the Growth of CH3NH3PbI3 Crystals in All Vacuum-Processed Perovskite Solar Cells.

In this study, we present a novel method for controlling the growth of perovskite crystals in the vacuum thermal evaporation process by utilizing a vacuum-processable additive, propylene urea (PU). By coevaporation of perovskite precursors with PU to form the perovskite layer, PU, acting as a Lewis base additive, retards the direct reaction between the perovskite precursors. This facilitates a larger domain size and reduced defect density. Following the removal of the residual additive, the perovskite layer, exhibiting improved crystallinity, demonstrates reduced charge recombination, as confirmed by a time-resolved microwave conductivity analysis. Consequently, there is a notable enhancement in open-circuit voltage and power conversion efficiency, increasing from 1.05 to 1.15 V and from 17.17 to 18.31%, respectively. The incorporation of a vacuum-processable and removable Lewis base additive into the fabrication of vacuum-processed perovskite solar cells offers new avenues for optimizing these devices.

Spray-Coated MoO3 Hole Transport Layer for Inverted Organic Photovoltaics.

This study focuses on the hole transport layer of molybdenum trioxide (MoO3) for inverted bulk heterojunction (BHJ) organic photovoltaics (OPVs), which were fabricated using a combination of a spray coating and low-temperature annealing process as an alternative to the thermal evaporation process. To achieve a good coating quality of the sprayed film, the solvent used for solution-processed MoO3 (S-MoO3) should be well prepared. Isopropanol (IPA) is added to the as-prepared S-MoO3 solution to control its concentration. MoO3 solutions at concentrations of 5 mg/mL and 1 mg/mL were used for the spray coating process. The power conversion efficiency (PCE) depends on the concentration of the MoO3 solution and the spray coating process parameters of the MoO3 film, such as flow flux, spray cycles, and film thickness. The results of devices fabricated from solution-processed MoO3 with various spray fluxes show a lower PCE than that based on thermally evaporated MoO3 (T-MoO3) due to a limiting FF, which gradually increases with decreasing spray cycles. The highest PCE of 2.8% can be achieved with a 1 mg/mL concentration of MoO3 solution at the sprayed flux of 0.2 mL/min sprayed for one cycle. Additionally, S-MoO3 demonstrates excellent stability. Even without any encapsulation, OPVs can retain 90% of their initial PCE after 1300 h in a nitrogen-filled glove box and under ambient air conditions. The stability of OPVs without any encapsulation still has 90% of its initial PCE after 1300 h in a nitrogen-filled glove box and under air conditions. The results represent an evaluation of the feasibility of solution-processed HTL, which could be employed for a large-area mass production method.

Improved performance in quantum-dot light-emitting diodes through current annealing

The impact of metallic diffusion, stemming from the thermal evaporation process of electrodes, exerts a substantial influence on solution-processed quantum-dot light-emitting diodes (QD-LEDs). This study highlights a significant enhancement in the performance of QD-LEDs achieved through post-metal-evaporation current annealing. The choice of different metal electrodes emerges as a critical factor affecting QD-LED performance during current annealing. In the case of red QD-LEDs with an Al cathode, the maximum external quantum efficiency (EQE) surged from 7.0% to an impressive 14.1%. Conversely, QD-LEDs with an Ag cathode exhibited a more modest improvement, progressing from 10.8% to 12.4%. Notably, an Al/Ag composite electrodes demonstrated the potential for further enhancement, achieving a remarkable maximum EQE of 18.3%. The observed performance improvements can be attributed to the formation of metal diffusion-induced Al-doped ZnO, facilitating electron injection, and Al-oxidized passivated quantum dots (QDs), effectively mitigating metal-induced quenching following current annealing. This study conclusively demonstrates that the application of current annealing can effectively counteract the adverse effects of metal diffusion in QD-LEDs, presenting itself as a promising method for elevating the overall performance of quantum-dot light-emitting diodes.

Modulating emission color in Mn-doped ZnS/ZnO microbelts via thermal evaporation process

Modulating emission color in Mn-doped ZnS/ZnO microbelts via thermal evaporation process

Preparation of black Ag films via a novel thermal evaporation process and comparisons of their properties at the constant thickness and the constant Ag amount

Preparation of black Ag films via a novel thermal evaporation process and comparisons of their properties at the constant thickness and the constant Ag amount

Sublimed C60 for efficient and repeatable perovskite-based solar cells

Thermally evaporated C60 is a near-ubiquitous electron transport layer in state-of-the-art p–i–n perovskite-based solar cells. As perovskite photovoltaic technologies are moving toward industrialization, batch-to-batch reproducibility of device performances becomes crucial. Here, we show that commercial as-received (99.75% pure) C60 source materials may coalesce during repeated thermal evaporation processes, jeopardizing such reproducibility. We find that the coalescence is due to oxygen present in the initial source powder and leads to the formation of deep states within the perovskite bandgap, resulting in a systematic decrease in solar cell performance. However, further purification (through sublimation) of the C60 to 99.95% before evaporation is found to hinder coalescence, with the associated solar cell performances being fully reproducible after repeated processing. We verify the universality of this behavior on perovskite/silicon tandem solar cells by demonstrating their open-circuit voltages and fill factors to remain at 1950 mV and 81% respectively, over eight repeated processes using the same sublimed C60 source material. Notably, one of these cells achieved a certified power conversion efficiency of 30.9%. These findings provide insights crucial for the advancement of perovskite photovoltaic technologies towards scaled production with high process yield.

Post-annealing-free BaOxFy/LiF-based stack electron-selective contacts for high efficiency crystalline silicon solar cells featuring ultra-low contact resistivity

In silicon heterojunction and tunnel oxide passivating contact crystalline silicon (c-Si) solar cells based on successful passivating contacts technologies, an annealing activation step is indispensable to achieve a suitably low contact resistivity (ρc), which is a costly and non-ideal process. Here, combined with a calcium aluminium (Ca:Al) alloy electrode, a low work function barium oxide and lithium fluoride (BaOxFy/LiF) stack electron-selective contact (ESC) without an annealing activation step on c-Si solar cells clinches an ultra-low ρc of 1.4 mΩ·cm2 delivering a power conversion efficiency (PCE) of 20.5 %. The BaOxFy/LiF/Ca:Al stack structure is built by BaOx/LiF/Ca/Al hybrid structure via a facile continuous thermal evaporation process. As a proof of concept, the stacked BaOxFy/LiF/Ca:Al/Al contact is applied to the rear side of c-Si solar cells, achieving a PCE of 20.5 % with an open-circuit voltage of 625.7 mV, an impressive fill factor of 83.5 % and a short-circuit current density of 39.2 mA/cm2. With the aid of a transient photovoltage setup, the carrier recombination mechanism of the stacked BaOxFy/LiF/Ca:Al structure is explored. This work demonstrates an alternative idea for undoped ESCs, showing potential for next-generation cost-effective ultrathin-slice c-Si solar cells (∼80 μm) with high efficiency, and low-parasitic light absorption losses.

Implementation of vacuum distillation system at PPLi: A case study on high-concentrated waste treatment and water recycling

This case study presents the successful implementation of a vacuum distillation system at PPLi for treatment of high-concentrated waste, with a focus on water recycling. The vacuum distillation unit employs advanced thermal heating and evaporation processes, facilitated by reduced pressure, to effectively separate contaminants from the waste stream. Operational parameters, including waste type, feed rate, temperature settings, and vacuum level, were meticulously optimized to achieve optimal treatment efficiency. The study conducted experimental trials over six months, rigorously monitoring and analyzing the treated water quality for chemical composition, total dissolved solids (TDS), and other relevant parameters. Results showed a remarkable reduction in TDS and chemical contaminants, ensuring compliance with stringent regulatory standards. Additionally, the case study explored potential reuse and recovery options for the separated concentrated waste. Laboratory tests examined the feasibility of utilizing the waste residues for energy generation or as raw materials for other processes. The successful implementation of the vacuum distillation system at PPLi underscores its practicality and effectiveness in treating high-concentrated waste while facilitating water recycling. This achievement represents a significant step towards reducing environmental impacts associated with waste disposal and conserving precious water resources. The insights gained from this study serve as a valuable reference for industrial facilities seeking sustainable waste management solutions, fostering a circular economy approach and promoting responsible environmental stewardship.