Vacuum Thermal Evaporation Research Articles

An evaluation and comparison of frictional resistance, surface roughness, and microbial colonization of silver-coated and uncoated stainless steel archwires – An in vivo study

Objectives: When undergoing fixed orthodontic treatment, white spot lesions and caries are frequently observed. The silver coating on brackets, archwires, and bands can help prevent these conditions. However, this might have an impact on friction and the oral environment, which would then impact the movement of the teeth. Thus, this study was taken up to evaluate and compare the frictional resistance, surface roughness, and microbial colonization of silver-coated and uncoated stainless steel archwire. Material and Methods: The investigation contained sixty samples, with 30 samples in each sub-group. Group 1 included 30 samples of 0.019 × 0.025” stainless steel wires coated in silver nanoparticles and Group 2 included 30 uncoated 0.019 × 0.025” stainless steel wires. A thermal vacuum evaporation technique was used to coat the wire with a 10 nm layer of coating. After placing the wire for 6 weeks in the oral cavity, it was retrieved and evaluated for frictional resistance, surface roughness, and microbial colonization. Results: After comparing the friction across the groups, the results did not show statistically significant differences. Scanning electron microscopy revealed that the surface roughness of wires coated in silver was lesser compared to the wire’s uncoated segment. As for the microbial colonization, Streptococcus mutans and Lactobacillus acidophilus showed reduced growth in the silver-coated portion. Conclusion: It can be concluded that silver coating does not alter the frictional properties of the wire. In the archwire’s silver-coated part, the surface roughness was lower. The silver coating showed significant anti-bacterial activity.

Silver doping effect on the electrochromic performance of the WO3 thin films produced by thermal evaporation in vacuum

Ag doped WO3 thin films are successfully fabricated by thermal evaporation method in vacuum as precursor, and then annealed at 450 °C in nitrogen gases atmosphere. Cyclic voltammetry, repeating chronoamperometry, chronocolumetry and optical transmittance are recorded in 1 M LiClO4/propylene carbonate electrolyte. The color of the WO3 thin films changes from transparent to the blue under the applied potential of -1.8 and +1.9 V. XRD studies show that all the films have a polycrystalline structure of WO3. The molecular formation is also confirmed by Raman and X-Ray photoelectron spectroscopy (XPS). The EDS elemental mappings clearly confirm the homogeneous distribution of Ag, W and O elements into the WO3 network. From the optical studies, indirect band gap energy of the WO3 decreases as Ag doping level increases. The best coloration and bleaching times (2.33 and 1.25 s) are obtained for the Ag(2%):WO3 thin films, compared to the pure WO3 (3.79 and 1.96 s). The produced WO3 films exhibit high reversibility (39.6/69.1%), high coloration efficiency values (26.3/141.2 cm2/C), and good cycling stability. From the EIS measurements, the charge-transfer resistance is Ag(2%):WO3 < the pure WO3 < Ag(5%):WO3 < Ag(8%):WO3, which means that Ag(2%):WO3 has the biggest electrochemically active surface area. Electronic energy levels of the pure WO3 and the Ag:WO3 thin films are also given. From the Mott-Schottky studies, it is determined that the donor concentration of the materials is of the order of 1014-1015 cm−3. In the literature, there are very limited studies related to electrochromic thin films by thermal evaporation in vacuum. In this sense, the reported results in this study are promising for the electrochromic applications.

Investigating the Electrical, Power Factor, and Figure of Merit Characteristics of Cadmium Oxide Nanostructures Fabricated via Thermal Evaporation in Vacuum

A cadmium dioxide nanostructure was fabricated on silicon and quartz substrates through oblique angle deposition (OAD). The synthesis involved the initial thermal evaporation of high-purity cadmium metal films at varying deposition angles on the substrates, followed by a 1.5-hour oxidation process at 773 K in a conventional furnace to produce cadmium oxide nanostructures. X-ray diffraction (XRD) analysis revealed the development of crystalline structures within the cadmium oxide (CdO) films. The deposition angle exhibited a significant impact, influencing the preferred orientation along the (111) planes more substantially than the normal incident angle. I-V measurements and assessments of electrical conductivity were conducted under both light and dark conditions for the CdO films. The photocurrent generated in an oblique (Al/CdO/p-Si/Al) heterojunction exceeded that of a standard detector under illumination. The investigation explored the thermoelectric properties of CdO nanomaterials, including the figure of merit (M), power factor (P.F.), and Seebeck coefficient (S), for both normally deposited and obliquely deposited films. The results demonstrated an enhancement in the figure of merit with oblique deposition, potentially attributed to increased roughness, resulting in reduced thermal conductivity and an elevated figure of merit. All findings indicated superior performance for deposition angles (θº = 50º &amp; 70º) in comparison to normal deposition (θº = 0º).

Impact of gamma irradiation on optical and nonlinear properties of Indium chloride phthalocyanine thin films

This study investigates the impact of gamma radiation on indium chloride phthalocyanine (lnPcCl) thin films, which were prepared via vacuum thermal evaporation. x-ray diffraction revealed the amorphous structure of the films, with increasing gamma doses causing more noticeable structural disorders. Optical analysis showed a slight decrease in the optical band gap energy and a significant reduction in the fundamental band gap energy. Additionally, higher gamma doses led to decreased transmittance and increased reflectance. The study also observed substantial enhancements in nonlinear optical parameters, such as third-order nonlinear susceptibility (χ(3)) and nonlinear refractive index (n 2). These findings suggest the potential of gamma-irradiated lnPcCl films for advanced optoelectronic and nonlinear optical applications.

Morphological and structural properties of antimony selenide thin films deposited with external electric field assistance

A method for producing a thin semiconductor film of antimony selenide (Sb2Se3) via vacuum thermal evaporation with the assistance of an electric field was presented. The morphological, elemental and structural properties of the thin films were characterized using X-ray diffraction and scanning electron microscopy (with energy dispersive X-ray spectroscopy). It was found that an applied constant electric field plays an important role in obtaining Sb2Se3 thin films with the desired morphological and structural properties. The latter is a useful tool for controlling charge transport properties in thin films.

Deep blue high-efficiency solution-processed triplet-triplet annihilation organic light-emitting diodes using bis(8-carbazol-N-yl)fluorene- and benzonitrile-modified anthracene/chrysene fluorescent emitters

Triplet-triplet annihilation (TTA) emitters can effectively utilize non-radiative triplet excitons through the interaction of low triplet energy excitons to produce high energy singlet excitons, but they are mostly restricted by their multilayered device structure fabricated using layer-by-layer thermal vacuum evaporation. It is a great challenge to develop, for the first time, efficient solution-processed non-doped TTA organic light-emitting diodes (OLEDs). In this study, two solution-processable blue emissive TTA molecules (FAnCN and FCsCN) bearing (anthracen-9-yl)benzonitrile (AnCN) and (chrysen-6-yl)benzonitrile (CsCN) as TTA emissive cores modified with 9,9′-bis(8-(carbazole-N-yl)octyl)fluorene (F) are designed and synthesized, respectively. The experimental and theoretical studies reveal that both molecules exhibit deep blue emissions, amorphous morphology with good thermal stability, high-quality solution-cast thin films, decent hole mobility, high-lying HOMO levels (∼-5.45 eV), and suitable lowest singlet (S1)/triplet (T1) excited states (2T1 > S1) for TTA process. FAnCN and FCsCN are successfully employed as solution-processed non-doped emissive layers (EML) in simple structured TTA OLEDs. These devices show intense blue emissions, low turn-on voltages (∼3.6 V), excellent electroluminescent (EL) performances (EQEmax = 5.47–6.84 % and LEmax = 5.66–5.83 cd/A), and TTA characteristics. Especially, FCsCN-based TTA OLED emits deep blue EL emission peaked at 435 nm with a high EQEmax of 6.84 %. This work not only presents a new strategic design for the preparation of solution-processable TTA emitter, but also further ratifies that the TTA mechanism can also be applicable in solution-processed OLEDs.

Near-Electrode Concentration Gradients of Bicarbonate and pH within Porous Gas Diffusion Electrode for Optimized Selective CO2 Electroreduction to C2+ Products.

With high current density, the intense near-electrode CO2 reduction reaction (CO2RR) will cause the concentration gradients of bicarbonate (HCO3-) and hydroxyl (OH-) ions, which affect the selectivity of high-value C2+ products of the CO2RR. In this work, we simulated the near-electrode concentration gradients of electrolyte species with different porous Cu-based CLs (catalyst layers) of GDE (gas diffusion electrode) by COMSOL Multiphysics. The higher porosity CL exhibits a better buffer ability of local alkalinity while ensuring a sufficient supply of H+ and local CO2 concentration. Subsequently, the different porosity CLs were prepared by vacuum-thermal evaporation with different evaporation rate. Structural characterizations and liquid permeability tests confirm the role of the porous CL structure in optimizing concentration gradients. As a result, the high-porosity CL (Cu-HP) exhibits a higher C2+ Faraday efficiency (FE) of ∼79.61% at 500 mA cm-2 under 1 M KHCO3, far more than the FEC2+ ≈ 38.20% with the low-porosity sample (Cu-LP).

Growth of CuO NPs layers on TiO2 NTs using vacuum thermal evaporation

CuO/TiO2 composites have been reported to exhibit higher potential for various applications (electronics, energy storage, and sensor technology…). This study investigates the impact of different film thicknesses on the properties of CuO NPs on TiO2 NTs. CuO NPs were deposited onto TiO2 NTs using vacuum thermal evaporation, with thicknesses ranging from 5 to 30 nm. A quartz crystal monitor measured evaporation rate and film thickness at a substrate temperature of 350 °C. Following the deposition process, the samples were thermally treated through air annealing at 400 °C for 1 h.XRD analysis showed that all films had an anatase phase. The annealed sample also had a confirmed CuO phase, indicating good crystallinity. Crystallite size and strain varied with film thickness, assessed using the Williamson-Hall method and Rietveld refinement. The deposition and distribution of CuO on TiO2 NTs were verified using Scanning Electron Microscopy (SEM) combined with energy dispersive spectroscopy (EDS). Optimizing the materials nanostructures requires controlling film thickness and annealing. Insights from this study can improve nanomaterial fabrication techniques, which could enhance their performance in technological applications.

High performance ultra-thin lithium metal anode enabled by vacuum thermal evaporation

The passivation layer that naturally forms on the lithium metal surface contributes to dendrite formation in lithium metal batteries by affecting lithium nucleation uniformity during charging. Herein, we propose using vacuum thermal evaporation to produce a high-performance ultra-thin lithium metal anode (≤25 µm) with a native layer much thinner than that of extruded lithium. The evaporated lithium metal shows significantly reduced charge-transfer resistance, resulting in uniform and dense lithium plating in both carbonate and ether electrolytes. This study reveals that the evaporated lithium metal outperforms the extruded version in ether electrolyte and with LiFePO4 cathodes, showing a 30% increase in cycle life. Additionally, when paired with LiNi0.6Mn0.2Co0.2O2 cathodes in carbonate electrolyte, the evaporated anode’s cycle life is tripled compared to the extruded lithium metal. This demonstrates that vacuum thermal evaporation is a viable method for producing ultra-thin lithium metal anodes that prevent dendrite growth due to their excellent surface condition.

Facile fabrication of Au-Ag alloy nanoparticles/Ag nanowires SERS substrates with bimetallic synergistic effect for ultra-sensitive detection of crystal violet and alkali blue 6B

The bimetallic nanostructure of Au and Ag can integrate two distinct properties into a novel substrate compared to single metal nanostructures. This work presents a rapid and sensitive surface-enhanced Raman scattering (SERS) substrate for detecting illegal food additives and dyes of crystal violet (CV) and alkali blue 6B (AB 6B). Au-Ag alloy nanoparticles/Ag nanowires (Au-Ag ANPs/Ag NWs) were prepared by solid-state ionics method and vacuum thermal evaporation method at 5μA direct current electric field (DCEF), the molar ratio of Au to Ag was 1:18.34. Many 40 nm-140 nm nanoparticles regularly existed on the surface of Ag NWs with the diameters from 80 nm to 150 nm. The fractal dimension of Au-Ag ANPs/Ag NWs is 1.69 due to macroscopic dendritic structures. Compared with single Ag NWs, the prepared Au-Ag ANPs/Ag NWs substrates show superior SERS performance because of higher surface roughness, the SERS active of Ag NWs and bimetallic synergistic effect caused by Au-Ag ANPs, so the limit of detections (LOD) of Au-Ag ANPs/Ag NWs SERS substrates toward detection of CV and AB 6B were as low as 10-16mol/L and 10-9mol/L, respectively. These results indicate that Au-Ag ANPs/Ag NWs substrates can be used for rapid and sensitive detection of CV and AB 6B and have great development potential for detection of illegal food additives and hazardous substances in the fields of environmental monitoring and food safety.

Significantly improved thermal conductivity of C/C composite by constructing 3D SiC nanowires network in carbon felt via vacuum thermal evaporation

Developing a nanoscale secondary thermal conduction network within carbon fiber performs is a challenging yet effective method to substantially enhance the thermal conductivity of C/C composites. In this study, a strategy for creating a three-dimensional (3D) SiC nanowires (SiCNWs) thermal conductivity network in carbon felts (CFs) was implemented using vacuum thermal evaporation technology to fabricate SiCNWs modified C/C composites (SiCNW–C/C). The growth mechanism of SiC nanowires within CFs and their impact on the microstructure and thermal conductivity of the C/C composite were thoroughly investigated. The findings indicate that a SiC nanowires thermal conduction network can be successfully established within carbon felts without catalysts by initiating nucleation sites and managing reaction pressure. An appropriate reaction pressure is crucial not only for the uniform growth of SiC nanowires but also as a key factor in modulating the content and microstructure of the SiC nanowires. SiC nanowires prepared at 150 Pa exhibit minimal structural defects and are evenly distributed throughout the carbon felts, markedly enhancing the thermal response rate of the felts. The thermal conductivity of these SiCNW-modified C/C composites, both parallel and perpendicular to the carbon fibers, increased to 173 W/m•K and 112 W/m•K, respectively, approximately tripling that of the pure C/C composite. The exceptional thermal management capabilities of SiCNW–C/C were empirically validated through simulated operational chips and finite element simulation. This work presents an effective approach for producing C/C composite with high thermal conductivity particularly through the thickness, offering promising applications in the thermal management of advanced electronics.

A Scalable Synthesis of Ag Nanoporous Film As an Efficient SERS-Substrates for Sensitive Detection of Nanoplastics.

Nanoplastics pollution has led to a severe environmental crisis because of a large accumulation of these smaller nanoplastic particles in the aquatic environment and atmospheric conditions. Detection of these nanoplastics is crucial for food safety monitoring and human health. In this work, we report a simple and eco-friendly method to prepare a SERS-substrate-based nanoporous Ag nanoparticle (NP) film through vacuum thermal evaporation onto a vacuum-compatible deep eutectic solvent (DES) coated growth substrate for quantitative detection of nanoplastics in environmental samples. The nanoporous Ag NP films with controlled pores were achieved by the soft-templating role of DESs over the growth substrate, which enabled the self-assembly of deposited Ag NPs over the surface of DES. The optimized nanoporous Ag substrate provides high sensitivity in the detection of analyte molecules, crystal violet (CV), and rhodamine 6G (R6G) with a limit of detection (LOD) up to 1.5 × 10-13 M, excellent signal reproducibility, and storage stability. Moreover, we analyzed quantitative SERS detection of polyethene terephthalate (PET, size of 200 nm) and polystyrene (PS, size of 100 nm) nanoplastics with an LOD of 0.38 and 0.98 μg/mL, respectively. In addition, the SERS substrate efficiently detects PET and PS nanoplastics in real environmental samples, such as tap water, lake water, and diluted milk. The enhanced SERS sensing ability of the proposed nanoporous Ag NP film substrate holds immense potential for the sensitive detection of various nanoplastic contaminants present in environmental water.

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.

An EPR study of point defects in zinc oxide thin films

We studied ZnO thin films deposited on glass slides by thermal evaporation in vacuum followed by heat treatment in open air or Ar flow. The samples were characterized using x-ray diffraction, Raman scattering, photoluminescence (PL), and electron paramagnetic resonance (EPR) spectroscopy. We observed a broad PL band in the visible region at spectral positions of 504 and 560 nm and a low-intensity band in the UV region at 390 nm. The EPR spectra display a clear first derivative structure at g=1.96 at temperatures below 200 K. The PL spectrum shows red-shifted valence to conduction band emission due to electron hole recombination through shallow surface states. We found an activation energy of E a = 4.2 meV using the Arrhenius plot and estimated concentrations of paramagnetic defects and spin–spin relaxation time constants of 1016 m−3 and 10–14 s, respectively.

Influence of phase state, conducting sublayer material and deposition method on mechanical properties and adhesion of Ge2Sb2Te5 thin films

Ge2Sb2Te5 (GST225) thin films are used as a functional element in multilayer cells of phase change random access memory (PCRAM, PCM) and have good prospects in electrically driven tunable reflective metasurfaces and on-chip waveguide devices, including those implemented on a flexible substrate. Knowledge of the mechanical properties of GST225 thin films, their adhesion to conductive layers, and the correct choice of conductive material is critical to the reliable operation of these devices. The present work focuses on the effect of phase change on mechanical parameters such as hardness, Young's modulus and stiffness, as well as on the adhesion of GST225 thin films to various metal sublayers (Al, Ti, TiN, W, Ni). The formation of GST225 films was carried out by vacuum thermal evaporation and DC magnetron sputtering, which made it possible to study layers with different distributions of elements over the thickness.

Effects of carbazolyl and diphenylamino substituents bearing methoxy groups on the performance of hole-transporting materials in OLEDs

Newly designed and synthesized derivatives of pentaphenylbenzene with methoxy-substituted carbazolyl or diphenylamino moieties were investigated to estimate their applicability as hole transport materials. Both the compounds exhibit high thermal stability. The intramolecular charge transfer is blocked for the film of the compound containing diphenylamino groups. The intermolecular charge transfer is induced in the film of carbazolyl-containing compound. The derivative of pentaphenylbenzene and diphenylamine exhibits higher hole drift mobility (2.4·10−3 cm2/V·s at the electric field of 5.5·105 V/cm) and by 0.1 eV lower ionization potential than the carbazolyl-containing compound. Both the compounds were utilized as hole-transporting materials in a series of organic light emitting diodes (OLEDs) based on of thermally activated delayed fluorescence. With the maximum values of external quantum efficiency of 25.9 % and power efficiency of 43.4 lm/W, OLEDs containing the layers of the synthesized compounds outperformed the device based on TCTA by 4 %, without the change in spectral properties. Variable angle spectroscopic ellipsometry revealed the moderate average roughness of the films of the compound deposited by the thermal vacuum evaporation technique with an arithmetic mean deviation of not more than 0.8 nm. The prominent hole transport characteristics of the compounds make them good candidates for utilization in optoelectronic devices.

Influence of the distance between evaporation source and substrate on formation of lead telluride (PbTe) nanostructures by vacuum thermal evaporation method

Lead telluride nanostructures were obtained on silicon substrates by thermal evaporation in vacuum. Growth occurred at three different distances between the evaporation source and the substrate. The distances between the evaporator and the evaporation source were 5 cm; 7.5 cm and 10 cm. Structural characteristics were studied using XRD, SEM, EDX, AFM analyses. These methods provided information about the crystal structure, morphology, microstructure and elemental composition of the material. X-ray diffraction analysis showed that thin films of lead telluride obtained by thermal evaporation in vacuum have a cubic crystal structure. This experimental work was carried out to determine the effect of distance on the structure of lead telluride (PbTe). During the experiment, the optimal modes for the formation of lead telluride (PbTe) nanostructures were determined, which was equal to d = 10 cm. It was found that lead telluride (PbTe) nanostructures are formed at this distance.

P‐208: Ultra High‐resolution patterning technology with Fine silicon mask

Side by side RGB OLEDs‐on‐Silicon backplane holds great promise for high brightness, high resolution and low cost Micro OLED displays. The main challenge of vacuum thermal evaporation (VTE) patterning technique is to get a submricon‐size shadow distance. Herein, we have explored the relation of shadow distance with mask‐substrate gap, as well as the relationship of shadow distance with evaporation angle. The achievements verify the possibility of manufacturing the ultra‐high resolution side by side RGB AMOLEDs with &gt;4000ppi. The study of ultra‐high resolution evaporation patterning need to be expanded for the OLED microdisplays futures.

Examination of structural and spectrophotometric optical characteristics of nano-like flower quinolinyl carbonyl pyrazole-1-carbodithioate films: a new trend for optoelectronic applications

The current investigation entailed the synthesis of benzyl 5-amino-4-[(1-ethyl-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)carbonyl]-1H-pyrazole-1-carbodithioate (referred as BAEHQP, compound 2) from 6-ethyl-4,5-dioxo-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carbonitrile (compound 1), followed by its characterization in nanocrystalline thin films produced through thermal evaporation in a high vacuum. Computational and experimental methodologies were employed for this purpose. Density functional theory (DFT) calculations using the B3LYP/6-311++G(d,p) basis set were utilized to predict the HOMO-LUMO gap and evaluate the global reactivity descriptors, elucidating the chemical hardness, kinetic stability, and electron-donating capabilities. X-ray diffraction (XRD) analysis verified the presence of a polycrystalline structure in the BAEHQP powder and indicated an amorphous nature in the thin film. Utilizing the Williamson-Hall formula, the mean crystallite size and microstrain were determined to be 63.36 nm and 0.00667, respectively. Scanning electron microscopy corroborated the nanoflower-like structure, and particle size analysis was conducted to determine the size distribution. The optical properties, encompassing both linear and nonlinear aspects, of BAEHQP thin film were investigated using spectrophotometric methods, delineating band transitions and identifying a fundamental direct energy gap of 2.2 eV. The distinct attributes of thin-film absorption and dispersion were outlined, and the unanticipated findings hold potential implications for advancing the industrialization of photodiode device manufacturing.

Study the Effect of Copper Oxide Nanorods Enhanced by Silver Nanoparticles on the Highly Sensitive Gas Sensor

In this paper, ammonia (NH3) gas sensitivity was enhanced by the development of highly dense copper oxide (CuO) nanorods on glass substrates. The layer of copper (Cu) was deposited using a vacuum thermal evaporation method. The grown layer of Cu was sequentially inserted into an oxidation furnace at (400 °C) for (120 min) under atmospheric pressure to produce copper oxide (CuO) nanorods. Silver (Ag) nanoparticles- deposited copper oxide nanoparticles were successfully enhanced via a photo assisted spray pyrolysis technique. A metal-semiconductor-metal (MSM) NH3 gas sensor with aluminum (Al) contact electrodes was fabricated on CuO nanorods. The structure of the crystal as well as the morphology of the CuO nanorods were evaluated with field-emission scanning electron microscopy (FE-SEM), X-ray diffraction, and UV-visible spectroscopy respectively. In order to create a high-performing MSM NH3 gas sensor, silver nanoparticles (NPs) were sprayed by the photo-assisted spray pyrolysis technique on the CuO nanorods, which are produced via the vacuum thermal evaporation method. The results showed that the modified CuO nanorods by Ag nanoparticles demonstrated great sensitivity to NH3 gas might be much improved, and the sensitivity rises from (376.4 to 700 %) , fast response and recovery times about (10.4 and 9.5 s) respectively to NH3 gas.