Uniform Thin Films Research Articles

Fabrication of Bi2Te3 and Sb2Te3 Thermoelectric Thin Films using Radio Frequency Magnetron Sputtering Technique.

Through various studies on thermoelectric (TE) materials, thin film configuration gives superior advantages over conventional bulk TEs, including adaptability to curved and flexible substrates. Several different thin film deposition methods have been explored, yet magnetron sputtering is still favorable due to its high deposition efficiency and scalability. Therefore, this study aims to fabricate a bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin film via the radio frequency (RF) magnetron sputtering method. The thin films were deposited on soda lime glass substrates at ambient temperature. The substrates were first washed using water and soap, ultrasonically cleaned with methanol, acetone, ethanol, and deionized water for 10 min, dried with nitrogen gas and hot plate, and finally treated under UV ozone for 10 min to remove residues before the coating process. A sputter target of Bi2Te3 and Sb2Te3 with Argon gas was used, and pre-sputtering was done to clean the target's surface. Then, a few clean substrates were loaded into the sputtering chamber, and the chamber was vacuumed until the pressure reached 2 x 10-5 Torr. The thin films were deposited for 60 min with Argon flow of 4 sccm and RF power at 75 W and 30 W for Bi2Te3 and Sb2Te3, respectively. This method resulted in highly uniform n-type Bi2Te3 and p-type Sb2Te3 thin films.

High quality a-InGaZnO and a-ZrAlO deposited at 375 °C by spray pyrolysis for low voltage operation TFTs

We report the high-performance, bottom-gate a-InGaZnO (IGZO) TFT with high-k ZrAlO (ZAO) gate insulator by spray pyrolysis (SP). The a-IGZO/ZAO TFT exhibits the average saturation mobility of 23.12 cm2 V−1 s−1, subthreshold swing of 121 mV dec-1, ION/OFFratio of ∼108 with no hysteresis and low off-state current of ∼10-19A µm−1. In addition, the TFT exhibits good interface quality with less trap density (∼9x1010 cm−2) and conduction band tail state (∼4.3x1018 cm−3) extracted from TCAD fitting. The high-performance is attributed to the formation of uniform and dense a-IGZO and ZAO thin films with low defect density. Therefore, the SP a-IGZO/ZAO TFTs have great potential to be employed in low-cost, low driving voltage TFTs for display application.

Structural and optical properties of ZnO thin films as a function of pH value and its effect on photoelectrochemical water splitting

ZnO nanoparticles were synthesised via sol–gel method, and then, deposited on a glass substrate using the spin-coating procedure to hand in ZnO thin films. In order to study the effect of alkaline sol on different properties of ZnO thin films, the pH value of sol was adjusted with ammonia. Then, the structural, optical, and photoelectrochemical properties of the prepared samples were analysed. According to XRD analyses, by increasing pH values, the size of ZnO particles increases and the films’ crystallinity improves. In addition, SEM micrographs affirm the uniformity of thin films. According to AFM findings, the morphology and roughness of the samples’ surface are affected by pH values in such a way that with increasing the pH, the roughness of the surface decreases, and the crystallinity improves. Also, both UV–vis peaks shift towards lower wavelengths with increasing pH value of ZnO sol. This means that the more the pH values of ZnO sol, the more the excitation energy of electrons. On the other hand, the numerical values of the energy bandgap decrease by increasing pH. According to PL results, the increase of pH causes the separated electrons and holes to have more energy and can move away from each other. So, the recombination process rate decreases; this result affirms by EIS findings. Increasing the optical absorption and reducing charge recombination are in favour of the photocatalytic reactions. Clearly, increasing the pH value causes the stable photocurrent to increase and the threshold voltage of (J-V) diagram to decrease. Also, the samples show recognisable sensitivity to light. As a final result, the best suggested amount of pH to fabricate ZnO photoanods for water splitting is 10.5.

Exploring the weak visible-near-infrared and NO2 detection capabilities of PbS/Sb2O5 heterostructures with DFT interpretations

The need for photosensors and gas sensors arises from their pivotal roles in various technological applications, ensuring enhanced efficiency, safety, and functionality in diverse fields. In this paper, interlinked PbS/Sb2O5 thin film has been synthesized by a magnetron sputtering method. We control the temperature to form the nanocomposite by using their different nucleation temperature during the sulfonation process. A nanostructured PbS/Sb2O5 with cross-linked morphology was synthesized by using this fast and efficient method. This method has also been used to grow a uniform thin film of nanocomposite. The photo-sensing and gas-sensing properties related to the PbS/Sb2O5 compared with those of other nanomaterials have also been investigated. The experimental and theoretical calculations reveal that the PbS/Sb2O5 exhibits extraordinarily superior photo-sensing and gas-sensing properties in terms of providing a pathway for electron transport to the electrode. The attractive highly sensitive photo and gas sensing properties of PbS/Sb2O5 make them applicable for many different kinds of applications. The responsivity and detectivity of PbS/Sb2O5 are 0.28 S/mWcm−2 and 1.68 × 1011 Jones respectively. The sensor response towards NO2 gas was found to be 0.98 at 10 ppb with an limit of detection (LOD) of 0.083 ppb. The PbS/Sb2O5 exhibits high selectivity towards the NO2 gas. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to analyze the geometries, electronic structure, and electronic absorption spectra of a light sensor fabricated by PbS/Sb2O5. The results are very analogous to the experimental results. Both photosensors and gas sensors are indispensable tools that contribute significantly to the evolution of technology and the improvement of various aspects of modern life.

Structure–Property Relationships of Solution‐Processable Diarylethene‐Based Main‐Chain Photochromic Polymers

AbstractA series of alternating copolymers of a dithienylethene with di‐n‐alkyl‐fluorene (P1–P3), di‐n‐hexylphenylene (P4), 9‐heptadecanylcarbazole (P5), and 4,8‐bis(3,5‐dioctyl‐2‐thienyl)‐1,5‐dithia‐s‐indacene (P6) are designed, synthesized, and characterized. All of the polymers are soluble in common organic solvents such as chloroform, dichloromethane, toluene, and tetrahydrofuran. The side‐chain length affected the solubility of the polymer, molecular weight, and the glass transition temperature. Solutions of P1–P6 show photochromism with high quantum yields of 6‐π electrocyclization (41–87%) and cycloreversion (0.4–1.1%). These polymers also formed uniform thin films and the rates of solid state photoisomerization are measured relative to P4, which has the highest cyclization and cycloreversion rates. The color of the photochromic polymer is tuned according to the comonomer and the maximum absorption wavelength ranged from 569 to 675 nm in the closed isomeric form. All the polymers are thermally stable and show no signs of photodegradation after being exposed to UV‐light for 120 min in air. Based on these promising results, these polymers may be useful for multifunctional organic electronic devices.

Effect of Holding Time on Structure and Optical Properties of PbSe Films Deposited in a Chemical Bath on Si(100) Substrates

Lead selenide (PbSe) thin films are widely used in the field of infrared detection due to their high infrared detection rate and sensitivity at room temperature. In recent years, PbSe thin films have been successfully grown on Si substrates. This article utilized the chemical bath deposition (CBD) method to prepare uniform and dense PbSe thin films on Si(100) substrates. The crystal structure, micro morphology, thickness, and energy band gap of polycrystalline PbSe thin films on Si(100) substrates were studied at a deposition temperature of 70 °C with a holding time of 30–120 min. Results showed that the prepared PbSe films bonded well with the Si(100) substrate. As the holding time increased, PbSe maintained [200] crystal orientation growth, and the crystallinity improved. The thickness of the PbSe thin film increased with the holding time, while the energy band gap first decreased and then increased. The PbSe thin film prepared with a holding time of 60 min had a thickness of about 388.5 nm, grew in the [200] crystal orientation, and had an energy band gap of 0.153 eV, showing the best optical properties.

Nucleation of highly uniform AlN thin films by high volume batch ALD on 200 mm platform

Nucleation of highly uniform AlN thin films by high volume batch ALD on 200 mm platform

Enhanced Thickness Uniformity of MoS2 Thin Films on SiO2/Si Substrates via Substrate Pre-Treatment with Oxygen Plasma

Enhanced Thickness Uniformity of MoS2 Thin Films on SiO2/Si Substrates via Substrate Pre-Treatment with Oxygen Plasma

Analysis of low-speed blade coating flows

From industrial-scale production to small-scale fabrication of functional films, the blade coating method is used widely to apply a uniform thin liquid film on a moving substrate. However, conventional hydrodynamic models are inadequate for laboratory-scale low-speed blade coating, where capillary forces dominate. In this study, the low-speed blade coating of non-evaporative Newtonian fluids was investigated in experimental, computational and analytical approaches. The transient free boundary problem was solved utilizing a two-dimensional finite element method, and a simple viscocapillary model was developed to describe the viscous stress and capillary forces within the puddle, and predict the thickness of the wet film as a function of the speed of the substrate. Comparing the predicted film thickness with the computational results, and a flow visualization experiment of blade coating with silicone oil, respectively, confirmed the model's validity. The study indicates that the proposed model may be a useful tool for optimizing laboratory coating processes, as it provides a greater understanding of the low-speed blade coating system on a laboratory scale.

Gallium oxide cantilevered thin film-based solar-blind photodetector and its arc detection applications

The performance of gallium oxide (Ga<sub>2</sub>O<sub>3</sub>) thin film detector based on metal-semiconductor-metal (MSM) is highly dependent on the uniformity of the Ga<sub>2</sub>O<sub>3</sub> thin film, and the manufacturing process is quite sophisticated, which poses a challenge for the scale-up and mass production of thin film photodetectors. In this work, an MSM Ga<sub>2</sub>O<sub>3</sub> thin film solar-blind photodetector with five-finger interdigital electrodes is fabricated by physically depositing Ga<sub>2</sub>O<sub>3</sub> thin film on the surface of a mass-produced cantilevered thin film chip. Through the microelectromechanical system (MEMS) process, the cantilever electrode structure is prepared, which protects the internal circuit and the integrity of the thin film. The Ga<sub>2</sub>O<sub>3</sub> thin film treated by argon plasma at a low temperature is amorphous, but the photodetector still possesses considerable ultraviolet detection performance. At a bias voltage of 18 V, it approaches the detection performance of crystalline Ga<sub>2</sub>O<sub>3</sub> thin film, with a detectivity of 7.9×10<sup>10</sup> Jones, an external quantum efficiency of 1779%, rise time and decay time of 1.22 s and 0.24 s, respectively. Moreover, a system of arc detection is built in outdoor environments. Without any optical focusing system, this photodetector achieves sensitive detection of pulsed arc in an outdoor sunlight environments. For pulsed arcs with an output voltage of 100 kV, the photodetector is capable of sensitive detection at a distance of 25 cm. Besides, the maximum detection distance of 155 cm indicates that the photodetector will have a favorable potential application value in the field of solar-blind detection. This work develops a sensitive functional thin film deposition technology based on the cantilever electrode structure fabricated by the MEMS process, which avoids the influence of the large-area uniformity of the functional thin film on the etching circuit. It provides a new technical approach and process route for preparing MSM photodetectors.

Durable silver nanowire transparent electrodes enabled by biorenewable nanocoating using chitin and cellulose nanofibers for flexible electronics.

The protection of silver nanowire (AgNW) networks is crucial for enhancing their durability and applicability to flexible electronics. In this study, we present a sustainable and efficient strategy to protect AgNW-based flexible transparent electrodes (FTEs) using a layer-by-layer (LBL) assembly of biorenewable chitin and cellulose nanofibers (Chi and Cell). These uniform LBL-assembled thin films were successfully fabricated on AgNW FTEs due to their opposite surface charges. The resulting (Chi/Cell)n bilayers, where n is the number of bilayers, did not degrade the optoelectrical properties of AgNW FTEs and significantly enhanced their stability under various harsh conditions. The optimized (Chi/Cell)10@Al-AgNW FTEs exhibited comprehensive stability against UV/O3 treatment for 40 min, thermal treatment at 250 °C for 350 min, Na2S (1%), HCl (10%), and NH3 (30%) treatments for 3, 30, and 105 min, respectively, sonication for 300 min, and 10 000 cycles of bending test. Therefore, the (Chi/Cell)10@Al-AgNW FTEs were successfully applied to transparent heaters (TH) and pressure sensors with remarkably improved applicability, durability, and performance compared to pristine AgNW FTEs, providing a reassuring solution to the stability issues of AgNW-based FTEs.

Inkjet printing high mobility indium-zinc-tin oxide thin film transistor

Metal oxide thin film transistor has been widely used in flat panel display industry because of its low leakage current, high mobility and large area uniformity. Besides, with the development of printed display technology, inkjet printing process can fabricate the customizable patterns on diverse substrates with no need of vacuum or lithography to be used, thus significantly reducing cost and receiving more and more attention. In this paper, we use inkjet printing technology to prepare a bottom gate bottom contact thin film transistor (TFT) by using indium-zinc-tin-oxide (IZTO) semiconductor. The surface morphology of the printed IZTO film is modified by adjusting the solvent composition and solute concentration of the printing precursor ink. The experimental result show that the use of binary solvents can effectively overcome the coffee ring shape caused by the accumulation of solute edge in the volatilization process of a single solvent, ultimately presenting a uniform and flat contour surface. Further increase in solute concentration is in favor of formation of convex surface topology. The reason for the formation of the flat surface of the oxide film is the balance between the inward Marangoni reflux of the solute and the outward capillary flow during volatilization. In addition, IZTO thin film transistor printed with binary solvents exhibits excellent electrical properties. The ratio of width/length = 50/30 exhibits a high on-off ratio of 1.21×10<sup>9</sup>, a high saturation field-effect mobility is 16.6 cm<sup>2</sup>/(V·s), a low threshold voltage is 0.84 V, and subthreshold swing is 0.24 V/dec. The uniform and flat active layer thin film pattern can form good contact with the source leakage electrode, and the contact resistances of TFT devices with different width-to-length ratios are less than 1000 Ω, which can reach the basic conditions of high mobility thin film transistors prepared by inkjet printing. Therefore, using solvent mixture provides a universal and simple way to print oxide films with required surface topology, and present a visible path for inkjet printing of high-mobility thin film transistors.

Detection of refractive index and imperfection in thin film transparent polymer by back focal plane imaging

Emission patterns from molecules at interfaces encode many details about their local environment and their axial position, along the microscope’s optical axis. We introduce an advanced approach that synergizes back focal plane (BFP) imaging with innovative ‘smart’ surfaces make surface imaging more qualitative, more reliable, and more robust. Our method is particularly focused on accurately measuring the refractive index (RI) of transparent thin films and their imperfections close to the interfaces. Our technique utilizes a ‘smart’ surface, which features a uniform fluorescent thin film of about 4 nm thickness together with back-focal plane (BFP) imaging. We manage to detect bubbles or other imperfection in 100 nm thin film of polymer with RI of 1.34.

Silver-deposited titanium as a prophylactic 'nano coat' for peri-implantitis.

Dental implant failures caused by bacterial infections are a significant concern for dental implantologists. We modified the titanium surface by depositing silver (Ti-Ag) using direct current (DC) sputtering and confirmed the formation of a 'nano coat' by X-ray photoelectron spectroscopy (XPS), surface profilometry and energy dispersive spectroscopy (EDS). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed the deposition of a uniform nano Ag thin film. A gradual increase in thickness was observed, and the film thickness (530 nm) at 5 min deposition time (Ti-Ag5) resulted in a reduction of the water contact angle (WCA, 15%) and an increase in surface energy (SFE, 22%) in comparison to the uncoated Ti surface. Using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), the slow, steady release of Ag from the coating was observed over 21 days. The Ti-Ag5 surface exhibited excellent antibacterial activity against Streptococcus oralis, Streptococcus sanguinis, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis, which belonged to the yellow, purple, and red complexes, representing specific periodontal pathogens. Furthermore, we observed excellent cytocompatibility of Ag-deposited Ti towards MG-63 osteoblasts with no inhibitory effect on their proliferative potential. Quantitation of alkaline phosphatase (ALP) activity, mineralization efficiency, and osteogenesis-related gene expression of MG-63 cells over 21 days was suggestive of rapid osseointegration. Overall, the 'nano coat' of Ag on Ti is indeed a prophylactic against peri-implantitis, ensuring increased implant success.

Study On the Uniformity Aluminum Nitrate Thin Film On 2-Inch Silicon Substrate Prepared by RF Magnetron Sputtering

Aluminum nitrate (AlN) has attracted the researcher's interest due to its unique properties in the semiconductor material and other high-performance devices. This results in numerous techniques to investigate the uniformity of AlN thin film. The deposition in this study is carried out on an AlN on a 2-inch silicon substrate using a magnetron sputtering technique. The RF magnetron sputtering can also produce better film quality and deposit a wide variety of insulators, metals, alloys and composites. In this study, the AlN film was deposited using the RF magnetron sputtering by using three different parameters for the growth of the AlN on the 2-inch Si substrate for uniformity analysis. The uniformity of AlN thin film includes analyses of the structural, thickness, topology and surface morphology by using the characterization of X-ray diffraction (XRD), atomic force microscopy (AFM), surface profiler and field emission scanning electron microscopy (FE-SEM). Based on the result from three parameters that have been done, parameter one shows the best results. For the crystalline structure results, the peak (100) AlN indicates the highly textured phases similar to a single crystal, and the cross-section result in FE-SEM shows the homogenous thickness.

Effect of Surface Pretreatment to Reduce the Incubation Period of Iridium Thin Films Grown by ALD on the Oxide Surface

Iridium (Ir) has low figure of merit(×λ) and high melting temperature properties, so it has been recently spotlighted as a very important copper (Cu) alternative interconnect material in next-generation semiconductor devices. In particular, in the case of depositing a thin film using atomic layer deposition (ALD) technology, it can be expected to deposit extremely thin film with conformal, uniform and excellent step coverage characteristics even in a very complex structure or a trench structure of several nm dimension due to the inherent self-limiting characteristic of ALD. In this regard, ALD-Ir is considered as one of the most suitable metallization process for the application of advanced semiconductor interconnects. Therefore, considerable efforts have been conducted to develop a reliable ALD-Ir process having improved film qualities. And, ALD-Ir process with excellent thin film properties such as low electrical resistivity and negligible oxygen impurities was recently reported using Tricarbonyl (1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl iridium (C18H27IrO3 or TICP) precursor and oxygen [1]. However, in the case of this TICP precursor, it was difficult to deposit extremely thin and continuous Ir films on the hydroxyl-terminated oxide layer due to its long incubation delay.Therefore, in this study, a method for depositing a very thin, uniform and continuous ALD-Ir thin film with low resistivity even on oxide materials was explored by reducing the incubation period and promoting nucleation using various surface pretreatment conditions. In addition, the nucleation behavior as well as film properties of ALD-Ir on the oxide material were systemically compared and analyzed according to the surface pretreatment conditions, and finally, ALD-Ir thin film with excellent properties on the oxide surface was obtained.

Surface engineering of Sio2-Zro2 films for augmenting power conversion efficiency performance of silicon solar cells

Improving solar cell performance hinges significantly on the application of anti-reflective surface coatings. A wide variety of coating techniques, including blade coating, spin coating, dip coating, and others were employed. The present research investigation employed various coating materials, namely SiO2 (Silicon dioxide), ZrO2 (Zirconium dioxide), and SiO2–ZrO2 blends, to apply a protective layer onto polycrystalline silicon solar cells using the sputter coating process. The efficiency of these solar cells with multilayer coating was assessed through diverse characterization methods. The uniform thin films were obtained using a 45-min coating process using an input voltage source of 17 kV, which was confirmed through analyses conducted using FESEM and AFM techniques. The UV–Vis spectroscopy and current-voltage source metre were employed to examine the light absorption and transmittance of bare and coated silicon solar cells. When compared to alternative solar cells, the solar cell coated with a combination of SiO2 and ZrO2 demonstrated uniform deposition and a low light reflectance of only 6 %. SiO2–ZrO2 gains a highest power conversion efficiency (PCE) of 17.6 % under controlled light source. This superior performance was due to the increase in photon transmittance in to the depletion region. Furthermore, the electrical resistivity of the SiO2–ZrO2 blend coated solar cell was measured using the four-probe method was found to be 2.89 × 10−3 Ω-cm, which was lower than that of other solar cells. From the experimental results, it was clear that SiO2 - ZrO2 blend-coated solar cells outperformed both other coated and uncoated solar cells. Consequently, SiO2–ZrO2 blends emerged as superior anti-reflective materials for achieving peak performance.

Fabrication of iron doped titanium dioxide photocatalytic nanocomposite supported by water-quenched blast furnace slag and photocatalytic degradation of wastewater

Metallurgical solid waste blast furnace water quenched slag (WBFS) was employed as carrier materials to prepare Fe–TiO2/WBFS composite photocatalyst using a sol-gel method for improving both the photocatalytic activity and the high-value utilization of metallurgical solid waste. The Fe3+ doping technology was adopted to increase the utilization of solar energy. The influencing factors and photocatalytic activity were systematically evaluated by thermogravimetry/differential thermal analyser (TG-DSC), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) method, scanning electron microscopy-energy spectrometer (SEM-EDS), X-ray photoelectric spectroscopy (XPS), UV–Vis absorption spectrum and photoluminescence spectra technology through the degradation rate of methylene blue (MB) solution. The results showed that the Fe3+ ions were successfully incorporated into the TiO2 lattice, which had no effect on the crystalline phase of TiO2 and expanded the spectral response range of TiO2 from the ultraviolet region to the visible light region. When the calcination temperature was at 450 °C and the number of Fe–TiO2 sol loading cycles was two times, the photocatalytic activity of Fe–TiO2/WBFS presented the strongest, and the degradation ratio of MB reach the maximum value of 98.9 %. A uniform and dense anatase TiO2 thin film was wrapped on the surface of WBFS. The photocatalytic activity first improved and then weakened with an increase of calcination temperature, Fe3+ doping amounts and the loading cycles of sol. The TiO2 film changed from thin to thick and uneven to uniform, until cracking and spalling phenomenon finally occurred with an increase of Fe–TiO2 sol loading cycle from 1 to 3 times. When the Fe–TiO2/WBFS was reused for four times, the degradation rate of MB could still show 67.4 %, being far higher than that of TiO2/WBFS of 25.4 %.

Synthesis and Methane Gas Sensing Study of Uniform Zinc Oxide Nanoparticles and Thin Film

Synthesis and Methane Gas Sensing Study of Uniform Zinc Oxide Nanoparticles and Thin Film

Comprehensive Crystal Regulation Reduces Interfacial Energy Loss for Efficient Blue Perovskite Light-Emitting Diodes.

As an essential component of future full-color displays, blue perovskite light-emitting diodes (PeLEDs) still lag far behind the red and green counterparts in the device performances. In the mainstream quasi-2D blue perovskite system, trap-mediated nonradiative loss, low energy transfer efficiency, and interface fluorescence quenching remain significant challenges. Herein, guanidinium thiocyanate (GASCN) and potassium cinnamate (PCA) are respectively introduced into the hole transport layer (HTL) and the perovskite precursor to achieve a dense and uniform perovskite thin film with greatly improved optoelectronic properties. Therefore, adequate GA+ acts as pre-nucleation sites on the HTL surface, regulating crystallization through strong hydrogen bonding with perovskite intermediates. The realized polydisperse domain distribution is conducive to cascade energy transfer, and the improved hole transport ability alleviates interface fluorescence quenching. In addition, the SCN- and CA- groups can form coordination bonds with the defects at the buried perovskite interface and grain boundaries, respectively, which effectively suppresses the detrimental nonradiative recombination. Benefitting from the comprehensive crystal regulation, blue PeLEDs featuring stable emission at 484 and 468nm exhibit improved external quantum efficiencies of 11.5% and 4.3%, respectively.