Papers by Keyword: Spin Coating

Abstract: An embedded system-based spin coating machine has been developed to grow thin films. Pure zinc oxide (ZnO) and magnesium-doped zinc oxide (ZnO: Mg) thin films with different doped samples have been prepared using the spin coating technique for LPG gas sensing application. The spin coating machine is fully controlled by a PIC microcontroller (PIC16f877A), which can drive a driver circuit to drive a spinning motor, and ZnO: Mg thin films are deposited using this machine. XRD results indicated that the movie has a hexagonal wurtzite structure with a preferred orientation, and the crystallite size increases with the increasing doping concentration of Mg. The surface morphology investigation shows that grains are irregular in shape, and doping concentrations do not influence the surface morphology. From the TEM image, particle sizes observed ranged between 23 and 28 nm, with an average value of ~25.8 nm. The maximum visible average transmittance was 96% for an optimum Mg doping concentration of 10 wt% %. The investigated DC electrical conductivity of Mg-doped ZnO thin films shows enhanced electrical conductivity compared to pure ZnO, and the AC conductivity is decreased with increasing Mg doping concentrations from 5 to 10 wt%. The operation and sensing mechanism of Pure ZnO and ZnO: Mg thin films behind their impressive results has been studied in depth.

Abstract: Herein we report a simple and cost-effective way for synthesis and application of ZnO-PVA nanocomposite using the spin coating technique in which an aqueous solution containing sources of above was deposited on a glass substrate using spin coating technique and further annealed at 120°C. The structural, optical and morphological properties investigated reveals polycrystalline nature of uniformly coated ZnO-PVA composite thin film with a band gap of 3.26 eV. Photo-detector device is made by patterning silver electrodes at two ends of thin film by keeping an electrode gap of ~ 1 mm. Current-voltage measurements are performed under dark and UV illumination. A linear rise in photocurrent under UV illumination (100 μW/cm²) indicate reliable photodetection properties of the device with ~ 6 μA photocurrent, 120 A/W responsivity, 5.8 x 10⁴external quantum efficiency, 6 x 10⁴ sensitivity and 0.6ms rise time, which is highly applicable for fabricating UV photodetectors going to be used for advance application in defence and space.

Abstract: To meet the requirements of second generation photovoltaics, spin coating and RF magnetron sputtering techniques have been utilized to fabricate zinc sulfide thin films for buffer layer optimization. During fabrication process, substrate temperatures for spin coating and RF magnetron sputtering processes are kept at room temperature and at 200 oC, respectively. Thin films are annealed at 500oC for 1 hour in an inert environment to acquire crystallinity and uniform surface morphology. XRD analysis reveals that thin films fabricated by spin coating and RF magnetron sputtering exhibit wurtzite and zinc blende crystal structures, respectively. SEM shows that the surface morphology of thin films fabricated by both techniques is uniform and homogeneous without voids and cracks. EDS results indicate that thin films fabricated via spin coating have equal stoichiometric ratio of zinc to sulfur (1:1). Whereas, an unequal stoichiometric ratio of zinc to sulfur is detected in RF magnetron sputtered thin films. According to optical studies, spin coated zinc sulfide thin films have 67% transmission with an energy band gap of 3.62 eV. While, RF magnetron sputtered thin films have 76% transmission with a wide energy band gap of 3.70 eV. Electrical properties depict that thin films fabricated by RF magnetron sputtering have higher carrier concentration, lower resistivity and higher conductivity than spin coated thin films. In comparison, RF magnetron sputtered zinc sulfide thin films exhibit best structural and optoelectronic properties for buffer layer in second generation solar cells.

Abstract: This work focuses on the preparation of pure nanocrystalline SnO2 and SnO2:Cu thin films on cleaned glass substrates utilizing a sol-gel spin coating and chemical bath deposition (CBD) procedures. The primary aim of this study is to investigate the possible use of these thin films in the context of gas sensor applications. The films underwent annealing in an air environment at a temperature of 500 ^◦C for duration of 60 minutes. The thickness of the film that was deposited may be estimated to be around 300 nm. The investigation included an examination of the structural, optical, electrical, and sensing characteristics, which were explored across various preparation circumstances, specifically focusing on varied concentrations of Cu-doping (2, 4, and 6 wt.%). The deposited films were analyzed by several techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical absorption spectroscopy. The films generated by the spin coating method had a tetragonal rutile structure, while the films created via the chemical bath deposition (CBD) technique displayed both tetragonal rutile and orthorhombic structures. The spin coating technique was used to make films of several weight percentages (0, 2, 4, and 6 wt.%). The resulting crystallite sizes were examined and found to be 23 nm, 18 nm, 14 nm, and 10.5 nm, respectively. Similarly, films made using the chemical bath deposition (CBD) method exhibited crystallite sizes of 22, 13.9, 9.3, and 8.15 nm, respectively. The obtained findings from atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses indicate a consistent trend whereby, as the concentration of Cu-doped material rises, there is a decrease in the average grain size. The transmittance and absorbance spectra were examined within the wavelength range of 300 to 1000 nm. The films generated by both approaches exhibit a significant level of light transmission throughout the visible spectrum. The bandgap energy of spin coating and CBD films decreases with increasing Cu-doped concentrations; the values were (3.88, 3.8, 3.68, and 3.63) eV and (3.8, 3.78, 3.66, and 3.55) eV, respectively. The electrical characteristics of the films include direct current (DC) electrical conductivity, which indicates the presence of two activation energies, Ea₁ and Ea₂. These activation energies exhibit an upward trend when the concentration of Cu doping is increased. The films were examined for their ability to detect carbon monoxide (CO) gas at a concentration of about 50 ppm at normal room temperature conditions. The sensitivity of the films to carbon monoxide (CO) gas was assessed at various time intervals and temperatures. The results indicated that the film generated using spin coating exhibited a notably high sensitivity at a temperature of 200 °C, while the film prepared using the chemical bath deposition (CBD) approach had heightened sensitivity at a temperature of 150 °C. Keywords: Spin coating, SnO₂ thin films, CBD, AFM, XRD, gas sensor.

Abstract: A typical spin coating technique entails three steps: dispense, in which the resin fluid is applied to the substrate surface; high-speed spin, in which the fluid is thinned; and drying, in which extra solvents are removed from the resultant film. For the growth of thin films, an embedded system-based spin coating machine has been developed. The PIC microcontroller (PIC16f877A), which might be powered by a driver circuit to drive a spinning motor, controls the spin coating machine effectively. The temperature sensor is used to determine the temperature, while the proximity sensor is used to determine the motor's speed. Using a temperature sensor, the temperature has been kept between 30 and 40 degrees Celsius. The developed system will coat thin films in a micro level thickness by adjusting the spinning speed and controlling the system using PIC microcontroller. To test the reliability and repeatability of the machine, Zinc oxide (ZnO) was prepared with the sol-gel technique and deposited on the glass substrate using embedded system based spin coating machine. ZnO thin films were prepared at different pH and exhibited the fundamental reflections of (100), (002), (101), and (102) with the hexagonal wurtzite crystal structure. The structural studies of ZnO thin films using XRD analysis confirm the presence of ZnO particles in the prepared films. Also, it ensures the prepared ZnO thin film is pure and that no other impurities have been observed in the XRD pattern.

Abstract: This paper investigates performance of ZnO/SnO₂ nanorods structure thin film deposited at two different ZnO seed layer (ZnO seed A and ZnO seed B) for humidity sensor application. ZnO seed A and ZnO seed B were deposited using two different method which were sputtering method and spin coating method respectively. ZnO/SnO₂ nanorods structure thin film that has been prepared on ZnO seed A and ZnO seed B using thermal chemical vapor deposition (CVD). The structural properties have been characterized using field emission scanning electron microscopy (FESEM) (JEOL JSM 6701F). Base on the FESEM image the size of ZnO seed A and ZnO seed B were ranging around 75 to 85 nm and 17 to 21 nm respectively. The results analyzed were for ZnO/SnO₂ composite nanorods structure size on ZnO seed A and ZnO seed B were averagely around 18 nm to 29 nm. The sensor properties were characterized by using current-voltage (I-V) measurement (Keithley 2400). ZnO/SnO₂ nanorods structure thin film deposited on ZnO Seed A performed highest sensitivity with 265 ratio compare to ZnO/SnO₂ nanorods structure thin film deposited on ZnO Seed B with 75 ratio of sensitivity.

Abstract: Shear Thickening Fluid (STF) is a highly preferred phase change material that helps in absorbing high impact shock waves and provides excellent protective properties when used along with Kevlar fabric. nanomaterials also offer superior functionality helping in creating many useful, smart and innovative textile fabrics. This research work aims to analyze the synthesis steps, properties and application methods of nanomaterials made from different chemical synthesis methods. The effect of many technical factors and process control parameters is also laid out and found to be important contributors for creating unique fabric property. This analysis provides a guideline to effectively and efficiently use the nanomaterials in the right way and apply the functional nanomaterials using suitable technology for coating which can enrich the functional property of the substrate.

Abstract: Transparent conducting oxides (TCOs) are wide band gap semiconductors having found their use in optoelectronics, flexible electronics, flat panel displays, electrochromic windows, transparent heater windows, and many more. Aluminum (Al) doped zinc oxide (AZO) is an important TCO material which is being widely investigated for such applications. Its optoelectronic properties can be tuned by adjusting the Al content. In this work we study the variation patterns of the electrical conductivity and the optical transparency of AZO thin films with altering the Al content between 0 and 8 at%. The AZO thin films were prepared by wet chemical synthesis from its stabilized sol of zinc acetate dihydrate and aluminum nitrate nonahydrate dissolved in an ethanol and methanol mix. The morphological, electrical, and optical characteristics of these films were explored employing optical microscopy, Hall effect measurements, and UV-Vis-NIR spectrophotometry, respectively. We found out that annealing induces cracks into the AZO thin films and can severely degrade its electrical conductivity. Therefore, it’s imperative to control the Al content as well as the film morphology and structure. Before studying the effects of the Al content, the cracks were mitigated by optimizing the deposition and annealing conditions. The films were spin coated from its sol at 3000 RPM for 30 seconds. The films were dried at 100 °C and were subsequently annealed at 450°C. Since annealing induced cracks, therefore three coats were applied and annealed each time to mitigate the number of transverse cracks across the thickness of the film. The crack minimization was also confirmed by the enhancement in electrical conductivity. For the uniform crack-free AZO films, the Al doping was found to significantly modify the electronic behavior of the films. We expect an initial increase in the conductivity up to around 2 at% Al doping beyond which a decrease in conductivity is expected due to Al₂O₃ formation.

Abstract: A high performance flexible temperature sensor for environmental and health monitoring has been fabricated using various combinations of composite blend of poly vinylidene fluoride / poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PVDF/PEDOT:PSS). The response curves and working principle were investigated and sensors were then fabricated to achieve highly linear and stable response for a wide range of temperature sensing (25°C to 120°C). The film was fabricated on flexible polyethylene terephthalate (PET) substrate using spin coating. The copper electrodes were fabricated using copper tape. The sensors showed stable and close to linear response of impedance change by varying temperature in the range 25°C to 120°C. The resistance of the sensors changed from ~70MΩ to ~52MΩ for the temperature change in the range 25°C to 120°C. The sensors are aimed to replace low performance, complex and expensive sensors in the market for environmental and health monitoring applications.

Abstract: The synthesis and characterization of spin-coated Al-doped ZnO (AZO) thin films with varying Al concentrations (0%, 5%, 10%, 15% and 20%) onto glass substrates have been demonstrated in this paper. The structural, electrical and optical properties of the spin-coated thin films have been investigated by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, Van Der Pauw method and UV-visible spectroscopy. The EDX study shows well-defined peaks which confirm the presence of only Zn, O and Al and no other impurities in the films. The increase of Al and decrease of Zn weight percentages with increasing doping level confirms the effective substitution of Zn by Al. SEM of the surfaces of the films shows that undoped ZnO films contain particle agglomeration which is reduced with Al doping and the surfaces of the films gradually became more uniform. The thickness of the AZO films varied from 86 to 699 nm with increasing Al doping concentration. The electrical conductivity of the films increased up to ~ 7 × 10^-2 (Ω.cm)^-1 due to doping with 5% Al concentration. The optical transmittance highly increased above 95% in the visible range with the introduction of Al dopant and it kept rising with the increase of Al concentration. The optical energy band gap of undoped ZnO increased from 3.275eV to 3.342 eV with 5% Al doping.