Atomic layer deposition (ALD) is a precision growth technique that is able to deposit either amorphous or epitaxial layer on a wide range of substrates. Multilayer thin films have been widely studied because their properties are different from those of bulk materials constituents owing to the two-dimensional films and high density of interfaces. Multilayer nanostructured thin films were fabricated on silicon and glass substrates by ALD. The optical and electrical of multilayer ZnO/TiO₂/ZnO films were investigated. The microstructure compositions and surface morphology of these multilayer films were analyzed by X-ray diffraction (XRD), Atomic force microscope (AFM) and Scanning electron microscope (SEM). The optical properties were characterized using photoluminescence (PL) and UV-VIS spectroscopy. XRD patterns confirmed that ZnO with wutrtize crystal structure and TiO₂ with anatase structure were presented. The degree of crystallinity of multilayer thin films has been improved through the deposition of ZnO. The intensity of UV luminescence of the multilayer has increased as compared to the single layer TiO₂ and bilayer ZnO/TiO₂. The multilayer ZnO/TiO₂/ZnO has high transmittance (above 80%) in visible region. All the result suggested that the use of multilayer thin films effectively enhanced the quality of films crystallinity and optical properties as compared to single layer ZnO and bilayer ZnO/TiO₂.

Metal oxide semiconductor material has great potential to act as window layer in p–n heterojunction solar cell thin film owing to low production cost and significant properties in photovoltaic mechanism. In this work, n-TiO₂/ZnO bilayer thin film was effectively constructed by means of sol-gel spin coating technique in an effort to diminish the electron-hole recombination rate from single-layered thin film. Annealing time is one of the important parameters in the fabrication process and was varied to study the impact of annealing treatment towards the thin film characteristics as window layer. It was found that the optimum parameter for the n-TiO₂/ZnO bilayer was 500 °C with an annealing time of 2 h. High crystallinity of the n-(101)-TiO₂/(002)-ZnO bilayer thin film was obtained, which consists of anatase and a hexagonal wurtzite structure, respectively. Orientation of (002)-ZnO is essential for deposition with the (111) Cu₂O-absorbing layer due to a low different lattice mismatch between these two interfaces. The homogenous morphology of n-TiO₂/ZnO bilayer was observed with a compact and dense layer. The improvement of transmittance has also been achieved in a range of 60%–80%, which indicated that the incident light can penetrate throughout the thin film directly. In addition, a p-Cu₂O absorbing layer was successfully fabricated on top of n-TiO₂/ZnO bilayer thin film to form a p-n junction in order to visualize significant electrical rectification properties. The existence of p-Cu₂O was confirmed by a (111)-peak orientation and triangular shape in structural and morphological properties, respectively.

Bilayer and multilayer thin films are becoming increasingly important in the development of faster, smaller and more efficient electronic and optoelectronic devices. One of the motivations of applying bilayer or multilayer structures is to modify the optical properties of materials. Atomic layer deposition (ALD) is a variant of Chemical Vapour Deposition that can produce uniform and conformal thin films with well controlled nanostructures. In this study, we have demonstrated new findings of the use of ALD fabricated bilayer TiO₂/ZnO thin films with enhanced crystallinity and optical properties. TiO₂ films have been deposited at 300 °C for 1000 (51 nm in thickness) or 3000 (161 nm in thickness) deposition cycles onto glass and Si substrates. ZnO films are subsequently deposited on the TiO₂ layers at 280 °C for 500 deposition cycles (55 nm). The crystallinity and optical properties of the TiO₂/ZnO thin films have been analysed by X-ray diffraction, photoluminescence, UV-Vis spectroscopy, Atomic Force Microscopy and Scanning Electron Microscopy. XRD diffraction pattern confirmed the presence of ZnO with wutrtize crystal structure and TiO₂ with anatase structure. It shows that the crystallinity of the TiO₂ films has been improved with the deposition of ZnO. The intensity of UV luminescence has increased by almost 30% for TiO₂/ZnO bilayer as compared to the single layer TiO₂. The possible mechanism for the enhancement of the optical properties of bilayer TiO₂/ZnO thin films will be discussed.

Titanium (Ti) alloy foam was prepared by using potassium bromide (KBr) as space holder with percentage between 20 to 40 wt.%. In this work, the potential of KBr as a new space holder was determined. The Ti alloy powder and space holder were first manually mixed before being compacted using hydraulic hand press. The green compacts were then sintered at temperature of 1160°C, 1200°C and 1240°C in a tube furnace. The microstructure of the Ti alloy foams were observed by Scanning Electron Microscope (SEM). It was revealed that the porosity content in the Ti foam was in the range of 16% to 31% and density in the range of 1.5 g/cm³ to 2.6 g/cm³. Moreover, the pore size of the titanium alloy foam is in the range of 187μm to 303μm. Although the sintering temperatures were found incapable of promoting overall densification to the Ti alloy foam, 1200°C was denoted to be the maximal temperature for promoting maximal porosity to the Ti alloy foam. Nonetheless, KBr was proven to be suitable as space holder for Ti foam preparation as referred to its stability and insolubility in the Ti alloy.

Natural fiber such as kapok (Ceiba pentandra L. Gaertn.) is an effective, environmentally friendly, and sustainable material for oil sorption due to its unique structure, which offers high sorption ability, good selectivity, and reusability. Kapok fiber was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and contact angle. The oil sorption characteristics of kapok fiber were evaluated across different types of cooking oil. The result demonstrated that kapok possesses excellent hydrophobic-oleophilic properties, including a hollow lumen structure of kapok fibers that enables it to absorb and retain large amounts of oil while repelling water. Additionally, a waxy substance on its surface further enhances its hydrophobic properties. Kapok fiber also exhibits a contact angle of 123.80º > 90º, proving that kapok has low water wettability. The reusability of 1g kapok fiber in oil sorption is tested by using various types of cooking oil with the following standard test method for sorbent performance of adsorbents (ASTM F726-12) across five types of cooking oil. The results show that the kapok fiber retained the oil absorbed even after being reused for 24 cycles, despite slight decreases.

Aluminium (Al)-doped Zinc Oxide (ZnO) was deposited on glass substrates by using the sol-gel dip coating technique. Next, AZO sol-gel solution was produced via sol-gel method. Al was used as doped element with molar ratios of 1%, 2%, and 3%, while the calcination temperatures were set at 400°C, 500°C, and 600°C for 2 hours. In fact, characterization was carried out in order to determine the effect of calcination temperature and molar ratio of doping by using several techniques, such as X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FESEM), and Ultraviolet-Visible spectroscopy (UV–Vis). XRD was performed to investigate the crystal structure in which the ZnO was in wurtzite hexagonal form. Next, Energy Dispersive Spectroscopy (EDS) was used to determine the composition of thin films where the result revealed the existence of zinc, oxygen, and aluminium. The roughness of the deposited film was later measured by using the AFM approach where the findings indicated increment in RMS from 8.496 nm to 35.883 nm as the temperature was increased. Additionally, FESEM was carried out to look into the microstructure surfaces of the deposited AZO thin film for increased temperature caused the particle to grow bigger for all molar ratio of dopant. Lastly, UV–Vis was conducted to study the optical properties of AZO, in which the result demonstrated that AZO thin film possessed the highest transmittance percentage among all samples above 90% with band gap value that ranged from 3.25 eV to 3.32 eV.