Papers by Keyword: Doping

Abstract: Close Space PVT (CS-PVT) is a modification of standard PVT exhibiting a short source-to-seed-distance and enabling a large variety of growth process variations to meet the specific requirements of the SiC material (i.e. special polytype and/or doping) to be grown. In this work, we study the growth of 4H-SiC p-i-n structures exhibiting thick SiC layers to be used as SiC photovoltaic cells for remote power transfer in space. Nevertheless, the found results are also applicable (i) to the SiC thick layer growth of power electronic devices and (ii) SiC pucks with a thickness of up to 10mm. In addition, we present the new type of growth machine TableTopCS^TM in its design being dedicated for the special crucible configuration of CS-PVT.

Abstract: Thermoelectric generators (TEGs) are vital, reliable energy sources for both extreme environments such as deep space exploration and off-grid terrestrial applications, as well as emerging fields like wearable energy harvesters and biocompatible medical sensors. This study focuses on tin selenide (SnSe) combined with ductile silver sulfide (Ag₂S) to leverage their complementary properties: SnSe’s promising thermoelectric performance and mechanical robustness for homojunction TEGs, and Ag₂S’s exceptional ductility and thermal sensitivity ideal for flexible, biocompatible devices. Materials were synthesized using scalable powder metallurgy and spark plasma sintering (SPS) techniques, ensuring reproducibility and microstructural control tailored for these diverse applications. Our Bi-doped polycrystalline SnSe exhibits a unique polarity switching phenomenon and anisotropic behavior influenced by dopants (Bi, Ag, In), enabling optimized thermoelectric and mechanical properties that reduce interfacial stresses and enhance durability in harsh conditions. Meanwhile, the Ag₂S materials combine thermoelectric efficiency with fast thermal response and flexibility, suited for continuous physiological monitoring in wearable systems. The hybrid integration of SnSe homojunctions with flexible Ag₂S devices opens new possibilities for durable, efficient thermoelectric energy harvesting across wide temperature gradients in aerospace and biomedical fields.

Abstract: This research is centered on an environmentally sustainable sol-gel coating, using silica extracted from rice husk ash (RHA), to foster the persistent deterioration of mild steel cause by corrosion for decades despite all efforts put in place by previous researchers. The research focus, was on the extraction of silica from rice hush to synthesize silica-base sol-gel formulation, doped in a graphene oxide to enhanced its efficiency. The formulated sol-gel coating was applied on the mild steel substrates and then characterized by evaluating its corrosion resistance through electrochemical and surface characterization techniques. Such as XRD, FT-IR, SEM, Tafel Polarization and Adhesion Test, which were carried out on the coated samples. Corrosion test was carried out by immersing coated and uncoated samples in 3.5% NaCl solution for seven (7) days and then conducted a Potentiodynamic polarization and Electrical Impedance Spectroscopy (EIS) test to analyze the corrosion rates, impedance and protection efficiency. It was observed that, the highest inhibition efficiency of 85% was achieved at a concentration of 1.0g/200ml after 7 days of exposure which revealed that, coated mild steel possess higher potential corrosion resistant when compared with the conventional anti-corrosion coating in use. Essentially, this research would definitely promote green chemistry by utilizing agricultural waste materials, avoiding uses of toxic precursors and offering an eco-friendly alternative to conventional anti-corrosion coatings.

Abstract: The remediation of palm oil mill effluent (POME) presents a considerable hurdle for Malaysia’s palm oil mill, requiring fulfillment with the environmental regulations before discharge. This work demonstrated a semiconductor-mediated photocatalytic technology to treat POME and synchronously evaluated the biogas generation. X-ray diffraction findings indicated that the fabricated ZnO product possessed wurtzite as a major crystalline phase. Its band gap energy was measured to be 3.27 eV via a UV-vis diffuse reflectance spectroscopy technique. The hierarchical ZnO microsphere morphology assembled by lots of layered nanosheets was observed via field-emission scanning electron microscopy. Under UV irradiation, the as-fabricated ZnO product displayed an enhanced photoactivity in comparison to the commercially available TiO₂ in treating the POME. Moreover, the ZnO/Ce and ZnO/Eu were also fabricated and showed greater photocatalytic efficacy after doping the rare earth ion in ZnO. Remarkably, the evaluation of biogas generation depicted that the ZnO/Ce and ZnO/Eu photocatalysis produced a greater quantity of CH₄ and CO₂ after 360 min irradiation. The work offered an environmentally friendly and efficient photocatalytic technology via ZnO/RE in treating wastewater and synchronously generating renewable energy.

Abstract: A vacuum-assisted thermal evaporation method for the preparation of undoped and Zn-doped erbium sesquiselenide Er₂Se₃ thin films on various substrates using independent elementary sources is developed. The electrophysical parameters, such as electrical resistivity and thermo-electromotive force of the films, are measured from 77 up to 650 K.

Abstract: A breakthrough high throughput WBG semiconductor dopant monitoring method has recently been introduced based on the novel concept of sweeping the electrical bias by near UV illumination-induced photoneutralization of corona charge. As originally discovered for 4H-SiC, the doping determination can be realized using the value of the photoneutralization time constant. In the present work this procedure is tested for β-Ga₂O₃ with a larger energy gap of 4.8eV, using a correspondingly deeper UV range. Such deep UV application to the AlGaN/GaN HEMT structure resulted in the development of a new measurement principle capable of increasing the HEMT wafer measurement throughput 10 times compared to previous corona noncontact C-V metrology. The new principle involves a linear illumination-induced corona charge bias sweep. Combined with surface voltage monitoring, it provides a means for fast and precise determination of the pinch-off voltage, V_P, the AlGaN electrical thickness, and the 2D electron gas density.

Abstract: This study explored eggshells as an eco-friendly and cost-effective material for synthesizing hydroxyapatite. The phase compositions and morphological structure of polylactic acid composite with and without co-doped hydroxyapatite addition via a melt blending approach were evaluated. Furthermore, the biodegradation profile of the polylactic acid composite in phosphate buffer solution was studied. The concentrations of PLA/HAp, PLA/7.5MgO-7.5ZnO, and PLA/12.5MgO-2.5ZnO samples, respectively, were examined in this study. The results of morphological evaluation showed a well-distributed irregular spherical phase of hydroxyapatite. Meanwhile, the co-doped hydroxyapatite phases have variations in sizes and shapes. The polylactic acid composites showed fractured, rough, and honeycomb surfaces with interconnected pores suitable for cell propagation and enhancement, and the elemental composition proved precipitation of apatite formation. Characteristics of absorption bands of the hydroxyapatite, magnesium, zinc, and polylactic acid were present, respectively. The XRD spectra confirmed the presence of crystalline and semi-crystalline structures with percent crystallinity of 48.57%, 56.64%, and 60.08%, respectively. Meanwhile, the addition of the co-doped hydroxyapatite results in shifts in the 2θ angles of the crystal phases. The biodegradation study revealed the beneficial role of reinforcing polylactic acid composite with biogenic hydroxyapatite and hybrid doped hydroxyapatite as fillers and their synergetic effect with the pH of 7.08±0.21, 6.63±0.46, & 7.28±0.44, the porosity of 52.26±7.29, 48.57±6.74, & 43.72±5.07 %, and the degradation rate (weight loss) of 51.83±7.03, 48.16±6.85, & 43.66±5.46, respectively. Findings revealed that the current study aligns with the sustainable biodegradable composite used in bone tissue repair and hence contributed towards sustainable material without polluting the environment.

Abstract: This research presented the preparation as well as characterization of high and low density Bi (Pb)-2223 cuprates superconductors doped with Eu₂O₃ nanoparticles (x = 0.00, 0.0025, 0.02 and 0.05) produced through a typical solid state reaction method. Low density sample was created by adding crystalline sucrose into mixed powders and burned at 400 °C for two hours. The crystalline structure was analyzed through X-ray diffraction (XRD) while electrical properties were studied using four-point probe measurement. Phase examination by XRD revealed that the crystallographic structure has shifted slightly from tetragonal to orthorhombic at higher Eu concentrations for both high and low density samples. The amount of 2223 phase steadily decreased as the Eu concentration increased, indicating that the substitution of Eu nanoparticles favours the formation of 2212 phases. Apparently, the T_c value of the high density Eu-free sample was determined at 89 K. The addition of polycrystalline sucrose as a filler raises the T_c up to 99 K in low density sample. However, increasing amount of Eu nanoparticles leads to the decrease in T_c value. Meanwhile, the J_c value is higher in low-density samples compared to high-density samples due to the presence of large surface area in a porous structure which enhances the grains connectivity. The best structural and electrical properties between the studied samples have been observed at sample with x = 0.0025 for both high and low density Eu-doped Bi (Pb)-2223.

Abstract: The study investigated the effect of iodine-doped pentacene film as a buffer layer in an organic light-emitting diode (OLED). In this study, an ITO (indium tin oxide)-based sample is used as a reference device for comparative purposes. In OLED devices, the buffer layers were deposited using the doping of iodine vapor with the pentacene materials under proper conditions. The thermal treatment of the doped pentacene film results in increasing the conductivity of the buffer layer. Surface morphology for the bilayer anode was carried out by FESEM (Field Emission Scanning Electron Microscope) analysis. In our work, maximum luminance of 2345 cd/m² and current efficiency of 5.4 cd/A are obtained, along with more stability performance under annealing treatment in the device structure of FTO/iodine-doped pentacene (30 nm)/TPD [N, N′-Bis(3-methyl phenyl)-N, N′-diphenylbenzidine] (44 nm)/Alq3 [Tris(8-hydroxyquinoline)aluminum(III)] (52 nm)/LiF (lithium fluoride) (5 nm)/Al (aluminum) (110 nm).

Abstract: The interaction of dopamine and Si-, Sn-, and BN-doped fullerenes was studied by using the density functional theory (DFT). Adsorption energies of dopamine–C60, dopamine–C59Si, dopamine–C58Sn, and dopamine–C58BN were -0.03 eV, -1.46 eV, -0.06 eV, and -0.05 eV, respectively. All systems had negative adsorption energies, indicating that dopamine can be adsorbed on fullerene. Furthermore, dopamine–C59Si had the smallest value and was chemisorbed shown by a created covalent bond between Si of fullerene and N of dopamine. Therefore, C59Si has a plausible potential as a drug carrier for dopamine molecules.