Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films, General Physics and Astronomy
9
Scopus Publications
Scopus Publications
Controlled Formation of Nanoislands During Microwave Annealing of Au Thin Films Ali Ghanim Gatea Al-Rubaye, Alaa Alasadi, Khalid Rmaydh Muhammed, Catalin-Daniel Constantinescu Metals, 2025 We present a systematic study on the fabrication of gold nanoislands by microwave-assisted annealing, a rapid and energy-efficient alternative to conventional thermal treatments. Gold thin films with nominal thicknesses of 4, 5, 6, 8, and 10 nm are deposited by thermal evaporation directly onto BK7 glass substrates, with and without a 3 nm chromium adhesion layer. The samples are subsequently annealed in a microwave kiln, where microwave irradiation is absorbed and converted to heat within the graphite-coated cavity (kiln), allowing the substrate temperature to exceed 550 °C, the threshold required for film dewetting. This process induces a controlled morphological evolution from continuous thin films to well-defined nanoislands, with the final size distribution strongly dependent on the initial film thickness. Compared with oven-based annealing, microwave treatment promotes faster and more uniform heating, which enhances atomic diffusion and accelerates dewetting while reducing the risk of substrate deformation or excessive coalescence. The resulting nanoislands exhibit tailored size-dependent plasmonic properties, with clear correlations between film thickness, crystallite size, and optical absorption features. Importantly, the method is cost-efficient, requiring shorter processing times and lower energy input, while enabling reproducible fabrication of high-quality plasmonic nanostructures on inexpensive glass substrates, suitable for applications in sensing, photonics, and nanophotonics.
Structural and Magnetic Investigations of High-Entropy Alloys for Potential Sensor Applications Lucian-Gabriel Petrescu, María-Catalina Petrescu, Chelariu Romeu, Cimpoeşu Nicanor, Axinte Mihai, Alaa Alasadi, Catalin-Daniel Constantinescu 2025 14th International Symposium on Advanced Topics in Electrical Engineering Atee 2025 Proceedings, 2025 FeNiCrMnAl high-entropy alloys (HEAs) offer a versatile platform for correlating structural features with magnetic behavior in multi-component systems. Their near-equiatomic compositions stabilize body-centered cubic (BCC) or mixed BCC-FCC phases, with Al addition enhancing lattice distortion and mechanical robustness. At the same time, the competing ferromagnetic contributions of Fe and Ni with the antiferromagnetic tendencies of Mn and Cr enable a wide range of magnetic responses. In this work, three FeNiCrMnAl alloys with varying Al content are synthesized and analyzed by energy-dispersive spectroscopy (EDS), laser-induced breakdown spectroscopy (LIBS), and vibrating sample magnetometry (VSM). The results show a consistent convergence between EDS and LIBS data, with some Mn discrepancies attributed to matrix effects. Magnetic characterization reveals predominantly soft ferromagnetic behavior with low coercivity and composition-dependent anisotropy, most notably in the Al-containing alloys. These findings confirm that FeNiCrMnAl alloys combine structural stability, magnetic tunability, and sustainability, making them promising candidates for cost-effective sensor applications.
Novel Method for Controlling the Number of Laser Pulses Per Length Unit Alaa Alasadi, Ghaiath A. Fadhil Aip Conference Proceedings, 2024 The separation and overlap between the laser pulses were controlled through sample's scan speed and pulse repetition frequency using a laser system of 0.8 nanosecond pulse width with a repetition frequency of 40 kHz. The laser beam has been focused on the sample surface using an objective lens with 0.75 numerical aperture to a spot with a diameter of 1.83 µm. The laser diode driver has been used for controlling the pulse repetition frequency through controlling the supplied electrical current, whereas the speed of the scanning stage has been used to control the pulses train under computer control. The pulses were successfully controlled from sorting with distance (single pulse per point), contiguous pulses to the overlapping of up to 90%. This control of overlapping between pulses offers an enhanced definition of wires width compared to our previous attempts [1]. This improvement is a further endorsement to Laser direct writing (LDW) as a simple rapid technique that can be used to produce micro/nano scale structures.
Formation of Magnetic Structures for Trapping of Breast Cancer Cell Alaa Alasadi, Ali Ghanim Gatea Al Rubaye Korean Journal of Materials Research, 2024 This work focuses on the fabrication of excellent magnetic structures for trapping breast cancer cells.Micro- magnetic structures were patterned for trapping cancer cells by depositing 30 nm of permalloy on a silicon substrate.These structures were designed and fabricated using two fabrication techniques: electron beam lithography and laser direct writing.Two types of magnetic structures, rectangular wire and zig-zagged wire, were created on a silicon substrate.The length of each rectangular wire and each straight line of zig-zagged wire was 150 m with a range of widths from 1 to 15 m for rectangular and 1, 5, 10 and 15 m for zigzag, respectively.The magnetic structures showed good responses to the applied magnetic field despite adding layers of silicon nitride and polyethylene glycol.The results showed that Si + Si 3 N 4 + PEG exhibited the best adhesion of cells to the surface, followed by Si + Py + Si 3 N 4 + PEG.concentration of 5-6 with permalloy indicates that this layer affected silicon nitride in the presence of Polyethylene glycolPEG.
Rapid Fabrication of 2-D Magnetic Microstructures by Laser Direct Writing (LDW) Alaa Alasadi, F. Claeyssens, D. A. Allwood IEEE Transactions on Magnetics, 2021 A 2-D permalloy (Ni81Fe19) microstructures have been patterned using laser direct writing (LDW). The magnetic structures were designed and fabricated in a single-step process using scanning stage system based on A3200 software from a thin film. This process was implemented under atmospheric conditions and room temperature by removing unwanted areas of thin film by laser ablation. The 2-D magnetic structures included: arrays of squares, rectangles with a range of aspect ratios, and rhombic elements. These elements exhibited shape-sensitive magnetic behavior with the increase in shape aspect ratio. The average fabrication time per element was 0.47 ms at a scanning speed of 7.5 mm/s and a laser repetition rate of 6 kHz. This demonstration of flexibility and speed of laser direct write processing being applied to magnetic microstructures may assist in prototyping and rapid manufacture of devices such as sensors and magnetic wires for interactions with biological cells.
Investigation of Laser Direct Writing as a Novel Method of Permalloy Patterning Alaa Alasadi Journal of Physics Conference Series, 2021 The abilities of laser direct writing have been explored on thin films of permalloy (Ni81Fe19) for range of film thicknesses with two types of substrates for creating micro-scale magnetic structures. The thin films of Permalloy were deposited on both silicon and glass substrates using thermal evaporator with ranging from 5 to 100 nm. The permalloy films were successively patterned using a laser system containing of a pico-second pulsed laser with an 800 ps pulse width and wavelength of 532 nm. A series of magnetic wires were patterned then characterised by Magneto-Optic Kerr Effect system and Scanning Electron Microscopy. The patterned magnetic wires showed good responses to an applied magnetic field. The corresponding coercivities of the patterned magnetic wires were affected by their observed quality. These results can improve the understanding of laser direct writing technique to fabricate the micromagnetic structures for future application as easy, low cost and high throughput technique.
Laser direct writing (LDW) of magnetic structures Alaa Alasadi, F. Claeyssens, D. A. Allwood Aip Advances, 2018 Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repetition rate allowed wire arrays across an area of 4 mm x 0.18 mm to be patterned in 85 s.Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repet...
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