Mohd Fairus Ahmad

Reconfigurable Intelligent Surfaces (RIS) have recently attracted significant attention as a means to control the propagation environment, enabling improved signal coverage, interference management, and more efficient spectrum utilization. This work presents a 1-bit RIS operating at 5.8 GHz, designed for wide-angle beam steering and real-time software-defined radio (SDR) validation. While many earlier 1-bit RIS designs demonstrated steering angles up to about 45°, the proposed design extends the range to 60°, with a realized gain of 22.60 dBi at 10° and 14.62 dBi at 60°. The unit cell, fabricated on a RO4350B substrate, features a tailored RF choke structure that suppresses mutual coupling and limits RF leakage, thereby improving phase stability, a key aspect rarely emphasized in prior RIS studies. Experimental validation using an SDR-based testbed confirms significant signal quality improvements, including a 57.4% reduction in error vector magnitude (EVM), from 57.30% to 24.39%, and a 7.42 dB increase in signal-to-noise ratio (SNR), resulting in better QPSK video transmission. Additionally, orbital angular momentum (OAM) beamforming capabilities were explored via full-wave simulations, demonstrating feasible generation of modes 1, 2, and 3 for potential multiplexing. This RIS offers a scalable, energy-conscious, and cost-effective solution by integrating low-cost PIN diodes (SMP1320-079LF) and an efficient biasing network. The presented RIS architecture aligns with emerging 5G/6G network requirements and can support applications including adaptive indoor coverage, UAV-assisted links, and holographic MIMO.

Rhenium disulfide (ReS₂) is a 2-dimensional transitional metal dichalcogenides that exhibits unique properties such as a direct band gap irrespective of thickness, weak interlayer coupling, and exceptional anisotropic properties, making it a promising material for optoelectronics applications. In this work, we synthesized ReS₂ nanoflakes on SiO₂/Si substrates using chemical vapor deposition (CVD). The effects of Re precursor-substrate distance (d) and growth temperature on flakes morphology were systematically investigated. Field-effect scanning electron microscopy images revealed that shorter Re precursor-substrate distance (d= 8 cm) favored the formation of high density and vertical flakes due to the high concentration of Re vapor. However, samples grown with the largest separation distance (d = 11 cm) and higher substrate temperature (850 °C) demonstrated a low density of planar flakes. Raman spectroscopy measurements showed the E _g, A _g, and C _p vibrational modes which belong to ReS₂. The full-width-at-half-maximum of the E _g mode at 212 cm⁻¹ is 6.7 cm⁻¹, comparable to the mechanically exfoliated ReS₂ reference. The thicknesses of the flakes range from bilayer to multilayer and the measured band gap energy is ∼1.57 eV. The XPS data verified that the atomic ratio between Re and S is 1.9, which confirms the stoichiometry of the ReS₂ flakes. Finally, the TEM images and diffraction pattern confirmed that the ReS₂ flake is a single-crystal with distorted 1 T-phase. This work emphasizes the influence of CVD parameters on the morphology of ReS₂ flakes, which is vital for developing high performance ReS₂ based optoelectronics devices.

The spin coating process became the most widely used technique in the fabrication industry for thin film coating on a substrate by centrifugal force. Unfortunat

The organic photovoltaic devices (OPVs) have potential in low-cost, large-area printing routes with high efficiency owing to the variety of organic materials. The active layer has a role to absorb photon and convert to electrostatic energy of separated electron and hole pair. If the separated charge in its active layer can be utilized to chemical reaction directly without collecting by electrodes, it would be a simple device for photoenergy conversion and has a great merit to use the photon energy. Here we introduce an large negative threshold potential of −0.35 V vs. Ag/AgCl by the use of ZnPc/PCBM:P3HT/ZnO electrode, which was prepared by removing PEDOT:PSS/Au electrode of an inverted OPV device [1] and coating with ZnPc. A co-photocatalysis property of ZnPc was observed in the photoelectrochemistry and scanning Kelvin probe microscopy. From the mother OPV, the gold electrode was removed mechanically and ZnPc was coated by vapor deposition. The detailed experimental conditions and characterizations of the electrode are shown in Ref [2]. Fig. shows voltammograms in a thiol solution for the BHJ electrode (a) and the ZnPc coated BHJ electrode (b). The photoanodic current (red) for the electrode with ZnPc (b) was much larger than that without ZnPc (a). For the ZnPc coated BHJ electrode with ZnO, the threshold potential of the photoanodic current was around −0.35 V vs. Ag/AgCl. On the other hand, for the ZnPc coated BHJ electrode without ZnO, the threshold potential of the photoanodic current was around −0.0 V vs. Ag/AgCl as shown in our previous paper [3]. The present larger gain than that without ZnO would be due to the effect of ZnO as a hole blocking layer. The threshold value of −0.35 V vs. Ag/AgCl was almost equal to the conduction band edge potential of ZnO, that is, the photogenerated electrons in the BHJ active layer can preferentially transfer to ZnO when the anodic polarization of ITO was deeper than the ZnO edge. Note that the ZnPc electrode exhibited an anodic current in the dark with the threshold potential of +0.25 V vs. Ag/AgCl, that is, the ZnPc can function as a catalyst of 2-mercaptoethanol oxidation. The large anodic photocurrent may be caused by such a catalytic function of ZnPc. References T. Kuwabara, et al., Sol. Energy Mater. Sol. Cells, 2008, 92, 1476. K. Nagai, et al., Chem. Commun. 2019, 55, 12491. T. Abe, et al. Chem. Phys. Lett., 2012, 549, 77. M.-F. Ahmad, et al. NPG Asia Mater., 2018, 10, 630. Figure 1

Photoelectrochemical oxidation of thiols was enhanced with a threshold potential of −0.35 V vs. Ag/AgCl by the use of a ZnPc/PCBM:P3HT/ZnO electode, which was prepared by removing the PEDOT:PSS/Au electrode of an inverted OPV device and coating it with ZnPc. A co-photocatalysis property of ZnPc was observed in the photoelectrochemistry and scanning Kelvin probe microscopy.