This paper focus on new modulation technique to improve the performance of the conventional modulation that uses intensity modulation/direct detection (IM/DD) for On-Off Keying (OOK) modulation. This new modulation technique that is Dual Diffuser Modulation (DDM) can create superior modulation with able to reduce scintillation index, enhance power received and threshold signal level. The analysis result shows that the free space optical (FSO) can have good performance of power received under strong turbulence. The DDM are better performance as compare with conventional IM/DD-OOK and IM/DD-OOK with diffuser. This can help FSO system to combat with severe turbulence effect for optimum operation.

The reaction-time-dependent synthesis of graphene oxide (GO) was carried out using a modified Hummer’s method. The drop-casting method was used to coat GO films on a glass substrate. Various techniques, including scanning electron microscopy, X-ray diffraction, UV–Vis spectroscopy (UV–Vis), Fourier transform infrared spectroscopy, and current–voltage characteristics, were performed to obtain the morphological, structural, optical, and electrical properties of GO. Morphological structural observations revealed that more oxygen functional groups were present as the reaction time increased from 24 to 96 h, which was confirmed by the optical properties of GO thin films. The resistivity of the as-deposited films increased from 9.74 × 10⁶ to 26.85 × 10⁶ Ω·cm as the reaction time increased. The optimized reaction time with a resistivity of 12.13 × 10⁶ Ω·cm was 48 h, as demonstrated by morphological and optical data.

The different cleaning solution; HCl and HF solution are used to remove the suboxide and oxide component on Ge surface. The HCl cleaning results chlorine (Cl) termination on Ge surface whereas no Fluorine (F) termination was observed just after HF cleaning. The growth of Ge oxide is studied after treated with HCl cleaning on two surface orientations; (100) and (111), respectively in dry oxygen ambient and cleanroom air by spectroscopic ellipsometry (SE) and x-ray photoelectron spectroscopy (XPS). A clear step and terrace trend was observed for the oxidation growth of Ge (100) and Ge (111) in dry oxygen ambient compared to in clean room air. This trend shows the difference in surface reaction of Ge oxidation as humidity varies. The stability of chlorine termination of Ge (111) than Ge (100) explains the slower growth of oxidation in dry oxygen ambient.

Purpose: The quality of GeOx–Ge interface and the equivalent oxide thickness (EOT) are the main issues in fabricating high-k/Ge gate stack due to the low-k of GeOx interfacial layer (IL). Therefore, a precise study of the formation of GeOx IL and its contribution to EOT is of utmost importance. In this study, the GeOx ILs were formed through post-oxidation annealing of sputtered Al₂O₃on the Ge substrate. The purpose of this paper is to report on growth kinetics and composition of IL between Al₂O₃and Ge for HCl- and HF-last Ge surface.Design/methodology/approach: After wet chemical cleaning with HCl or HF, Al₂O₃was grown onto the Ge surface by RF sputtering. Thickness and composition of IL formed after post-anneal deposition at 400°C in dry oxygen ambience were evaluated as a function of deposition time by FESEM and characterized by X-ray photoelectron spectroscopy, respectively.Findings: It was observed that the composition and thickness of IL were dependent on the starting surface and an aluminum germinate-like composition was formed during RF sputtering for both HF- and HCl-last starting surface.Originality/value: The novelty of this work is to investigate the starting surface of Ge to IL growth between Al₂O₃/Ge that will lead to the improvement in Ge metal insulator field effect transistors (MISFETs) application.

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