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The fabrication of reliable and cost‐effective gas sensor for low concentrations of toxic gases such as ammonia is still a challenging task, in this work the authors report structural, topography, and optical properties of pure and Ba‐doped Mn3O4 thin films prepared by chemical spray pyrolysis (CSP) as well as its gas sensing performance toward low concentrations of ammonia gas. XRD analyses prove the films have tetragonal spinel structure with a preferred orientation along the direction (103). AFM and SEM measurements show the films have homogeneous with rough surfaces and porous structures. EDS measurement confirms the presence of Mn, O, and Ba elements according to a doping concentration ratio. Optical measurements show the optical band gap redshifts and the bond length expands as Ba concentration increases. The optimal results are achieved in Mn3O4:Ba1% thin films where porous structure, rough surface, high crystallinity, and maximum response toward (20, 30, 40, and 50 ppm) of ammonia gas with great stability. Empirical equations are suggested to evaluate the sensitivity in terms of relative bond length and RMS roughness. These results show the films are good candidates in p‐type MOS gas sensors.

This work reports the attempts to carry out pulsed laser ablation in liquid (PLAL) for synthesizing colloidal Titanium dioxide nanoparticles (NPs). TiO2 NPs was synthesized by 7ns Nd:YAG laser ablation of high purity titanium target (99.99 %) immersed in water ,and deposited the film on silicon solar cell to increase the efficiency of the Si solar cell. The surface morphology of the deposits materials have been studied by using atomic force microscopes (AFM). Atomic Force Microscopy(AFM) analysis showed that the average grain size of TiO2NPsinwater were 150 nm and rms roughness values are (2.27 nm) for TiO2 thin film. The photovoltaic characteristics before and after deposited Titanium dioxide nanoparticles (NPs) included short circuit current (Jsc),open circuit voltage (Voc), where the maximum (Jsc), (Voc)and fill factor (FF) obtained at AM1after deposited were 40.2 (mA cm-2) , 630(mV) and(0.7) respectively. After deposited Titanium dioxide nanoparticles (NPs)increase the efficiency of the Si solar cell13.8 % instead of 10.3% conversion efficiency before the deposited.

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