K. Mohan Rao

This study explores defect evolution in ceria thin films through combined experimental and theoretical approaches. Structural analyses confirm the retention of the cubic fluorite phase, with Raman spectra revealing additional features associated with oxygen vacancies and lattice disorder. Phonon lifetime evaluation indicates that vibrational stability is highly dependent on defect density and precursor concentration. Optical measurements show a progressive reduction in band gap energy, attributed to defect-induced states and variations in Urbach energy. Complementary DFT simulations demonstrate that oxygen vacancies create localized 4f levels, modify charge distribution, and stabilize mixed valence states of Ce ³⁺ /Ce ⁴⁺ . These findings highlight the strong interplay between structural defects, phonon dynamics, and electronic behavior in CeO ₂ thin films.

This work provides a detailed investigation on the physical characteristics of spin-coated CdO thin films and the transport phenomena in p-Si/n-CdO/Al heterojunction diodes based on the number of layers. The GI-XRD studies clearly depicted the presence of the cubic CdO structure with (111) preferred orientation, signifying an improvement in crystallinity. FESEM and AFM observations disclosed that although the films were homogeneous at lower deposited layers, surface agglomeration and roughness were evident in higher deposited layers. Optical analysis depicted a marginal reduction in the band gap value up to 12 layers, followed by a slight increase, indicating modifications in the electronic structure. The XPS measurements indicated a variation in Cd ²⁺ concentration, thereby indicating the presence of oxygen vacancies. The electrical analysis using the thermionic emission and Cheung models revealed that the barrier height values increased with an increased number of layers. A rectification ratio of three orders is obtained in the device at 10 layers. The results clearly signify that optimising the layers can significantly improve the performance of metal oxide-based heterojunction diodes in electronic and optoelectronic devices.

Herein, we report a comprehensive analysis of dependence of pre-heating temperature on CdO thin films deposited on glass substrates via sol-gel spin coating method. This study investigates the impact of pre-heating temperatures on the physical properties of CdO thin films. XRD confirmed a polycrystalline structure with good crystallinity. SEM showed smooth and uniform surface, while AFM revealed increased surface roughness due to enhanced coalescence. Optical studies showed that the films remained transparent, with a slight decrease in band gap from 2.57 eV to 2.46 eV. PL indicated the presence of defects like oxygen vacancies, which contribute to electrical conductivity. XPS spectroscopy analysis showed that the Cd3d core spectra split into Cd3d _5/2 and Cd3d _3/2 . Hall effect results confirmed n-type conductivity with low resistivity of 10⁻ ³ Ω-cm. Although the 150 °C film shows a higher figure of merit, the 200 °C sample offers the most optimized combination of optical transmittance and electrical conductivity, making it the superior choice overall. Thus, our findings indicate that choice of proper pre-heating temperature is optimal for the growth of CdO thin film making it an ideal candidate for device applications.

Increasing health concerns due to pollution has led to the development of various materials to control exposure to pollutants such as toxic gases and contaminated water. In this study, novel manganese stannate (MTO) composite thin films were synthesized via sol–gel spin coating and their structural, morphological, and chemical properties were extensively characterized. In addition, their photocatalytic and gas-sensing abilities were evaluated. In photocatalysis, degradation efficiency measures of how well a photocatalyst can degrade pollutants or dyes under light exposure. Remarkably, the MTO film exhibited a high degradation efficiency of 67% for methyl orange (MO) dye when exposed to UV light for 150 minutes. We also examined the gas-sensing properties of the MTO thin films, particularly their response to acetone. In gas sensors, sensitivity is often reported as a percentage, indicating the relative change in the sensor's response per unit change in analyte concentration. Herein, the sensors displayed a linear response within the 1–9 ppm range of acetone concentration at an operating temperature of 200 °C. They also exhibited excellent selectivity, sensitivity, and repeatability, thus emerging as promising candidates for acetone gas-sensing applications. A sensitivity of 22% was achieved by the sensors, allowing for a low detection limit of 1 ppm, which indicated their high sensitivity towards acetone gas. Moreover, the MTO sensor exhibited response and recovery times of 15 and 16 seconds, respectively. Based on these results, the MTO thin film is a potential material for photocatalytic MO degradation and a gas sensor for acetone detection.

Recent studies suggest that HfO₂ material shows promising energy storage properties upon doping. In this work we have attempted to study the structural, optical, morphological and compositional properties of HfO₂ films as well as codoped HfO₂ films by annealing at 600 °C and 800 °C. Synthesis method adopted for film preparation is sol-gel based spin coating method. Dopants chosen for codoping were zinc and samarium ions as the main intention of research was to stabilize high temperaure phase so that dielectric capacity can be enhanced. XRD studies revealed transformation to cubic phase with codoping as well as increament in XRD peak intensity upon annealing from 600 °C to 800 °C. From UV-Visible studies, films are found to be transparent in the range 200 to 1100 nm. Tauc plot showed decrement in band gap upon doping as well as upon increasing the temperature of annealing from 600°C to 800 °C. The prepared thin films exhibited homogeneous surface as observed upon FESEM examination. From EDS the presence of essential elements was confirmed. These experimental observations conclude that annealing and co-doping can be crucial parameters for enhancing properties of HfO₂ films.

In this article, the capping action of Sodium carboxymethyl cellulose (NaCMC) on ZnS nanoparticles synthesized by microwave-assisted method is reported. The X-ray diffraction and electron diffraction studies corroborated nanocrystalline nature of cubic ZnS. Discontinuous cluster growth of particles was implied by optical absorption studies. This was reflected in transmission electron microscope images. Fourier-transform infrared studies confirmed NaCMC capping on the surface of ZnS nanoparticles. Effective encapsulation of ZnS nanoparticles by NaCMC was further supported by Raman scattering, thermal studies and photoluminescence studies. Surface modification of ZnS nanoparticles with NaCMC appear to be suitable for specific biomedical applications due to the nontoxicity of ZnS and NaCMC.