Role of annealing temperature on optimizing the linear and nonlinear optical properties of As40Se50Ge10 films

Investigation on the growth aspects and properties of rubidium hydrogen succinate hydrate single crystal for NLO applications

A novel semiorganic nonlinear optical single crystal of rubidium hydrogen succinate hydrate (RbHSH) was grown at room temperature using the slow evaporation solution growth technique (SEST) with water as a solvent for nonlinear optical applications. The grown crystal is a triclinic system with a centrosymmetric space group of P1̄ and the compound is stabilized by intramolecular O-H-O and C-H-O bonding. FTIR spectral studies were used to determine the various functional groups present in the material. The optical transmission spectra of the grown crystal demonstrated that a transparency of 89%, with a low cut off wavelength of 240 nm and an energy band gap of 5.21 eV, which is beneficial to developing advanced photonic and optoelectronic devices in the solar blind UV area. The grown crystal is thermally stable upto 174 °C. The electrical properties of RbHSH crystal exhibit low dielectric loss and a low dielectric constant at high frequencies tends to have good optical characteristics. Mechanical analysis demonstrated that the grown crystal shows the normal indentation size effect (ISE) and falls into the hard material category with n = 1.4. Photoconductivity measurements revealed negative photoconductivity. Photoluminescence studies showed that RbHSH emits blue light with a wavelength of 484 nm. Hirshfeld surface analysis was used to analyze intermolecular interactions in the RbHSH crystal. The grown RbHSH crystal piezoelectric charge coefficient have been calculated (d33 = 13 pC N-1) and it is suitable for piezoelectric device applications. Under continuous-wave laser excitation, the third order nonlinear refractive index (n2), absorption coefficient (β), and susceptibility (χ(3)) of the RbHSH crystal were found to be 1.6639 × 10-12 (cm2 W-1), 1.1739 × 10-5 (cm W-1) and 4.86331 × 10-9 esu, respectively.

Annealing-induced phase transformation in In10Se70Te20 thin films and its structural, optical and morphological changes for optoelectronic applications

In2Se3 and In2Te3 have great importance in various device fabrications. The present report is based on the annealing-induced phase formation of both In2Se3 and In2Te3 from In10Se70Te20 thin films at different annealing temperatures as found from the XRD analysis and well supported by the Raman study. The average crystallite size increased with a decrease in the dislocation density. The surface morphology changed with annealing and increased in particle size as noticed from the FESEM images. The uniform distribution and presence of constituent elements in the film were verified using EDX data. The increase in transmittance is accompanied by a decrease in extinction coefficient, optical density and increase in skin depth with annealing. The increase in optical bandgap from 0.418 eV to 0.645 eV upon annealing at 250 °C is associated with a decrease in disorder. The steepness parameter increased and the Se-p value decreased with annealing. The refractive index decreased with an increase in oscillator energy and decrease in dispersion energy. The quality factor, dielectric loss, optical conductivity and electrical susceptibility decreased. The optical electronegativity and plasma frequency increased with annealing. There is a significant change in the non-linear susceptibility and non-linear refractive index with annealing. The observed changes in the film structure and optical behaviour are due to the annealing-induced phase formation from the In10Se70Te20 host matrix upon annealing. Such materials are suitable for optoelectronic and phase change devices.

The impact of fluence dependent 120 MeV Ag swift heavy ion irradiation on the changes in structural, electronic, and optical properties of AgInSe2 nano-crystalline thin films for optoelectronic applications

Swift heavy ion (SHI) irradiation in thin films significantly modifies the structure and related properties in a controlled manner. In the present study, the 120 MeV Ag ion irradiation on AgInSe₂ nanoparticle thin films prepared by the thermal evaporation method and the induced modifications in the structure and other properties are being discussed. The ion irradiation led to the suppression of GIXRD and Raman peaks with increasing ion fluence, which indicated amorphization of the AgInSe₂ structure along the path of 120 MeV Ag ions. The Poisson's fitting of the ion fluence dependence of the normalized area under the GIXRD peak of AgInSe₂ gave the radius of the ion track as 5.8 nm. Microstructural analysis using FESEM revealed a broad bi-modal distribution of particles with mean particle sizes of 67.5 nm and 159 nm in the pristine film. The ion irradiation led to the development of uniform particles on the film surface with a mean size of 36 nm at high ion fluences. The composition of the film was checked by the energy dispersive X-ray fluorescence (EDXRF) spectrometer. The UV-visible spectroscopy revealed the increase of the electronic bandgap of AgInSe₂ films with an increase in ion fluence due to quantum confinement. The Hall measurement and EDXRF studies showed that the unirradiated and irradiated AgInSe₂ films have n-type conductivity and vary with the ion fluence. The changes in the films were tuned with different ion fluence and are favorable for both optical and electronic applications.

Swift heavy ion (SHI) irradiation in thin films significantly modifies the structure and related properties in a controlled manner.

In situ laser irradiation: the kinetics of the changes in the nonlinear/linear optical parameters of As50Se40Sb10 thin films for photonic applications

The photosensitivity of amorphous chalcogenide thin films brings out light-induced changes in the nonlinear and linear optical parameters upon sub-bandgap and bandgap laser irradiation. The present work reports the in situ laser irradiated changes in the optical properties of As50Se40Sb10 thin films. The thermally evaporated film showed an exponential decrease in optical bandgap and increase in Urbach energy. The decay rate of the bandgap was 6.24 min and growth rate of Urbach energy was 6.67 min respectively. The dynamics of photo-induced changes were observed from the changes in linear refractive index and its dependent parameters such as 3rd order nonlinear susceptibility, nonlinear refractive index, dispersion and dielectric parameters. The conversion of heteropolar to homopolar bonds induced the photodarkening mechanism that changed the dispersion parameters. The decrease in E d and E o reduced the oscillator strength along with the zero-frequency dielectric constant. The optical and electrical conductivity changed significantly with time. The changes were saturated with time which brings stability in the film properties that is useful for various optical applications. However, no structural and compositional changes upon laser irradiation were noticed from the X-ray diffraction and EDX studies respectively. The surface homogeneity was checked from the FESEM picture.