Eric Kumi Barimah

Bio: Eric Kumi Barimah is an academic researcher from University of Leeds. The author has contributed to research in topics: Thin film & Photoluminescence. The author has an hindex of 3, co-authored 8 publications receiving 27 citations.

Erbium-Doped Nanoparticle–Polymer Composite Thin Films for Photonic Applications: Structural and Optical Properties

Abstract: Erbium-doped nanocrystal (NC)-dispersed polymer thin films are attractive core materials for use in optical waveguides as they can provide high optical gain and enable the formation of compact wave...

Infrared optical properties modulation of VO2 thin film fabricated by ultrafast pulsed laser deposition for thermochromic smart window applications

Abstract: Over the years, vanadium dioxide, (VO2(M1)), has been extensively utilised to fabricate thermochromic thin films with the focus on using external stimuli, such as heat, to modulate the visible through near-infrared transmittance for energy efficiency of buildings and indoor comfort. It is thus valuable to extend the study of thermochromic materials into the mid-infrared (MIR) wavelengths for applications such as smart radiative devices. On top of this, there are numerous challenges with synthesising pure VO2 (M1) thin films, as most fabrication techniques require the post-annealing of a deposited thin film to convert amorphous VO2 into a crystalline phase. Here, we present a direct method to fabricate thicker VO2(M1) thin films onto hot silica substrates (at substrate temperatures of 400 °C and 700 °C) from vanadium pentoxide (V2O5) precursor material. A high repetition rate (10 kHz) femtosecond laser is used to deposit the V2O5 leading to the formation of VO2 (M1) without any post-annealing steps. Surface morphology, structural properties, and UV-visible optical properties, including optical band gap and complex refractive index, as a function of the substrate temperature, were studied and reported below. The transmission electron microscopic (TEM) and X-ray diffraction studies confirm that VO2 (M1) thin films deposited at 700 °C are dominated by a highly texturized polycrystalline monoclinic crystalline structure. The thermochromic characteristics in the mid-infrared (MIR) at a wavelength range of 2.5-5.0 μm are presented using temperature-dependent transmittance measurements. The first-order phase transition from metal-to-semiconductor and the hysteresis bandwidth of the transition were confirmed to be 64.4 °C and 12.6 °C respectively, for a sample fabricated at 700 °C. Thermo-optical emissivity properties indicate that these VO2 (M1) thin films fabricated with femtosecond laser deposition have strong potential for both radiative thermal management or control via active energy-saving windows for buildings, and satellites and spacecraft.

Erbium-doped glass nanoparticle embedded polymer thin films using femtosecond pulsed laser deposition

Abstract: Polymer materials doped with rare-earth ions are promising candidates for the formation of low-cost integrated optical amplifiers. However, there are significant technical challenges associated with the integration of these dissimilar materials and the formation of high-quality Er-doped polymer films. In this paper, therefore, we present for the first time the fabrication of polymer thin layers modified with erbium-doped sodium zinc tellurite (Er-TZN) glass nanoparticles (NPs) using femtosecond (fs) pulsed laser deposition (PLD) and the characterisation of their basic properties. The surface morphology and the compositional and structural characteristics of the samples produced with this method are evaluated using scanning and transmission electron microscopy (SEM and TEM) and X-ray diffraction (XRD), while photoluminescence (PL) measurements are carried out at room temperature under a 980 nm laser diode excitation. The studies indicate that the Er-doped TZN NPs are successfully integrated in the polymer layers. The obtained average NP size is measured to be in the range of 12 to 21 nm depending on the fabrication parameters, while broad PL emission at 1534 nm that corresponds to the 4I13/2 →4I15/2 transition of Er3+ is observed from the samples. The full-width at half-maximum (FWHM) of the PL spectra is found to be ~39 nm while the fluorescence lifetime is measured to be in the range of 3.52 to 4.18 ms. The obtained results clearly demonstrate the potential to efficiently dope polymer layers with glass NPs using fs-PLD and is a first step towards the successful formation of hybrid polymer-glass waveguide amplifiers.

Thermal, Mechanical and Optical Properties of TiO2-doped Sodium Silicate Glass-Ceramics

Abstract: In this study, local mineral (silica sand) obtained from Hazara division, Khyber Pakhtunkhwa, Pakistan was fabricated into soda-lime silicate glass. Titanium dioxide (TiO2) concentration in the range of 1-3 wt% was added as a nucleating agent to investigate its effect on crystallization phase, density, hardness, thermal expansion coefficient (α), glass transition temperature (Tg), micro hardness and optical bandgap of soda-lime silicate glass. XRD analysis revealed the formation of different crystalline phases such as cristobalite (SiO2), wollastonite (CaSiO2), and rutile (unrefined TiO2, often with iron, F3+) at different processing temperatures. The coefficient of thermal expansion and the optical gap energies varied from 72.5×10–7/K to 77×10–7/K and 3.71-3.93 eV with TiO2 concentration, respectively. The mechanical properties were also in good agreement with those of commercially used glass-ceramics.

The Impact of Fuelwood Moisture Content on the Emission of Gaseous and Particulate Pollutants from a Wood Stove

Abstract: The amount of moisture in wood fuel has a significant influence on the emissions of particulate matter (PM) and gaseous pollutants when burned in small-scale domestic appliances. Previous studies h...

Erbium-doped chalcogenide glass thin film on silicon using femtosecond pulsed laser with different deposition temperatures

Abstract: The properties of Er3+-doped gallium lanthanum sulphide thin films prepared on a silicon substrate by femtosecond pulsed laser deposition were studied as a function of process temperature. The films were characterised using transition electron microscopy imaging, X-ray diffractometry, Raman spectroscopy, fluorescence spectroscopy, and UV–Vis–NIR spectroscopy. The results show that by increasing the substrate temperature, the deposited layer thickness increases and the crystallinity of the films changes. The room temperature photoluminescence and lifetimes of the 4I13/2→4I15/2 transition of Er3+ are reported in the paper.

Structural, Elastic Moduli, and Radiation Shielding of SiO 2 -TiO 2 -La 2 O 3 -Na 2 O Glasses Containing Y 2 O 3

Abstract: Quaternary glasses with the chemical composition 50SiO2-25TiO2-5La2O3- (20-x) Na2O-xY2O3 by use the melt-quench method. The FT-IR spectroscopy investigated the structural change in these glasses. XRD examined the nature of these glasses. While the density is increased, the molar volume of the glass system is reduced. Ultrasonic velocities and elastic modulus of these glasses were experimentally and theoretically calculated based on the Makishima-Mackenzie model. Moreover, the radiation shielding capacity was evaluated for the studied glasses. The mass attenuation coefficient (μ/ρ), half value layer(HVL), tenth value layer (TVL), mean free path (MFP), effective atomic number (Zeff), electron density (Neff), equivalent atomic number Zeq, and effective removal cross section (ΣR) of prepared glasses were simulated for gamma photon energies between 0.015 and 15 MeV. Exposure build-up factor (EBF) and (EABF) of prepared glasses were evaluated.

Optical Properties of SiO2 – TiO2 – La2O3 – Na2O – Y2O3 glasses and A novel process of preparing the parent glass-ceramics

Abstract: Quaternary glasses with the composition 50SiO2 – 25TiO2 – 5La2O3 – (20-x) Na2O – xY2O3 where x : (0 ≤ x ≥ 10) were synthesized using the melt-quench technique. XRD examined the nature of prepared glasses. UV-spectroscopic of investigated glass system studied at room temperature. Both optical bandgap and refractive index of the present glass have been increased. The polarizability and basicity were determined. Thermal parameter values increased as Y2O3 increased. Under controlling heat, the glass-ceramic were prepared and confirmed using XRD. Glass-ceramics are examined using SEM to evaluate a microstructure. Ultrasonic velocities and elastic-moduli of glass-ceramic samples are increased because of the increase in internal energy. The role of Y2O3 modifier in the glass system is clearly demonstrated. Y2O3 also works as an excellent nucleating agent that can induce crystallizations, supporting in the creation of the sub-phase of glass-ceramics.

The effect of ZrO2 on the linear and non-linear optical properties of sodium silicate glass

Abstract: Recently our work exhibited the influence of Zirconium oxide on the linear and non-linear optical properties of Sodium silicate glass. The optical constants were computed by Kramer-Kroing relation based on the reflectance spectra, which measured in typical mode spectra by the spectrometer ranging from 200 to 1000 nm. The refractive index, n, was reduced by an increase in the concentrations of ZrO2, while the extinction coefficient, k, was increased. The real and imaginary dielectric constants were calculated. Based on the Miller’s equation, the non-linear optical properties were computed and decreased with an increase in zirconium oxide concentration, which implied that an important factor for controlling the optical properties of Sodium silicate glass which useful to utilize in several photonic applications. XRD studied structural properties.

Phase evolution, morphological, optical and electrical properties of femtosecond pulsed laser deposited TiO 2 thin films

Abstract: In this paper, we report anatase and rutile titanium oxide (TiO2) nanoparticulate thin films fabricated on silica and Indium Tin Oxide (ITO) substrates using femtosecond pulsed laser deposition (fs-PLD) Depositions were carried-out at substrate temperatures of 25 °C, 400 °C and 600 °C from anatase and rutile phase target materials Effect of substrate temperature on the surface morphology, microstructural, optical, and electrical properties of these films were systematically investigated by using various range of measurements such as scanning electron microscopy, (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Ultraviolet–visible-near infrared (UV–Vis–NIR) spectroscopy, and Hall Effect measurements It is observed that the TiO2 thin films surface are predominated with nanoparticulates of diameter less 35 nm, which constitute about ~ 70%; while the optical bandgaps and electrical resistivity decrease with increasing substrate temperature A mixed-phase (anatase/rutile) TiO2 thin film was produced at a substrate temperature of 400 °C when samples are fabricated with anatase and rutile target materials The results of this study indicate that the structural and crystallinity, optical, and electrical properties can be controlled by varying fs-PLD process parameters to prepare TiO2 thin films, which are suitable for applications in photovoltaics, solar cells, and photo-catalysis