Influence of the preparation method on the morpho-structural and optical properties of bismuth oxide thin films (original) (raw)
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On the optical properties of bismuth oxide thin films prepared by pulsed laser deposition
Thin Solid Films, 2005
The optical properties of bismuth oxide films prepared by pulsed laser deposition (PLD), absorption in the photon energy range 2.50-4.30 eV and optical functions (n, k, e 1 , and e 2 ) in the domain 3.20-6.50 eV, have been investigated. As-prepared films (d=0.05-1.50 Am) are characterized by a mixture of polycrystalline and amorphous phases. The fundamental absorption edge is described by direct optical band-toband transitions with energies 2.90 and 3.83 eV. The dispersion of the optical functions provided values of 4.40-6.25 eV for electron energies of respective direct transitions. In the spectral range 400-1000 nm, bismuth oxide films show a normal dispersion, which can be interpreted in the frame of a single oscillator model. D
Structural and optical characteristics of bismuth oxide thin films
Surface Science, 2002
The formation of different phases of Bi-O system during oxidizing process of Bi films from the viewpoint of structure characteristics and optical properties, is investigated. As revealed by structure and surface investigations, the thermal oxidation, in air, of Bi films on glass results in polycrystalline and multiphase bismuth oxide films. At substrate-film interface an amorphous oxide layer forms up, to whom surface the growth processes of crystallites belonging to divers phases, with different geometric shapes occur. For nanometric up to submicronic thicknesses, BiO is predominant phase, while in case of micronic films, a-Bi 2 O 3 and Bi 2 O 3 are the main phase components. From absorption curves the band gap values, (E g ¼ 2:29-3:31 eV), for direct transitions, have been determined and an energy gap of $2 eV for amorphous phase was found. Ó
Applied Surface Science, 2008
Monoclinic bismuth oxide (Bi 2 O 3) films have been prepared by thermal oxidation of vacuum evaporated bismuth thin films onto the glass substrates. In order to obtain the single phase Bi 2 O 3 , the oxidation temperature was varied in the range of 423-573 K by an interval of 50 K. The asdeposited bismuth and oxidized Bi 2 O 3 films were characterized for their structural, surface morphological, optical and electrical properties by means of X-ray diffraction, scanning electron microscopy (SEM), optical absorption and electrical resistivity measurements, respectively. The Xray analyses revealed the formation of polycrystalline mixed phases of Bi 2 O 3 (monoclinic, a-Bi 2 O 3 and tetragonal, b-Bi 2 O 3) at oxidation temperatures up to 523 K, while at an oxidation temperature of 573 K, a single-phase monoclinic a-Bi 2 O 3 was formed. From SEM images, it was observed that of as-deposited Bi films consisted of the well-defined isolated crystals of different shapes while after thermal oxidation the smaller dispersed grains were found to be merged to form bigger grains. The changes in the optical properties of Bi 2 O 3 films obtained by thermal oxidation at various temperatures were studied from optical absorption spectra. The electrical resistivity measurement depicted semiconducting nature of Bi 2 O 3 with high electrical resistivity at room temperature.
Bi2O3 thin films were deposited on ultrasonically-cleaned glass and mica substrates by close-spaced vacuum sublimation technique. Films surface morphology was studied using scanning electron microscopy (SEM). Structural study based on the transmission-electron microscopy (TEM) and selected-area electron diffraction (SAED) analysis has been shown that deposited films were polycrystalline with face-centered cubic structure. Optical study was carried out by spectral photometry analysis in the wavelengths range 320-900 nm using the optical transmittance and absorbance measurements. For determination optical band gap Eg the Tauc plot was used and the band gap energy Eg is determined in the range of 3.50-3.62 eV, respectively. Fourier-transform infra-red (FTIR) analysis shown that obtained films are well-crystalline and have a good optical quality.
KRAMERS-KRONIG METHOD APPLIED FOR THIN FILMS OF BISMUTH OXIDE PREPARED BY PLD
Pulsed laser deposition (PLD) was employed for the preparation of thin films of bismuth oxide, by varying several deposition parameters. The atomic force microscopy (AFM) analysis showed crystallites with sub-micrometer heights distributed on the surface of the films. Kramers-Kronig method was used to infer the refractive index of the films as a function of wavelength, from the optical reflection data. The analyzed bismuth oxide films proved to reach up to 2.4 refractive index in the near-Infrared.
Synthesis of Bismuth Oxide Thin Films Deposited by Reactive Magnetron Sputtering
Acta Physica Polonica A, 2011
In this work Bi 2 O 3 thin films were deposited onto the Si (111) and soda lime glass substrates by the reactive direct current magnetron sputtering system using pure Bi as a sputtering target. The dependences of electro-optical characteristics of the films on the substrate type and temperature were investigated. Transmittance and reflectance of the Bi 2 O 3 films were measured with ultraviolet and visible light spectrometer. It was found that the substrate temperature during deposition has a very strong influence on the phase components of thin films. The results indicate that the direct allowed transitions dominate in the films obtained in this work. For the direct allowed transitions the band gap energy is found to be about 1.98 eV and 2.2 eV. The reflectance of thin bismuth oxide film depends on the substrate. Small transparency of thin films grown on glass is more related to large reflectance than absorption. The reflectance spectra of the bismuth oxide thin films deposited on the Si substrates show higher quality of optical characteristics compared to the samples deposited on glass substrates.
Bismuth oxide thin films prepared by chemical bath deposition (CBD) method: annealing effect
Applied Surface Science, 2005
Bismuth oxide thin films have been deposited by room temperature chemical bath deposition (CBD) method and annealed at 623 K in air. They were characterized for structural, surface morphological, optical and electrical properties. From the X-ray diffraction patterns, it was found that after annealing a non-stoichiometric phase, Bi 2 O 2.33 , was removed and phase pure monoclinic Bi 2 O 3 was obtained. Surface morphology of Bi 2 O 3 film at lower magnification SEM showed rod-like structure, however, higher magnification showed a rectangular slice-like structure perpendicular to substrate, giving rise to microrods on the surface. The optical studies showed the decrease in band gap by 0.3 eV after annealing. The electrical resistivity variation showed semiconductor behavior and from thermoemf measurements, the electrical conductivity was found to be of n-type. #
Deposition and characterisation of bismuth oxide thin films
Journal of The European Ceramic Society, 2005
Owing to their peculiar characteristics, bismuth oxides are used in various domains, such as microelectronics, sensor technology, optical coatings, transparent ceramic glass manufacturing, etc. Bismuth oxide system exhibit high oxide ionic conductivity and have been proposed as good electrolyte materials for application, such as solid oxide fuel cell (SOFC) and oxygen sensor.Antimony doped and undoped Bi2O3 films were deposited onto glass substrate from bismuth nitrate and antimony precursor solutions. As chelating agent polyethyleneglycol (PEG) was used and the above-mentioned precursor solutions were sufficiently viscous.In the present paper, the formation of different phases belonging to Bi–O system during thermal treatments of the Bi-based films is investigated by means of spectroscopic ellipsometry (SE), polarising microscope observation, X-ray diffractometry (XRD), and infrared spectrometry (IR). The thickness and the porosity of the films were evaluated. These preparation techniques, differing mainly in precursor materials and method of deposition, lead to different quality of the resulting films.
Laser Induced Oxidation Effects in Bismuth Thin Films
MRS Proceedings, 2012
ABSTRACTThe Laser induced oxidation process of bismuth was investigated using Raman spectroscopy. Upon laser irradiation (λ = 532 nm) pure Bismuth was transformed gradually into Bi2O3. Raman spectra of the samples showed the characteristics peaks for pure Bi located at 71 cm-1 and 96 cm-1. The oxidation process was monitored by Raman spectra with four additional bands located at about 127 cm-1, 241 cm-1, 313 cm-1 and 455 cm-1. Maintaining constant the exposure time of irradiation, the intensity of these bands depended on laser irradiation power. The presence of Bi2O3 in the sample was confirmed through by energy dispersion spectroscopy (EDS).