Influence Of Bi Addition On The Optical Properties Of As40Se60 Thin Films (original) (raw)
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X-ray Microanalysis and Optical Properties of Thin As - S - Bi(Tl) Films
Chalcogenide glasses are an important class of materials because of their wide range of applications in infrared optics, infrared detectors, electronic and optical switching devices and phase optical recording. In this paper, we discuss the results obtained studying the in#uence of the conditions of deposition (temperature and rate of evaporation), thin "lm concentration and light exposure on the optical properties of thin As-containing chalcogenide "lms. A technique named`phase contribution methoda (PCM) is used for quantitative elemental analysis of thin layers from the system As}S}Bi (Tl) deposited on soda-lime glass substrates. The method has been tested with thin chalcogenide "lms with di!erent thicknesses deposited on glass and graphite substrates. The relationship between the changes in the composition and optical properties has been derived. The changes allow the practical application of thin-layered information recording media and high-resolution inorganic photoresists.
Nanocrystallites in Bi–As–S system
Journal of Non-Crystalline Solids, 2007
Bi 2 S 3-As 2 S 3 composite formation was performed by two methods: by the direct insertion of Bi 2 S 3 nanocrystals into a molten As 2 S 3 glass which was further solidified and by the crystallization of a rapidly quenched (As 2 S 3) 1Àx (Bi 2 S 3) x glasses with x = 0.005, 0.01, 0.02 and 0.04 at different conditions. Fine tuning of the annealing of the quenched glass as well as the mixing of nanocrystals in to the molten glass resulted glass-crystalline composites with different amounts and distribution of 20-50 nm large Bi 2 S 3 nanocrystals as well as larger, up to few micrometer long, needle-like crystals. Structural and optical investigations support the presence of the Bi 2 S 3 crystalline phase in all composites. Optical absorption and the photoconductivity of bulk composite samples follow the structural changes of the structure in the amorphous and amorphous-crystalline phase. In addition, the 290 cm À1 characteristic band in Raman spectra may be used for tracing the formation of the nanocomposites.
Effect of Te additions on the optical properties of (As–Sb–Se) thin films
Thin Solid Films, 2007
Amorphous (As 30 Sb 15 Se 55 ) 100−x Te x (with 0 ≤ x ≤ 12.5 at.%) were prepared by thermal evaporation. The optical transmission and reflection spectra of these films were measured in the wavelength range of 400-900 nm. The mechanism of the optical absorption follows the rule of allowed non-direct transition. It was found that, the optical band gab E 0 decreases while the width of localized states (Urbach energy) E c increases by increasing Te content. The relationship between E 0 and chemical composition of the (As 30 Sb 15 Se 55 ) 100−x Te x system were discussed in terms of Cohesive energy (CE), the average heat of atomization H s , and the average coordination number N r . The later are computed from the heat of atomization and the coordination number of used elements, respectively.
LIGHT INDUCED CHANGES IN THE OPTICAL PROPERTIES OF THIN As - S - Ge(Bi, Tl) FILMS
In this paper we report results from studying changes in the optical properties of thin vacuum deposited films from the systems As 40-x Ge x S 60 (0 ≤ x ≤ 40) and (As 2 S 3 ) 100-x Bi(Tl) x (0 ≤ x ≤ 15) depending on the composition and conditions of evaporation and illumination to light. The optical transmission and reflection of thin layers deposited on BK-7 optical glass substrates have been measured in the spectral region of 350 -1500 nm and the refractive indices and optical band gap E g were calculated. It was found that the method of evaporation influences considerably the properties of thin chalcogenide films. The addition of Bi or Tl in As 2 S 3 leads to an increase in the refractive index while Ge causes its decreasing. The illumination of as-deposited films leads to an effect of photodarkening and decreasing in the optical band gap for As-containing films and photobleaching for As -Ge -S layers. Using TRR m methods (R m is the reflection of 100 nm thick films deposited on Si substrate), the thickness of very thin layers from the systems As -S and As -S -Ge have been determined to an accuracy of ±2 nm. At the same time, the accuracy in the determination of the refractive index, n, was less than ±0.005. For the absorption coefficient, k, around the absorption edge, it was about ±0.01, using a combination of TTR m and TR methods. A comparison between the results obtained from the spectrophotometric and ellipsometric measurements has been made.
Spectral dependence of photoinduced optical effects in As40S60-xSex thin films
Thin Solid Films
Spectral dependence of photoinduced structural transformation and related changes of E g opt , α and n of thermally evaporated ternary As 40 S 60-x Se x thin films have been studied under the exposure to bandgap and super-/sub-bandgap light of LED. The irradiation by bandgap and super-bandgap light with intensity 0.1 W/cm 2 leads to partial photoinduced polymerization of molecular structural units into continuous network that is characteristic for the bulk glasses with appropriate stoichiometric composition. The efficiency of structural transformation depends on penetration depth of excitation beam. The maximum photosensitivity (i.e. changes of E g opt , α and n) were achieved at the wavelengths ~ 100 nm above the bandgap wavelength for each appropriate composition. Beyond the region of maximal photosensitivity the values of optical parameters and kinetics of photoinduced changes depend on relation between exposed and unexposed sublayer for super-bandgap beams or on absorption coefficient for sub-bandgap light.
Structural, electrical and optical properties of Bi 2Se 3 and Bi 2Se (3− x) Te x thin films
Materials Research Bulletin, 2005
Nanocrystalline thin films of silicon (Si) were grown on glass substrates using pulsed laser deposition technique. Si nanoparticles thin films were investigated employing X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, low temperature electrical transport measurements, and UV-visible absorption spectroscopy. XRD data show that Si films are polycrystalline having cubic crystal structure with preferred (111) orientation. SEM and AFM micrographs exhibit dense and slightly rough surface morphology with well defined columnar grains. Temperature dependence of the resistivity has been fitted with ln ρ(T) 1 T À 1/4 which indicates three dimensional variable range hopping conduction mechanism as well as semiconducting behavior of films. Finally, the optical absorbance edge of Si thin films is described in terms of indirect transition model proposed by Tauc in the strong absorption region, and according to Urbach's rule in the medium absorption region.
Raman Spectra and Structure of Bi2S3 and As2S3 Amorphous Films
Non-crystalline As2S3 and Bi2S3 films with different thickness were obtained by methods of discrete thermal evaporation. The broad band with maximum at ~238 cm-1, characteristic band for non-crystal films, was observed in the Raman spectra of Bi2S3 film with thickness of ~1000 Å. This band is characteristic for non-crystalline state. The Raman spectrum of non-crystalline As2S3 film has multimode structure and in thickness ranges 1000 – 10000 Å the spectra are nearly the same. The performed ab initio calculations of the vibration spectra of As(Bi)nSm clusters are in good accordance with the experimental Raman spectra.
Optical Materials, 2018
The chalcogenide thin films belongs to a special category of important materials due to the unique IR transparency and light induced linear and non linear optical properties change. The optical band gap tuning in thermally evaporated As 40 Se 53 Sb 07 chalcogenide thin film is being probed under the influence of 532 nm laser illumination. The gradual decrease in transmission and red shift of optical absorption edge with illumination at different time scale is recorded by Fourier transmission infrared spectroscopy. The simultaneous increase in refractive index and absorption coefficient of the illuminated film makes the material as useful candidate for optical switching. The dispersion of refractive index is being analyzed by using WempleeDiDomenico (WDD) single oscillator model and static refractive index (n 0) has also been reported. The exponential decrease of optical band gap with time is attributed to the increase in density of localized states and vacancies. The entire mechanism is explained by the microscopic model in which heteropolar bonds are converted to homopolar ones by the absorption of high energy photons investigated by X-ray photoelectron spectra. The amorphous nature of the studied films was revealed from X-ray diffraction and composition of the film was determined from energy dispersive X-ray analysis. The surface morphology was determined from the scanning electron microscopy. The optical change in absorption coefficient, refractive index, band gap by influence in laser irradiation in such materials may be suitable for optical disc(memory) application for optical time division switch.