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Investigation on Electrical Properties and Band Structure of Barium Strontium Titanate Thin Films Grown by Pulsed Laser Deposition

Kashir, Alireza | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44203 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Nemati, Ali; Mahdavi, Mohammad
  7. Abstract:
  8. In this research the microstructural, electrical and optical properties of Strontium Titanate and Barium Strontium Titante thin films, fabricated through Pulsed Laser Deposition (PLD), were investigated. X-ray Photoelectron Spectroscopy and X-ray Diffraction study showed that the stoichiometry of the target material was highly preserved by using PLD method. Scanning Electon Microscopy as well as Atomic Force Microscopy depicted that the using of pressed and sintered target is a suitable metod for improving the surface quality of the thin films. Using the pressed target decreased the quality of the thin films and the average roughness of the films increased. The main reason for this phenamenon is the interaction between the laser and the target.Optical investigations on all film specimens showed that the annealing process is decreasing the transparancy and the optical band gap of the films. Mn presence in these two compositions, probably due to substitution of Ti positions by Mn in the pervoskite structure, decreased the optical band gap.The current density versus voltage curves of the Pt/STO/Pt, Si/STO/Pt, Pt/STO/Au and Pt/BST/Pt capacitors showed that the current behavior is not Ohmic and the presence of the Mn as dopant in the dielectric composition decreased the current density. Considering the probable conductivity mechanisms in these capacitors increasing in shotckey barrier, increasing in depletion layer and decreasing in the conduction electrons are the main reasons for this variation of conduction via the introduction of the Mn into the capacitor structure
  9. Keywords:
  10. Electrical Properties ; Band Structure ; Barium Strontium Titanate ; Pulsed Laser Deposition (PLD) ; X-Ray Photoelectron Spectroscopy (XPS) ; Thin Films

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