Arabian Journal for Science and Engineering

, Volume 44, Issue 1, pp 603–612 | Cite as

Bandgap Engineering in \(\hbox {TiO}_{2}\)–Ge Nanocomposite Thin Films

  • Asma Nazir
  • Ehsan Ullah Khan
  • Ali Nadeem
  • Arshad Mahmood Janjua
  • Ahmed Shuja Syed
  • Shaista ShahzadaEmail author
Research Article - Physics


Titanium dioxide–germanium (\(\hbox {TiO}_{2}\)–Ge) composite thin films were prepared by pulse laser deposition technique using third harmonic (355 nm) of Nd:YAG laser at fluence of \(12.73\,\hbox {J/cm}^{2}\). Films were grown on n-type Si (100) substrate using \(\hbox {TiO}_{2}\)–Ge composite target. The bandgap was tailored by varying the composition of \(\hbox {TiO}_{2}\)–Ge composite films based on the variable substrate–target distance from 5–8 cm. Ge concentration in \(\hbox {TiO}_{2}\) matrix was measured through electron-dispersive X-ray spectroscopy and concentration variation from 0.9–25.3% was observed. Crystalline structure of thin films was analysed through X-ray diffraction, whereas micro-strains and dislocation density is also calculated through different X-ray diffraction peaks. A detailed study of the various polymorphs of \(\hbox {TiO}_{2}\) and presence of Ge in crystalline form was carried out through Raman spectroscopy. Direct and indirect absorption transitions were observed through ultraviolet and visible spectroscopy. Absorption edge shifted to visible region of electromagnetic spectrum is associated with a possible quantum confinement effect in Ge or strain generated due to lattice mismatch of Si substrate and Ge with \(\hbox {TiO}_{2}\). Absorption transitions of thin film containing 2.6% Ge were observed in visible region along with the emission in the same spectral region observed through photoluminescence spectra.


Pulsed laser deposition (PLD) \(\hbox {TiO}_{2}\)–Ge composites Raman spectroscopy X-ray diffraction Band-gap engineering 


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Thin Films and Laser Spectroscopy Labs at NILOP, Advance Characterization Lab at NILOP, XRD lab at COMSATS Institute of Information Technology, FESEM lab at Institute of Space Technology, Advance Electronics Laboratories at International Islamic University are acknowledged for variety of facility access and continued support to this work. Dr Manzar Abbas from COMSATS Institute of Information Technology is also acknowledged to provide us with wafers used in our experiment. Higher Education Commission, Pakistan is also acknowledged for awarding indigenous scholarship to PhD scholar Ms. Asma Nazir (HEC Pin # 063-112702-PS3-114).


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Copyright information

© King Fahd University of Petroleum & Minerals 2018

Authors and Affiliations

  1. 1.Department of PhysicsInternational Islamic UniversityIslamabadPakistan
  2. 2.National Institute of Laser and Optronics (NILOP)IslamabadPakistan
  3. 3.Advanced Electronics Labs. (AEL)International Islamic UniversityIslamabadPakistan

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