Effect of Strain Due to Substrates on Mn-Doped ZnO Dilute Magnetic Semiconductor Thin Films
Date of Graduation
Master of Science in Materials Science
Physics, Astronomy, and Materials Science
semiconductor, strain, pulsed laser deposition, zinc oxide, spintronics
Materials Science and Engineering
Dilute magnetic semiconductors (DMS) are semiconductors doped with ions that have a net spin. The interface amongst these spins leads to a ferromagnetic state at low temperatures. Potential applications of DMS are in the field of spin-dependent semiconductors electronics and optoelectronics, or so-called spintronics and opto-spintronics. Thin films of ZnO and TiO₂ doped with Mn and Co have been studied over a long time because of their interesting magnetic behavior. The degree of film densification and size of specific defects (such as pores, grain boundaries, and cavities.) is stongly dependent on the processing temperature and substrate. The substrate material can influence the kinetics of film growth due to different thermal conductivity, specific heat, and emissivity. Its selection is moreover very significant for growth of thin films because matching in lattice parameters and crystal structure between the film and substrate strongly affects the crystal growth behavior of the film. In this work, the effect of substrate on the domain structure growth and electrical and magnetic properties of highly c-axis oriented Mn-doped Zn₀.₈₅MN₀.₁₅O (ZnMnO) thin films has been investigated. The effects of annealing on the surface morphology, structural, and optical properties of ZnMnO films were investigated using scanning electron microscopy, X-Ray diffraction, Raman spectroscopy, and temperature dependent resistivity. The resistivity of ZnMnO films decreased after annealing. It was found that the quality of ZnMnO film could be improved through annealing. X-Ray diffraction and Raman spectroscopy show that the films are highly c-axis oriented with different induced strains. Electrical resistivity and Hall effect data indicate that carrier concentration decreases and mobility increases for more strained films on silicon and quartz substrates compared to less strain film of ZnMnO on sapphire substrate has been reported by other groups. All these results indicated that the strain has been induced in thin films and due to annealing the quality of thin film was improved.
© Srikanth Manchiraju
Manchiraju, Srikanth, "Effect of Strain Due to Substrates on Mn-Doped ZnO Dilute Magnetic Semiconductor Thin Films" (2007). MSU Graduate Theses. 2324.