Ph. D. (Banaras Hindu Univ., India)
Ph. D. (Banaras Hindu Univ., India)
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I studied swift heavy ion (SHI) irradiation induced modifications in magnetic-metal/Si interfaces.
I studied swift heavy ion (SHI) irradiation induced modifications in magnetic-metal/Si interfaces.
Topic of my Ph.D. thesis: A Study on Magnetic Metal/Silicon Interface Devices; with and without swift heavy ion irradiation
Topic of my Ph.D. thesis: A Study on Magnetic Metal/Silicon Interface Devices; with and without swift heavy ion irradiation
Most straight forward approach for the spin-injection in ferromagnetic-metal/semiconductor systems, is the formation of an ohmic contact between a ferromagnetic-metal and semiconductor, anticipating a spin-polarized current in the semiconductor. Typical metal- semiconductor ohmic contacts result from heavily doping the semiconductor, leading to spin-flip scattering and loss of the spin-polarization. This could be overcome by tailoring the interface, and this exactly which I tried in this work using Swift Heavy Ion irradiation.
Most straight forward approach for the spin-injection in ferromagnetic-metal/semiconductor systems, is the formation of an ohmic contact between a ferromagnetic-metal and semiconductor, anticipating a spin-polarized current in the semiconductor. Typical metal- semiconductor ohmic contacts result from heavily doping the semiconductor, leading to spin-flip scattering and loss of the spin-polarization. This could be overcome by tailoring the interface, and this exactly which I tried in this work using Swift Heavy Ion irradiation.
I grown Fe/Si, Ni/Si, and Fe20Ni80/Si bilayers using electron-beam evaporation. The samples were irradiated by using 100 MeV Fe7+ ions. During these studies, giant magneto-resistance (GMR) and superparamagnetic (SPM) like behavior were observed which were understood in realm of spin dependent scattering model.
I grown Fe/Si, Ni/Si, and Fe20Ni80/Si bilayers using electron-beam evaporation. The samples were irradiated by using 100 MeV Fe7+ ions. During these studies, giant magneto-resistance (GMR) and superparamagnetic (SPM) like behavior were observed which were understood in realm of spin dependent scattering model.
Irradiated Fe/Si and Ni/Si bilayer samples have shown nanogranular magnetic metallic Fe5Si3 and Ni2Si silicides respectively whereas irradiated Fe20Ni80/Si bilayer samples have shown semiconducting beta-FeSi2 along with magnetic Ni2Si silicides.
Irradiated Fe/Si and Ni/Si bilayer samples have shown nanogranular magnetic metallic Fe5Si3 and Ni2Si silicides respectively whereas irradiated Fe20Ni80/Si bilayer samples have shown semiconducting beta-FeSi2 along with magnetic Ni2Si silicides.
The observed ion induced nano granular silicide phase formation has been understood in the realm of thermal spike model. In this framework, after the passage of the ions, the system gets highly excited due to intense electronic energy deposition and may get to a molten state, which quenches very fast to room temperature in a very short period of time (~10-11- 10-12 s). This ultrafast quenching process freezes the atoms from an excited state to a metastable one with expanded lattice spacing, since the timescale is insufficient for recrystallization to the equilibrium state.
The observed ion induced nano granular silicide phase formation has been understood in the realm of thermal spike model. In this framework, after the passage of the ions, the system gets highly excited due to intense electronic energy deposition and may get to a molten state, which quenches very fast to room temperature in a very short period of time (~10-11- 10-12 s). This ultrafast quenching process freezes the atoms from an excited state to a metastable one with expanded lattice spacing, since the timescale is insufficient for recrystallization to the equilibrium state.
These studies help us to tune the structural and magnetic properties of the bilayers and to understand the mechanism of swift heavy ion induced synthesis of novel silicide phases.
These studies help us to tune the structural and magnetic properties of the bilayers and to understand the mechanism of swift heavy ion induced synthesis of novel silicide phases.
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