Metallic to Insulating Transition in Disordered Pulsed Laser Deposited Silicide Thin Films PDF Download
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Author: Houssam Abou Mourad
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Languages : en
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ABSTRACT: A metal-to-insulating transition has been observed in iron, iron oxide, iron silicide and cobalt silicide thin films when deposited on Si substrate with a native SiOx layer. This transition produced a change in resistance of 5 orders of magnitude at a temperature of 250 K. To the best of the author's knowledge, this effect has not been reported in the literature prior to this study. This work reports a systematic experimental investigation carried out to understand the fundamental mechanism involved in the manifestation of this metal-to-insulator transition. The films were deposited using the pulsed laser deposition technique (PLD) in a base vacuum of the order of 10-6 torr at 400o C and room temperature. Several experiments were systematically conducted to understand the nature of the transition and the current path.
Author: Houssam Abou Mourad
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ISBN:
Category :
Languages : en
Pages :
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ABSTRACT: A metal-to-insulating transition has been observed in iron, iron oxide, iron silicide and cobalt silicide thin films when deposited on Si substrate with a native SiOx layer. This transition produced a change in resistance of 5 orders of magnitude at a temperature of 250 K. To the best of the author's knowledge, this effect has not been reported in the literature prior to this study. This work reports a systematic experimental investigation carried out to understand the fundamental mechanism involved in the manifestation of this metal-to-insulator transition. The films were deposited using the pulsed laser deposition technique (PLD) in a base vacuum of the order of 10-6 torr at 400o C and room temperature. Several experiments were systematically conducted to understand the nature of the transition and the current path.
Author: Bamidele S. Allimi
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ISBN:
Category :
Languages : en
Pages : 178
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Author: Hasitha C. Weerasinghe
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Category :
Languages : en
Pages :
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ABSTRACT: Iron Silicide (FeSi) films deposited on silicon substrates with the native SiO2 layer have shown a Metal-to-Insulator Transition (MIT) of more than four order of magnitude change in resistance. Modification of the SiO2/Si interface due to Fe diffusion has been attributed to the formation of this effect. In this research a systematic experimental investigation has been carried out to study the effect of the growth parameters and substrate doping type in the transition. In addition, transport properties of continuous and discontinuous films have been investigated to understand the mechanism of this metal-to-insulator transition. Four probe measurements of films deposited in p- and n-type doped Si substrates with resistivity in the range of 1-10 Omega cm showed similar temperature dependent resistance behavior with transition onsets at 250 K and 300 K respectively. These results indicate that the current transport takes place via tunneling through the SiO2 layer into the Si substrate up to the transition temperature. Current appears to switch to the film after the transition point due to the development of high interface resistance. Discontinuous FeSi films on silicon substrates showed similar resistance behavior ruling out possibility of current transport through inversion layer at the SiO2/Si interface. To investigate the role of the magnetic ion Fe, transport measurements of FeSi films were compared with those of non-magnetic metals such as Platinum (Pt) and Aluminum (Al). Absence of Metal-to-insulator transition on Pt and Al films show that the presence of magnetic moment is required for this transition. Temperature dependent Hall voltage measurements were carried out to identify the carrier type through the substrate for FeSi films deposited on p- and n-type Si substrates. Results of Hall voltage measurements proved that the type of conductivity flips from majority carriers to minority after the transition. Metal-to-insulating transition behavior of FeSi films depending on different laser fluences has been also investigated. Our results revealed as laser fluence is increased observed transition of the FeSi films reduces rapidly showing a highest magnitude of transition of about 1 M Omega for the films deposited with lowest laser fluence (0.64 J/cm2) and a lowest of about 10 Omega for the films deposited with highest laser fluence (3.83 J/cm2). Ion probe measurements indicated that the average kinetic energy of the ablated ion in the plume is considerably increased with the increase of the laser fluence. Consequently, magnitude drop in the transition can be considered due to the deeper penetration on Fe ion through the SiO2 layer. Thickness dependence study carried out for FeSi films deposited with high and low laser fluencies indicated transition slightly drops as thickness is increased, concluding the current transportation through the film becomes dominant after the transition temperature.
Author: Charles H. Olk
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ISBN:
Category :
Languages : en
Pages : 302
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Author: Elizabeth Lee Radue
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Category : Raman spectroscopy
Languages : en
Pages : 119
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Vanadium dioxide is an intensely studied material, since it goes through an insulator-metal transition at a critical temperature just above room temperature at 340~K. The dramatic change in conductivity and the easily accessible transition temperature makes it an attractive material for novel technologies. Thin films of VO2 have a reversible transition without any significant degradation in contrast, and depending on the microstructure of the films, the properties of the transition are tunable. In this work, I study the dynamics of the insulator-transition in thin films grown on different substrates using a pump-probe configuration. The energy needed to trigger the transition, as well as the time constants of the change in reflectivity are affected by the strain in the VO2 films. I also characterized the samples using Raman spectroscopy and XRD measurements in order to identify what underlies the differences in behavior. Finally, in collaboration with Dr. Yamaguchi's group at RPI, I show that it is possible to trigger the transition using a THz pulse that directly pumps energy into the lattice, and at lower energies than needed to pump films by photoinducing the electrons across the band gap.
Author: Abdul Lateef Ali Mohammed
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ISBN:
Category :
Languages : en
Pages : 166
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Category :
Languages : en
Pages :
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Author: Anna Marie Widdowson
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Category :
Languages : en
Pages :
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Author: Ning Shu
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Category : Dissertations, Academic
Languages : en
Pages : 244
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Author:
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Category : Aeronautics
Languages : en
Pages : 892
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