Among the well-known methods to form or modify the composition and physical properties of thin films, ion implantation has shown to be a very powerful technique. In particular, ion beam syntheses of binary iron silicide have been studied by several groups. Further, the interests in transition metal silicide systems are triggered by their potential use in advanced silicon based opto-electronic devices. In addition, ternary silicides have been by far less studied than their binary counterparts despite the fact that they have interesting magnetic and electronic properties. In this study, we investigate ion beam synthesis of Fe-Si binary structures and Fe-Co-Si ternary structures. This work involves fundamental investigation into development of a scalable synthesis process involving binary and ternary transitional metal silicide thin films and Nano-structures using low energy ion beams.
Binary structures were synthesized by implanting Fe- at 50 keV energy. Since ion implantation is a dynamic process, Dynamic simulation techniques were used in these studies to determine saturation fluences for ion implantation. Also, static and dynamic simulation results were compared with experimental results. The outcome of simulations and experimental results indicate, dynamic simulation codes are more suitable than static version of the TRIM to simulate high fluence, low energy and, heavy ion implantation processes. Furthermore, binary Fe-Si phase distribution was determined at different implantation fluences and annealing temperatures. A higher fluence implantation at 2.16×1017 atoms/cm2 and annealing at 500 oC showed three different Fe-Si phase formations (β-FeSi2, FeSi and Fe3Si) in substrate. Further, annealing the samples at 800 oC for 60 minutes converted the Fe3Si phase into FeSi2 and FeSi phases. As an extension, a second set of Fe- ion implantations was carried with the same parameters while the substrate was placed under an external magnetic field. External magnetic fields stimulate the formation of magnetic phase centers in the substrate. X-ray diffraction (XRD) results shows formation of ferromagnetic Fe3Si phase in the Si matrix after annealing at 500 oC for 60 minutes. In addition, X-ray photoelectron spectra (XPS) provide further evidence for ferromagnetic metallic behavior of Fe3Si in the substrate. Ternary Fe-Co-Si structures were synthesized by implanting Fe- & Co- into a Si (100) substrate at an energy of 50 keV at saturation fluences. Both Fe- & Co- co-implantation were performed under external magnetic fields to enhance magnetic phase formation. Fe(1-x)CoxSi B20-type cubic structure can be synthesized on Si(100) substrate with 0.4≤x≤0.55 concentration range using ion implantation under external magnetic field. Moreover, magnetic measurement indicates a possible magnetic phase transformation at ~50 K. Further, XPS results also provide evidence for metallic & ferromagnetic properties in the thin film structure
| Identifer | oai:union.ndltd.org:unt.edu/info:ark/67531/metadc955104 |
| Date | 12 1900 |
| Creators | Lakshantha, Wickramaarachchige Jayampath |
| Contributors | Rout, Bibhudutta, McDaniel, Floyd D., Glass, Gary A., Reinert, Tilo, Weathers, Duncan L. |
| Publisher | University of North Texas |
| Source Sets | University of North Texas |
| Language | English |
| Detected Language | English |
| Type | Thesis or Dissertation |
| Format | Text |
| Rights | Public, Lakshantha, Wickramaarachchige Jayampath, Copyright, Copyright is held by the author, unless otherwise noted. All rights Reserved. |
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