Investigation Of β-FeSi₂ Thin Films By Pulsed Laser Deposition

The semiconducting low temperature phase of iron disilicide, Orthorhombic,β-FeSi₂ has attracted strong technological interest, since it is a promising material for silicon based optoelectronics, it could be grown epitaxially on Si substrates and a direct bandgap of about 0.87eV; its photo- and electroluminescence are well matched to the transmission window of optical silica fibers at 1.55μm. And it is a potential application for active component applications such as in light detectors, near-infrared sources, solar cell material and thermoelectric material.β-FeSi₂ has other excellent features, such as the rich abundance of its constituents in natural resources and its no toxicity.(1) A review of the investigation of synthesize ofβ-FeSi₂ thin films and its characteristic were present;And a summarization about pulsed laser deposition process (PLD) was present also.(2) The principle of pulsed laser deposition process were introduced, some experiment results and its discussion were present.(3) Iron powders and silicon powders with analytical pure, were used as the origin materials to synthesize a FeSi₂ alloy target by a standard ceramics sintered process. The main ingredient in the alloy target wasα-FeSi₂.(4) The even single phaseβ-FeSi₂ thin films were gained by fsPLD below 400℃, and the proper temperature of nsPLD is about 500℃; theβ-FeSi₂ thin films prepared by fsPLD were free of micro drop; the deposition efficiency at unit average laser power in the process of depositingβ-FeSi₂ thin films, the fsPLD system was 1000 times of nsPLD system.(5) X-ray Diffraction (XRD), Field Scanning Electron Microscopy (FSEM), Scanning Probe Microscopy (SPM), Electron Back Scattered Diffraction pattern (EBSD), High Resolution Transmission Electron Microscopy (HRTEM) were used to characterize the structure, composition, and properties of theβ-FeSi₂ films.(6) Fourier-Transform Raman Infrared Spectroscopy (FTRIS), UV-VIS-NIR spectrophotometer and Raman microscope spectroscopy were used to characterize the optical properties of theβ-FeSi₂ films; the photoluminescence from the grown single phaseβ-FeSi₂/Si thin film at a wavelength of 1.53μm was observed at room temperature (20°C). Normal incidence spectral transmittance and reflectance data indicate a minimum, direct energy gap of 0.85 eV. The two most intense lines of Raman scattering peaked at 181.3 cm-1 and 235.5 cm-1 for the film on fused quartz, but at 191.2 cm-1 and 243.8 cm-1 for the film on Si (100), were observed. 8 Raman peaks ofβ-FeSi₂/Si at 192.9 cm-1, 243.9 cm-1 and some points were observed by a Raman microscope with 514.5nm argon laser.(7) One way to manufacture Hall cell was introduced, and a Hall cell based onβ-FeSi₂/Si (100) thin film was finished, which was deposited and sintered at 500℃for 5 hours; the resistance ratio (ρ) and Hall coefficient (RH) were measured to be 8.28×10-3 cm and 4.3×10² cm³/coul by a PPMS (Physical Properties Measurement System), respectively. And more, another simple way for Hall coefficient measurement given matched results, also. The I -V characteristic curves ofβ-FeSi₂/Si (100) andβ-FeSi₂/Si (111) deposited at 500℃were measured by Keithley 2400 with a solar simulator; the photo voltage of the configuration forβ-FeSi₂/Si (100) andβ-FeSi₂/Si (111) were 0.22V and 0.25V, respectively.(8) The Synthesize of the polycrystalline Bi₄Ti₃O₁₂ thin films by femtosecond laser deposition on Si (111) wafers were present. The Bi₄Ti₃O₁₂ thin film deposited at room temperature (20℃) was highly c-axis-oriented; but the film deposited at 500℃was highly a-axis-oriented. A circuit with distributed constants of Bi₄Ti₃O₁₂/Si was introduced to interpret the relationship between the I-V characteristic curve and the Ferroelectric hysteresis loop of Bi₄Ti₃O₁₂ deposited on Si.