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A magnetron co-sputtering system was used for producing nickel-doped Ge2Sb2Te5 (GST-Ni) thin films. The nickel content in the thin film was adjusted by the ratio of the plasma discharge power applied to the GST and nickel targets, as well as a physical shuttering technique to further control the nickel deposition rate. The doping concentration of the film was con firmed using Energy Dispersion Spectroscopy (EDS) technique. Results from a four-point probe measurement indicate that the nickel doping can reduce the resistivity of GST in the amorphous state by nearly three orders of magnitude. The dopant's influence on crystallization behavior was studied by analyzing X-Ray Diffraction (XRD) patterns of the pure GST and GST-Ni at different annealing temperatures. To examine the structural changes due to the nickel dopant, the thin films were investigated with the aid of Raman scattering. Additionally, we extracted the optical constants for both the amorphous and crystalline states of undoped-GST and GST-Ni films by ellipsometry. The results indicate that at low doping concentrations nickel does not appreciably affect the optical constants, but dramatically improves the electrical conductivity. Therefore, nickel-doping of GST a viable method for designing optical devices for lower operating voltages at higher switching speeds.
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Pump-probe microscopy in a Sagnac interferometer
An interferometric pump-probe microscope with two counterpropagating probe beams is developed and characterized. Application of the technique to a porphyrin derivative thin film shows that the technique is sensitive to variations in local film morphology that are undetectable with conventional pump-probe techniques. Analysis of the material response shows that the technique enhances signal levels measuring transient changes in the optical constants, limited by the asymmetry of the probe beam beamsplitter. The technique also provides the ability to distinguish contributions to the overall pump-probe response from changes to the real and imaginary components of the optical constants.
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- Award ID(s):
- 2016360
- PAR ID:
- 10657273
- Publisher / Repository:
- Optica
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 50
- Issue:
- 23
- ISSN:
- 0146-9592
- Page Range / eLocation ID:
- 7404
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1364/OL.580950
