Optical characterization of layer semiconductors by thermoreflectance modulation technique
| Autor: | Hong-Wen Li, 李宏文 |
|---|---|
| Rok vydání: | 2004 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 92 Modulation spectroscopy is a powerful characterization tool of semiconductors. In this article, we present a practical design for implementing the thermoreflectance (TR) measurements more effective. Detailed design diagrams of the electronic circuits containing operational amplifier、n-type MOSFT and 1Ω/10Watt high power resistor are described. The three components are connected in a negative feedback configuration to form an adjustable constant current source. Glass substrate is used as a heat sink, which is evaporated with a winding path of aluminium tracks as the heating element. The heated pulses of low frequency and long duty cycle seem to be more efficient in the periodic thermal perturbation of the layered crystals. Polarization sensitive behavior of the band-edge transitions in ReS2 and ReSe2 layered compounds was studied using polarized-transmission and polarized-thermoreflectance (PTR) measurements with the polarization angles from q = 0° (E b-axis) to q = 90° (E ^ b-axis) at 300 K. Polarization dependence of the polarized energy gaps of ReS2 and ReSe2 simultaneously shows a sinusoidal-like variation with respect to the angular change of the linearly polarized lights. The polarized transition intensities of the band-edge excitons ( E1 andE2 ) of ReX2 (X=S, Se) demonstrate a sinusoidal variation with respect to the angular change of the linearly polarized lights. Angular dependence of the polarized transition probabilities of E1 and E2 is analyzed. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|