| Terahertz (THz) radiation, which covers the frequency range from 1011 Hz to 1013 Hz, has unique characteristics like typical narrow pulse width in the order of picoseconds and low photon energy. It lead to a promising future of applications in various fields such as high-speed communications, radar, astronomy, medical science, non-destructive evaluation and security control. Due to the lack of coherent high-powered THz sources with narrow linewidth at THz frequencies, THz technology has developed quite slowly in early years.High temperature superconductor (HTS) Bi2Sr2CaCuO8+δ (BSCCO) intrinsic Josephson junctions (IJJ) stack can emit frequency-tunable, continuous terahertz radiations under the DC bias condition. Research on the spatial distribution of radiation can help to understand the radiation mechanism.Klemm etc., proposed a dual-source model to explain the resonant mode of mesa-structured BSCCO sample when it was emitting. The relation between radiation power and spatial angle obtained with primitive manual testing method shows relatively discrete data. Thus, convincing conclusions can’t been drawing from these results.Due to the excellent frequency tunable characteristics of HTS BSCCO THz sources, the relevant studies have become an important emerging field. At the same time, materials industry and relative applications on basis of the semiconductor also confront great opportunities for development. In recent years, the development of low-cost, low-weight and high efficiency solar cells have attracted a lot of interests, because of the challenge to energy crisis and environmental pollution. The majority of solar cell modules are based on expensive crystalline Si. To reduce the cost of manufacturing, a new generation of Si thin film solar cells has been proposed and realized. However the low photoelectric conversion efficiency of this Si thin film still limits the utilization of optical energy. Therefore, developing a new generation of thin film Si solar cells which can enhance the photoelectric conversion efficiency while preserving low fabrication cost is considered as a promising way.The surface state is one of the key physical parameters in semiconductors, particularly important to Si nanowires (SiNWs) solar cells. As it’s difficult to distinguish the surface defects of solar cells, numerous microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscope (TEM) have been applied to study local variations in PV performance. But most of the microscopes can only get the information of surface morphology, but not the photoelectric response at the same time. Thus, to develop a system based on intrinsic laser source for nondestructive characterization of NWs solar cell is one of the effective means.The thesis is to study the far field spatial distribution of terahertz emission from HTS BSCCO THz solid-state sources and characterization of solar cells of silicon nanowires. The main contents contain the following two aspects:(1) We set up a rotating cryogenic measuring system which can realize real-time control and data acquisition through LabVIEW program. The sample stage can continuously rotate within 360° range and the rotational accuracy is better than 1 degree at low temperature. The radiation power of each angle was detected automatically and power angle-resolved images were drawn. This system will not only contribute to the research on terahertz radiation, but also benefit the study of properties of various superconducting devices.(2) In this paper, we also developed a room temperature scanning photoelectric microscope. A laser with wavelength of 637 nm was used to detect the SiNWs solar cells nondestructively. We focused on the research of its surface defects and optical conversion efficiency. LabVIEW program was used to achieve real-time control and data acquisition. The development of this system, which occupies fast scanning speed, will contribute to the research on light-sensitive material at room temperature. |
PDF Full Text Request