Synthesis Of ZnO And Inn Nanomaterials And Study On The Terahertz Detector Based On Single ZnO Nanowire

Terahertz(THz) photon, the corresponding energy is ranged from 0.41 to 41.4me V, which locates in millimeter wave and infrared wave, is one of promising technologies for characterization and operation of materials due to matching with the low frequency of elementally vibrate and roll energy. At present, great efforts have made to improve the THz detection signal. In this dissertation, we performed an in-depth investigation on the synthesis, device fabrication and terahertz response measurement of high mobility single nanowire Zn O FET, the results can be listed as follows:(1) The basic knowledge of Zn O and In N materials, including physical,optical, and electrical properties, the basic preparation methods and corresponding applications, are introduced; Nanomaterials and nanosemiconductor devices at home and abroad are reviewed.(2) Zn O nanostructures including nanorod, nanowire, nanocomb, tripod-liked nanostructures, nanoarray and hedgehog-like nanostructures have been grown on substrate by chemical vapor deposition. The morphology and structure of the products were characterized by scanning electron microscopy, X-ray diffraction,Raman spectroscopy, as well as transmission electron microscopy, which reveals a structurally perfect surface, and unambiguously resolves the(002) atomic planes of wurtzite-structured Zn O with an inter-plane spacing of ca. 0.25 nm through the whole length of the nanowire. The TEM study also further confirmed the outstanding single-crystalline nature and the preferential [001] direction growth of the side-growing nanowire. The optical quality of Zn O nanostructures were characterized by photoluminescence spectra, indicating that the strong emission peak at 380 nm can be observed. It is attributed to the near band edge emission of the wide band gap Zn O. The almost negligible green bands indicate a very low concentration of oxygen vacancies and other defects in Zn O. The growth mechanism of the hedgehog-like Zn O nanostructures was studied. It revealed a three-step process during the entire growth. Finally, the roomtemperature photoluminescence spectra of Zn O hedgehog-like nanostructures showed that the center excitation would render much stronger photoluminescence emission intensity. The photoluminescence intensity at the nuclei is 14 times stronger than the edge position. Furthermore, simulation results indicated that the enhanced emission came from light-trapping-induced excitation light field enhancement. It is seen that the centerexcitation will render much stronger light field inside the hedgehog-like structures by more than five times, and this will boost the PL emission intensity accordingly.(3) With single Zn O nanowires dissolved in solution were randomly dispersed on a 400 μm thick high resistivity p-Si substrate with a 300 nm thick Si O2 insulating layer, field effect transistors were successfully fabricated by focused ion beam(FIB) technique. The morphology of the single Zn O nanowire field effect transistor was characterized by scanning electron microscopy. The optical quality of target Zn O nanowire were characterized by photoluminescence spectra,indicating that the strong emission peak at 380 nm can be observed. It is attributed to the near band edge emission of the wide band gap Zn O. The almost negligible green bands indicate a very low concentration of oxygen vacancies and other defects in Zn O. Electrical transport measurements demonstrated that the nanowire had good transfer characteristics and fairly high electron mobility.The electron concentration was calculated to be 8.1 × 1017cm-3, and the field effect mobility of 220 cm2/Vs was achieved.(4) It is shown that single Zn O nanowire can be used as terahertz detectors based on a one-dimensional plasmon detection configuration. Clear terahertz wave(~0.3 THz) induced photovoltages were obtained at room temperature under 800 μW power value,which rendered 34 m V/W peak responsivity at room temperature. The maximum of the responsivity curve coincides with the threshold voltage ~-9 V. This behavior of the response was predicted by the Theory. The operating mechanism of a FET detector is discussed in detail. The standard uncertainty of the maximum responsivities of ~34 m V/W can be calculated as 0.24, suggests that the estimated responsivity is with reasonable accuracy. The long-term stability and reproducibility of the detector was characterized. Further analysis showed that the terahertz photoresponse is closelyrelated to the high electron mobility of the Zn O nanowire sample, which suggests that oxide nanoelectronics may find useful terahertz applications.(5) In N nanostructures including nanowire, nanonecklace and nanoleaf structures have been grown on substrate by chemical vapor deposition process with 60 nm gold colloid catalytic. The morphology and structure of the products were characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, as well as transmission electron microscopy. Room temperature photoluminescence spectra of the three nanostructures showed near band edge emissions around 0.73 e V. By using Win X-morph Software on the basis of the The BFDH growth rate equation according to the Wulff construction rule, it can be determined that the crystal unit of the In N nanonecklace. Finally, the growth mechanism of the In N nanonecklace was studied and a three-step process was suggested for the growth.