2007 NSTI Nanotechnology Conference and Trade Show - Nanotech 2007 - 10th Annual

Electric field induced self-assembled nanostructures in spray deposited nanocrystalline CdX and HgX(X= Se, Te) thin films

V. Dutta and A. RangaRao
Indian Institute of Technology Delhi, IN

Keywords:
nanorods, spray deposition, II-VI semiconductors

Abstract:
In this paper we report on electric field induced self assembled nanostructures in the spray deposited nanocrystalline CdX and HgX thin films. Nanoparticles of II-VI semiconductors (CdX, HgX; X= Se, Te) have been synthesized using Solvothermal method [3]. Thus prepared nanoparticles have been dispersed in 1-Butanol for spray solution, and the solution is sprayed on the glass substrates kept in air at 200oC. Deposition has been done without and with applying an external voltage (300V-3kV) to the nozzle and the metal electrode placed 2 mm below the nozzle [3, 4]. The films have been characterized for structural (Rigaku X-ray diffractometer) and morphological (SEM, TEM and HRTEM techniques) properties. The X-ray diffractograms of the CdSe films deposited without and with voltages show the hexagonal crystal structure with (002) as dominant peak. In case of CdTe, films deposited without voltage show the cubic crystal structure with (111) as dominant peak. Whereas, CdTe films deposited with voltages show the hexagonal crystal structure. In case of HgSe and HgTe films deposited without and with voltages show the cubic crystal structure. Electron microscopy (SEM and TEM) images of all the films deposited without voltage show the randomly distributed spherical particles. On the other hand, the films deposited under electric field show nano-rod structures. In case of CdSe, less voltage (300V) is needed to obtain the nanorod structures (diameters 20-50 nm). The diameter of the nanorods decreases with increase in the voltage and at the same time the length of the rods increased with increase in the applied voltage. In case of CdTe films deposited with voltages also show the formation of nanorods (diameters 20-100nm), but the nanorods formation taking place at higher voltages (>=700V). In case of HgSe and HgTe films under voltage show the formation of nano to submicron rods (300-600nm). The growth direction of the nanorods is analyzed by HRTEM studies, and is supported by the X-ray diffraction data. The difference in the dimensions of the nanorods is due to the difference in the ionicity of the materials under study. The role of ionicity in the creation of electric field induced self-assembled nanostructures has been discussed.

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