Structural and optical properties of CdSe, CdTe and CdSeTe nanoparticles dispersed in SiO 2 films
- PDF / 193,571 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 71 Downloads / 252 Views
N1.8.1
Structural and optical properties of CdSe, CdTe and CdSeTe nanoparticles dispersed in SiO2 films P. Babu Dayal *1, N. V. Rama Rao1, B. R. Mehta 1, S. M. Shivaprasad 2 and P. D. Paulson 3 1 Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi-16, India. 2 Surface Physics Group, National Physical Laboratory, New Delhi-42, India. 3 Institute of Energy Conversion, University of Delaware, Newark, USA.
Abstract CdSexTe1-x nanoparticles (with different stoichiometry ratio x) dispersed in silicon dioxide films have been grown by magnetron sputtering technique followed by thermal annealing. Effect of thermal annealing conditions on the structural, compositional, optical and electronic properties of nanoparticles has been studied using GAXRD, XPS, TEM, and spectroscopic ellipsometry techniques. A structural transformation in the nanoparticle core mediated purely by surface layer effects in the case of CdTe and a spontaneous self-organization of nanoparticles into nanorods in the case of CdSe via fractal growth has been observed. Preliminary observations from the ellipsometry measurements carried out on some of these nanoparticle films shows a blue shift of absorption edge. Introduction: Electronic and optical properties of semiconductor nanoparticles can be controlled by varying size, shape and surface layers [1-4]. In recent years, chacogenide semiconductor nanoparticles have attracted considerable attention due to remarkable electronic response and ultra-fast optical gain [5-9]. In the case of semiconductor nanoparticles dispersed in glass matrix, the transparent glass matrix provides an effective way of maintaining the individual nanoparticle characteristics and preserving the surface structure [10-13]. This is advantageous in comparison to chemically capped or nanoparticles dispersed in polymeric materials [14]. Although sizedependent properties of semiconductor nanoparticles of I-VII, II-VI, III-V and IV groups in glass matrix have been widely reported [15-16], the synthesis parameters used for controlling size also effect the composition of binary or ternary phases. This is especially important as different elements (Cd, Se and Te) have widely varying vapor pressure and diffusion co-efficient in the glass matrix. Thus it is difficult to control nanoparticle size, without varying the composition or surface structure. To some extent, this problem has been circumvented by using elemental Cd, Se and Te along with SiO2 targets for growing binary and ternary CdSexTe1-x semiconductor nanoparticles in glass films by keeping the area of elemental targets in proportion to the sputtering yield. This method of making semiconductor nanoparticles using elemental targets seems to be superior in comparison to conventional melting and quenching techniques [17]. The central objective of this study is to give an overview of the results of the structural, compositional, optical, and electronic characterization of CdSexTe1-x nanoparticles dispersed in SiO2films prepared by the above method.
Data Loading...
