Development of ZnO/Ta 2 O 5 heterojunction using low-temperature technological processes
- PDF / 378,850 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 101 Downloads / 206 Views
Development of ZnO/Ta2O5 heterojunction using low-temperature technological processes R. Baca1, J. A. Andraca1, M. G. Arellano1, G. R. Paredes1 and R. P. Sierra1 1 CINVESTAV IPN, Av. Instituto Politécnico Nacional No. 2508, D.F., C.P. 7360, México. ABSTRACT ZnO/Ta2O5 heterojunctions were formed on glass substrates using low temperature processes. Formerly insulating Ta2O5 films were deposited on glass substrates by vacuum evaporation using Ta2O5 powder, Afterwards transparent and conductive ZnO films were formed on the Ta2O5 films by thermal oxidation at 3200C in air atmosphere of zinc (Zn) films deposited by dc sputtering process. Structural and optical properties of ZnO were investigated by X-ray diffraction (XRD) and photoluminescence (PL). The Ta2O5 insulating films were characterized by Raman scattering. The ZnO/Ta2O5 heterojunction was characterized by current-voltage measurements at room temperature as well as transient response under a rectangular-pulse voltage source. The electrical and the transient response suggest that the ZnO/Ta2O5 heterojunction is a potential alternative for the fabrication of alternating-current-driven thin film electroluminescent (ACTFEL) devices. INTRODUCTION Although alternating current thin-film electroluminescent (ACTFEL) devices have been the subject of considerable study over the past 3 decades, challenges remain [1]. ZnS has been studied as a blue emission material, but S is easily dissociated. This property causes the material to have the short durability, which plays a role in undermining the light emission property of ACTFEL devices [2]. Zinc oxide (ZnO) is one of the most remarkable materials, for it has a large band gap of 3.3eV as well as a free exciton energy of 60meV at room temperature [3]. The origin of electroluminescence in ZnO based thin-film electroluminescent devices is the result of the recombination of electron-hole pairs produced by the impact of hot electrons, in order to produce devices with high structural stability [4]. Tantalum pentoxide (Ta2O5) has a dielectric constant of 25, and seems to be the most promising candidate because of its high dielectric constant, thermal stability and adequate breakdown voltage [5, 6]. In this paper, we demonstrate the realization of ZnO/Ta2O5 heterojunction with Ta2O5 films by vacuum evaporation of tantalum powder and annealing in air atmosphere, followed by ZnO films deposited using dc sputtering and thermal oxidation in air atmosphere at a low temperature (3200C). In addition, structural and optical characteristics of ZnO films are obtained by XRD and PL. Structural characterization of Ta2O5 films by Raman studies has been obtained. EXPERIMENTAL PROCEDURE Figure 1 shows the schematic diagram of the proposed ZnO/Ta2O5 heterojunction. Ta2O5 thin films of 150nm were grown on glass substrates by vacuum evaporation of tantalum oxide powder (99.99% of purity) and annealed in air atmosphere at 3200C for 10min. On Ta2O5 films,
Zn films were deposited by dc sputtering from Zn target of 99.999% in purity under a pressure of 9
Data Loading...
