Geçiş Metalleri ile Katkılanmış ZnO Nano Çubuk Sentezi ve I-V Karakterizasyonu
Özet
In this study, the optimum parameters was determined to synthesis zinc oxide (ZnO) nanorods. Also the effect of the size of the nanorods and the manganese doping on the electro-optical properties was investigated. The hydrotermal pressure cell and the system which were used to synthesise the samples were designed and manufactured by our laboratory. Optimum conditions were determined by changing the core size, time, temperature and solution molarity for the hydrothermal method. ZnO thin films were coated on the surface of the Si (100) substrate at different thicknesses (100, 150 and 200 nm) and these substrates were annealed at 350 and 400 ° C. The optimum temperature was determined as 350 ° C (Figure 4.1). To determine the molarity of the solution to be used, aqueous solutions of hexamethylenetetramine (HMT) and zinc nitrate hexahydrate compounds of 0.05 and 0.1 M were prepared. Experiments using these aqueous solutions showed that the optimum molarity value is 0.05 M (Figure 4.2). Experiments were carried out at temperatures of 70, 80 and 90 ° C and 2, 4, 6 and 8 hours to understand the effect of reaction temperature and experiment time on the formation of ZnO nanorods. SEM images were used to obtain the appropriate temperature and time to synthesis the ZnO nanorods with the hydrothermal method (Figure 4.3) (Figure 4.4). As a result of these experiments, the annealing temperature, solution molarity, reaction temperature and experiment time were determined as 350 °C, 0.05 M, 90 °C and 4 hours respectively. Under optimum conditions experiments were carried out using ZnO thin film coated substrates of 100, 150 and 200 nm thickness. X-ray powder diffraction measurements were used to determine the structure of the films. The morphology of the films revealed from the SEM images. As seen from the SEM images with the increasing coating thickness, diameter/length ratio was decreased (Table 4.1). I-V measurements were done by using four probe method. These measurements showed that under 1.2 V excitation voltage with the decrease in diameter / length ratio, the dark current increased from 2.31x10-8 A to 3.60x10-6 A and the photocurrent increased from 2,18x10-7 A to 1,28x10-5 A. Manganese chloride compound was used for Mn doping. New aqueous solutions were prepared with adding manganese chloride 5% of the zinc nitrate hexahydrate by mass to the aqueous solution. The synthesis of Mn / ZnO nanorods was carried out under optimum conditions as previously determined. Structural analyzes of the samples were performed by XRD, XPS and SEM measurements. The current voltage measurements were carried out by the four-point method same as the undoped samples. From these measurement one can see that with the manganese doping the both the dark and photo currents were increased. The dark currents increased from 7,12x10-8 A to 5,75x10-6 A and the photo currents increased from 2,97x10-7 A to 6,45x10-5 A ass seen from the results.
