Papers by Author: J. Rouhi

Abstract: A simple method for fabricating lateral Si diodes with various gap widths were designed using the special properties of anisotropic TMAH wet etching and local anodic oxidation. The electrical performance of lateral diode was characterized using an HP4156c semiconductor parameter analyzer (SPA300HV, Agilent) at room temperature in a vacuum environment lower than 10^-8 Torr. The emission current from the silicon emitter cathode was measured as a function of the applied anode voltage. The effect of changing the anode-cathode gap was observed in the I-V characteristics, with a distinct reduction in the device turn-on with a decrease in the gap. For narrowed nanogaps from 55 nm to 35 nm, the turn-on voltage was decreased from 21 V to 16 V. Values of field enhancement factor β and emitting area A for different gap width were measured using Fowler-Nordheim plot. Our results indicate that β reduces and emitting area increases with increasing of gap width.

Abstract: In this study, the response surface methodology was utilized to optimize width of linear oxide for fabrication of Si oxide nanowires using local anodic oxidation lithography. A collection of experiments was designed using central composite design to evaluate the results statistically. The functional relationships were studied between the ambient humidity, applied voltage and tip speed as independent variables. Furthermore, a new approach was indicated by using design of experiment (DOE) to determine the significant parameters that affects on dimensional characteristics of the linear oxide. Numerical optimization was prepared by the DOE software to obtain the optimal conditions of parameters in order to perform the requirements as desired. These results indicate that the technique has a great potential for the fabrication of individual metal and semiconductor nanowires.

Abstract: In this study, ZnO nanocone arrays were grown on polycarbonate (PC) substrate using a voltage-assisted chemical bath deposition in a Zn (NO₃)₂ aqueous solution. To optimize the properties of ZnO nanorods grown on the PC substrate, the effects of current density were examined with respect to the morphological, structural, and photoluminescence properties of the nanorods. Field emission scanning electron microscopy and photoluminescence spectrum confirmed that ZnO nanorod arrays were vertically aligned with highly c-axis oriented, and the sample treated at 0.05 mA had the best crystallization among all samples. Based on the combined results of this study, the vertical ZnO nanocons produced on the PC substrate hold great promise for use in the development of flexible solar cell and other applications.

Abstract: The effect of various substrates on the morphology of ZnO nanorods synthesized by a low temperature solution method has been investigated. ZnO seed layers on the substrates were prepared by radio-frequency sputtering. ZnO nanorods have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM. FESEM results showed that hexagon-shaped ZnO nanorods with a diameter in the range of 30 nm to 80 nm and a length of about 1 μm were formed. The sharp (0002) peak in the XRD spectra indicates that the synthesized nanorods are single crystalline, grown along the [0001] direction. These findings have shown that the morphology of ZnO nanorods strongly depend on the substrate.