Papers by Keyword: EBL

Abstract: A simple method for the fabrication of silicon nanowires using Electron Beam Lithography (EBL) combined with thermal oxidation size reduction method is presented. EBL is used to define the initial silicon nanowires of dimensions approximately 100 nm. Size-reduction method is employed for reaching true nanoscale of dimensions approximately 20 nm. Dry oxidation of silicon is well investigated process for self-limited size-reduction of silicon nanowires. In this paper, successful size reduction of silicon nanowires is presented and surface topography characterizations using Atomic Force Microscopy (AFM) are reported.

Abstract: MgZnO thin films are proposed as a new dielectric material for 1 GHz monolithic microwave integrated circuit (MMIC) applications. The high permittivity of this material enables size reduction; furthermore this can be fabricated using a low cost processing method. In this work, MgZnO/Pt/Si thin films were synthesized using a sol-gel spin coating method. The samples were annealed at various temperatures with the effects on physical and electrical properties investigated at direct current (DC) and high frequencies. The physical properties of MgZnO thin film were analyzed using X-Ray diffraction, with the improvements shown in crystalline structure and grain size with increasing temperature up to 700 °C. DC resistivity of 77 Ωcm at higher annealing temperature obtained using a four point probe station. In order to prove the feasibility at high frequencies, a test structure consisting of a 50 Ω transmission line and capacitors with 50 × 50 μm electrode area were patterned on the films using electron beam lithography. The radio frequency (RF) properties were measured using a Wiltron 37269A vector network analyzer and Cascade Microtech on-wafer probes measured over a frequency range of 0.5 to 3 GHz. The dielectric constant, loss tangent and return loss, S₁₁ improve with the increment annealing temperature. The dielectric constant was found to be 18.8, with loss tangent of 0.02 at 1 GHz. These give a corresponding size reduction of ten times compared to conventional dielectrics, silicon nitride (Si₃N₄). These indicate that the material is suitable to be implemented as a new dielectric material for 1GHz MMIC applications.

Abstract: We report on investigation of the AC dielectrophoresis aligned assembly deposition (DAAD) of gallium nitride nanowires (GaN NWs) with both the variation of the electric field and the frequency. Our DAAD methods were used to align and manipulate GaN nanowires as well as to extract the electrical properties of semiconducting nanowires. We observed that the ability of the alignment strongly depends on the magnitude of the AC electric field and frequencies. For the higher AC peak-to-peak electric fields (up to 20 Vp-p), the GaN nanowires have a better alignment across the patterned Ti / Au electrodes with a high yield rate of ~ 90% over the entire arrays (in our case, 20 arrays) in the chip at the 20 kHz. From the transport measurements of our AC aligned GaN nanowires using conventional three-probe schemes in field-effect transistor structures, we found that the conductance of the GaN NWs increased for gating voltage greater than zero and decreased for gating voltage less than zero, indicating these GaN nanowires have n-type dopants.