پیاده سازی تصحیح اثر نزدیکی پرتو E با استفاده از روش برنامه ریزی خطی برای ساخت نامتقارن آنتن پاپیونمانند

Asymmetric nano-bow-tie antennas offer the possibility of direct light-to-electrical energy conversion. These nano-antennas are easily integrated with Metal-Insulator-Metal (MIM) tunnel junctions in between the antenna segments for the purpose of coupled signal rectification. The architecture of the tunnel junction together with the antenna size precision require nano-scale patterning accuracy. Electron Beam Lithography (EBL) is used for patterning purposes. In this paper Proximity Effect (PE), a very common resolution problem in EBL, is reduced by a dose modulation technique employing linear programming (LP) algorithms. Production of tightly controlled antenna segment dimensions is achieved in conjunction with a small area tip and a small tunnel junction gap. It is expected that precise control of the gap geometry will enhance detection speed, enabling the utilization of the device for the visible range energy harvest purposes.

Advancements in nanometer-scale patterning have enabled new device technologies. Researchers, inspired by radio-frequency antennas, have paid great attention to nano-sized optical antennas for the direct rectification of visible and infrared light. The asymmetric bow-tie optical antenna is an example of such a structure. It offers great advantages, as it is a relatively broad band antenna with low polarization dependence. However, since the architecture of this device requires high patterning accuracy, its fabrication represents a significant obstacle. In this paper, we focus on the fabrication of asymmetric bow-tie optical antennas using E-Beam Lithography (EBL) techniques and we aim to improve the resolution of this technique by correcting Proximity Effects (PE) through dose modulation guided by Linear Programming (LP) algorithms. Another advantage of the bow-tie structure is the ease with which a rectifying element (a Metal-Insulator-Metal, or MIM diode) can be integrated directly into the antenna. This is shown in Fig. 1. The structure is geometrically asymmetric, as we have shown in other publication, this property of the device contributes to the field enhancement at the junction and yields a higher tunnel current [1]. The conducting parts of the junction are formed by the metal antenna sections and the barrier is the gap in between the antenna parts. Full-size image (5 K) Fig. 1. Schematic of asymmetric bow-tie antenna. Figure options The most important prerequisite for success in infrared (IR) and visible light detection is that the response time must be faster than one cycle of the wave to be detected. The tunneling mechanism does not restrict the device speed because its cut-off frequency is much higher than the wave frequency. However, since the distance between the conductors affects the tunneling probability, it is necessary to keep the junction gap small (⩽5 nm) for a high rectification efficiency. On the other hand, the equivalent circuit of this device has a junction capacitor across the barrier (CD) and an antenna resistor (RA) in series with the junction capacitance. These elements introduce a time constant and define the cut-off frequency limit. It is clear that in order to assure a high cut-off frequency (or, equivalently, a fast response time) a small junction capacitance and a small resistance are required.

In this work, we focused on the fabrication of asymmetric bow-tie antennas. One of the crucial components of bow-tie antennas is the nano-size gap between the antenna sections. Due to PE, the creation of a such small gap represents the biggest fabrication challenge. It was not possible to create a nano-scale gap without PEC. A dose modulation technique that utilizes linear optimization methods in order to correct Proximity Effects was used for our applications. We were able to fabricate structures with gap sizes up to 2 nm using PEC techniques while maintaining predetermined antenna dimensions. This unique approach, which enables the fine control of the gap size, opens the way for the implementation of the device for energy harvest purposes in the IR and visible range.