# A High-Performance Thin-Film Sensor in 6G for Remote Sensing of the Sea Surface
## 1 Introduction
Photoconductive detection, which is primarily used for single-photon detection, offers a higher response rate compared to thermal detection due to the smaller transfer rate of heat compared to electrical signals [26; 27]. However, photoconductive detectors suffer from a significant drawback of a relatively high dark current, which hampers their responsiveness and detection rate. Photovoltaic-type devices partially address the issue of high dark current but are limited in their ability to achieve highly sensitive detection and are challenging to use in imaging applications. The performance of the detector largely depends on the material used, which should possess high carrier mobility, specific resistance, and unique structures. Currently, THz detectors primarily rely on IIIA-VA and IVA group semiconductor materials, semi-metallic materials, graphene, and two-dimensional materials. However, conventional semiconductors like Si or Ge with lower carrier mobility cannot achieve higher sensitivity. Semi-metallic materials, although capable of achieving broadband detection, suffer from high dark currents, limiting their sensitivity. Graphene and two-dimensional materials, despite their thinness, exhibit high resistance and increased susceptibility to defects, resulting in photodetectors based on such materials with high noise and slow response speed. It is evident that the response rate and detection threshold of THz detectors are influenced by two crucial factors in the medium: the appropriate band gap (topology) and carrier mobility. Achieving high carrier mobility and selecting a suitable band gap are still significant challenges in enhancing detector performance. Currently, the development of THz detectors using new materials primarily concentrates on achieving micro-area responses in nanoscale sheet-like structures, while the production of large-area detectors at the millimeter scale remains limited [28; 29; 30]. A Te thin film is a chiral crystal composed of a single element, exhibiting an energy band structure typical of a conventional semiconductor. Notably, the film possesses intersections of non-interdigitated energy bands in its three-dimensional momentum space, which are protected by symmetry. These intersections give rise to Weyl points located near the band gap edge, which can be manipulated to induce various states of transport currents [31; 32; 33]. Consequently, the Te thin film serves as an ideal active layer for the fabrication of millimeter-scale detectors with effective detection areas. The performance of such detectors is heavily influenced by parameters such as the carrier mobility of the crystalline film, as well as its stability in complex environments. By annealing the Te film, we are able to crystallize it, significantly enhancing its detection capabilities. In our pursuit of advancing remote sensing technology for ocean water quality detection in the context of 6G technology, we focus on developing high-performance functional devices operating in the THz band. To this end, we have successfully prepared high-quality Te films over large areas and evaluated their detection performance in the THz band at room temperature. Additionally, we have investigated important properties such as the electromagnetic wave transmission rate and complex conductivity under different annealing conditions, thereby enhancing our understanding of the crystalline film's behavior. These findings establish crystalline films as excellent room-temperature THz detectors and demonstrate the feasibility of producing Te films in large quantities for this purpose. Our research contributes to the advancement of ocean remote sensing detection using 6G technology and furthers the development of this field.