3D Microstructured Frequency Selective Surface Based on Carbonized Polyimide Films for Terahertz Applications

Abstract

In recent years, frequency selective surface (FSS)‐based two‐dimensional (2D) and three‐dimensional (3D) carbon materials such as carbon nanofibers, carbon nanotubes, and carbon‐filled filaments are essential tools to design millimeter‐wave radomes, absorbers, electromagnetic interference (EMI) shielding, and antenna reflectors in gigahertz (GHz) regimes. Terahertz (THz) technologies are gaining attentions from medical imaging to security surveillance. In this work, a 3D microstructured FSS using carbon‐based polyimide as a precursor to enhance the resonant frequency at the THz range. Furthermore, gold nanoparticles (AuNPs) are embedded on 3D microsturctured carbonized polyimide (3D‐CPI) film to improve their FSS property through plasmonic effects. From the time domain spectroscopy measurements, 3D‐CPI FSS film shows band‐stop filter properties in the frequency range of 0.5–1.5 THz and with a maximum return loss (RL) of 40.5 dB (at the resonant frequency of 1 THz). The 3D‐CPI/AuNPs film demonstrates the highest RL of 43.7 dB at the higher excitation resonance frequency ≈1.06 THz due to the interaction of plasmonic electrons with scattered delocalized electrons in carbon, which induces the mechanisms for EMI shielding. The results will open insight into 3D plasmonic carbon microstructures as an EMI shielding material at THz frequency.

3D Architectural MXene‐based Composite Films for Stealth Terahertz Electromagnetic Interference Shielding Performance

“…The observed peaks of the polyimide phase at 720, 1365, 1778, and 1717 cm −1 correspond to C═O bending during the formation of the imide ring while preparing the PI solution, C─N stretching, C═O asymmetric stretching, and symmetric stretching, respectively . [1] For all the composite films with different PI/MXene ratios, we observed the characteristic transmittance peaks of MXene (Ti 3 C 2 T x ) at 550, 1200, and 2400 cm −1 relating to Ti─O, Ti─O─C, and C─H bond vibrations, respectively. As shown in Figure 1c, Raman spectroscopy reveals the presence of characteristic Ti 3 C 2 T x (E 1 g mode at 156 cm −1 and E g mode at 400 cm −1 ) peaks and carbon (D band at 1352 cm −1 and G band at 1579 cm −1 ) peaks in all the composite samples.…”

“…The skin depth under the surface of a conductor is the depth at which the electric field's strength drops to (1/e) of the incident strength. The skin depth is calculated using Equation (1).…”

“…The terahertz frequency band of 0.1-10 THz in the electromagnetic (EM) spectrum is gaining interest in frontier applications such as security screeners, radar systems, optoelectronic devices, and the development of future wireless communication. [1][2][3][4] According to previous reports, traditional EMI shielding materials can be divided into two main categories, namely, i) metals and metal matrix composites (MMCs) and ii) polymer-carbonbased composites. [4,9] However, the main drawbacks of metals and MMCs are their high specific weight, high density of defects, susceptibility to oxidation and corrosion, high cost, and low flexibility.…”

“…[3,9] In general, EMI shielding with frequency selective surface (FSS) is a popular design strategy for achieving strong shielding efficiency in the specific resonance bandwidth frequency. [1,14] Recently Hlaing et al [1] designed a carbon-based 3D pyramidal periodic architecture for improved FSS terahertz shielding with plasmonic enhancements. Choi et al [14] developed a slot antenna array filled with MXenes that achieved a strong resonance at specific frequencies in the terahertz frequency regime.…”

Lightweight MXene-Based Hybrid Aerogels with Ultrabroadband Terahertz Absorption and Anisotropic Strain Sensitivity

“…Naturally, the exploration of the MXene-based 3D network structure expands to THz, leading to a critical branch of the THz absorber, ranging from MXene to magnetic metal/MXene-based sponges/foams. As usually studied in the language of electromagnetic interference (EMI), the absorption shielding effectiveness and absolute absorption of these composites have achieved remarkable values, ,,− e.g., 42.7 dB and 99.9% between 0.1 and 2.2 THz for the reported 3D Ni/MXene decorated polyurethane sponge composites at 1 mm thickness . Unfortunately, their structure, strength, and flexibility are still limited, owing to the weak interactions between rigid MXene flakes and the large pore/wall size for broadband absorption, i.e., ∼100 μm.…”