Periodic Reporting for period 1 - 3D-AM-TERA (3D architectures of Mxenes for Terahertz Applications)
Periodo di rendicontazione: 2022-02-01 al 2024-01-31
Terahertz (THz) technology has been used for almost two decades for investigations of nanomaterials, including nanocrystals, nanoparticles, nanowires, nanotubes, or 2D crystals. Detecting and manipulating the THz radiation is of high interest for medical imaging, security checks, quality control, nano- and opto-electronic devices, atmospheric and space chemistry, etc. The current THz detector technology, however, often lacks good sensitivity, speed, spectral range, or room-temperature operation. The work being carried out addressed our understanding of this subject in two areas on which we focused synergistically. The first relates to the development of engineered materials and structures from 2D MXene to 3D graphene, which represents a new way to build materials with novel properties, particularly in the THz electromagnetic wave range. The second is on the use of materials as device, such as THz photodetector and modulator.
Terahertz technology lies at the heart of modern technology for its potential applications in spectroscopy, imaging, and wireless communications. The terahertz wave is easily transmitted through most non-metallic and non-polar media because its photon energy is so low; for this reason, it also poses no threat to human health. Therefore, detecting and manipulating the THz radiation is of high interest for different applications. The materials and structures developed in this project (MXene sheets & Graphene aerogels) are desirable and are expected to promote THz light absorption and modulation properties. By using a low-cost technique, we were able to create an MXene THz photodetector with precise detectivity, good responsivity, and a consistent, fast photoswitching response. It is proven that a straintronic modulator based on 3D graphene can modulate THz radiation absorption and reflection in real-time over a broad range of 0.1–3 THz. These findings open up a world of hitherto undiscovered physical phenomena with enormous promise for radar, electromagnetic, and THz imaging applications.
To address the conception of novel devices made of MXene sheets with enhanced light-matter interaction, we designed a structural architecture of MXene which populates the sample interaction area with specifically arranged 2D sheets (by multilayer and few-layer arrangements) where the THz light is exposed to every atom. This made it possible for the complete photoactive assembly to absorb as many photons as possible, resulting in the highest possible generation of photocurrent. A 3D graphene straintronic approach for real-time THz modulation allows on-demand tuning between electromagnetic shielding and stealth in a single device. This multifunctional dynamic modulator uses strain-induced changes in atomic bond configurations, enabling efficient THz radiation absorption, reflection, and transmission, offering vast potential for advanced applications.
Terahertz technology lies at the heart of modern technology for its potential applications in spectroscopy, imaging, and wireless communications. The terahertz wave is easily transmitted through most non-metallic and non-polar media because its photon energy is so low; for this reason, it also poses no threat to human health. Therefore, detecting and manipulating the THz radiation is of high interest for different applications. The materials and structures developed in this project (MXene sheets & Graphene aerogels) are desirable and are expected to promote THz light absorption and modulation properties. By using a low-cost technique, we were able to create an MXene THz photodetector with precise detectivity, good responsivity, and a consistent, fast photoswitching response. It is proven that a straintronic modulator based on 3D graphene can modulate THz radiation absorption and reflection in real-time over a broad range of 0.1–3 THz. These findings open up a world of hitherto undiscovered physical phenomena with enormous promise for radar, electromagnetic, and THz imaging applications.
To address the conception of novel devices made of MXene sheets with enhanced light-matter interaction, we designed a structural architecture of MXene which populates the sample interaction area with specifically arranged 2D sheets (by multilayer and few-layer arrangements) where the THz light is exposed to every atom. This made it possible for the complete photoactive assembly to absorb as many photons as possible, resulting in the highest possible generation of photocurrent. A 3D graphene straintronic approach for real-time THz modulation allows on-demand tuning between electromagnetic shielding and stealth in a single device. This multifunctional dynamic modulator uses strain-induced changes in atomic bond configurations, enabling efficient THz radiation absorption, reflection, and transmission, offering vast potential for advanced applications.
We embark on a systematic investigation of the steady-state and ultrafast photo-induced THz response of Ti3C2Tx MXene in multi-layer and few-layer forms. Akin to 2D graphene, Ti3C2Tx MXenes are stacks of 2D layers, typically produced by top-down wet-chemical root by selectively etching out the Al layers from its parent MAX phase (Ti3AlC2). In addition, we involved for the first time a comparative study with the charge carrier transport in the original Ti3AlC2 (MAX) phase films as fabricated by pulsed laser deposition. MAX confirms band-like charge transport by displaying the free charge Drude response. However, the THz spectra of MXene are understood in terms of the modified Drude-Smith model, which introduces a drift-diffusion current restoring the thermal equilibrium in systems without translational invariance due to, e.g. energy barriers. The ultrafast photoconductivity in MAX has a long-lived nanosecond component after a brief sub-ps fast component. In contrast, the photoconductivity in MXenes shows a long-lived negative contribution (induced transparency) and the ultrafast component is absent.
From a technical perspective, developing methods to engineer the electronic and optical properties of MXene films will push them towards new technologies such as flexible transparent electrodes, electromagnetic interference shielding, THz detectors and modulators, and others. We followed the thermal evaporation deposition technique for the deposition of interdigital gold electrodes to fabricated two-terminal, planar photodetectors with channel length and width defined by the shadow mask of 500 and 50 μm, respectively. Our photodetector can detect incident THz field power over a wide range with a good responsivity, precise detectivity, and fast photoswitching behavior. 2D sheets often undergo van der Waals layer restacking during device fabrication, affecting their physical properties. A 3D architecture promotes light absorption and introduces a new dimension for controlling light-matter interaction due to volumetric light confinement.
We also looked into the dynamics of charge carriers in the three-dimensional graphene aerogel structures. It is shown that the annealing temperature can be used to advantageously control the defect density, the charge transport efficiency in graphene aerogels and, consequently, to modulate the THz opto-electronic properties of the structures. Because of the presence of shallow states, higher annealing temperatures increase the high-frequency hopping contribution as well as the Drude conductivity. The results on ultrafast time scale demonstrate that the Drude photoconductivity of photoexcited samples decays very quickly in less than 1 ps. Based on spectroscopic results, we developed a novel broadband dynamic THz modulating technology, which makes use of 3D graphene straintronics with a significant tunability between shielding and absorption features by the strain in the structure. We demonstrate that the properties of the THz straintronic modulator can be dynamically tuned at kHz frequency.
We have followed the Horizon 2020 Open Access policy for publication of the results. Two research papers were published in open-access journals (Nanoscale Advances and Advanced Electronic Materials) and two manuscripts are under preparation on Terahertz charge transport in the structural architecture of MXene and the second one on TiO2 doped 3D Graphene. I have presented the research findings at three international conferences and one national conference. I have given two presentations in the department: one at the Young Scientist Meet Talk Series and the other as a part of the Department Seminar Series.
From a technical perspective, developing methods to engineer the electronic and optical properties of MXene films will push them towards new technologies such as flexible transparent electrodes, electromagnetic interference shielding, THz detectors and modulators, and others. We followed the thermal evaporation deposition technique for the deposition of interdigital gold electrodes to fabricated two-terminal, planar photodetectors with channel length and width defined by the shadow mask of 500 and 50 μm, respectively. Our photodetector can detect incident THz field power over a wide range with a good responsivity, precise detectivity, and fast photoswitching behavior. 2D sheets often undergo van der Waals layer restacking during device fabrication, affecting their physical properties. A 3D architecture promotes light absorption and introduces a new dimension for controlling light-matter interaction due to volumetric light confinement.
We also looked into the dynamics of charge carriers in the three-dimensional graphene aerogel structures. It is shown that the annealing temperature can be used to advantageously control the defect density, the charge transport efficiency in graphene aerogels and, consequently, to modulate the THz opto-electronic properties of the structures. Because of the presence of shallow states, higher annealing temperatures increase the high-frequency hopping contribution as well as the Drude conductivity. The results on ultrafast time scale demonstrate that the Drude photoconductivity of photoexcited samples decays very quickly in less than 1 ps. Based on spectroscopic results, we developed a novel broadband dynamic THz modulating technology, which makes use of 3D graphene straintronics with a significant tunability between shielding and absorption features by the strain in the structure. We demonstrate that the properties of the THz straintronic modulator can be dynamically tuned at kHz frequency.
We have followed the Horizon 2020 Open Access policy for publication of the results. Two research papers were published in open-access journals (Nanoscale Advances and Advanced Electronic Materials) and two manuscripts are under preparation on Terahertz charge transport in the structural architecture of MXene and the second one on TiO2 doped 3D Graphene. I have presented the research findings at three international conferences and one national conference. I have given two presentations in the department: one at the Young Scientist Meet Talk Series and the other as a part of the Department Seminar Series.
The reported modulator can be included in THz systems to protect electronic components and reduce their observability to radar systems and other electromagnetic detection devices. The THz photodetector described here has several applications, such as remote sensing, medical diagnosis, and security inspection.