Periodic Reporting for period 1 - OssCaNa (On-Surface Synthesis, Transfer and Device Fabrication of Novel Carbon-based Nanomaterials)
Berichtszeitraum: 2021-04-01 bis 2023-03-31
Issue being adressed: The study of on-surface chemical reactions has attracted recently an enormous interest demonstrating to be a versatile tool for the fabrication of atomically precise covalently bonded carbon nanomaterials that cannot be synthesized in conventional solution-based chemistry. Over the last decade, a plethora of on-surface reactions based on C−C coupling such as cyclodehydrogenation, or aryl-aryl coupling, have been successfully investigated on several single crystal metallic surfaces under a well-controlled environment such as ultra-high vacuum (UHV) with the help of advanced scanning probe and complementary surface analysis techniques, combined with theoretical calculations. Such techniques also serve as adequate tools to undertake a sequential study of reaction steps, contributing to the investigation of mechanistic insights on the synthetic pathway toward targeted products. However, despite of these extraordinary advances realized in the field of on-surface synthesis, a gap between ideal nanomaterials and the accessible synthetic pathways to reach them still persists.
Importancy for society: OssCaNa provides a multidisciplinary approach toward the understanding of innovative carbon-based nanomaterials as active materials in foreseen functional devices for real-world applications. carbon-based nanomaterials in the natural world have been around since the beginning of time. They are undoubtedly involved in comfort and facilitation of human life, being ubiquitous in our daily lives. However, the synthesis of well-defined carbon-based nanomaterials with unique structural, electronic and magnetic properties under conventional solution chemistry methods is often hampered by their low solubility and high reactivity. Such nanomaterials might enable completely new functionalities with prospects, as key components of high-level technologies, in a wide field such as organic electronics.
Overall objectives: the goal of the OssCaNa project presents two steps. First, it aims at the study of carbon-based nanomaterials combining a broad variety of surface science techniques such as low temperature scanning probe microscopy/spectroscopy STM/STS and non-contact atomic force microscopy (nc-AFM). Second, it focusses on the efficient transfer of the targeted nanomaterials fabricated and characterized on a metallic substrate in the previous step, to appropriate substrates for further electrical transport characterization and high-performance device fabrication:
• SO1: Design and synthesis of novel carbon-based nanomaterials obtained through on-surface chemical reactions on metallic substrates.
• SO2: Unravel the structural and electronic properties of the desired nanomaterials synthetized in SO1 via surface science techniques.
• SO3: Transfer of the desired nanomaterials fabricated and characterized on metallic substrates in SO1 and SO2, to technologically appropriate semiconducting or insulating substrates.
• SO4: Electrical transport characterization and high-performance device fabrication of the targeted carbon-based nanomaterials.
Importancy for society: OssCaNa provides a multidisciplinary approach toward the understanding of innovative carbon-based nanomaterials as active materials in foreseen functional devices for real-world applications. carbon-based nanomaterials in the natural world have been around since the beginning of time. They are undoubtedly involved in comfort and facilitation of human life, being ubiquitous in our daily lives. However, the synthesis of well-defined carbon-based nanomaterials with unique structural, electronic and magnetic properties under conventional solution chemistry methods is often hampered by their low solubility and high reactivity. Such nanomaterials might enable completely new functionalities with prospects, as key components of high-level technologies, in a wide field such as organic electronics.
Overall objectives: the goal of the OssCaNa project presents two steps. First, it aims at the study of carbon-based nanomaterials combining a broad variety of surface science techniques such as low temperature scanning probe microscopy/spectroscopy STM/STS and non-contact atomic force microscopy (nc-AFM). Second, it focusses on the efficient transfer of the targeted nanomaterials fabricated and characterized on a metallic substrate in the previous step, to appropriate substrates for further electrical transport characterization and high-performance device fabrication:
• SO1: Design and synthesis of novel carbon-based nanomaterials obtained through on-surface chemical reactions on metallic substrates.
• SO2: Unravel the structural and electronic properties of the desired nanomaterials synthetized in SO1 via surface science techniques.
• SO3: Transfer of the desired nanomaterials fabricated and characterized on metallic substrates in SO1 and SO2, to technologically appropriate semiconducting or insulating substrates.
• SO4: Electrical transport characterization and high-performance device fabrication of the targeted carbon-based nanomaterials.
I have divided the work performed so far in three different results according to the different workpackages planned:
WP1) Design and synthesis of surface-confined novel carbon-based nanomaterials
We took advantage of a large variety of carbon-based molecular precursors equipped with different functional groups, which have been ex-situ designed and synthetized. More in detail, carbon-based precursors functionalized with halogen atoms, gem- dibromides and isopropyl functional groups have been appropriately designed.
WP2) Detailed structural and electronic characterization of surface-confined novel carbon-based nanomaterials
The resolution of STM and nc-AFM using a q-Plus sensor and CO-functionalized tip allowed for structural conclusions by analysing the electronic density of states compared to computed ones, obtaining a deep understanding of on-surface processes by investigating intermediate and final products of different synthetic pathways. Furthermore, local Scanning Tunneling Spectroscopy (STS) was used to unravel the electronic and magnetic properties of the studied nanomaterials.
WP3) Transfer of carbon-based nanomaterials onto device substrates
The fabrication of low-dimensional carbon-based nanomaterials presents a common feature of the bottom-up approaches where a metallic substrate to trigger and promote the chemical reaction of precursor monomers is required. As a result, at the end of the reaction, all the nanomaterials are supported on metal substrates, which is clearly not adequate for many types of characterization and device development. To transfer carbon-based nanomaterials for further electrical transport characterization and high-performance device fabrication, we took advance of the membrane-free transfer method to transfer ex-situ the fabricated nanomaterials from their growth substrate to technologically relevant target substrates.
Results obtained:
- Generating Antiaromaticity: Thermally-selective Skeletal Rearrangements at Interfaces (not published yet). WP1 and 2
- Interplay between π-Conjugation and Exchange Magnetism in One-Dimensional Porphyrinoid Polymers (published). WP1 and 2
- Surface‐Assisted Synthesis of N‐Containing π‐Conjugated Polymers (published). WP1 and 2
- Synthesis and Characterization of peri‐Heptacene on a Metallic Surface (published). WP1 and 2
- Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes (published). WP1 and 2
- On‐Surface Synthesis of a Dicationic Diazahexabenzocoronene Derivative on the Au (111) Surface (published). WP1 and 2
- Cumulene-like bridged indeno [1, 2-b] fluorene π-conjugated polymers synthesized on metal surfaces (published). WP1 and 2
- On-surface polyarylene synthesis by cycloaromatization of isopropyl substituents (published). WP1 and 2
- Study of the chemical stability of pentacene-based polymers under air conditions (not published yet). WP3
In total 7 publications in top quality chemistry journals have been obtained (and at least two more will be published in the near future). Results related to the objective described in WP4 were not performed due to the lack of time.
WP1) Design and synthesis of surface-confined novel carbon-based nanomaterials
We took advantage of a large variety of carbon-based molecular precursors equipped with different functional groups, which have been ex-situ designed and synthetized. More in detail, carbon-based precursors functionalized with halogen atoms, gem- dibromides and isopropyl functional groups have been appropriately designed.
WP2) Detailed structural and electronic characterization of surface-confined novel carbon-based nanomaterials
The resolution of STM and nc-AFM using a q-Plus sensor and CO-functionalized tip allowed for structural conclusions by analysing the electronic density of states compared to computed ones, obtaining a deep understanding of on-surface processes by investigating intermediate and final products of different synthetic pathways. Furthermore, local Scanning Tunneling Spectroscopy (STS) was used to unravel the electronic and magnetic properties of the studied nanomaterials.
WP3) Transfer of carbon-based nanomaterials onto device substrates
The fabrication of low-dimensional carbon-based nanomaterials presents a common feature of the bottom-up approaches where a metallic substrate to trigger and promote the chemical reaction of precursor monomers is required. As a result, at the end of the reaction, all the nanomaterials are supported on metal substrates, which is clearly not adequate for many types of characterization and device development. To transfer carbon-based nanomaterials for further electrical transport characterization and high-performance device fabrication, we took advance of the membrane-free transfer method to transfer ex-situ the fabricated nanomaterials from their growth substrate to technologically relevant target substrates.
Results obtained:
- Generating Antiaromaticity: Thermally-selective Skeletal Rearrangements at Interfaces (not published yet). WP1 and 2
- Interplay between π-Conjugation and Exchange Magnetism in One-Dimensional Porphyrinoid Polymers (published). WP1 and 2
- Surface‐Assisted Synthesis of N‐Containing π‐Conjugated Polymers (published). WP1 and 2
- Synthesis and Characterization of peri‐Heptacene on a Metallic Surface (published). WP1 and 2
- Defect-Induced π-Magnetism into Non-Benzenoid Nanographenes (published). WP1 and 2
- On‐Surface Synthesis of a Dicationic Diazahexabenzocoronene Derivative on the Au (111) Surface (published). WP1 and 2
- Cumulene-like bridged indeno [1, 2-b] fluorene π-conjugated polymers synthesized on metal surfaces (published). WP1 and 2
- On-surface polyarylene synthesis by cycloaromatization of isopropyl substituents (published). WP1 and 2
- Study of the chemical stability of pentacene-based polymers under air conditions (not published yet). WP3
In total 7 publications in top quality chemistry journals have been obtained (and at least two more will be published in the near future). Results related to the objective described in WP4 were not performed due to the lack of time.
A big breakthrough in the design of novel low-dimensional carbon-based nanomaterials with deterministically defined electronic properties of great interest for the development of high performance FETs has beed achieved. Furthermore, the reaction pathways as well as the final products obtained on metallic substrates were extensively investigated. Apart from the results abovementioned, investigations regarding the chemical stability of different carbon-based nanomaterials and their integration into switching devices with the aim of inspecting their device performance are on the way. If successful, such investigations will lead to the replacement of silicon technologies in the mid/long term due to a better performance in terms of sustainability, costs and conducivity.