Main research areas:
LNM group is working on the synthesis of single-walled carbon nanotubes, graphene-based materials and metal-based nanowires.
Single-walled carbon nanotubes (SWCNTs) are a unique material with diverse exceptional properties, which could be utilized in many fields of science and technology. SWCNTs are the strongest known material with exceptionally high Young's modulus of elasticity and tensile strength. SWCNTs possess very high porosity and high specific surface area. The most fascinating properties of SWCNTs are their electronic structure, which provides many interesting applications in photonics and electronics. SWCNT's optical and electrical optical and electrical properties can be varied by changing the chirality from semiconducting to metallic SWCNTs (Fig. 1). Both thermal and electrical conductivities of SWCNTs show remarkably high values. The charge carrier mobility in the semiconducting SWCNTs is extremely high and comparable to that of free-standing graphene. Due to very high current density, which tubes can withstand without destruction, up to 109 A/cm2, SWCNTs are believed to be an ideal material for copper and aluminium replacement in integrated circuits. Taking into account high transparency, SWCNT films are a strong candidate for the replacement of commonly used transparent electrodes, such as ITO. The group developed synthesis of SWCNTs by aerosol1-5 and substrate6-10 CVD synthesis. Both methods allow synthesising high quality SWCNTs (e.g., Fig. 2).
Graphene possesses very similar properties to SWCNTs. Graphene is strictly two-dimensional material exhibits exceptionally high crystal and electronic quality and, despite its short history, has already revealed a cornucopia of new physics and potential applications. It is tougher than diamond, but stretches like rubber. It is very transparent and conducts electricity and heat better than copper nanowires. The importance of graphene as a material for flexible optoelectronic applications is not in doubt.
The group is working on the CVD synthesis of graphene and fabrication of graphene layers by deposition and subsequent reduction of graphene oxide. One of the directions of the group is to hybridize the SWCNT and graphene into a uniform single hybrid structure (Fig. 3), which take advantage of the synergistic effects between the tubes and graphene.
LNM group focuses on the aerosol CVD synthesis of SWCNTs and thin film applications of the tubes (Fig. 2). The most important publications related to the synthesis of SWCNTs and investigations of the mechanisms of their synthesis are listed below 1, 3-5, 11-18.
Metal-based nanowires (NWs) can be used for a wide range of applications and especially for nano- and microelectronics19, 20. We have introduced a very simple and rapid method for the synthesis of NWs by resistive heating of metal wires at ambient conditions. We demonstrated the possibility of fabrication of different metal oxide NWs: CuO, a-Fe2O3, ZnO, V2O5 (Fig. 4) and showed the possibility of utilization of other metals – Al, Mo and W for the NW growth. The simplicity of our discovered production method allows elaborating methods for the patterned growth, transferring method as well as high yield synthesis of NWs.
Additionally, we have recently elaborated two methods for the controlled synthesis of ZnO tetrapod (ZnO-T) structures (Fig. 5), which possess very interesting electrical and optical properties20, 21. We demonstrated high performance UV light sensor based on ZnO-T film (Fig. 6). The fabricated flexible transparent UV sensors showed 45 fold current increase under UV irradiation with the intensity of 30 µW/cm2 at the wavelength of 365 nm and response time of 0.9 s, which the shortest response for the sensor made of any other ZnO structures.
Fig. 1. a) Sinlge-walled carbon nanotubes of different charalities: semiconducting zig-zag (10,0) and chiral (8,4) tubes, metallic armchair (6,6) tube. b) A schematic presentation of construction of a zig-zag (10, 0) CNT by rolling a cylinder joining hexagons (0,0) and (10,0). Also, the possibility of creating arm-chair (6, 6) and chiral (8,4) tubes are shown.
Fig. 2. Transmission (TEM) and scanning (SEM) electron microscopy images of aerosol synthesised SWCNTs.
Fig. 3. Fabrication of a hybrid structure SWCNT and reduced graphene oxide.
Fig. 4. SEM images of metal oxide NWs: -Fe2O3, CuO, V2O5, ZnO.
Fig. 5. a) ZnO-Ts synthesized at 700 oC by aerosol method. b) ZnO-Ts covered by 15 nm-sized Au particles.
Fig. 6. ZnO-T UV sensor: a) schematics of UV response measurement inset is a photo of the sensor; b) the sensor response to excitation at 365 nm.
One cannot even imagine how our world would change, if materials with high conductivity, transparency and flexibility were available in the market. New generation electronic devices will be invented and developed. Novel concepts from World leading electronic companies (Apple, Samsung, HuaWei, Lenovo, LG, Nokia, HTC, etc.) predict the revolutionary changes in the current functionality, shape and view of the electronic devices (Fig. 8).
We elaborated a method for the room temperature deposition of CNTs onto any substrate22, 23, which presents an interesting and useful nanotechnological applications (Fig. 9, MOVIE 1). We proposed a method to directly integrate the CNTs into applications without time-consuming sample purification, dispersion them in liquid and subsequent deposition. Since the CNTs are clean, they can be directly utilized in the form they come from the reactor. Since the aerosol CNTs are collected at room temperature, they can be deposited onto any substrate including temperature sensitive polymers (Fig. 10). CNTs simply filtered and subsequently transferred onto the secondary support demonstrate a state-of-the-art performance of thin and transparent electrodes with the performance approaching ITO (Fig. 11) 4, 5,22-24.
We have also developed a fabrication method of high-performance thin film field effect transistors (FETs) on the basis of deposited SWCNTs from the aerosol reactor. First devices exhibited on/off ratios of up to 105 and charge mobilities of up to 4 cm2V-1s-1.25 Later, in collaboration with Prof. Y. Ohno we reported significant increase of the transistor mobility up to 634 cm2V-1s-1 at the on/off ratio of 6x106. Also, we demonstrated the possibility to build flexible integrated circuits, including a 21-stage ring oscillator and master-slave delay flip-flops that are capable of sequential logic (Fig. 12)26, 27.
Importantly, the SWCNTs synthesized by the aerosol method [25,113,163] meet all the requirements for low-cost, flexible, transparent and stretchable electronics, which could be used in many high tech applications like touch sensors and displays, thin film transistors, flexible and transparent electrodes in photovoltaic devices, field emitters, optoelectronic devices, OLEDs, etc.14, 22-24, 26-32
Fig. 7. Applications of transparent conductors.
Fig. 8. The concept of flexible and stretchable electronic devices.
Fig. 9. Dry and direct deposition method of SWCNT films.
Fig. 10. a) A photograph of a filter covered by SWCNTs after filtering the flow at the outlet of the reactor and various substrates with dry transferred SWCNT-networks: on PET, silicon wafer, Fe and Cu foils. b) Multifunctional free-standing SWCNT film.
Fig. 11. Comparison of different transparent electrode materials: sheet resistance versus optical transmittance at 550 nm. Our current data are shown by open and solid pentagons; the red lines show theoretical fits to our data.
Fig. 12. CNT TFTs and ICs on flexible substrate. a) Photograph of fabricated devices on a flexible and transparent PEN substrate. b) Schematic cross section of a bottom gate TFT on PEN substrate with Al2O3 gate insulator. c) Transfer characteristics of a typical TFT with =100 Ојm at =-0.5 V, =100 Ојm. d) Input-output and gain characteristics of an inverter. Insets show the optical micrograph, circuit diagram and symbol of the inverter. e, f) Optical micrograph and circuit diagram of a 21-stage ring oscillator. g) Output characteristics of the ring oscillator with oscillation frequency of 2.0 kHz at =-4 V. h) Mobility and on/off ratio. Comparison between our 36 CNT TFTs with other representative TFTs based on CNT network, amorphous-Si, polycrystalline Si, ZnO-based semiconductors, and organic materials.
SWCNTs possess a wide range of direct bandgaps matching the solar spectrum, strong photoabsorption, from infrared to ultraviolet, and high carrier mobility and reduced carrier transport scattering, which make themselves ideal photovoltaic material.
Research on a new kind of heterojunction solar cells is based on silicon and SWCNT films33 (Fig. 13). Detailed insight of the heterojunction of silicon and SWCNTs and the charge transfer mechanism in the CNT network is necessary. This will open up the path towards to all carbon solar cells (Fig. 14)28. We are interested in a deep understanding of the processes limiting the life time and collection efficiency of charge carriers as well as photon absorption in this device structure. Our work focuses on flexible heterojunction solar cells, which will be based on nanocrystalline and amorphous silicon to further improve the mechanical properties of the solar cells (to add flexibility and stretchability).
Fig. 13 (a) Schematic of the SWNT/Si solar cell with dimensional parameters. (b) Magnified SEM image of contact window edge of the SWNT/Si solar cell. A region of the SWNT film with the width of 300 nm was suspended between the Si substrate and the Pt electrode. d) J-V characteristics of the SWNT/Si solar cell measured immediately as well as after 1, 6 and 10 months exposed in the ambient condition.
Fig.14. Demonstration of all-carbon nanotube photovoltaic effect: a) The edge of the SWNT film observed under SEM, and b) SEM image of this film showing SWNT network. c) Schematic view of the contact formation between two SWNT films: Yellow stars symbolize the junctions between bundles, (1)–(3) represent three different inclination angles. d) I–V characteristics at “first touch” conditions: under dark and light illumination.
- Nasibulin, A. G.; Moisala, A.; Brown, D. P.; Jiang, H.; Kauppinen, E. I. A Novel Aerosol Method for Single Walled Carbon Nanotube Synthesis. Chem. Phys. Lett. 2005, 402, 227-232.
- Moisala, A.; Nasibulin, A. G.; Shandakov, S. D.; Jiang, H.; Kauppinen, E. I. On-line Detection of Single-walled Carbon Nanotube Formation during Aerosol Synthesis Methods. Carbon 2005, 43, 2066-2074.
- Moisala, A.; Nasibulin, A. G.; Brown, D. P.; Jiang, H.; Khriachtchev, L.; Kauppinen, E. I. Single-walled Carbon Nanotube Synthesis Using Ferrocene and Iron Pentacarbonyl in a Laminar Flow Reactor. Chem. Eng. Sci. 2006, 61, 4393-4402.
- Anoshkin, I. V.; Nasibulin, A. G.; Tian, Y.; Liu, B.; Jiang, H.; Kauppinen, E. I. Hybrid carbon source for single-walled carbon nanotube synthesis by aerosol CVD method. Carbon 2014, 78, 130-136.
- Reynaud, O.; Nasibulin, A. G.; Anisimov, A. S.; Anoshkin, I. V.; Jiang, H.; Kauppinen, E. I. Aerosol feeding of catalyst precursor for CNT synthesis and highly conductive and transparent film fabrication. Chem. Eng. J. 2014, 255, 134-140.
- Nasibulin, A. G.; Shandakov, S. D.; Nasibulina, L. I.; Cwirzen, A.; Mudimela, P. R.; Habermehl-Cwirzen, K.; Grishin, D. A.; Gavrilov, Y. V.; Malm, J. E. M.; Tapper, U.; Tian, Y.; Penttala, V.; Karppinen, M. J.; Kauppinen, E. I. A novel cement-based hybrid material. New J. Phys. 2009, 11, 023013.
- Mudimela, P. R.; Nasibulin, A. G.; Jiang, H.; Susi, T.; Chassaing, D.; Kauppinen, E. I. Incremental Variation in the Number of Carbon Nanotube Walls with Growth Temperature. J. Phys. Chem. C 2009, 113, 2212-2218.
- Mudimela, P. R.; Nasibulina, L. I.; Nasibulin, A. G.; Cwirzen, A.; Valkeapaa, M.; Habermehl-Cwirzen, K.; Malm, J. E. M.; Karppinen, M. J.; Penttala, V.; Koltsova, T. S.; Tolochko, O. V.; Kauppinen, E. I. Synthesis of Carbon Nanotubes and Nanofibers on Silica and Cement Matrix Materials. Journal of Nanomaterials 2009, 2009, 526128.
- Queipo, P.; Nasibulin, A. G.; Shandakov, S. D.; Jiang, H.; Gonzalez, D.; Kauppinen, E. I. CVD synthesis and radial deformations of large diameter single-walled CNTs. Current Applied Physics 2009, 9, 301-305.
- Nasibulin, A. G.; Shandakov, S. D.; Mudimela, P. R.; Kauppinen, E. I. Morphology and structure of carbon nanotubes synthesized on iron catalyst in the presence of carbon monooxide. Nanotechnologies in Russia 2010, 5, 198-208.
- Nasibulin, A. G.; Pikhitsa, P. V.; Jiang, H.; Kauppinen, E. I. Correlation between catalyst particle and single-walled carbon nanotube diameters. Carbon 2005, 43, 2251-2257.
- Nasibulin, A. G.; Queipo, P.; Shandakov, S. D.; Brown, D. P.; Jiang, H.; Pikhitsa, P. V.; Tolochko, O. V.; Kauppinen, E. I. Studies on mechanism of single-walled carbon nanotube formation. J. Nanosci. Nanotech. 2006, 6, 1233-46.
- Nasibulin, A. G.; Brown, D. P.; Queipo, P.; Gonzalez, D.; Jiang, H.; Kauppinen, E. I. An Essential Role of CO2 and H2O During Single-walled CNT Synthesis from Carbon Monoxide. Chem. Phys. Lett. 2006, 417, 179-184.
- Nasibulin, A. G.; Pikhitsa, P. V.; Jiang, H.; Brown, D. P.; Krasheninnikov, A. V.; Anisimov, A. S.; Queipo, P.; Moisala, A.; Gonzalez, D.; Lientschnig, G.; Hassanien, A.; Shandakov, S. D.; Lolli, G.; Resasco, D. E.; Choi, M.; Tomanek, D.; Kauppinen, E. I. A Novel Hybrid Carbon Material. Nat. Nanotechnol. 2007, 2, 156-61.
- Anisimov, A. S.; Nasibulin, A. G.; Jiang, H.; Launois, P.; Cambedouzou, J.; Shandakov, S. D.; Kauppinen, E. I. Mechanistic investigations of single-walled carbon nanotube synthesis by ferrocene vapor decomposition in carbon monoxide. Carbon 2010, 48, 380-388.
- Tian, Y.; Timmermans, M.; KivistГ¶, S.; Nasibulin, A.; Zhu, Z.; Jiang, H.; Okhotnikov, O.; Kauppinen, E. Tailoring the diameter of single-walled carbon nanotubes for optical applications. Nano Res. 2011, 4, 807-815.
- Tian, Y.; Nasibulin, A. G.; Aitchison, B.; Nikitin, T.; Pfaler, J. v.; Jiang, H.; Zhu, Z.; Khriachtchev, L.; Brown, D. P.; Kauppinen, E. I. Controlled Synthesis of Single-Walled Carbon Nanotubes in an Aerosol Reactor. J. Phys. Chem. C 2011, 115, 7309-7318.
- Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Susi, T.; Jiang, H.; Nasibulin, A. G.; Kauppinen, E. I. Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities. Appl. Phys. Lett. 2015, 107, 013106.
- Rackauskas, S.; Jiang, H.; Wagner, J. B.; Shandakov, S. D.; Hansen, T. W.; Kauppinen, E. I.; Nasibulin, A. G. In Situ Study of Noncatalytic Metal Oxide Nanowire Growth. Nano Lett. 2014, 14, 5810-5813.
- Rackauskas, S.; Klimova, O.; Jiang, H.; Nikitenko, A.; Chernenko, K. A.; Shandakov, S. D.; Kauppinen, E. I.; Tolochko, O. V.; Nasibulin, A. G. A Novel Method for Continuous Synthesis of ZnO Tetrapods. J. Phys. Chem. C 2015, 119, 16366-16373.
- Rackauskas, S.; Mustonen, K.; JГ¤rvinen, T.; Mattila, M.; Klimova, O.; Jiang, H.; Tolochko, O.; Lipsanen, H.; Kauppinen, E. I.; Nasibulin, A. G. Synthesis of ZnO tetrapods for flexible and transparent UV sensors. Nanotechnol. 2012, 23, 095502.
- Kaskela, A.; Nasibulin, A. G.; Timmermans, M. Y.; Aitchison, B.; Papadimitratos, A.; Tian, Y.; Zhu, Z.; Jiang, H.; Brown, D. P.; Zakhidov, A.; Kauppinen, E. I. Aerosol Synthesized SWCNT Networks with Tuneable Conductivity and Transparency by Dry Transfer Technique. Nano Lett. 2010, 10, 4349вЂ“4355.
- Nasibulin, A. G.; Kaskela, A.; Mustonen, K.; Anisimov, A. S.; Ruiz, V.; Kivisto, S.; Rackauskas, S.; Timmermans, M. Y.; Pudas, M.; Aitchison, B.; Kauppinen, M.; Brown, D. P.; Okhotnikov, O. G.; Kauppinen, E. I. Multifunctional Free-Standing Single-Walled Carbon Nanotube Films. ACS Nano 2011, 5, 3214-3221.
- Mustonen, K.; Laiho, P.; Kaskela, A.; Susi, T.; Nasibulin, A. G.; Kauppinen, E. I. Uncovering the ultimate performance of single-walled carbon nanotube films as transparent conductors. Appl. Phys. Lett. 2015, 107, 143113.
- Zavodchikova, M. Y.; Kulmala, T.; Nasibulin, A. G.; Ermolov, V.; Franssila, S.; Grigoras, K.; Kauppinen, E. I. Carbon nanotube thin film transistors based on aerosol methods. Nanotechnol. 2009, 20, 085201.
- Sun, D.-M.; Timmermans, M. Y.; Nasibulin, A. G.; Kauppinen, E. I.; Kishimoto, S.; Mizutani, T.; Ohno, Y. High-performance carbon nanotube thin-film transistors and logic circuits on flexible substrate. Nat. Nanotechnol. 2011, 6, 156вЂ“161.
- Sun, D.-M.; Timmermans, M. Y.; Kaskela, A.; Nasibulin, A. G.; Kishimoto, S.; Mizutani, T.; Kauppinen, E. I.; Ohno, Y. Mouldable all-carbon integrated circuits. Nat Commun 2013, 4.
- Nasibulin, A. G.; Funde, A. M.; Anoshkin, I. V.; Levitsky, I. A. All-carbon nanotube diode and solar cell statistically formed from macroscopic network. Nano Res. 2015, 8, 2800-2809.
- Jeon, I.; Cui, K.; Chiba, T.; Anisimov, A.; Nasibulin, A. G.; Kauppinen, E. I.; Maruyama, S.; Matsuo, Y. Direct and Dry Deposited Single-Walled Carbon Nanotube Films Doped with MoOx as Electron-Blocking Transparent Electrodes for Flexible Organic Solar Cells. J. Am. Chem. Soc. 2015, 137, 7982-7985.
- Cui, K.; Anisimov, A. S.; Chiba, T.; Fujii, S.; Kataura, H.; Nasibulin, A. G.; Chiashi, S.; Kauppinen, E. I.; Maruyama, S. Air-stable high-efficiency solar cells with dry-transferred single-walled carbon nanotube films. Journal of Materials Chemistry A 2014, 2, 11311-11318.
- Mikheev, G. M.; Nasibulin, A. G.; Zonov, R. G.; Kaskela, A.; Kauppinen, E. I. Photon-Drag Effect in Single-Walled Carbon Nanotube Films. Nano Lett. 2011.
- Aitola, K.; Halme, J.; Halonen, N.; Kaskela, A.; Toivola, M.; Nasibulin, A. G.; KordГЎs, K.; TГіth, G.; Kauppinen, E. I.; Lund, P. D. Comparison of dye solar cell counter electrodes based on different carbon nanostructures. Thin Solid Films2011, 519, 8125-8134.
- Cui, K.; Anisimov, A. S.; Chiba, T.; Fujii, S.; Kataura, H.; Nasibulin, A.; Chiashi, S.; Kauppinen, E.; Maruyama, S. Air-Stable High-Efficiency Solar Cells with Dry-Transferred Single-Walled Carbon Nanotube Films. Journal of Materials Chemistry A 2014.