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Pathak DK, Dayanand D, Thakur OP, Kumar R. Raman area- and thermal- mapping studies of faceted nano-crystalline α-Fe2O3 thin films deposited by spray pyrolysis. CAN J CHEM 2021. [DOI: 10.1139/cjc-2021-0302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Different advanced techniques including Raman area mapping and Raman thermal imaging has been used to investigate various properties of large area iron oxide thin films deposited by spray pyrolysis, on a large area of crystalline silicon substrates under controlled external parameters. Morphological studies reveal that the obtained films acquire lateral faceted crystalline structure of iron oxide. The Raman and SEM images, in unison, confirm the presence and large area distribution of the nano crystals of Fe2O3 phase. Thermal Raman imaging reveals that the obtained iron oxide thin films are robust and thus can be used for appropriate technological applications like electromagnetic shielding.
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Affiliation(s)
- Devesh K. Pathak
- IIT Indore, 226957, Department of Physics, Indore, Madhya Pradesh, India
| | | | | | - Rajesh Kumar
- IIT Indore, 226957, Physics, POD 1A-211, Khandwa Road, Simrol, Indore, MP, India, 453552
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Gorenskaia E, Turner KL, Martín S, Cea P, Low PJ. Fabrication of metallic and non-metallic top electrodes for large-area molecular junctions. NANOSCALE 2021; 13:9055-9074. [PMID: 34042128 DOI: 10.1039/d1nr00917f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Molecular junctions have proven invaluable tools through which to explore the electronic properties of molecules and molecular monolayers. In seeking to develop a viable molecular electronics based technology it becomes essential to be able to reliably create larger area molecular junctions by contacting molecular monolayers to both bottom and top electrodes. The assembly of monolayers onto a conducting substrate by self-assembly, Langmuir-Blodgett and other methods is well established. However, the deposition of top-contact electrodes without film penetration or damage from the growing electrode material has proven problematic. This Review highlights the challenges of this area, and presents a selective overview of methods that have been used to solve these issues.
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Affiliation(s)
- Elena Gorenskaia
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
| | - Kelly L Turner
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
| | - Santiago Martín
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain and Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009, Zaragoza, Spain and Laboratorio de Microscopias Avanzadas (LMA). Universidad de Zaragoza, Edificio I+D+i. 50018, Zaragoza, Spain
| | - Pilar Cea
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, Zaragoza 50009, Spain and Departamento de Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009, Zaragoza, Spain and Laboratorio de Microscopias Avanzadas (LMA). Universidad de Zaragoza, Edificio I+D+i. 50018, Zaragoza, Spain
| | - Paul J Low
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia.
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Abo Ghazala M, Othman HA, Sharaf El-Deen LM, Nawwar MA, Kashyout AEHB. Fabrication of Nanocrystalline Silicon Thin Films Utilized for Optoelectronic Devices Prepared by Thermal Vacuum Evaporation. ACS OMEGA 2020; 5:27633-27644. [PMID: 33134727 PMCID: PMC7594337 DOI: 10.1021/acsomega.0c04206] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Accepted: 09/30/2020] [Indexed: 06/11/2023]
Abstract
Metal-induced crystallization of amorphous silicon is a promising technique for developing high-quality and cheap optoelectronic devices. Many attempts tried to enhance the crystal growth of polycrystalline silicon via aluminum-induced crystallization at different annealing times and temperatures. In this research, thin films of aluminum/silicon (Al/Si) and aluminum/silicon/tin (Al/Si/Sn) layers were fabricated using the thermal evaporation technique with a designed wire tungsten boat. MIC of a:Si was detected at annealing temperature of 500 °C using X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy. The crystallinity of the films is enhanced by increasing the annealing time. In the three-layer thin films, MIC occurs because of the existence of both Al and Sn metals forming highly oriented (111) silicon. Nanocrystalline silicon with dimensions ranged from 5 to 300 nm is produced depending on the structure and time duration. Low surface reflection and the variation of the optical energy gap were detected using UV-vis spectroscopy. Higher conductivities of Al/Si/Sn films than Al/Si films were observed because of the presence of both metals. Highly rectifying ideal diode manufactured from Al/Si/Sn on the FTO layer annealed for 24 h indicates that this device has a great opportunity for the optoelectronic device applications.
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Affiliation(s)
- Magdy
S. Abo Ghazala
- Physics
Department, Faculty of Science, Menoufia
University, Shebin
El-Kom, Menoufia 32511, Egypt
| | - Hosam A. Othman
- Physics
Department, Faculty of Science, Menoufia
University, Shebin
El-Kom, Menoufia 32511, Egypt
| | - Lobna M. Sharaf El-Deen
- Physics
Department, Faculty of Science, Menoufia
University, Shebin
El-Kom, Menoufia 32511, Egypt
| | - Mohamed A. Nawwar
- Physics
Department, Faculty of Science, Menoufia
University, Shebin
El-Kom, Menoufia 32511, Egypt
| | - Abd El-hady B. Kashyout
- Electronic
Materials Department, Advanced Technology and New Materials Research
Institute, City of Scientific Research and
Technological Applications (SRTA-City), New Borg El-Arab City, Alexandria 21934, Egypt
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McCreery RL. Effects of electronic coupling and electrostatic potential on charge transport in carbon-based molecular electronic junctions. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2016; 7:32-46. [PMID: 26925350 PMCID: PMC4734416 DOI: 10.3762/bjnano.7.4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 12/15/2015] [Indexed: 06/05/2023]
Abstract
Molecular junctions consisting of 2-20 nm thick layers of organic oligomers oriented between a conducting carbon substrate and a carbon/gold top contact have proven to be reproducible and reliable, and will soon enter commercial production in audio processing circuits. The covalent, conjugated bond between one or both sp(2)-hybridized carbon contacts and an aromatic molecular layer is distinct from the more common metal/molecule or silicon/molecule structures in many reported molecular junctions. Theoretical observations based on density functional theory are presented here, which model carbon-based molecular junctions as single molecules and oligomers between fragments of graphene. Electronic coupling between the molecules and the contacts is demonstrated by the formation of hybrid orbitals in the model structure, which have significant electron density on both the graphene and the molecule. The energies of such hybrid orbitals correlate with tunneling barriers determined experimentally, and electronic coupling between the two graphene fragments in the model correlates with experimentally observed attenuation of transport with molecular layer thickness. Electronic coupling is affected significantly by the dihedral angle between the planes of the graphene and the molecular π-systems, but is absent only when the two planes are orthogonal. Coupling also results in partial charge transfer between the graphene contacts and the molecular layer, which results in a shift in electrostatic potential which affects the observed tunneling barrier. Although the degree of partial charge transfer is difficult to calculate accurately, it does provide a basis for the "vacuum level shift" observed in many experiments, including transport and ultraviolet photoelectron spectroscopy of molecular layers on conductors.
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Affiliation(s)
- Richard L McCreery
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada and National Institute for Nanotechnology, National Research Council, Canada
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McCreery RL, Yan H, Bergren AJ. A critical perspective on molecular electronic junctions: there is plenty of room in the middle. Phys Chem Chem Phys 2013; 15:1065-81. [DOI: 10.1039/c2cp43516k] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Kumar R, Pillai RG, Pekas N, Wu Y, McCreery RL. Spatially Resolved Raman Spectroelectrochemistry of Solid-State Polythiophene/Viologen Memory Devices. J Am Chem Soc 2012; 134:14869-76. [DOI: 10.1021/ja304458s] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Rajesh Kumar
- Department
of Chemistry, University of Alberta, Edmonton,
Alberta, Canada
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta,
Canada
| | - Rajesh G. Pillai
- Department
of Chemistry, University of Alberta, Edmonton,
Alberta, Canada
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta,
Canada
| | - Nikola Pekas
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta,
Canada
| | - Yiliang Wu
- Xerox Research Centre of Canada, 2660 Speakman Drive Mississauga, Ontario,
L5K 2L1, Canada
| | - Richard L. McCreery
- Department
of Chemistry, University of Alberta, Edmonton,
Alberta, Canada
- National
Institute for Nanotechnology, National Research Council Canada, Edmonton, Alberta,
Canada
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Charge transport in molecular electronic junctions: compression of the molecular tunnel barrier in the strong coupling regime. Proc Natl Acad Sci U S A 2012; 109:11498-503. [PMID: 22660930 DOI: 10.1073/pnas.1201557109] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Molecular junctions are essentially modified electrodes familiar to electrochemists where the electrolyte is replaced by a conducting "contact." It is generally hypothesized that changing molecular structure will alter system energy levels leading to a change in the transport barrier. Here, we show the conductance of seven different aromatic molecules covalently bonded to carbon implies a modest range (< 0.5 eV) in the observed transport barrier despite widely different free molecule HOMO energies (> 2 eV range). These results are explained by considering the effect of bonding the molecule to the substrate. Upon bonding, electronic inductive effects modulate the energy levels of the system resulting in compression of the tunneling barrier. Modification of the molecule with donating or withdrawing groups modulate the molecular orbital energies and the contact energy level resulting in a leveling effect that compresses the tunneling barrier into a range much smaller than expected. Whereas the value of the tunneling barrier can be varied by using a different class of molecules (alkanes), using only aromatic structures results in a similar equilibrium value for the tunnel barrier for different structures resulting from partial charge transfer between the molecular layer and the substrate. Thus, the system does not obey the Schottky-Mott limit, and the interaction between the molecular layer and the substrate acts to influence the energy level alignment. These results indicate that the entire system must be considered to determine the impact of a variety of electronic factors that act to determine the tunnel barrier.
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Mccreery RL. The merger of electrochemistry and molecular electronics. CHEM REC 2011; 12:149-63. [DOI: 10.1002/tcr.201100006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Indexed: 01/30/2023]
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