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Baraskar BG, Kolekar YD, Thombare BR, James AR, Kambale RC, Ramana CV. Enhanced Piezoelectric, Ferroelectric, and Electrostrictive Properties of Lead-Free (1-x)BCZT-(x)BCST Electroceramics with Energy Harvesting Capability. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2300549. [PMID: 37203304 DOI: 10.1002/smll.202300549] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 03/30/2023] [Indexed: 05/20/2023]
Abstract
Next-generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)-free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials' design with multi-phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead-free piezoelectric materials (1-x)Ba0.95 Ca0.05 Ti0.95 Zr0.05 O3 -(x)Ba0.95 Ca0.05 Ti0.95 Sn0.05 O3 , are reported, which are represented as (1-x)BCZT-(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1-x)BCZT-(x)BCST materials are synthesized by high-temperature solid-state ceramic reaction method by varying x in the full range (x = 0.00-1.00). In-depth exploration research is performed on the structural, dielectric, ferroelectric, and electro-mechanical properties of (1-x)BCZT-(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca2+ , Zr4+ , and Sn4+ are well dispersed within the BaTiO3 lattice. For all (1-x)BCZT-(x)BCST ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 + P4mm) phases at room temperature. The steady transition of Amm2 crystal symmetry to P4mm crystal symmetry with increasing x content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral-orthorhombic (TR-O ), orthorhombic- tetragonal (TO-T ), and tetragonal-cubic (TC ), gradually shift toward lower temperature with increasing x content. For (1-x)BCZT-(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constant εr ≈ 1900-3300 (near room temperature), εr ≈ 8800-12 900 (near Curie temperature), dielectric loss, tan δ ≈ 0.01-0.02, remanent polarization Pr ≈ 9.4-14 µC cm-2 , coercive electric field Ec ≈ 2.5-3.6 kV cm-1 . Further, high electric field-induced strain S ≈ 0.12-0.175%, piezoelectric charge coefficient d33 ≈ 296-360 pC N-1 , converse piezoelectric coefficient( d 33 ∗ ) ave ${( {d_{33}^*} )}_{{\rm{ave}}}$ ≈ 240-340 pm V-1 , planar electromechanical coupling coefficient kp ≈ 0.34-0.45, and electrostrictive coefficient (Q33 )avg ≈ 0.026-0.038 m4 C-2 are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT-(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead-free piezoelectric (1-x)BCZT-(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1-x)BCZT-(x)BCST ceramics as a potentially strong contender within the family of Pb-free piezoelectric materials for future electronics and energy harvesting device technologies.
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Affiliation(s)
- Bharat G Baraskar
- Department of Physics, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, 411007, India
| | - Yesappa D Kolekar
- Department of Physics, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, 411007, India
| | - Balu R Thombare
- Department of Physics, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, 411007, India
- Institute of Geography and Geology, University of Greifswald, Friedrich-Ludwig-Jahn Str. 17A, 17489, Greifswald, Germany
| | - Ajit R James
- Defence Metallurgical Research Laboratory, Hyderabad, Telangana, 500058, India
| | - Rahul C Kambale
- Department of Physics, Savitribai Phule Pune University, Ganeshkhind, Pune, Maharashtra, 411007, India
| | - C V Ramana
- Center for Advanced Materials Research (CMR), University of Texas at El Paso, El Paso, TX, 79968, USA
- Department of Aerospace & Mechanical Engineering, University of Texas at El Paso, El Paso, TX, 79968, USA
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Gieraltowska S, Wachnicki L, Dluzewski P, Witkowski BS, Godlewski M, Guziewicz E. Atomic Layer Deposition of HfO 2 Films Using TDMAH and Water or Ammonia Water. MATERIALS (BASEL, SWITZERLAND) 2023; 16:ma16114077. [PMID: 37297215 DOI: 10.3390/ma16114077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 05/25/2023] [Accepted: 05/29/2023] [Indexed: 06/12/2023]
Abstract
Atomic layer deposition of HfO2 from TDMAH and water or ammonia water at different temperatures below 400 °C is studied. Growth per cycle (GPC) has been recorded in the range of 1.2-1.6 Å. At low temperatures (≤100 °C), the films grew faster and are structurally more disordered, amorphous and/or polycrystalline with crystal sizes up to 29 nm, compared to the films grown at higher temperatures. At high temperatures of 240 °C, the films are better crystallized with crystal sizes of 38-40 nm but grew slower. GPC, dielectric constant, and crystalline structure are improved by depositing at temperatures above 300 °C. The dielectric constant value and the roughness of the films have been determined for monoclinic HfO2, a mixture of orthorhombic and monoclinic, as well as for amorphous HfO2. Moreover, the present study shows that the increase in the dielectric constant of the films can be achieved by using ammonia water as an oxygen precursor in the ALD growth. The detailed investigations of the relationship between HfO2 properties and growth parameters presented here have not been reported so far, and the possibilities of fine-tuning and controlling the structure and performance of these layers are still being sought.
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Affiliation(s)
- Sylwia Gieraltowska
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Lukasz Wachnicki
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Piotr Dluzewski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Bartlomiej S Witkowski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Marek Godlewski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
| | - Elzbieta Guziewicz
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668 Warsaw, Poland
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Satish M, Shashanka HM, Saha S, Haritha K, Das D, Anantharamaiah PN, Ramana CV. Effect of High-Anisotropic Co 2+ Substitution for Ni 2+ on the Structural, Magnetic, and Magnetostrictive Properties of NiFe 2O 4: Implications for Sensor Applications. ACS APPLIED MATERIALS & INTERFACES 2023; 15:15691-15706. [PMID: 36939288 DOI: 10.1021/acsami.2c23025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
This work reports on the effect of substituting a low-anisotropic and low-magnetic cation (Ni2+, 2μB) by a high-anisotropic and high-magnetic cation (Co2+, 3μB) on the crystal structure, phase, microstructure, magnetic properties, and magnetostrictive properties of NiFe2O4 (NFO). Co-substituted NFO (Ni1-xCoxFe2O4, NCFO, 0 ≤ x ≤ 1) nanomaterials were synthesized using glycine-nitrate autocombustion followed by postsynthesis annealing at 1200 °C. The X-ray diffraction measurements coupled with Rietveld refinement analyses indicate the significant effect of Co-substitution for Ni, where the lattice constant (a) exhibits a functional dependence on composition (x). The a-value increases from 8.3268 to 8.3751 Å (±0.0002 Å) with increasing the "x" value from 0 to 1 in NCFO. The a-x functional dependence is derived from the ionic-size difference between Co2+ and Ni2+, which also induces grain agglomeration, as evidenced in electron microscopy imaging. The chemical bonding of NCFO, as probed by Raman spectroscopy, reveals that Co(x)-substitution induced a red shift of the T2g(2) and A1g(1) modes, and it is attributed to the changes in the metal-oxygen bond length in the octahedral and tetrahedral sites in NCFO. X-ray photoelectron spectroscopy confirms the presence of Co2+, Ni2+, and Fe3+ chemical states in addition to the cation distribution upon Co-substitution in NFO. Chemical homogeneity and uniform distribution of Co, Ni, Fe, and O are confirmed by EDS. The magnetic parameters, saturation magnetization (MS), remnant magnetization (Mr), coercivity (HC), and anisotropy constant (K1) increased with increasing Co-content "x" in NCFO. The magnetostriction (λ) also follows a similar behavior and almost linearly varies from -33 ppm (x = 0) to -227 ppm (x = 1), which is primarily due to the high magnetocrystalline anisotropy contribution from Co2+ ions at the octahedral sites. The magnetic and magnetostriction measurements and analyses indicate the potential of NCFO for torque sensor applications. Efforts to optimize materials for sensor applications indicate that, among all of the NCFO materials, Co-substitution with x = 0.5 demonstrates high strain sensitivity (-2.3 × 10-9 m/A), which is nearly 2.5 times higher than that obtained for their intrinsic counterparts, namely, NiFe2O4 (x = 0) and CoFe2O4 (x = 1).
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Affiliation(s)
- Mudalagiriyappa Satish
- Department of Chemistry, Faculty of Mathematical and Physical Sciences, M. S. Ramaiah University of Applied Sciences, Bangalore 560058, India
| | - Hadonahalli Munegowda Shashanka
- Department of Chemistry, Faculty of Mathematical and Physical Sciences, M. S. Ramaiah University of Applied Sciences, Bangalore 560058, India
| | - Sujoy Saha
- Materials Research Centre, Indian Institute of Science, Bangalore 560012, India
| | - Keerthi Haritha
- Environmental Science and Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | - Debabrata Das
- Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
- Department of Aerospace & Mechanical Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
| | | | - C V Ramana
- Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
- Department of Aerospace & Mechanical Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, Texas 79968, United States
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Anantharamaiah PN, Shashanka HM, Srinivasan S, Das D, El-Gendy AA, Ramana CV. Structural, Magnetic, and Magnetostriction Properties of Flexible, Nanocrystalline CoFe 2O 4 Films Made by Chemical Processing. ACS OMEGA 2022; 7:43813-43819. [PMID: 36506167 PMCID: PMC9730308 DOI: 10.1021/acsomega.2c04943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 10/20/2022] [Indexed: 06/17/2023]
Abstract
We report on the simple, single-step, and cost-effective fabrication, characterization, and performance evaluation of cobalt ferrite (CoFe2O4; CFO) nanocrystalline (NC) thin films on a flexible mica substrate. The chemical solution-based drop-casting method employed to fabricate crystalline CFO films and their characterization was performed by studying the phase formation, surface morphology, and magnetic parameters, while sensor applicability was evaluated using combined magnetic and magnetostrictive properties. X-ray diffraction (XRD) indicates the single-phase and nanocrystalline nature of CFO films, where the crystallite size is ∼60 nm. The optimum conditions employed resulted in CFO NC films with surface particles exhibiting a spherical shape morphology with a homogeneous size distribution, as revealed by scanning electron microscopy analyses. Raman spectroscopic characterization of the chemical bonding indicates all of the active bands that are characteristic of the ferrite phase confirm the spinel structure, which is in agreement with XRD studies. The saturation magnetization (M S) and coercivity (H C), which are extracted from the field-dependent magnetization data, of CFO NC films were found to be 15.8 emu/g and 1.6 kOe, respectively, while the first-order magnetocrystalline anisotropy constant K 1 was ∼1.07 × 106 erg/cm3. The magnetostriction strain curve indicates that the CFO NC films exhibit a strain value of ∼86 ppm at an applied magnetic field of 8 kOe, indicating their suitability for flexible sensor devices.
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Affiliation(s)
| | - Hadonahalli Munegowda Shashanka
- Department
of Chemistry, Faculty of Mathematical and Physical Sciences, M. S. Ramaiah University of Applied Sciences, Bangalore560058, India
| | - Srikari Srinivasan
- Department
of Aerospace Engineering, Faculty of Engineering and Technology, M. S. Ramaiah University of Applied Sciences, Bangalore560058, India
| | - Debabrata Das
- Center
for Advanced Materials Research, University
of Texas at El Paso, 500 West University Avenue, El Paso, Texas79968, United States
| | - Ahmed A. El-Gendy
- Center
for Advanced Materials Research, University
of Texas at El Paso, 500 West University Avenue, El Paso, Texas79968, United States
- Department
of Physics, University of Texas at El Paso, El Paso, Texas79968, United States
| | - C. V. Ramana
- Center
for Advanced Materials Research, University
of Texas at El Paso, 500 West University Avenue, El Paso, Texas79968, United States
- Department
of Mechanical Engineering, University of
Texas at El Paso, 500
West University Avenue, El Paso, Texas79968, United
States
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5
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Kharat SP, Gaikwad SK, Kambale RC, Kolekar YD, Ramana CV. Correlation between Cation Distribution and Magnetic and Dielectric Properties of Dy 3+-Substituted Fe-Rich Cobalt Ferrite. Inorg Chem 2022; 61:19319-19332. [DOI: 10.1021/acs.inorgchem.2c03125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Affiliation(s)
- Shahaji P. Kharat
- Department of Physics, Savitribai Phule Pune University, Pune411007, Maharashtra, India
- Department of Physics, Fergusson College (Autonomous), Pune411004, Maharashtra, India
| | - Swati K. Gaikwad
- Department of Physics, Savitribai Phule Pune University, Pune411007, Maharashtra, India
- Department of Physics, Fergusson College (Autonomous), Pune411004, Maharashtra, India
| | - Rahul C. Kambale
- Department of Physics, Savitribai Phule Pune University, Pune411007, Maharashtra, India
| | - Yesh D. Kolekar
- Department of Physics, Savitribai Phule Pune University, Pune411007, Maharashtra, India
| | - C. V. Ramana
- Center for Advanced Materials Research (CMR), University of Texas at El Paso, El Paso, Texas79968, United States
- Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas79968, United States
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Makeswaran N, Kelly JP, Haslam JJ, McKeown JT, Ross MS, Ramana CV. Crystallization, Phase Stability, Microstructure, and Chemical Bonding in Ga 2O 3 Nanofibers Made by Electrospinning. ACS OMEGA 2022; 7:32816-32826. [PMID: 36120052 PMCID: PMC9476513 DOI: 10.1021/acsomega.2c05168] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 08/25/2022] [Indexed: 05/27/2023]
Abstract
We report on the crystal structure, phase stability, surface morphology, microstructure, chemical bonding, and electronic properties of gallium oxide (Ga2O3) nanofibers made by a simple and economically viable electrospinning process. The effect of processing parameters on the properties of Ga2O3 nanofibers were evaluated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Thermal treatments in the range of 700-900 °C induce crystallization of amorphous fibers and lead to phase stabilization of α-GaOOH, β-Ga2O3, or mixtures of these phases. The electron diffraction analyses coupled with XPS indicate that the transformation sequence progresses by forming amorphous fibers, which then transform to crystalline fibers with a mixture of α-GaOOH and β-Ga2O3 at intermediate temperatures and fully transforms to the β-Ga2O3 phase at higher temperatures (800-900 °C). Raman spectroscopic analyses corroborate the structural evolution and confirm the high chemical quality of the β-Ga2O3 nanofibers. The surface analysis by XPS studies indicates that the hydroxyl groups are present for the as-synthesized samples, while thermal treatment at higher temperatures fully removes those hydroxyl groups, resulting in the formation of β-Ga2O3 nanofibers.
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Affiliation(s)
- Nanthakishore Makeswaran
- Centre
for Advanced Materials Research (CMR), University
of Texas at El Paso, 500 W University Ave, El Paso, Texas 79968, United
States
- Materials
Engineering Division, Lawrence Livermore
National Laboratory, 7000 East Avenue, Livermore, California 94550-5507, United States
| | - James P. Kelly
- Materials
Engineering Division, Lawrence Livermore
National Laboratory, 7000 East Avenue, Livermore, California 94550-5507, United States
| | - Jeffery J. Haslam
- Materials
Engineering Division, Lawrence Livermore
National Laboratory, 7000 East Avenue, Livermore, California 94550-5507, United States
| | - Joseph T. McKeown
- Materials
Science Division, Lawrence Livermore National
Laboratory, 7000 East
Avenue, Livermore, California 94550-5507, United States
| | - Michael S. Ross
- Materials
Engineering Division, Lawrence Livermore
National Laboratory, 7000 East Avenue, Livermore, California 94550-5507, United States
| | - C. V. Ramana
- Centre
for Advanced Materials Research (CMR), University
of Texas at El Paso, 500 W University Ave, El Paso, Texas 79968, United
States
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Ansari SM, Sinha BB, Sen D, Sastry PU, Kolekar YD, Ramana CV. Effect of Oleylamine on the Surface Chemistry, Morphology, Electronic Structure, and Magnetic Properties of Cobalt Ferrite Nanoparticles. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3015. [PMID: 36080053 PMCID: PMC9458106 DOI: 10.3390/nano12173015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/12/2022] [Accepted: 08/23/2022] [Indexed: 06/15/2023]
Abstract
The influence of oleylamine (OLA) concentration on the crystallography, morphology, surface chemistry, chemical bonding, and magnetic properties of solvothermal synthesized CoFe2O4 (CFO) nanoparticles (NPs) has been thoroughly investigated. Varying OLA concentration (0.01-0.1 M) resulted in the formation of cubic spinel-structured CoFe2O4 NPs in the size-range of 20-14 (±1) nm. The Fourier transform spectroscopic analyses performed confirmed the OLA binding to the CFO NPs. The thermogravimetric measurements revealed monolayer and multilayer coating of OLA on CFO NPs, which were further supported by the small-angle X-ray scattering measurements. The magnetic measurements indicated that the maximum saturation (MS) and remanent (Mr) magnetization decreased with increasing OLA concentration. The ratio of maximum dipolar field (Hdip), coercivity (HC), and exchanged bias field (Hex) (at 10 K) to the average crystallite size (Dxrd), i.e., (Hdip/Dxrd), (HC/Dxrd), and (Hex/Dxrd), increased linearly with OLA concentration, indicating that OLA concurrently controls the particle size and interparticle interaction among the CFO NPs. The results and analyses demonstrate that the OLA-mediated synthesis allowed for modification of the structural and magnetic properties of CFO NPs, which could readily find potential application in electronics and biomedicine.
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Affiliation(s)
- Sumayya M. Ansari
- Department of Physics, Savitribai Phule Pune University, Pune 411 007, Maharashtra, India
| | - Bhavesh B. Sinha
- National Center for Nanoscience and Nanotechnology, University of Mumbai, Mumbai 400 032, Maharashtra, India
| | - Debasis Sen
- Bhabha Atomic Research Centre (BARC), Solid State Physics Division, Mumbai 400 085, Maharashtra, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, Maharashtra, India
| | - Pulya U. Sastry
- Bhabha Atomic Research Centre (BARC), Solid State Physics Division, Mumbai 400 085, Maharashtra, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400 094, Maharashtra, India
| | - Yesh D. Kolekar
- Department of Physics, Savitribai Phule Pune University, Pune 411 007, Maharashtra, India
| | - C. V. Ramana
- Centre for Advanced Materials Research (CMR), University of Texas, El Paso, TX 79968, USA
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Zhao L, Xi X, Liu Y, Ma L, Nie Z. Growth mechanism and visible-light-driven photocatalysis of organic solvent dependent WO3 and nonstoichiometric WO3-x nanostructures. J Taiwan Inst Chem Eng 2020. [DOI: 10.1016/j.jtice.2020.10.031] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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9
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Nivedita LR, Haubert A, Battu AK, Ramana CV. Correlation between Crystal Structure, Surface/Interface Microstructure, and Electrical Properties of Nanocrystalline Niobium Thin Films. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1287. [PMID: 32629967 PMCID: PMC7407818 DOI: 10.3390/nano10071287] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 06/14/2020] [Accepted: 06/26/2020] [Indexed: 11/16/2022]
Abstract
Niobium (Nb) thin films, which are potentially useful for integration into electronics and optoelectronics, were made by radio-frequency magnetron sputtering by varying the substrate temperature. The deposition temperature (Ts) effect was systematically studied using a wide range, 25-700 °C, using Si(100) substrates for Nb deposition. The direct correlation between deposition temperature (Ts) and electrical properties, surface/interface microstructure, crystal structure, and morphology of Nb films is reported. The Nb films deposited at higher temperature exhibit a higher degree of crystallinity and electrical conductivity. The Nb films' crystallite size varied from 5 to 9 (±1) nm and tensile strain occurs in Nb films as Ts increases. The surface/interface morphology of the deposited Nb films indicate the grain growth and dense, vertical columnar structure at elevated Ts. The surface roughness derived from measurements taken using atomic force microscopy reveal that all the Nb films are characteristically smooth with an average roughness <2 nm. The lowest electrical resistivity obtained was 48 µΩ cm. The correlations found here between growth conditions electrical properties as well as crystal structure, surface/interface morphology, and microstructure, could provide useful information for optimum conditions to produce Nb thin films for utilization in electronics and optoelectronics.
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Affiliation(s)
- L. R. Nivedita
- Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA; (L.R.N.); (A.K.B.)
| | - Avery Haubert
- Department of Physics, University of California, Santa Barbara, Broida Hall, Santa Barbara, CA 93106, USA;
| | - Anil K. Battu
- Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA; (L.R.N.); (A.K.B.)
- Department of Mechanical Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA
| | - C. V. Ramana
- Center for Advanced Materials Research, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA; (L.R.N.); (A.K.B.)
- Department of Mechanical Engineering, University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA
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10
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Zhao L, Xi X, Liu Y, Ma L, Nie Z. Facile synthesis of WO3 micro/nanostructures by paper-assisted calcination for visible-light-driven photocatalysis. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2019.110515] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ramana CV, Baghmar G, Rubio EJ, Hernandez MJ. Optical constants of amorphous, transparent titanium-doped tungsten oxide thin films. ACS APPLIED MATERIALS & INTERFACES 2013; 5:4659-4666. [PMID: 23682744 DOI: 10.1021/am4006258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We report on the optical constants and their dispersion profiles determined from spectroscopic ellipsometry (SE) analysis of the 20%-titanium (Ti) doped of tungsten oxide (WO3) thin films grown by sputter-deposition. The Ti-doped WO3 films grown in a wide range of temperatures (25-500 °C) are amorphous and optically transparent. SE data indicates that there is no significant interdiffusion at the film-substrate interface for a W-Ti oxide film growth of ~90 nm. The index refraction (n) at λ = 550 nm vary in the range of 2.17-2.31 with a gradual increase in growth temperature. A correlation between the growth conditions and optical constants is discussed.
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Affiliation(s)
- C V Ramana
- Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, United States
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Noor-A-Alam M, Choudhuri AR, Ramana CV. Structure and Thermal Conductivity of Nanostructured Hafnia-Based Thermal Barrier Coating Grown on SS-403. J Nanotechnol Eng Med 2013. [DOI: 10.1115/1.4024046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Yttria-stabilized hafnia (YSH) coatings were grown onto stainless steel 403 (SS-403) and Si substrates. The deposition was made at various growth temperatures ranging from room temperature (RT) to 500 °C. The microstructure and thermal properties of the YSH coatings were evaluated employing grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and photoacoustic measurements. GIXRD studies indicate that the coatings crystalize in cubic structure with a (111) texturing. Well-grown triangular dense morphology was evident in SEM data. EDS analysis indicates the composition stability of YSH coatings. The grain size increases with the increasing growth temperature. Thermal conductivity measurements indicate lower thermal conductivity of YSH coatings compared to either pure hafnia or yttria-stabilized zirconia.
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Affiliation(s)
| | | | - C. V. Ramana
- e-mail: Department of Mechanical Engineering, University of Texas at El Paso, El Paso, TX 79968
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Vemuri RS, Engelhard MH, Ramana CV. Correlation between surface chemistry, density, and band gap in nanocrystalline WO3 thin films. ACS APPLIED MATERIALS & INTERFACES 2012; 4:1371-1377. [PMID: 22332637 DOI: 10.1021/am2016409] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Nanocrystalline WO(3) thin films were produced by sputter-deposition by varying the ratio of argon to oxygen in the reactive gas mixture during deposition. The surface chemistry, physical characteristics, and optical properties of nanocrystalline WO(3) films were evaluated using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray reflectivity (XRR), and spectrophotometric measurements. The effect of ultramicrostructure was significant on the optical properties of WO(3) films. The XPS analyses indicate the formation of stoichiometric WO(3) with tungsten existing in fully oxidized valence state (W(6+)). However, WO(3) films grown at high oxygen concentration (>60%) in the sputtering gas mixture were over stoichiometric with excess oxygen. XRR simulations based on isotropic WO(3) film-SiO(2) interface-Si substrate modeling indicate that the density of WO(3) films is sensitive to the oxygen content in the sputtering gas. The spectral transmission of the films increased with increasing oxygen. The band gap of these films increases from 2.78 to 3.25 eV with increasing oxygen. A direct correlation between the film density and band gap in nanocrystalline WO(3) films is established on the basis of the observed results.
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Affiliation(s)
- R S Vemuri
- Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, USA
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Ramana CV, Noor-A-Alam M, Gengler JJ, Jones JG. Growth, structure, and thermal conductivity of yttria-stabilized hafnia thin films. ACS APPLIED MATERIALS & INTERFACES 2012; 4:200-204. [PMID: 22148322 DOI: 10.1021/am2012596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Yttria-stabilized hafnia (YSH) films of 90 nm thickness have been produced using sputter-deposition by varying the growth temperature (T(s)) from room-temperature (RT) to 400 °C. The effect of T(s) on the structure, morphology, and thermal conductivity of YSH films has been investigated. Structural studies indicate that YSH films crystallize in the cubic phase. The lattice constant decreases from 5.15 to 5.10 Å with increasing T(s). The average grain size (L) increases with increasing T(s); L-T(s) relationship indicates the thermally activated process of the crystallization of YSH films. The analyses indicate a critical temperature to promote nanocrystalline, cubic YSH films is 300 °C, which is higher compare to that of pure monoclinic HfO(2) films. Compared to pure nanocrystalline hafnia, the addition of yttria lowers the effective thermal conductivity. The effect of grain size on thermal conductivity is also explored.
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Affiliation(s)
- C V Ramana
- Department of Mechanical Engineering, University of Texas at El Paso, El Paso, Texas 79968, USA.
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