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Le LV, Nguyen TT, Nguyen XA, Cuong DD, Nguyen TH, Nguyen VQ, Cho S, Kim YD, Kim TJ. A Systematic Study of the Temperature Dependence of the Dielectric Function of GaSe Uniaxial Crystals from 27 to 300 K. NANOMATERIALS (BASEL, SWITZERLAND) 2024; 14:839. [PMID: 38786795 PMCID: PMC11124486 DOI: 10.3390/nano14100839] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 05/02/2024] [Accepted: 05/07/2024] [Indexed: 05/25/2024]
Abstract
We report the temperature dependences of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and pz orbitals at the Γ-point.
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Affiliation(s)
- Long V. Le
- Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam;
| | - Tien-Thanh Nguyen
- Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi 100000, Vietnam;
| | - Xuan Au Nguyen
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea; (X.A.N.); (Y.D.K.)
| | - Do Duc Cuong
- Faculty of Physics and Engineering Physics, University of Science, VNU-HCM, Ho Chi Minh City 700000, Vietnam;
| | - Thi Huong Nguyen
- Department of Physics, Nha Trang University, Nha Trang 650000, Vietnam;
- Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea; (V.Q.N.); (S.C.)
| | - Van Quang Nguyen
- Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea; (V.Q.N.); (S.C.)
- Advanced Process Development Team, ISAC Research Inc., Techno2ro 340, Tabrip-dong, Yuseong-gu, Daejeon 34036, Republic of Korea
| | - Sunglae Cho
- Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan 44610, Republic of Korea; (V.Q.N.); (S.C.)
| | - Young Dong Kim
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea; (X.A.N.); (Y.D.K.)
| | - Tae Jung Kim
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea; (X.A.N.); (Y.D.K.)
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Azam N, Mahjouri-Samani M. Time-Resolved Growth of 2D WSe 2 Monolayer Crystals. ACS NANO 2023. [PMID: 37339265 DOI: 10.1021/acsnano.3c02280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/22/2023]
Abstract
Understanding and controlling the growth evolution of atomically thin monolayer two-dimensional (2D) materials such as transition metal dichalcogenides (TMDCs) are vital for next-generation 2D electronics and optoelectronic devices. However, their growth kinetics are not fully observed or well understood due to the bottlenecks associated with the existing synthesis methods. This study demonstrates the time-resolved and ultrafast growth of 2D materials by a laser-based synthesis approach that enables the rapid initiation and termination of the vaporization process during crystal growth. The use of stoichiometric powder (e.g., WSe2) minimizes the complex chemistry during the vaporization and growth process, allowing rapid initiation/termination control over the generated flux. An extensive set of experiments is performed to understand the growth evolution, achieving subsecond growth as low as 10 ms along with a 100 μm/s growth rate on a noncatalytic substrate such as Si/SiO2. Overall, this study allows us to observe and understand the 2D crystal evolution and growth kinetics with time-resolved and subsecond time scales.
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Affiliation(s)
- Nurul Azam
- Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36849, United States
| | - Masoud Mahjouri-Samani
- Electrical and Computer Engineering Department, Auburn University, Auburn, Alabama 36849, United States
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Computational probe for the geometrical structure and spectroscopic properties of Ga2Mgn+ (n = 1–11) clusters. COMPUT THEOR CHEM 2021. [DOI: 10.1016/j.comptc.2021.113500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Liu C, Liu F, Jin C, Zhang S, Zhang L, Han M. Formation Mechanism of Well-Ordered Densely Packed Nanoparticle Superlattices Deposited from Gas Phase on Template-Free Surfaces. NANOSCALE RESEARCH LETTERS 2021; 16:172. [PMID: 34850309 PMCID: PMC8633269 DOI: 10.1186/s11671-021-03635-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 11/24/2021] [Indexed: 06/13/2023]
Abstract
Superlattices of nanoparticles are generally produced based on solution chemistry processes. In this paper, we demonstrate that self-assembled monolayer structures of nanoparticles with superlattice periodicities can also be produced on template-free surfaces in the gas-phase cluster beam deposition process. It is found that the packing of Fe nanoparticles corresponds to an average of two-dimensional densely packed lattice with a hexagonal summary. By controlling the nanoparticle coverage, the two-dimensional densely packed monolayer morphology can spread to the whole substrate surface being deposited. A formation mechanism of the ordered monolayers is proposed. The densely packed morphologies are formed by the balance between the diffusion rate of the nanoparticles and their filling speed on the substrate surface determined by the deposition rate, and the ordering of the nanoparticle arrays is driven by the inter-particle attractive interactions. The model is strongly supported by a series of carefully designed cluster deposition experiments.
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Affiliation(s)
- Chang Liu
- National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Department of Materials Science and Engineering and Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, China
| | - Fei Liu
- National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Department of Materials Science and Engineering and Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, China
| | - Chen Jin
- National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
- Department of Materials Science and Engineering and Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, China
| | - Sishi Zhang
- Department of Materials Science and Engineering and Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, China
| | - Lianhua Zhang
- National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Min Han
- National Laboratory of Solid State Microstructures and Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
- Department of Materials Science and Engineering and Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, Nanjing, 210093, China.
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Iram S, Mahmood A, Ehsan MF, Mumtaz A, Sohail M, Sitara E, Mushtaq S, Malik MA, Fatima SA, Shaheen R, Ahmad NM, Malik SN. Impedance Spectroscopy Analysis of PbSe Nanostructures Deposited by Aerosol Assisted Chemical Vapor Deposition Approach. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:2817. [PMID: 34835581 PMCID: PMC8622599 DOI: 10.3390/nano11112817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/20/2021] [Accepted: 08/21/2021] [Indexed: 11/17/2022]
Abstract
This research endeavor aimed to synthesize the lead (II) diphenyldiselenophosphinate complex and its use to obtain lead selenide nanostructured depositions and further the impedance spectroscopic analysis of these obtained PbSe nanostructures, to determine their roles in the electronics industry. The aerosol-assisted chemical vapor deposition technique was used to provide lead selenide deposition by decomposition of the complex at different temperatures using the glass substrates. The obtained films were revealed to be a pure cubic phase PbSe, as confirmed by X-ray diffraction analysis. SEM and TEM micrographs demonstrated three-dimensionally grown interlocked or aggregated nanocubes of the obtained PbSe. Characteristic dielectric measurements and the impedance spectroscopy analysis at room temperature were executed to evaluate PbSe properties over the frequency range of 100 Hz-5 MHz. The dielectric constant and dielectric loss gave similar trends, along with altering frequency, which was well explained by the Koops theory and Maxwell-Wagner theory. The effective short-range translational carrier hopping gave rise to an overdue remarkable increase in ac conductivity (σac) on the frequency increase. Fitting of a complex impedance plot was carried out with an equivalent circuit model (Rg Cg) (Rgb Qgb Cgb), which proved that grains, as well as grain boundaries, are responsible for the relaxation processes. The asymmetric depressed semicircle with the center lower to the impedance real axis provided a clear explanation of non-Debye dielectric behavior.
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Affiliation(s)
- Sadia Iram
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
- Department of Materials, University of Manchester, Manchester M13 9PL, UK;
| | - Azhar Mahmood
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | - Muhammad Fahad Ehsan
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | - Asad Mumtaz
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | - Manzar Sohail
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | - Effat Sitara
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | - Shehla Mushtaq
- School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan; (S.I.); (M.F.E.); (A.M.); (M.S.); (E.S.); (S.M.)
| | | | - Syeda Arooj Fatima
- Central Diagnostic Laboratory, Physics Division, PINSTECH, P.O. Nilore., Islamabad 45500, Pakistan; (S.A.F.); (R.S.)
| | - Rubina Shaheen
- Central Diagnostic Laboratory, Physics Division, PINSTECH, P.O. Nilore., Islamabad 45500, Pakistan; (S.A.F.); (R.S.)
| | - Nasir Mahmood Ahmad
- Department of Materials Engineering, School of Chemical and Materials Engineering (SCME)-National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan; (N.M.A.); (S.N.M.)
| | - Sajid Nawaz Malik
- Department of Materials Engineering, School of Chemical and Materials Engineering (SCME)-National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan; (N.M.A.); (S.N.M.)
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Ahmadi Z, Fathi-Hafshejani P, Kayali E, Beidaghi M, Mahjouri-Samani M. Rapid laser nanomanufacturing and direct patterning of 2D materials on flexible substrates-2DFlex. NANOTECHNOLOGY 2021; 32:055302. [PMID: 33075755 DOI: 10.1088/1361-6528/abc285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Direct synthesis, large-scale integration, and patterning of two-dimensional (2D) quantum materials (e.g. MoS2, WSe2) on flexible and transparent substrates are of high interest for flexible and conformal device applications. However, the growth temperatures (e.g. 850 °C) of the emerging 2D materials in the common gas-phase synthesis methods are well beyond the tolerances limit of flexible substrates, such as polydimethylsiloxane (PDMS). In addition, random nucleation and growth process in most growth systems limits the predicted integration and patterning freedoms. Here, we report a rapid direct laser crystallization and mask-free large-scale patterning of MoS2 and WSe2 crystals on PDMS substrates. A thin layer of stoichiometric amorphous 2D film is first laser-deposited via pulsed laser deposition (PLD) system onto the flexible substrates followed by a controlled crystallization and direct writing process using a tunable nanosecond laser (1064 nm). The influences of pulse duration, number of pulses, and the thickness of the deposited amorphous 2D layer on the crystallization of 2D materials are discussed. Optical spectroscopy and electrical characterizations are performed to confirm the quality of crystallized 2D materials on flexible substrates. This novel method opens up a new opportunity for the crystallization of complex patterns directly from computer-aided design models for the future 2D materials-based wearable, transparent, and flexible devices.
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Affiliation(s)
- Zabihollah Ahmadi
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, 36849, United States of America
| | - Parvin Fathi-Hafshejani
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, 36849, United States of America
| | - Emre Kayali
- Department of Mechanical and Material Engineering, Auburn University, Auburn, AL, 36849, United States of America
| | - Majid Beidaghi
- Department of Mechanical and Material Engineering, Auburn University, Auburn, AL, 36849, United States of America
| | - Masoud Mahjouri-Samani
- Department of Electrical and Computer Engineering, Auburn University, Auburn, AL, 36849, United States of America
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