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Scott JI, Adams RL, Martinez-Gazoni RF, Carroll LR, Downard AJ, Veal TD, Reeves RJ, Allen MW. Looking Outside the Square: The Growth, Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO 2 Nanotubes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023:e2300520. [PMID: 37191281 DOI: 10.1002/smll.202300520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 03/31/2023] [Indexed: 05/17/2023]
Abstract
Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO2 nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO2 nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.
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Affiliation(s)
- Jonty I Scott
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Ryan L Adams
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Rodrigo F Martinez-Gazoni
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Liam R Carroll
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Alison J Downard
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Tim D Veal
- Stephenson Institute for Renewable Energy and Department of Physics, University of Liverpool, Liverpool, L69 7ZF, UK
| | - Roger J Reeves
- School of Physical and Chemical Sciences and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
| | - Martin W Allen
- Department of Electrical and Computer Engineering and MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Canterbury, Christchurch, 8140, New Zealand
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2
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Shi J, Zhang J, Yang L, Qu M, Qi DC, Zhang KHL. Wide Bandgap Oxide Semiconductors: from Materials Physics to Optoelectronic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006230. [PMID: 33797084 DOI: 10.1002/adma.202006230] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2020] [Revised: 12/30/2020] [Indexed: 06/12/2023]
Abstract
Wide bandgap oxide semiconductors constitute a unique class of materials that combine properties of electrical conductivity and optical transparency. They are being widely used as key materials in optoelectronic device applications, including flat-panel displays, solar cells, OLED, and emerging flexible and transparent electronics. In this article, an up-to-date review on both the fundamental understanding of materials physics of oxide semiconductors, and recent research progress on design of new materials and high-performing thin film transistor (TFT) devices in the context of fundamental understanding is presented. In particular, an in depth overview is first provided on current understanding of the electronic structures, defect and doping chemistry, optical and transport properties of oxide semiconductors, which provide essential guiding principles for new material design and device optimization. With these principles, recent advances in design of p-type oxide semiconductors, new approaches for achieving cost-effective transparent (flexible) electrodes, and the creation of high mobility 2D electron gas (2DEG) at oxide surfaces and interfaces with a wealth of fascinating physical properties of great potential for novel device design are then reviewed. Finally, recent progress and perspective of oxide TFT based on new oxide semiconductors, 2DEG, and low-temperature solution processed oxide semiconductor for flexible electronics will be reviewed.
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Affiliation(s)
- Jueli Shi
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Jiaye Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Lu Yang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Mei Qu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Dong-Chen Qi
- Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, Queensland, 4001, Australia
| | - Kelvin H L Zhang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
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3
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Liang Y. The substitution modulation on Ca site of CaTiO3 for transparent conductive oxides from first principles study. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.139111] [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]
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4
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Sopiha KV, Malyi OI, Persson C, Wu P. Chemistry of Oxygen Ionosorption on SnO 2 Surfaces. ACS APPLIED MATERIALS & INTERFACES 2021; 13:33664-33676. [PMID: 34251174 PMCID: PMC8397246 DOI: 10.1021/acsami.1c08236] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Accepted: 06/28/2021] [Indexed: 06/02/2023]
Abstract
Ionosorbed oxygen is the key player in reactions on metal-oxide surfaces. This is particularly evident for chemiresistive gas sensors, which operate by modulating the conductivity of active materials through the formation/removal of surface O-related acceptors. Strikingly though, the exact type of species behind the sensing response remains obscure even for the most common material systems. The paradigm for ab initio modeling to date has been centered around charge-neutral surface species, ignoring the fact that molecular adsorbates are required to ionize to induce the sensing response. Herein, we resolve this inconsistency by carrying out a careful analysis of all charged O-related species on three naturally occurring surfaces of SnO2. We reveal that two types of surface acceptors can form spontaneously upon the adsorption of atmospheric oxygen: (i) superoxide O2- on the (110) and the (101) surfaces and (ii) doubly ionized O2- on the (100) facet, with the previous experimental evidence pointing to the latter as the source of sensing response. This species has a unique geometry involving a large displacement of surface Sn, forcing it to attain the coordination resembling that of Sn2+ in SnO, which seems necessary to stabilize O2- and activate metal-oxide surfaces for gas sensing.
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Affiliation(s)
- Kostiantyn V. Sopiha
- Solar
Cell Technology, Department of Materials Science and Engineering, Uppsala University, Box 534, SE-75121 Uppsala, Sweden
| | - Oleksandr I. Malyi
- Renewable
and Sustainable Energy Institute, University
of Colorado, Boulder, Colorado 80309, United States
| | - Clas Persson
- Centre
for Materials Science and Nanotechnology/Department of Physics, University of Oslo, P.O.
Box 1048, Blindern, NO-0316 Oslo, Norway
- Division
of Applied Materials Physics, Department of Materials Science and
Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Ping Wu
- Entropic
Interface Group, Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
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5
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Sopiha KV, Malyi OI, Persson C, Wu P. Chemistry of Oxygen Ionosorption on SnO 2 Surfaces. ACS APPLIED MATERIALS & INTERFACES 2021. [PMID: 34251174 DOI: 10.24435/materialscloud:zv-bg] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ionosorbed oxygen is the key player in reactions on metal-oxide surfaces. This is particularly evident for chemiresistive gas sensors, which operate by modulating the conductivity of active materials through the formation/removal of surface O-related acceptors. Strikingly though, the exact type of species behind the sensing response remains obscure even for the most common material systems. The paradigm for ab initio modeling to date has been centered around charge-neutral surface species, ignoring the fact that molecular adsorbates are required to ionize to induce the sensing response. Herein, we resolve this inconsistency by carrying out a careful analysis of all charged O-related species on three naturally occurring surfaces of SnO2. We reveal that two types of surface acceptors can form spontaneously upon the adsorption of atmospheric oxygen: (i) superoxide O2- on the (110) and the (101) surfaces and (ii) doubly ionized O2- on the (100) facet, with the previous experimental evidence pointing to the latter as the source of sensing response. This species has a unique geometry involving a large displacement of surface Sn, forcing it to attain the coordination resembling that of Sn2+ in SnO, which seems necessary to stabilize O2- and activate metal-oxide surfaces for gas sensing.
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Affiliation(s)
- Kostiantyn V Sopiha
- Solar Cell Technology, Department of Materials Science and Engineering, Uppsala University, Box 534, SE-75121 Uppsala, Sweden
| | - Oleksandr I Malyi
- Renewable and Sustainable Energy Institute, University of Colorado, Boulder, Colorado 80309, United States
| | - Clas Persson
- Centre for Materials Science and Nanotechnology/Department of Physics, University of Oslo, P.O. Box 1048, Blindern, NO-0316 Oslo, Norway
- Division of Applied Materials Physics, Department of Materials Science and Engineering, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden
| | - Ping Wu
- Entropic Interface Group, Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore
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Morphology of Ga 2O 3 Nanowires and Their Sensitivity to Volatile Organic Compounds. NANOMATERIALS 2021; 11:nano11020456. [PMID: 33670141 PMCID: PMC7916880 DOI: 10.3390/nano11020456] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 02/06/2021] [Accepted: 02/08/2021] [Indexed: 12/25/2022]
Abstract
Gas sensitive structures made of nanowires exhibit extremally large specific surface area, and a great number of chemically active centres that can react with the ambient atmosphere. This makes the use of nanomaterials promising for super sensitive gas sensor applications. Monoclinic β-Ga2O3 nanowires (NWs) were synthesized from metallic gallium at atmospheric pressure in the presence of nitrogen and water vapor. The nanowires were grown directly on interdigitated gold electrodes screen printed on Al2O3 substrates, which constituted the gas sensor structure. The observations made with transmission electron microscope (TEM) have shown that the nanowires are monocrystalline and their diameters vary from 80 to 300 nm with the average value of approximately 170 nm. Au droplets were found to be anchored at the tips of the nanowires which may indicate that the nanowires followed the Vapor-Liquid-Solid (VLS) mechanism of growth. The conductivity of β-Ga2O3 NWs increases in the presence of volatile organic compounds (VOC) even in the temperature below 600 °C. The gas sensor based on the synthesized β-Ga2O3 NWs shows peak sensitivity to 100 ppm of ethanol of 75.1 at 760 °C, while peak sensitivity to 100 ppm of acetone is 27.5 at 690 °C.
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Abstract
Sulvanites have the parent formula Cu3MCh4. The metal M belongs to group 5 and Ch is a chalcogen. The tantalum sulvanites Cu3TaS4 and Cu3TaSe4 are predicted to have wide band gaps and p-type conductivity and show promise in optoelectronic applications. Their potential as p-type transparent conductors or efficient photocatalysts for visible-light water splitting is a valuable incentive to explore these materials in their nanoscale form, toward bottom-up processing opportunities. Reported herein are the first syntheses of nanosized Cu3TaS4 and Cu3TaSe4 sulvanites, which preserve the parent cubic crystal structure but show that morphology at the nanoscale is dependent of the reaction conditions. The two solution-based methods for synthesizing the tantalum S and Se sulvanites result in Cu3TaS4 or Cu3TaSe4 nanocrystals (NCs) with prismatic morphology, or, in the case of Cu3TaSe4, could lead to core-shell spherical nanostructures. The Cu3TaS4 NCs and Cu3TaSe4 NCs have good absorption in the UV-Vis region, while the Cu3TaSe4 core-shell NCs possess broad absorption bands not only in the UV-Vis but also in the near-infrared region. Photoluminescence measurements of Cu3TaS4 and Cu3TaSe4 reveal optical bandgaps of 2.54 and 2.32 eV, respectively, consistent with the values measured in bulk. Additionally, the current–voltage (I-V) curve of Cu3TaS4 NCs proves its electrical conductivity.
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Foglia L, Vempati S, Tanda Bonkano B, Gierster L, Wolf M, Sadofev S, Stähler J. Revealing the competing contributions of charge carriers, excitons, and defects to the non-equilibrium optical properties of ZnO. STRUCTURAL DYNAMICS (MELVILLE, N.Y.) 2019; 6:034501. [PMID: 31123699 PMCID: PMC6506340 DOI: 10.1063/1.5088767] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 04/14/2019] [Indexed: 06/09/2023]
Abstract
Due to its wide band gap and high carrier mobility, ZnO is, among other transparent conductive oxides, an attractive material for light-harvesting and optoelectronic applications. Its functional efficiency, however, is strongly affected by defect-related in-gap states that open up extrinsic decay channels and modify relaxation timescales. As a consequence, almost every sample behaves differently, leading to irreproducible or even contradicting observations. Here, a complementary set of time-resolved spectroscopies is applied to two ZnO samples of different defect density to disentangle the competing contributions of charge carriers, excitons, and defects to the nonequilibrium dynamics after photoexcitation: time-resolved photoluminescence, excited state transmission, and electronic sum-frequency generation. Remarkably, defects affect the transient optical properties of ZnO across more than eight orders of magnitude in time, starting with photodepletion of normally occupied defect states on femtosecond timescales, followed by the competition of free exciton emission and exciton trapping at defect sites within picoseconds, photoluminescence of defect-bound and free excitons on nanosecond timescales, and deeply trapped holes with microsecond lifetimes. These findings not only provide the first comprehensive picture of charge and exciton relaxation pathways in ZnO but also uncover the microscopic origin of previous conflicting observations in this challenging material and thereby offer means of overcoming its difficulties. Noteworthy, a similar competition of intrinsic and defect-related dynamics could likely also be utilized in other oxides with marked defect density as, for instance, TiO2 or SrTiO3.
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Affiliation(s)
- Laura Foglia
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
| | - Sesha Vempati
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
| | - Boubacar Tanda Bonkano
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
| | - Lukas Gierster
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
| | - Martin Wolf
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
| | - Sergey Sadofev
- AG Photonik, Institut für Physik, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany
| | - Julia Stähler
- Department of Physical Chemistry, Fritz Haber Institute of the Max Planck Society, Faradayweg 4–6, 14195 Berlin, Germany
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9
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Anzai H, Takahashi T, Suzuki M, Kanai M, Zhang G, Hosomi T, Seki T, Nagashima K, Shibata N, Yanagida T. Unusual Oxygen Partial Pressure Dependence of Electrical Transport of Single-Crystalline Metal Oxide Nanowires Grown by the Vapor-Liquid-Solid Process. NANO LETTERS 2019; 19:1675-1681. [PMID: 30827116 DOI: 10.1021/acs.nanolett.8b04668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In general, the electrical conductivities of n-type semiconducting metal oxide nanostructures increase with the decrease in the oxygen partial pressure during crystal growth owing to the increased number of crystal imperfections including oxygen vacancies. In this paper, we report an unusual oxygen partial pressure dependence of the electrical conductivity of single-crystalline SnO2 nanowires grown by a vapor-liquid-solid (VLS) process. The electrical conductivity of a single SnO2 nanowire, measured using the four-probe method, substantially decreases by 2 orders of magnitude when the oxygen partial pressure for the crystal growth is reduced from 10-3 to 10-4 Pa. This contradicts the conventional trend of n-type SnO2 semiconductors. Spatially resolved single-nanowire electrical transport measurements, microstructure analysis, plane-view electron energy-loss spectroscopy, and molecular dynamics simulations reveal that the observed unusual oxygen partial pressure dependence of the electrical transport is attributed to the intrinsic differences between the two crystal growth interfaces (LS and VS interfaces) in the critical nucleation of the crystal growth and impurity incorporation probability as a function of the oxygen partial pressure. The impurity incorporation probability at the LS interface is always lower than that at the VS interface, even under reduced oxygen partial pressures.
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Affiliation(s)
- Hiroshi Anzai
- Interdisciplinary Graduate School of Engineering Sciences , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Tsunaki Takahashi
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Masaru Suzuki
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Masaki Kanai
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Guozhu Zhang
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Takuro Hosomi
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Takehito Seki
- Institute of Engineering Innovation , The University of Tokyo , 2-11-16 Yayoi , Bunkyo, Tokyo 113-8656 , Japan
| | - Kazuki Nagashima
- Interdisciplinary Graduate School of Engineering Sciences , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
| | - Naoya Shibata
- Institute of Engineering Innovation , The University of Tokyo , 2-11-16 Yayoi , Bunkyo, Tokyo 113-8656 , Japan
| | - Takeshi Yanagida
- Interdisciplinary Graduate School of Engineering Sciences , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
- Institute for Materials Chemistry and Engineering , Kyushu University , 6-1 Kasuga-Koen , Kasuga, Fukuoka 816-8580 , Japan
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10
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Copper Delafossites under High Pressure—A Brief Review of XRD and Raman Spectroscopic Studies. CRYSTALS 2018. [DOI: 10.3390/cryst8060255] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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11
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Catellani A, Calzolari A. Codoping and Interstitial Deactivation in the Control of Amphoteric Li Dopant in ZnO for the Realization of p-Type TCOs. MATERIALS 2017; 10:ma10040332. [PMID: 28772691 PMCID: PMC5506896 DOI: 10.3390/ma10040332] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/07/2017] [Accepted: 03/21/2017] [Indexed: 11/23/2022]
Abstract
We report on first principle investigations about the electrical character of Li-X codoped ZnO transparent conductive oxides (TCOs). We studied a set of possible X codopants including either unintentional dopants typically present in the system (e.g., H, O) or monovalent acceptor groups, based on nitrogen and halogens (F, Cl, I). The interplay between dopants and structural point defects in the host (such as vacancies) is also taken explicitly into account, demonstrating the crucial effect that zinc and oxygen vacancies have on the final properties of TCOs. Our results show that Li-ZnO has a p-type character, when Li is included as Zn substitutional dopant, but it turns into an n-type when Li is in interstitial sites. The inclusion of X-codopants is considered to deactivate the n-type character of interstitial Li atoms: the total Li-X compensation effect and the corresponding electrical character of the doped compounds selectively depend on the presence of vacancies in the host. We prove that LiF-doped ZnO is the only codoped system that exhibits a p-type character in the presence of Zn vacancies.
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Affiliation(s)
- Alessandra Catellani
- CNR-NANO Istituto Nanoscienze, Centro S3, via Campi 213A, I-41125 Modena, Italy.
| | - Arrigo Calzolari
- CNR-NANO Istituto Nanoscienze, Centro S3, via Campi 213A, I-41125 Modena, Italy.
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McNeill AR, Hyndman AR, Reeves RJ, Downard AJ, Allen MW. Tuning the Band Bending and Controlling the Surface Reactivity at Polar and Nonpolar Surfaces of ZnO through Phosphonic Acid Binding. ACS APPLIED MATERIALS & INTERFACES 2016; 8:31392-31402. [PMID: 27768292 DOI: 10.1021/acsami.6b10309] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
ZnO is a prime candidate for future use in transparent electronics; however, development of practical materials requires attention to factors including control of its unusual surface band bending and surface reactivity. In this work, we have modified the O-polar (0001̅), Zn-polar (0001), and m-plane (101̅0) surfaces of ZnO with phosphonic acid (PA) derivatives and measured the effect on the surface band bending and surface sensitivity to atmospheric oxygen. Core level and valence band synchrotron X-ray photoemission spectroscopy was used to measure the surface band bending introduced by PA modifiers with substituents of opposite polarity dipole moment: octadecylphosphonic acid (ODPA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid (F13OPA). Both PAs act as surface electron donors, increasing the downward band bending and the strength of the two-dimensional surface electron accumulation layer on all of the ZnO surfaces investigated. On the O-polar (0001̅) and m-plane (101̅0) surfaces, the ODPA modifier produced the largest increase in downward band bending relative to the hydroxyl-terminated unmodified surface of 0.55 and 0.35 eV, respectively. On the Zn-polar (0001) face, the F13OPA modifier gave the largest increase (by 0.50 eV) producing a total downward band bending of 1.00 eV, representing ∼30% of the ZnO band gap. Ultraviolet (UV) photoinduced surface wettability and photoconductivity measurements demonstrated that the PA modifiers are effective at decreasing the sensitivity of the surface toward atmospheric oxygen. Modification with PA derivatives produced a large increase in the persistence of UV-induced photoconductivity and a large reduction in UV-induced changes in surface wettability.
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Affiliation(s)
- Alexandra R McNeill
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Adam R Hyndman
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Roger J Reeves
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Alison J Downard
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
| | - Martin W Allen
- MacDiarmid Institute for Advanced Materials and Nanotechnology , Wellington 6140, New Zealand
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Choi DS, Singh M, Zhou H, Milchak M, Hahm JI. Scattering attributes of one-dimensional semiconducting oxide nanomaterials individually probed for varying light-matter interaction angles. APPLIED PHYSICS LETTERS 2015; 107:151110. [PMID: 26549887 PMCID: PMC4608960 DOI: 10.1063/1.4933400] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/06/2015] [Indexed: 05/16/2023]
Abstract
We report the characteristic optical responses of one-dimensional semiconducting oxide nanomaterials by examining the individual nanorods (NRs) of ZnO, SnO2, indium tin oxide, and zinc tin oxide under precisely controlled, light-matter interaction geometry. Scattering signals from a large set of NRs of the different types are evaluated spatially along the NR length while varying the NR tilt angle, incident light polarization, and analyzer rotation. Subsequently, we identify material-indiscriminate, NR tilt angle- and incident polarization-dependent scattering behaviors exhibiting continuous, intermittent, and discrete responses. The insight gained from this study can advance our fundamental understanding of the optical behaviors of the technologically useful nanomaterials and, at the same time, promote the development of highly miniaturized, photonic and bio-optical devices utilizing the spatially controllable, optical responses of the individual semiconducting oxide NRs.
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Affiliation(s)
- Daniel S Choi
- Department of Chemistry, Georgetown University , 37th & O Sts., N.W., Washington, DC 20057, USA
| | - Manpreet Singh
- Department of Chemistry, Georgetown University , 37th & O Sts., N.W., Washington, DC 20057, USA
| | - Hebing Zhou
- Department of Chemistry, Georgetown University , 37th & O Sts., N.W., Washington, DC 20057, USA
| | - Marissa Milchak
- Department of Chemistry, Georgetown University , 37th & O Sts., N.W., Washington, DC 20057, USA
| | - Jong-In Hahm
- Department of Chemistry, Georgetown University , 37th & O Sts., N.W., Washington, DC 20057, USA
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14
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Song J, Zeng H. Transparent Electrodes Printed with Nanocrystal Inks for Flexible Smart Devices. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/anie.201501233] [Citation(s) in RCA: 124] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jizhong Song
- State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)
- Institute of Optoelectronics and Nanomaterials, Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)
| | - Haibo Zeng
- State Key Laboratory of Mechanics and Control of Mechanical Structures, College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China)
- Institute of Optoelectronics and Nanomaterials, Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)
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15
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Song J, Zeng H. Transparente Elektroden aus Nanokristalltinten für flexible Bauelemente. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201501233] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition. Sci Rep 2015; 5:10952. [PMID: 26042724 PMCID: PMC4650706 DOI: 10.1038/srep10952] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 04/29/2015] [Indexed: 12/23/2022] Open
Abstract
Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm3/V.s) and concentration (×1019 cm−3). XPS indicated the presence of both W6+ and W4+ in the TiO2 matrix, with the substitutional doping of W4+ inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2.
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Song J, Kulinich SA, Li J, Liu Y, Zeng H. A General One-Pot Strategy for the Synthesis of High-Performance Transparent-Conducting-Oxide Nanocrystal Inks for All-Solution-Processed Devices. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201408621] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kim DW, Kodama S, Sekiguchi H, Park DW. Preparation of indium oxide powders by microwave plasma dehydration of indium hydroxide powders. ADV POWDER TECHNOL 2014. [DOI: 10.1016/j.apt.2013.04.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Barbul I, Johnson AL, Kociok-Köhn G, Molloy KC, Silvestru C, Sudlow AL. The Reaction and Materials Chemistry of [Sn6(O)4(OSiMe3)4]: Chemical Vapour Deposition of Tin Oxide. Chempluschem 2013; 78:866-874. [DOI: 10.1002/cplu.201300104] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Indexed: 11/10/2022]
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Zhang KHL, Egdell RG, Offi F, Iacobucci S, Petaccia L, Gorovikov S, King PDC. Microscopic origin of electron accumulation in In2O3. PHYSICAL REVIEW LETTERS 2013; 110:056803. [PMID: 23414041 DOI: 10.1103/physrevlett.110.056803] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Indexed: 06/01/2023]
Abstract
Angle-resolved photoemission spectroscopy reveals the presence of a two-dimensional electron gas at the surface of In(2)O(3)(111). Quantized subband states arise within a confining potential well associated with surface electron accumulation. Coupled Poisson-Schrödinger calculations suggest that downward band bending for the conduction band must be much bigger than band bending in the valence band. Surface oxygen vacancies acting as doubly ionized shallow donors are shown to provide the free electrons within this accumulation layer. Identification of the origin of electron accumulation in transparent conducting oxides has significant implications in the realization of devices based on these compounds.
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Affiliation(s)
- K H L Zhang
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, United Kingdom
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Wildsmith T, Hill MS, Johnson AL, Kingsley AJ, Molloy KC. Exclusive formation of SnO by low temperature single-source AACVD. Chem Commun (Camb) 2013; 49:8773-5. [DOI: 10.1039/c3cc45676e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Zheng H, Kröger J, Berndt R. Spectroscopy of single donors at ZnO(0001) surfaces. PHYSICAL REVIEW LETTERS 2012; 108:076801. [PMID: 22401235 DOI: 10.1103/physrevlett.108.076801] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Indexed: 05/31/2023]
Abstract
Donors near the polar (0001) surface of nominally undoped ZnO were investigated with scanning tunneling microscopy at 5 K. Spatially resolved spectroscopy reveals single and double charging. Equidistant peaks in spectra of ionized donors are attributed to polaron excitation. The data are consistent with doping due to Zn interstitials or complexes.
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Affiliation(s)
- Hao Zheng
- Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
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Jiang Y, Li Y, Yan M, Bahlawane N. Abnormal behaviors in electrical transport properties of cobalt-doped tin oxide thin films. ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm32801a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Walsh A, Da Silva JLF, Wei SH. Multi-component transparent conducting oxides: progress in materials modelling. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:334210. [PMID: 21813942 DOI: 10.1088/0953-8984/23/33/334210] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Transparent conducting oxides (TCOs) play an essential role in modern optoelectronic devices through their combination of electrical conductivity and optical transparency. We review recent progress in our understanding of multi-component TCOs formed from solid solutions of ZnO, In(2)O(3), Ga(2)O(3) and Al(2)O(3), with a particular emphasis on the contributions of materials modelling, primarily based on density functional theory. In particular, we highlight three major results from our work: (i) the fundamental principles governing the crystal structures of multi-component oxide structures including (In(2)O(3))(ZnO)(n) and (In(2)O(3))(m)(Ga(2)O(3))(l)(ZnO)(n); (ii) the relationship between elemental composition and optical and electrical behaviour, including valence band alignments; (iii) the high performance of amorphous oxide semiconductors. On the basis of these advances, the challenge of the rational design of novel electroceramic materials is discussed.
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Affiliation(s)
- Aron Walsh
- Kathleen Lonsdale Materials Chemistry, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
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