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Olszewski K, Sobanska M, Dubrovskii VG, Leshchenko ED, Wierzbicka A, Zytkiewicz ZR. Geometrical Selection of GaN Nanowires Grown by Plasma-Assisted MBE on Polycrystalline ZrN Layers. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2587. [PMID: 37764616 PMCID: PMC10537475 DOI: 10.3390/nano13182587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 09/13/2023] [Accepted: 09/15/2023] [Indexed: 09/29/2023]
Abstract
GaN nanowires grown on metal substrates have attracted increasing interest for a wide range of applications. Herein, we report GaN nanowires grown by plasma-assisted molecular beam epitaxy on thin polycrystalline ZrN buffer layers, sputtered onto Si(111) substrates. The nanowire orientation was studied by X-ray diffraction and scanning electron microscopy, and then described within a model as a function of the Ga beam angle, nanowire tilt angle, and substrate rotation. We show that vertically aligned nanowires grow faster than inclined nanowires, which leads to an interesting effect of geometrical selection of the nanowire orientation in the directional molecular beam epitaxy technique. After a given growth time, this effect depends on the nanowire surface density. At low density, the nanowires continue to grow with random orientations as nucleated. At high density, the effect of preferential growth induced by the unidirectional supply of the material in MBE starts to dominate. Faster growing nanowires with smaller tilt angles shadow more inclined nanowires that grow slower. This helps to obtain more regular ensembles of vertically oriented GaN nanowires despite their random position induced by the metallic grains at nucleation. The obtained dense ensembles of vertically aligned GaN nanowires on ZrN/Si(111) surfaces are highly relevant for device applications. Importantly, our results are not specific for GaN nanowires on ZrN buffers, and should be relevant for any nanowires that are epitaxially linked to the randomly oriented surface grains in the directional molecular beam epitaxy.
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Affiliation(s)
- Karol Olszewski
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland (Z.R.Z.)
| | - Marta Sobanska
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland (Z.R.Z.)
| | - Vladimir G. Dubrovskii
- Faculty of Physics, St. Petersburg State University, Universitetskaya Embankment 13V, 199034 St. Petersburg, Russia; (V.G.D.)
| | - Egor D. Leshchenko
- Faculty of Physics, St. Petersburg State University, Universitetskaya Embankment 13V, 199034 St. Petersburg, Russia; (V.G.D.)
| | - Aleksandra Wierzbicka
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland (Z.R.Z.)
| | - Zbigniew R. Zytkiewicz
- Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw, Poland (Z.R.Z.)
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Auzelle T, Ullrich F, Hietzschold S, Sinito C, Brackmann S, Kowalsky W, Mankel E, Brandt O, Lovrincic R, Fernández-Garrido S. External Control of GaN Band Bending Using Phosphonate Self-Assembled Monolayers. ACS APPLIED MATERIALS & INTERFACES 2021; 13:4626-4635. [PMID: 33439013 DOI: 10.1021/acsami.0c17519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report on the optoelectronic properties of GaN(0001) and (11̅00) surfaces after their functionalization with phosphonic acid derivatives. To analyze the possible correlation between the acid's electronegativity and the GaN surface band bending, two types of phosphonic acids, n-octylphosphonic acid (OPA) and 1H,1H,2H,2H-perfluorooctanephosphonic acid (PFOPA), are grafted on oxidized GaN(0001) and GaN(11̅00) layers as well as on GaN nanowires. The resulting hybrid inorganic/organic heterostructures are investigated by X-ray photoemission and photoluminescence spectroscopy. The GaN work function is changed significantly by the grafting of phosphonic acids, evidencing the formation of dense self-assembled monolayers. Regardless of the GaN surface orientation, both types of phosphonic acids significantly impact the GaN surface band bending. A dependence on the acids' electronegativity is, however, only observed for the oxidized GaN(11̅00) surface, indicating a relatively low density of surface states and a favorable band alignment between the surface oxide and acids' electronic states. Regarding the optical properties, the covalent bonding of PFOPA and OPA on oxidized GaN layers and nanowires significantly affects their internal quantum efficiency, especially in the nanowire case due to the large surface-to-volume ratio. The variation in the internal quantum efficiency is related to the modification of both the internal electric fields and surface states. These results demonstrate the potential of phosphonate chemistry for the surface functionalization of GaN, which could be exploited for selective sensing applications.
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Affiliation(s)
- Thomas Auzelle
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Florian Ullrich
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Materials Science Department, Technische Universität Darmstadt, Otto-Berndt-Strasse 3, 64287 Darmstadt, Germany
| | - Sebastian Hietzschold
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
| | - Chiara Sinito
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Stefan Brackmann
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
| | - Wolfgang Kowalsky
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
- Kirchhoff Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - Eric Mankel
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Materials Science Department, Technische Universität Darmstadt, Otto-Berndt-Strasse 3, 64287 Darmstadt, Germany
| | - Oliver Brandt
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Robert Lovrincic
- InnovationLab, Speyerer Str. 4, 69115 Heidelberg, Germany
- Institute for High-Frequency Technology, Technische Universität Braunschweig, Schleinitzstrasse 22, 38106 Braunschweig, Germany
| | - Sergio Fernández-Garrido
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
- Grupo de Electrónica y Semiconductores, Dpto. Física Aplicada, Universidad Autónoma de Madrid, C/Francisco Tomás y Valiente 7, 28049 Madrid, Spain
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Ramesh C, Tyagi P, Kaswan J, Yadav BS, Shukla AK, Senthil Kumar M, Kushvaha SS. Effect of surface modification and laser repetition rate on growth, structural, electronic and optical properties of GaN nanorods on flexible Ti metal foil. RSC Adv 2020; 10:2113-2122. [PMID: 35494595 PMCID: PMC9048994 DOI: 10.1039/c9ra09707d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 01/03/2020] [Indexed: 12/14/2022] Open
Abstract
The effect of flexible Ti metal foil surface modification and laser repetition rate in laser molecular beam epitaxy growth process on the evolution of GaN nanorods and their structural, electronic and optical properties has been investigated. The GaN nanostructures were grown on bare- and pre-nitridated Ti foil substrates at 700 °C for different laser repetition rates (10–30 Hz). It is found that the low repetition rate (10 Hz) promotes sparse growth of three-dimensional inverted-cone like GaN nanostructures on pre-nitridated Ti surface whereas the entire Ti foil substrate is nearly covered with film-like GaN consisting of large-sized grains for 30 Hz growth. In case of the GaN growth at 20 Hz, uniformly-aligned, dense (∼8 × 109 cm−2) GaN nanorods are successfully grown on pre-nitridated Ti foil whereas sparse vertical GaN nanorods have been obtained on bare Ti foil under similar growth conditions for both 20 and 30 Hz. X-ray photoemission spectroscopy (XPS) has been utilized to elucidate the electronic structure of GaN nanorods grown under various experimental conditions on Ti foil. It confirms Ga–N bonding in the grown structures, and the calculated chemical composition turns out to be Ga rich for the GaN nanorods grown on pre-nitridated Ti foil. For bare Ti substrates, a preferred reaction between Ti and N is noticed as compared to Ga and N leading to sparse growth of GaN nanorods. Hence, the nitridation of Ti foil is a prerequisite to achieve the growth of dense and aligned GaN nanorod arrays. The X-ray diffraction, high resolution transmission electron microscopy and Raman studies revealed the c-axis growth of wurtzite GaN nanorods on Ti metal foil with good crystallinity and structural quality. The photoluminescence spectroscopy showed that the dense GaN nanorod possesses a near band edge emission at 3.42 eV with a full width at half maximum of 98 meV at room temperature. The density-controlled growth of GaN nanorods on a flexible substrate with high structural and optical quality holds promise for potential applications in futuristic flexible GaN based optoelectronics and sensor devices. The effect of flexible Ti metal foil surface modification and laser repetition rate in laser molecular beam epitaxy growth process on the evolution of GaN nanorods and their structural, electronic and optical properties has been investigated.![]()
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Affiliation(s)
- Ch Ramesh
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
| | - P Tyagi
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
| | - J Kaswan
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
| | - B S Yadav
- Solid State Physics Laboratory Lucknow Road, Timarpur Delhi India 110054
| | - A K Shukla
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
| | - M Senthil Kumar
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
| | - S S Kushvaha
- CSIR-National Physical Laboratory Dr K. S. Krishnan Road New Delhi India 110012 .,Academy of Scientific and Innovative Research (AcSIR) Ghaziabad India 201002
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