1
|
Dubrovskii VG. Can Nanowires Coalesce? NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:2768. [PMID: 37887919 PMCID: PMC10609440 DOI: 10.3390/nano13202768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 10/08/2023] [Accepted: 10/11/2023] [Indexed: 10/28/2023]
Abstract
Coalescence of nanowires and other three-dimensional structures into continuous film is desirable for growing low-dislocation-density III-nitride and III-V materials on lattice-mismatched substrates; this is also interesting from a fundamental viewpoint. Here, we develop a growth model for vertical nanowires which, under rather general assumptions on the solid-like coalescence process within the Kolmogorov crystallization theory, results in a morphological diagram for the asymptotic coverage of a substrate surface. The coverage is presented as a function of two variables: the material collection efficiency on the top nanowire facet a and the normalized surface diffusion flux of adatoms from the NW sidewalls b. The full coalescence of nanowires is possible only when a=1, regardless of b. At a>1, which often holds for vapor-liquid-solid growth with a catalyst droplet, nanowires can only partly merge but never coalesce into continuous film. In vapor phase epitaxy techniques, the NWs can partly merge but never fully coalesce, while in the directional molecular beam epitaxy the NWs can fully coalesce for small enough contact angles of their droplets corresponding to a=1. The growth kinetics of nanowires and evolution of the coverage in the pre-coalescence stage is also considered. These results can be used for predicting and controlling the degree of surface coverage by nanowires and three-dimensional islands by tuning the surface density, droplet size, adatoms diffusivity, and geometry of the initial structures in the vapor-liquid-solid, selective area, or self-induced growth by different epitaxy techniques.
Collapse
Affiliation(s)
- Vladimir G Dubrovskii
- Faculty of Physics, St. Petersburg State University, Universitetskaya Emb. 13B, 199034 St. Petersburg, Russia
| |
Collapse
|
2
|
Dyachenko RR, Matveev SA, Krapivsky PL. Finite-size effects in addition and chipping processes. Phys Rev E 2023; 108:044119. [PMID: 37978711 DOI: 10.1103/physreve.108.044119] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 09/22/2023] [Indexed: 11/19/2023]
Abstract
We investigate analytically and numerically a system of clusters evolving via collisions with clusters of minimal mass (monomers). Each collision either leads to the addition of the monomer to the cluster or the chipping of a monomer from the cluster, and emerging behaviors depend on which of the two processes is more probable. If addition prevails, monomers disappear in a time that scales as lnN with the total mass N≫1, and the system reaches a jammed state. When chipping prevails, the system remains in a quasistationary state for a time that scales exponentially with N, but eventually, a giant fluctuation leads to the disappearance of monomers. In the marginal case, monomers disappear in a time that scales linearly with N, and the final supercluster state is a peculiar jammed state; i.e., it is not extensive.
Collapse
Affiliation(s)
- R R Dyachenko
- Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, Moscow, 119991, Russia
- Marchuk Institute of Numerical Mathematics RAS, Moscow, 119333, Russia
| | - S A Matveev
- Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, Moscow, 119991, Russia
- Marchuk Institute of Numerical Mathematics RAS, Moscow, 119333, Russia
| | - P L Krapivsky
- Department of Physics, Boston University, Boston, Massachusetts 02215, USA
- Santa Fe Institute, Santa Fe, New Mexico 87501, USA
| |
Collapse
|
3
|
Carapezzi S, Boschetto G, Todri-Sanial A. Capillary-force-driven self-assembly of carbon nanotubes: from ab initio calculations to modeling of self-assembly. NANOSCALE ADVANCES 2022; 4:4131-4137. [PMID: 36285210 PMCID: PMC9514721 DOI: 10.1039/d2na00295g] [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: 05/10/2022] [Accepted: 08/22/2022] [Indexed: 06/16/2023]
Abstract
In elasto-capillary driven self-assembly of arrays of carbon nanotubes (CNTs) different factors play a role, from the mechanical properties of CNTs to the array geometry. In this work, we provide a multi-scale investigation where we first use density functional theory (DFT) to predict fully ab initio relevant mechanical properties such as Young's modulus, Poisson's ratio, and surface energy. To the best of our knowledge, we are the first to report DFT calculations of the surface energy of CNTs. Then, we feed the computed DFT parameters into a model for capillary-force-driven self-assembly of CNTs. By doing so, we are able to derive and predict cross-correlation between material parameters and array architecture.
Collapse
Affiliation(s)
- Stefania Carapezzi
- Microelectronics Department, LIRMM, University of Montpellier, CNRS 161 Rue Ada Montpellier France
| | - Gabriele Boschetto
- Microelectronics Department, LIRMM, University of Montpellier, CNRS 161 Rue Ada Montpellier France
| | - Aida Todri-Sanial
- Microelectronics Department, LIRMM, University of Montpellier, CNRS 161 Rue Ada Montpellier France
| |
Collapse
|
4
|
Volkov R, Borgardt NI, Konovalov OV, Fernández-Garrido S, Brandt O, Kaganer VM. Cross-sectional shape evolution of GaN nanowires during molecular beam epitaxy growth on Si(111). NANOSCALE ADVANCES 2022; 4:562-572. [PMID: 36132694 PMCID: PMC9419090 DOI: 10.1039/d1na00773d] [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: 10/25/2021] [Accepted: 12/03/2021] [Indexed: 06/16/2023]
Abstract
We study the cross-sectional shape of GaN nanowires (NWs) by transmission electron microscopy. The shape is examined at different heights of long NWs, as well as at the same height for NWs of different lengths. Two distinct trends in the evolution of the cross-sectional shape along the NW length are observed. At the top, merging NWs develop common {11̄00} side facets. At the bottom, the NWs acquire roundish shapes. This observation is explained by the entirely different NW environments at the top and the bottom of the NWs. At the top, NWs are exposed to the Ga and N atomic fluxes giving rise to axial growth, resulting in the equilibrium growth shape with zero growth rate at the {11̄00} facets. At the bottom, NWs are shadowed from the impinging fluxes and are only annealed, allowing them to eventually approach the equilibrium crystal shape. The study of identical samples by grazing incidence small-angle X-ray scattering independently confirms these trends in the shape evolution of the sidewall facets.
Collapse
Affiliation(s)
- Roman Volkov
- National Research University of Electronic Technology - MIET Bld. 1, Shokin Square, Zelenograd Moscow 124498 Russia
| | - Nikolai I Borgardt
- National Research University of Electronic Technology - MIET Bld. 1, Shokin Square, Zelenograd Moscow 124498 Russia
| | - Oleg V Konovalov
- ESRF - The European Synchrotron 71 avenue des Martyrs 38043 Grenoble France
| | - Sergio Fernández-Garrido
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V. Hausvogteiplatz 5-7 10117 Berlin Germany
| | - Oliver Brandt
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V. Hausvogteiplatz 5-7 10117 Berlin Germany
| | - Vladimir M Kaganer
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V. Hausvogteiplatz 5-7 10117 Berlin Germany
| |
Collapse
|
5
|
Liu B, Liu Q, Yang W, Li J, Labbe C, Portier X, Zhang X, Yao J. Homoepitaxial growth of high-quality GaN nanoarrays for enhanced UV luminescence. CrystEngComm 2022. [DOI: 10.1039/d1ce01519b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this work, we demonstrate the homoepitaxial growth of high-quality GaN nanoarrays on [0001]-oriented GaN substrate with/without Au catalysts through an accessible chemical vapor deposition process. The morphology observation and...
Collapse
|
6
|
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.
Collapse
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
| |
Collapse
|
7
|
Kaganer VM, Konovalov OV, Fernández-Garrido S. Small-angle X-ray scattering from GaN nanowires on Si(111): facet truncation rods, facet roughness and Porod's law. Acta Crystallogr A Found Adv 2021; 77:42-53. [PMID: 33399130 PMCID: PMC7842208 DOI: 10.1107/s205327332001548x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2020] [Accepted: 11/22/2020] [Indexed: 12/17/2022] Open
Abstract
Small-angle X-ray scattering from GaN nanowires grown on Si(111) is measured in the grazing-incidence geometry and modelled by means of a Monte Carlo simulation that takes into account the orientational distribution of the faceted nanowires and the roughness of their side facets. It is found that the scattering intensity at large wavevectors does not follow Porod's law I(q) ∝ q-4. The intensity depends on the orientation of the side facets with respect to the incident X-ray beam. It is maximum when the scattering vector is directed along a facet normal, reminiscent of surface truncation rod scattering. At large wavevectors q, the scattering intensity is reduced by surface roughness. A root-mean-square roughness of 0.9 nm, which is the height of just 3-4 atomic steps per micrometre-long facet, already gives rise to a strong intensity reduction.
Collapse
Affiliation(s)
- Vladimir M. Kaganer
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e. V., Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Oleg V. Konovalov
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38043 Grenoble, France
| | - 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, Departamento Física Aplicada, Universidad Autónoma de Madrid, C/ Francisco Tomás y Valiente 7, 28049 Madrid, Spain
| |
Collapse
|
8
|
Fernández-Garrido S, Pisador C, Lähnemann J, Lazić S, Ruiz A, Redondo-Cubero A. Coalescence, crystallographic orientation and luminescence of ZnO nanowires grown on Si(001) by chemical vapour transport. NANOTECHNOLOGY 2020; 31:475603. [PMID: 32914764 DOI: 10.1088/1361-6528/abadc8] [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
We analyse the morphological, structural and luminescence properties of self-assembled ZnO nanowires grown by chemical vapour transport on Si(001). The examination of nanowire ensembles by scanning electron microscopy reveals that a non-negligible fraction of nanowires merge together forming coalesced aggregates during growth. We show that the coalescence degree can be unambiguously quantified by a statistical analysis of the cross-sectional shape of the nanowires. The examination of the structural properties by x-ray diffraction evidences that the nanowires crystallize in the wurtzite phase, elongate along the c-axis, and are randomly oriented in plane. The luminescence of the ZnO nanowires, investigated by photoluminescence and cathodoluminescence spectroscopy, is characterized by two bands, the near-band-edge emission and the characteristic defect-related green luminescence of ZnO. The cross-correlation of scanning electron micrographs and monochromatic cathodoluminescence intensity maps reveals that: (i) coalescence joints act as a source of non-radiative recombination, and (ii) the luminescence of ZnO nanowires is inhomogeneously distributed at the single nanowire level. Specifically, the near-band-edge emission arises from the nanowire cores, while the defect-related green luminescence originates from the volume close to the nanowire sidewalls. Two-dimensional simulations of the optical guided modes supported by ZnO nanowires allow us to exclude waveguiding effects as the underlying reason for the luminescence inhomogeneities. We thus attribute this observation to the formation of a core-shell structure in which the shell is characterized by a high concentration of green-emitting radiative point defects as compared to the core.
Collapse
Affiliation(s)
- S Fernández-Garrido
- Grupo de Electrónica y Semiconductores, Dpto. Física Aplicada, Universidad Autónoma de Madrid, C/ Francisco Tomás y Valiente 7, 28049 Madrid, Spain
| | | | | | | | | | | |
Collapse
|
9
|
Xu Z, Zhang S, Gao F, Wen L, Yu Y, Li G. Correlations among morphology, composition, and photoelectrochemical water splitting properties of InGaN nanorods grown by molecular beam epitaxy. NANOTECHNOLOGY 2018; 29:475603. [PMID: 30207545 DOI: 10.1088/1361-6528/aae0d4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The mechanism underlying the effect of growth condition on the morphology evolution of InGaN nanorods (NRs) has been systematically investigated. The increased Ga flux enhances both the axial and the radial growth at the growth stage. However, the changed Ga flux influences not only the growth but also the nucleation of InGaN NRs. At the nucleation stage, the increased Ga flux shortens the delay time for NR formation, and prolongs the growth stage for a fixed total growth time. Those two aspects result in the increase of NR diameter and height with the supplied Ga flux. In addition, the continuous nucleation is ended much earlier due to the accelerated saturation of substrate area with the increased Ga flux, resulting in a decreased final NR density. In addition to the morphology evolution with the Ga flux, the composition characteristic of InGaN NRs has been also studied. The In distribution of InGaN NRs depends critically on the NR diameter along the NR growth direction, and the NRs show a morphology-dependent In incorporation. Interestingly, the InGaN NRs discussed here show a radial Stark effect induced by the pinned Fermi level. The radial Stark effect shifts the absorption edge of the InGaN NRs toward longer wavelengths, makes the InGaN NRs attractive for photoelectrochemical water splitting applications. The photoelectrochemical measurements present a significant increase in the photocurrent with the increased total surface area of the InGaN NRs, which is due to the enhanced light absorption effects and the enlarged interfacial area of the semiconductor/electrolyte.
Collapse
Affiliation(s)
- Zhenzhu Xu
- State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, People's Republic of China. Engineering Research Center on Solid-State Lighting and its Informationisation of Guangdong Province, South China University of Technology, Guangzhou 510640, People's Republic of China
| | | | | | | | | | | |
Collapse
|
10
|
Corfdir P, Calabrese G, Laha A, Auzelle T, Geelhaar L, Brandt O, Fernández-Garrido S. Monitoring the formation of GaN nanowires in molecular beam epitaxy by polarization-resolved optical reflectometry. CrystEngComm 2018. [DOI: 10.1039/c8ce00431e] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Accessing in situ relevant information on the fluctuations in length and covered area fraction at the μm scale of vertical nanowire ensembles by polarization resolved optical reflectometry.
Collapse
Affiliation(s)
- Pierre Corfdir
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Gabriele Calabrese
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Apurba Laha
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Thomas Auzelle
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Lutz Geelhaar
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Oliver Brandt
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
| | - Sergio Fernández-Garrido
- Paul-Drude-Institut für Festkörperelektronik
- Leibniz-Institut im Forschungsverbund Berlin e.V
- 10117 Berlin
- Germany
- Grupo de Electrónica y Semiconductores
| |
Collapse
|
11
|
Fedorov VV, Bolshakov AD, Kirilenko DA, Mozharov AM, Sitnikova AA, Sapunov GA, Dvoretckaia LN, Shtrom IV, Cirlin GE, Mukhin IS. Droplet epitaxy mediated growth of GaN nanostructures on Si (111) via plasma-assisted molecular beam epitaxy. CrystEngComm 2018. [DOI: 10.1039/c8ce00348c] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate that the use of a GaN seeding layer prepared prior to the growth of epitaxial GaN on Si (111) can lead to the formation of oriented arrays of Y-shaped nanoislands and nanowires and affects the surface density of the nanostructures.
Collapse
Affiliation(s)
- V. V. Fedorov
- St. Petersburg Academic University
- St. Petersburg
- Russia
| | | | - D. A. Kirilenko
- ITMO University
- St. Petersburg
- Russia
- Ioffe Institute
- Saint Petersburg
| | | | | | - G. A. Sapunov
- St. Petersburg Academic University
- St. Petersburg
- Russia
| | | | - I. V. Shtrom
- Ioffe Institute
- Saint Petersburg
- Russia
- Institute for Analytical Instrumentation RAS
- St. Petersburg
| | - G. E. Cirlin
- St. Petersburg Academic University
- St. Petersburg
- Russia
- ITMO University
- St. Petersburg
| | - I. S. Mukhin
- St. Petersburg Academic University
- St. Petersburg
- Russia
- ITMO University
- St. Petersburg
| |
Collapse
|
12
|
Controlling bottom-up rapid growth of single crystalline gallium nitride nanowires on silicon. Sci Rep 2017; 7:17942. [PMID: 29263368 PMCID: PMC5738410 DOI: 10.1038/s41598-017-17980-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 12/04/2017] [Indexed: 11/25/2022] Open
Abstract
We report single crystalline gallium nitride nanowire growth from Ni and Ni-Au catalysts on silicon using hydride vapor phase epitaxy. The growth takes place rapidly; efficiency in time is higher than the conventional nanowire growth in metal-organic chemical vapor deposition and thin film growth in molecular beam epitaxy. The effects of V/III ratio and carrier gas flow on growth are discussed regarding surface polarity and sticking coefficient of molecules. The nanowires of gallium nitride exhibit excellent crystallinity with smooth and straight morphology and uniform orientation. The growth mechanism follows self-assembly from both catalysts, where Au acts as a protection from etching during growth enabling the growth of ultra-long nanowires. The photoluminescence of such nanowires are adjustable by tuning the growth parameters to achieve blue emission. The practical range of parameters for mass production of such high crystal quality and uniformity of nanowires is suggested.
Collapse
|
13
|
Ajay A, Lim CB, Browne DA, Polaczyński J, Bellet-Amalric E, Bleuse J, den Hertog MI, Monroy E. Effect of doping on the intersubband absorption in Si- and Ge-doped GaN/AlN heterostructures. NANOTECHNOLOGY 2017; 28:405204. [PMID: 28787278 DOI: 10.1088/1361-6528/aa8504] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this paper, we study band-to-band and intersubband (ISB) characteristics of Si- and Ge-doped GaN/AlN heterostructures (planar and nanowires) structurally designed to absorb in the short-wavelength infrared region, particularly at 1.55 μm. Regarding the band-to-band properties, we discuss the variation of the screening of the internal electric field by free carriers, as a function of the doping density and well/nanodisk size. We observe that nanowire heterostructures consistently present longer photoluminescence decay times than their planar counterparts, which supports the existence of an in-plane piezoelectric field associated to the shear component of the strain tensor in the nanowire geometry. Regarding the ISB characteristics, we report absorption covering 1.45-1.75 μm using Ge-doped quantum wells, with comparable performance to Si-doped planar heterostructures. We also report similar ISB absorption in Si- and Ge-doped nanowire heterostructures indicating that the choice of dopant is not an intrinsic barrier for observing ISB phenomena. The spectral shift of the ISB absorption as a function of the doping concentration due to many body effects confirms that Si and Ge efficiently dope GaN/AlN nanowire heterostructures.
Collapse
Affiliation(s)
- A Ajay
- Université Grenoble-Alpes, F-38000 Grenoble, France. CEA-Grenoble, INAC-PHELIQS, 17 av. des Martyrs, F-38000 Grenoble, France
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Xu L, Zhang J, Zhao H, Sun H, Xu C. Enhanced photoluminescence intensity by modifying the surface nanostructure of Nd 3+-doped (Pb, La)(Zr, Ti)O 3 ceramics. OPTICS LETTERS 2017; 42:3303-3306. [PMID: 28957089 DOI: 10.1364/ol.42.003303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 07/30/2017] [Indexed: 06/07/2023]
Abstract
Quasi-period cylindrical nanostructures with both diameters and intervals of about 100 nm are manufactured on the surfaces of Nd3+-doped lanthanum lead zirconate titanate ceramics by femtosecond laser irradiation under SF6 atmosphere. A light-emission enhancement of more than 20 times is investigated, accompanied by an extremely long trailing-off time of light emission and lower threshold. A specific polarization state of the light emission is achieved and tuned by changing the incident regions of the pumping source. The increased absorption coefficient of the specimen is discussed based on multiple scattering and weak localization of light. In addition, both the scatterers provided by the laser-machined nanostructure and the recurrent photoinduced trapping and re-excitation process participated in the enhancement of the light emission. This Letter offers new insight to improve the luminescence property of laser materials, as well as to broaden the range of exploring the weak localization of light and random lasers.
Collapse
|
15
|
Liu Q, Liu B, Yang W, Yang B, Zhang X, Labbé C, Portier X, An V, Jiang X. Alignment control and atomically-scaled heteroepitaxial interface study of GaN nanowires. NANOSCALE 2017; 9:5212-5221. [PMID: 28397937 DOI: 10.1039/c7nr00032d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Well-aligned GaN nanowires are promising candidates for building high-performance optoelectronic nanodevices. In this work, we demonstrate the epitaxial growth of well-aligned GaN nanowires on a [0001]-oriented sapphire substrate in a simple catalyst-assisted chemical vapor deposition process and their alignment control. It is found that the ammonia flux plays a key role in dominating the initial nucleation of GaN nanocrystals and their orientation. Typically, significant improvement of the GaN nanowire alignment can be realized at a low NH3 flow rate. X-ray diffraction and cross-sectional scanning electron microscopy studies further verified the preferential orientation of GaN nanowires along the [0001] direction. The growth mechanism of GaN nanowire arrays is also well studied based on cross-sectional high-resolution transmission electron microscopy (HRTEM) characterization and it is observed that GaN nanowires have good epitaxial growth on the sapphire substrate following the crystallographic relationship between (0001)GaN∥(0001)sapphire and (101[combining macron]0)GaN∥(112[combining macron]0)sapphire. Most importantly, periodic misfit dislocations are also experimentally observed in the interface region due to the large lattice mismatch between the GaN nanowire and the sapphire substrate, and the formation of such dislocations will favor the release of structural strain in GaN nanowires. HRTEM analysis also finds the existence of "type I" stacking faults and voids inside the GaN nanowires. Optical investigation suggests that the GaN nanowire arrays have strong emission in the UV range, suggesting their crystalline nature and chemical purity. The achievement of aligned GaN nanowires will further promote the wide applications of GaN nanostructures toward diverse high-performance optoelectronic nanodevices including nano-LEDs, photovoltaic cells, photodetectors etc.
Collapse
Affiliation(s)
- Qingyun Liu
- Shenyang National Laboratory for Materials Science (SYNL), Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS), No. 72, Wenhua Road, Shenhe District, Shenyang 110016, China.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
de Souza Schiaber Z, Calabrese G, Kong X, Trampert A, Jenichen B, Dias da Silva JH, Geelhaar L, Brandt O, Fernández-Garrido S. Polarity-Induced Selective Area Epitaxy of GaN Nanowires. NANO LETTERS 2017; 17:63-70. [PMID: 28073259 DOI: 10.1021/acs.nanolett.6b03249] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a conceptually novel approach to achieve selective area epitaxy of GaN nanowires. The approach is based on the fact that these nanostructures do not form in plasma-assisted molecular beam epitaxy on structurally and chemically uniform cation-polar substrates. By in situ depositing and nitridating Si on a Ga-polar GaN film, we locally reverse the polarity to induce the selective area epitaxy of N-polar GaN nanowires. We show that the nanowire number density can be controlled over several orders of magnitude by varying the amount of predeposited Si. Using this growth approach, we demonstrate the synthesis of single-crystalline and uncoalesced nanowires with diameters as small as 20 nm. The achievement of nanowire number densities low enough to prevent the shadowing of the nanowire sidewalls from the impinging fluxes paves the way for the realization of homogeneous core-shell heterostructures without the need of using ex situ prepatterned substrates.
Collapse
Affiliation(s)
- Ziani de Souza Schiaber
- Laboratório de Filmes Semicondutores, Universidade Estadual Paulista Bauru , 17033-360 São Paulo, Brazil
| | - Gabriele Calabrese
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Xiang Kong
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Achim Trampert
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Bernd Jenichen
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | | | - Lutz Geelhaar
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | - Oliver Brandt
- Paul-Drude-Institut für Festkörperelektronik , Hausvogteiplatz 5-7, 10117 Berlin, Germany
| | | |
Collapse
|