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1.
We have investigated one phonon resonant Raman scattering in GaN nanowires (NWs) with ring geometry. We consider the Fröhlich electron–phonon interaction in the framework of the dielectric continuum approach. The selection rules are studied. For the GaN NWs with small radius, results reveal that the main contribution to the differential cross-section (DCS) stems from the surface optical (SO) phonons especially from the high-frequency of SO phonons, with a minor contribution from the longitudinal optical (LO) phonons. Meanwhile, dispersions of the two branches of the SO phonon modes are obvious when the wire is thin. Moreover, compared to GaAs NWs, the GaN NWs make more contribution to the DCS in the small quantum size. 相似文献
2.
Silver nanowires have been fabricated using electrochemical deposition within the confined nanochannels of anodic alumina membrane on aluminum substrate. The characterization of structure, morphology, and composition indicates that the silver nanowires are uniform with about 50?nm diameter corresponding to the pore diameter of the anodic alumina membrane and almost single crystal with preferred growth along the [111] direction. Electrical measurements at room temperature showed that these silver nanowires were high conductive with a conductivity of approximately 0.13×105?S/cm. Also, individual silver nanowires were investigated by measuring current as a function of bias voltage until the point of failure. This study will be very useful for the development of future nanoelectronic devices and circuits that employ Ag nanowires. 相似文献
3.
Free-standing fine wires of metals, insulators and semiconductors are expected to show both quantum-size phenomena and one-dimensional behaviour in their electrical and thermal properties at low temperatures. We summarise some of these effects and describe the methods for fabricating test structures. 相似文献
4.
Quasi-horizontal GaN nanowire array network has been grown on Au-film-coated MgO substrates via a sublimation sandwich technique. These GaN nanowire arrays principally grew along two directions which were perpendicular to each other and nearly parallel to the substrate, forming a regular network. The formation of the nanowire network was a hetero-epitaxial vapor-liquid-solid (VLS) process assisted by Au catalysts and was dependent on the substrates. Transmission electron microscopy revealed that the nanowires were single-crystalline wurtzite GaN. Raman scattering spectrum of the nanowire network presented some new features. 相似文献
5.
Highly oriented GaN nanowire arrays have been achieved by the catalytic reaction of gallium with ammonium. The resulting materials
were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), energy dispersive X-ray
spectroscopy (EDS), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). SEM images show
that the resulting materials are nanowire arrays with a uniform length of about 10 μm. XRD, EDS, TEM and SAED indicate that
the nanowire arrays are single-crystal hexagonal GaN with a wurtzite structure. They have diameters of 10 to 20 nm.
Received: 2 October 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. E-mail: wwwangjc@sina.com 相似文献
6.
7.
We present a systemic study of the structural and electronic properties of Cun nanowires (n=5, 9 and 13) encapsulated in armchair (8,8) gallium nitride nanotubes (GaNNTs) using the first-principles calculations. We find that the formation processes of these systems are all exothermic. The initial shapes are preserved without any visible changes for the Cu5@(8,8) and Cu9@(8,8) combined systems, but a quadratic-like cross-section shape is formed for the outer nanotube of the Cu13@(8,8) combined system due to the stronger attraction between nanowire and nanotube. The electrons of Ga and N atoms in outer GaN sheath affect the electron conductance of the encapsulated metallic nanowire in the Cu13@(8,8) combined system. But in the Cu5@(8,8) and Cu9@(8,8) combined systems, the conduction electrons are distributed only on the copper atoms, so charge transport will occur only in the inner copper nanowire, which is effectively insulated by the outer GaN nanotube. Considering the maximal metal filling ratio in nanotube, we know that the Cu9@(8,8) combined system is top-priority in the ultra-large-scale integration (ULSI) circuits and micro-electromechanical systems (MEMS) devices that demand steady transport of electrons. 相似文献
8.
Cathodoluminescent and electrical properties of an individual ZnO nanowire with oxygen vacancies
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A single ZnO nanowire with intrinsic oxygen vacancies is utilized to fabricate four-contact device with focus ion beam lithography technique. Cathodoluminescent spectra indicate strong near-UV and green emission at both room temperature and low temperatures. Experimental measurement shows the temperature-dependent conductivity of the ZnO nanowire at low temperatures (below 100 K). The further theoretical analysis confirms that weak localization plays an important role in the electrical transport, which is attributed to the surface states induced by plenty of oxygen vacancies in ZnO nanowire. 相似文献
9.
《中国物理 B》2020,(2)
Nowadays,the superior detection performance of semiconductor neutron detectors is a challenging task.In this paper,we deal with a novel GaN micro-structured neutron detector(GaN-MSND) and compare three different methods such as the method of modulating the trench depth,the method of introducing dielectric layer and p-type inversion region to improve the width of depletion region(W).It is observed that the intensity of electric field can be modulated by scaling the trench depth.On the other hand,the electron blocking region is formed in the detector enveloped with a dielectric layer.Furthermore,the introducing of p-type inversion region produces new p/n junction,which not only promotes the further expansion of the depletion region but also reduces the intensity of electric field produced by main junction.It can be realized that all these methods can considerably enhance the working voltage as well as W.Of them,the improvement on W of GaN-MSND with the p-type inversion region is the most significant and the value of W could reach 12.8 μm when the carrier concentration of p-type inversion region is 10~(17) cm~(-3).Consequently,the value of W is observed to improve200% for the designed GaN-MSND as compared with that without additional design.This work ensures to the researchers and scientific community the fabrication of GaN-MSND having superior detection limit in the field of intense radiation. 相似文献
10.
Hosein Eshghi 《Physics letters. A》2009,373(20):1773-1776
Experimental data for temperature dependence of electron transport properties in a bulk, low dislocation density, GaN sample at atmospheric pressure and 7.1 kbar have been presented. The data are representing a weak hydrostatic pressure dependence. Our quantitative analysis on its material parameters including: high and low dielectric constants (ε∞,εs), longitudinal and transverse optical phonons (ωLO,ωTO), and electronic effective mass show a small fractional change of −0.12,−0.14,0.05,0.058 and 0.089 (percent/kbar), respectively. These results are confirmed by the Hall-effect data analysis on the basis of charge neutrality condition and various scattering mechanisms. 相似文献
11.
Fabrication and electrical properties of axial and radial GaAs nanowire pn junction diode arrays
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We report on the fabrications and characterizations of axial and radial Ga As nanowire pn junction diode arrays.The nanowires are grown on n-doped Ga As(111)B substrates using the Au-catalyzed vapor–liquid–solid mechanism by metal–organic chemical vapor deposition(MOCVD). Diethyl–zinc and silane are used as p- and n-type dopant precursors,respectively. Both the axial and radial diodes exhibit diode-like J–V characteristics and have similar performances under forward bias. Under backward bias, the axial diode has a large leakage current, which is attributed to the bending of the pn junction interface induced by two doping mechanisms in Au-catalyzed nanowires. The low leakage current and high rectification ratio make the radial diode more promising in electrical and optoelectronic devices. 相似文献
12.
GaN layers and Al1−xInxN/AlN/GaN heterostructures have been studied by scanning probe microscopy methods. Threading dislocations (TDs), originating from the GaN (0 0 0 1) layer grown on sapphire, have been investigated. Using Current-Atomic Force Microscopy (C-AFM) TDs have been found to be highly conductive in both GaN and AlInN, while using semi-contact AFM (phase-imaging mode) indium segregation has been traced at TDs in AlInN/AlN/GaN heterostructures. It has been assessed that In segregation is responsible for high conductivity at dislocations in the examined heterostructures. 相似文献
13.
The optical and electrical properties of silicon-doped epitaxial gallium nitride layers grown on sapphire have been studied. The studies have been performed over a wide range of silicon concentrations on each side of the Mott transition. The critical concentrations of Si atoms corresponding to the formation of an impurity band in gallium nitride (~2.5 × 1018 cm?3) and to the overlap of the impurity band with the conduction band (~2 × 1019 cm?3) have been refined. The maximum of the photoluminescence spectrum shifts nonmonotonically with increasing doping level. This shift is determined by two factors: (1) an increase in the exchange interaction leading to a decrease in the energy gap width and (2) a change in the radiation mechanism as the donor concentration increases. The temperature dependence of the exciton luminescence with participating optical phonons has been studied. The energies of phonon-plasmon modes in GaN: Si layers with different silicon concentrations have been measured using Raman spectroscopy. 相似文献
14.
15.
CUI AJuan HAO TingTing LI Wu Xia SHEN TieHan LIU Zhe JIANG QianQing GU ChangZhi 《中国科学:物理学 力学 天文学(英文版)》2015,(4):89-95
Free-standing metallic nanostructures are considered to be highly relevant to many branches of science and technology with applications of three dimensional metallic nanostructures ranging from optical reflectors,actuators,and antenna,to free-standing electrodes,mechanical,optical,and electrical resonators and sensors.Strain-induced out-of-plane fabrication has emerged as an effective method which uses relaxation of strain-mismatched materials.In this work,we report a study of the thermal annealing-induced shape modification of free-standing nanostructures,which was achieved by introducing compositional or microstructural nonuniformity to the nanowires.In particular gradient,segmented and striped hetero-nanowires were grown by focused-ion-beam-induced chemical vapor deposition,followed by rapid thermal annealing in a N2 atmosphere.Various free-standing nanostructures were produced as a result of the crystalline/grain growth and stress relief. 相似文献
16.
Influence of dislocations in the GaN layer on the electrical properties of an AlGaN/GaN heterostructure
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This paper reports on a comparative study of the spatial
distributions of the electrical, optical, and structural properties
in an AlGaN/GaN heterostructure. Edge dislocation density in the GaN
template layer is shown to decrease in the regions of the wafer
where the heterostructure sheet resistance increases and the GaN
photoluminescence band-edge energy peak shifts to a high wavelength.
This phenomenon is found to be attributed to the local compressive
strain surrounding edge dislocation, which will generate a local
piezoelectric polarization field in the GaN layer in the opposite
direction to the piezoelectric polarization field in the AlGaN layer and
thus help to increase the two-dimensional electron gas
concentration. 相似文献
17.
Yong Lin Qiming Li Andrew Armstrong George T. Wang 《Solid State Communications》2009,149(39-40):1608-1610
A lithography-free technique for measuring the electrical properties of n-type GaN nanowires has been investigated using nanoprobes mounted in a scanning electron microscope (SEM). Schottky contacts were made to the nanowires using tungsten nanoprobes, while gallium droplets placed in situ at the end of tungsten nanoprobes were found to be capable of providing Ohmic contacts to GaN nanowires. Schottky nanodiodes were fabricated based on single n-type nanowires, and measured current–voltage (I–V) results suggest that the Schottky nanodiodes deviate from ideal diodes mainly due to their nanoscopic contact area. Additionally, the effect of the SEM electron beam on the I–V characteristics was investigated and was found to impact the transport properties of the Schottky nanodiodes, possibly due to an increase in carrier density in the nanodiodes. 相似文献
18.
Lei Li Lei Liu Lei Wang Ding Li Jie Song Ningyang Liu Weihua Chen Yuzhou Wang Zhijian Yang Xiaodong Hu 《Applied Physics A: Materials Science & Processing》2012,108(4):857-862
AlN with different thicknesses were grown as interlayers (ILs) between GaN and p-type Al0.15Ga0.85N/GaN superlattices (SLs) by metal organic vapor phase epitaxy (MOVPE). It was found that the edge-type threading dislocation density (TDD) increased gradually from the minimum of 2.5×109?cm?2 without AlN IL to the maximum of 1×1010?cm?2 at an AlN thickness of 20 nm, while the screw-type TDD remained almost unchanged due to the interface-related TD suppression and regeneration mechanism. We obtained that the edge-type dislocations acted as acceptors in p-type Al x Ga1?x N/GaN SLs, through the comparison of the edge-type TDD and hole concentration with different thicknesses of AlN IL. The Mg activation energy was significantly decreased from 153 to 70?meV with a?10-nm AlN IL, which was attributed to the strain modulation between AlGaN barrier and GaN well. The large activation efficiency, together with the TDs, led to the enhanced hole concentration. The variation trend of Hall mobility was also observed, which originated from the scattering at TDs. 相似文献
19.
T.B. Wei R.F. Duan J.X. Wang J.M. Li Z.Q. Huo P. Ma Zh. Liu Y.P. Zeng 《Applied Surface Science》2007,253(18):7423-7428
Large-scale GaN free-standing substrate was obtained by hydride vapor phase epitaxy directly on sapphire with porous network interlayer. The bottom surface N-face and top surface Ga-face showed great difference in anti-etching and optical properties. The variation of optical and structure characteristics were also microscopically identified using spatially resolved cathodoluminescence and micro-Raman spectroscopy in cross-section of the GaN substrate. Three different regions were separated according to luminescent intensity along the film growth orientation. Some tapered inversion domains with high free carrier concentration of 5 × 1019 cm−3 protruded up to the surface forming the hexagonal pits. The dark region of upper layer showed good crystalline quality with narrow donor bound exciton peak and low free carrier concentration. Unlike the exponential dependence of the strain distribution, the free-standing GaN substrate revealed a gradual increase of the strain mainly within the near N-polar side region with a thickness of about 50 μm, then almost kept constant to the top surface. 相似文献