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A nanowire is a sort of nanostructure, which has a diameter in nanometer scope. In add-on, the quantum mechanical effects are of import at the 10s of nanometers or less nanoscales. In this instance, it besides named quantum wires.

There are several types of nanowires, such as, insulating nanowires ( e.g. SiO2 and TiO2 ) , semiconducting nanowires ( e.g. GaN, InP, and Si ) and metallic nanowires ( e.g. Au, Pt, and Ni ) . [ 1 ] Additionally, whether the nanowire perform metallic, semiconducting or insulating, the conductive belongingss of nanowire is chiefly depends on the diameter of the nanowire. [ 2 ] In this instance, a nanowire can exchange itself from metallic to insulating. Furthermore, non merely the conductive belongings of nanowire depends on the nanowire ‘s diameter, but besides the runing point of the nanowire depends on the diameter of the nanowire. [ 2 ]

There are besides many methods for synthesizing nanowires, such as cutting ( e.g. start from thin movie or multilayer, cut by proverb ) , gas stage synthesis ( e.g. vapour-liquid-solid procedure, VLS ) , template synthesis ( e.g. inside C nanotube, around C nanotube with/without C nanotube ) , measure border ornament, and Ion or e-beam aided wire deposition. [ 2 ] Additionally, the nanowires can be used in many electronics, such as, detector and FET-transistors. [ 2 ]

Furthermore, the heterostructure nanowire is a sort of nanowire which consists of different stuffs. There are chiefly two types of heterostructure nanowires, the 1 with alternate elements along the wire way, the other 1 with alternate interior and outside of the rod. In this instance, the heterostructure nanowires non merely have the nanowires ‘ unique belongingss, but besides derive some chemical and physical belongingss from the different constituents. Therefore, the heterostructure nanowires are expected to hold the chemical and physical belongingss of the constituents. There are several sorts of heterostructure nanowires, such as, MgO/SnO2 core-shell heteronanowires, Bi/Bi2S3 heteronanowires, and M/M2S ( M=Ag, Cu ) heteronanowires. In this study, the fiction and possible applications of MgO/SnO2 core-shell heteronanowires and M/M2S ( M=Ag, Cu ) heteronanowires will be introduced.

MgO/SnO2 Core-Shell Heterostructure Nanowires

The Mg oxide ( MgO ) is a sort of broad bandgap dielectric, which can be widely used in electronics and it is besides of import for utilizing in pigment, toxic waste redress, furnace lining and superconductors. [ 3 ]

The Sn oxide ( SnO2 ) is a sort of broad bandgap n-type semiconducting material ( Eg=3.6eV at 300k ) , which is chiefly used in transistors [ 4 ] , transparent carry oning electrodes [ 5 ] , solar cells [ 6 ] , and gas detectors [ 7 ] .

Due to the little dimensions and alone belongingss of the unidimensional ( 1D ) hetero-nanowires, they are assuring for the applications of the nanodevices. [ 3 ] Therefore, the heterostructure nanowires that consist of both of MgO and SnO2 are expected to hold the alone chemical and physical belongingss. Furthermore, due to the alone belongingss of heteronanowires, the MgO/SnO2 heteronanowires might be used in detectors, accelerators and nanoscale optoelectronics. [ 3 ] A schematic of the MgO nucleus, SnO2 shell heteronanowire is shown below.

Conventional 1. Structure of MgO nucleus, SnO2 shell heteronanowire.

During the experiment, the two-step vaporization technique was used for bring forthing MgO nucleus, SnO2 shell nanowires. [ 3 ] In item, the pure MgB2 pulverizations were heated at 900 & A ; deg ; C under Ar and O2 status for fixing the nucleus MgO nanowires. Then the ensuing merchandises were deposited on gold coated Si substrates and the Si substrates were located inside a quartz tubing. The vaporization method was used with Sn pulverization for manufacturing the MgO nucleus, SnO2 shell nanowires. The A piece of MgO nanowires adult substrate was placed with the deposition side downwards which on the top of the aluminum oxide boat with the Sn pulverizations. Then it was heated at 900 & A ; deg ; C under Ar and O2 status and the per centums of Ar and O2 gas are 3 % and 97 % . The resulting nanowires were tested by XRD, SEM and TEM. In order to prove the belongingss of the resulting nanowires, in the undermentioned measure, the some of the ensuing nanowires were placed in quartz tubing and heated at 800 & A ; deg ; C for 10min and tested by XRD, SEM and TEM. Some images of MgO nucleus, SnO2 shell nanowires is shown below. [ 3 ]

Figure 1. ( a ) SEM image of MgO nucleus, SnO2 shell nanowires, ( B ) Elemental map of Mg for nanowires, ( degree Celsius ) Elemental map of Sn for nanowires. [ 3 ]

Fig 1a shows the SEM image of the MgO nucleus, SnO2 shell heterostructure nanowires. Fig 1b and 1c shows the elemental map of Mg and Sn for the heteronanowires. Harmonizing to the Fig 1b and 1c, the elemental distribution of the heteronanowires shows clearly. Fig 1b shows that, the Mg component chiefly distributes in the Centre of the nanowires ( nucleus ) , and Fig 1c shows that the Sn component distributes in the outer place ( shell ) of the nanowires.

Additionally, after 10min tempering of the vitreous silica tubing at 800 & A ; deg ; C, the sample ‘s SEM image and elemental map are shown below.

Figure 2. ( a ) SEM image of annealed MgO nucleus, SnO2 shell heteronanowires, ( B ) Elemental map of Mg in heteronanowires, ( degree Celsius ) Element map of Sn in heteronanowires. [ 3 ]

Fig 2a shows the SEM image of 10min 800 & A ; deg ; C annealed MgO nucleus, SnO2 shell heterostructure nanowires, which represent that the surface of heteronanowires became unsmooth by tempering. Both of the Fig 2b and 2c are the elemental map of Mg and Sn, due to the tempering of the MgO nucleus, SnO2 shell heteronanowires, both of the Mg and Sn elements distribution non merely the nucleus of the heteronanowires, but besides the outer place of the heteronanowires.

As a consequence, the MgO nucleus, SnO2 shell heterostructure nanowires can be fabricated by heating the Sn pulverizations onto the adult MgO nanowires. In add-on, 10min 800 & A ; deg ; C tempering of the MgO nucleus, SnO2 shell heteronanowires can do the SnO2 of the heteronanowires become unsmooth and do the Mg and Sn administer more equally.

M/M2S ( M=Ag, Cu ) Heterostructure Nanowires

Since the negatrons and ions reaction and migration, the complexness and structural word picture of the assorted music directors remain ill-defined. [ 8 ] Thus, the microscopic mechanism remains ill-defined nether. Therefore, analyzing the assorted ionic-electronic music directors ( MIECs ) at the nanoscale for look intoing nanoscale solid electrochemistry is of import, particularly for low dimensional nanostructure stuffs, for case, arrays of nanowires and nanowires. In add-on, the metallic contacts of MIEC, for case, Cu or Ag can be governable formed by using a pulse current or electromotive force to the Cu2S or Ag2S crystal. Therefore, more attending were attracted to Ag2S and Cu2S like metal chalcogenides nanostructures, and the metal ( Ag or Cu ) /metal chalcogenides ( Ag2S or Cu2S ) heterostructure nanowires can be used for researching MIEC-based nanoelectronics. [ 8 ]

The M/M2S ( M=Ag, Cu ) heteronanowires were fabricated by the template-confined step-electrochemical technique. [ 8 ] Additionally, the templet confined step electrochemical technique is scalable, effectual and low-priced. [ 8 ]

For the templet synthesis, anodic oxidised aluminium oxide ( AAO ) membranes that with a pore diameter in a scope of 20-200 nanometers were used. [ 8 ] The branch side of the AAO membrane were plasma sputtered with a bed of Ag or Pt. In this instance, the AAO membrane can be used as a on the job electrode and a standard one-compartment, three-electrode cell was used for electrochemical fiction. It besides was used for the measurings with a Pt home base and a KCl saturated Ag/AgCl mention electrode as a counter electrode. [ 8 ]

First, at a changeless and low plating current denseness ( 0.3-0.8mA/cm2 ) , the metal ( Cu or Ag ) nanowire array was electroplated into the cylinder pores of the AAO membrane from AgNO3- and CuSO4- based solutions. [ 8 ] Then, in an aqueous 0.01-M Na2S solution ( pH?12.0 ) , the anodal polarization was applied to turn the metal chalcogenides at a changeless current denseness ( 0.2-9.5 mA/cm2 ) . In add-on, the hydrosulfide ( HS- ) is the chief S species beginning in the solution. [ 9 ] The resulting merchandises were tested by XRD, SEM and TEM, and a schematic of the template synthesis from AAO membrane is shown below.

Conventional 2. The template synthesis from AAO membrane. [ 8 ]

The SEM and TEM images of Ag/Ag2S heteronanowires and Cu/Cu2S heteronanowires are shown below.

Figure 3. ( a ) SEM image of Ag/Ag2S heteronanowires, ( B ) SEM image of Cu/Cu2S heteronanowires, ( degree Celsius ) TEM image of Ag/Ag2S heteronanowire, ( vitamin D ) Schematic of Ag/Ag2S heteronanowire and Cu/Cu2S heteronanowires.

Harmonizing to the Fig 3a, SEM image of Ag/Ag2S nanowires have a similar diameter of 20nm. The formed Ag stage has a face centred three-dimensional and the formed Ag2S stage has a monoclinic construction. [ 8 ] Fig 3b shows the SEM image of Cu/Cu2S heteronanowires and all of them have a similar diameter every bit good. Compared with the Ag/Ag2S heteronanowires with Cu/Cu2S heteronanowires, the heteronanowires in each sample have a similar diameter and it is obvious that the Cu/Cu2S heteronanowires have a more complex construction than the Ag/Ag2S heteronanowires. Fig 3c shows the TEM image of a individual Ag/Ag2S heteronanowire, it shows clearly that the heteronanowire contains of Ag and Ag2S at low declaration transmittal negatron microscopy. However, when it was imaged by the high declaration transmittal negatron microscopy, the construction of the Ag/Ag2S heteronanowire was damaged by negatron beam irradiation. [ 8 ] In add-on, compared with Cu/Cu2S heteronanowire, the Ag/Ag2S heteronanowire was damaged harder than Cu/Cu2S heteronanowire, when they were imaged by high declaration transmittal negatron microscopy. [ 8 ]

As a consequence, the M/M2S ( M=Ag or Cu ) heterostructure nanowires were fabricated successfully by the templet confined step electrochemical technique, which is low cost, scalable and effectual. Both of the produced Ag/Ag2S heterostructure nanowires and Cu/Cu2S heterostructure nanowires have an even diameter and were damaged by the negatron beam irradiation of the high declaration TEM.

Comparison

The MgO nucleus, SnO2 shell heterostructure nanowires can be fabricated by a two-step vaporization procedure. The Mg and Sn component distribute in the nucleus and surface of the produced heterostructure nanowire. However, when the produced heteronanowire was heated at 800 & A ; deg ; C for 10min, the surface of the heteronanowire became unsmooth and the Mg and Sn element distribute more equally. The MgO nucleus, SnO2 shell heterostructure nanowires can supply a broad scope of applications of nanoscale optoelectronics, accelerators and detectors.

The M/M2S ( M=Ag or Cu ) heterostructure nanowires can be fabricated successfully by the template-confined step-electrochemical technique. In add-on, the synthesis methos is low cost, scalable and effectual. The heteronanowires contain both of the metal stage and metal chalcogenides. In add-on, this sort of heterostructure will be damaged by the negatron beam irradiation of the high declaration TEM. The M/M2S ( M=Ag or Cu ) heterostructure nanowires can be used in nanoelectronics devices.

Although both of the MgO nucleus, SnO2 shell heterostructure nanowire and M/M2S ( M=Ag or Cu ) heterostructure nanowires have different synthesis method, they are fabricated successfully and can be used in the nanoelectronics devices.

Decision

In decision, the fiction and possible applications of the MgO nucleus, SnO2 shell heterostructure nanowire and M/M2S ( M=Ag or Cu ) heterostructure nanowires are introduced in this essay. In add-on, both of the two mentioned nanowires are fabricated successfully by different methods and can be used in nanoelectronics devices.

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