The Influence Of Magnetic Field On Nanostructures Engineering Essay

Published: 2020-06-06 13:11:04
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We are traveling to analyze about the assorted nano constructions. The assorted nanostructures can be classified harmonizing to their size. These construction can be classified as 0-d, 1-d, 2-d and 3-d. Quantum points are the illustrations of 0-d. Quantum wire and quantum good are the best illustrations for 1 & A ; 2-d. The majority semiconducting material is the 3-d illustration. We are traveling to analyze about the inorganic semiconducting material nano constructions. We will analyze the effects of using magnetic field on these nanostructures.
Nanostructures are the functional constructions with at least one characteristic dimension measured in nanometers. Nanostructures are the objects of size between molecular and microscopic constructions. Decrease or parturiency of atoms or quasi atoms in a peculiar crystallographic way within a construction by and large leads to alter in physical belongingss of the system in that way. Nanostructures stuffs can be classified, harmonizing to the alteration in the way of the dimensions. They are system confined in 3-Dimensions, 2-Dimensions, 1-Dimensions and 0-dimensions. The majority semiconducting material is an illustration for three-dimensional construction. If the thickness of the stuff alterations to nanoscale it is a two-dimensional alteration and besides known as nanotexture surfaces. If there a alteration in thickness and breadth of the stuff it is a 1-Dimensional alteration and nanotube & A ; quantum wire are its illustrations. If there a alteration in thickness, breadth and length of the stuff it is 0 – dimensional alteration and nanopaticle, quantum points are its illustration.
Figure 1: – Different Nanostructures
The information engineering revolution has been the based steadfastly on the development and application of inorganic semiconducting materials. [ 1 ] Vast bulk electronics devices were made of compound semiconducting material like GaAs. The bearer belongingss of nanostructures are governed by the Torahs of quantum mechanics. The inorganic semiconducting material nanostructure exhibits a broad scope of unusual belongingss. These are used to manufacture improved and fresh electronic and electro-optical devices.
The influence of magnetic field on nanostructure can be explained by taking 3 conditions. They are consequence of magnetic field on 3 dimensions, 2 dimensions, 1 dimension and besides 0-dimension. The best illustrations for this dimensions are bulk semiconducting material, quantum good, quantum wire and quantum points. So we will analyze the effects of magnetic field on quantum good, quantum wire, quantum points and the majority semiconducting material.
Influence of magnetic field on 0 dimensions ( quantum points ) :
A quantum point is semiconducting material in which all the dimensions are confined. It has really zero dimensions. We can analyze the non degenerated excitons by the application of magnetic field in the plane of the sample. This magnetic field response splits the excitons of the sample. The splitting of excitons due to magnetic field depends on the all right construction and g factor of each points. The additive polarisation splitting can be tuned to zero by the application of an in-plane magnetic field of type 1 ( GaAs ) & A ; type 2 ( AlGaAs ) . [ 2 ] The additive polarisation splitting can be tuned to zero by the application of magnetic field ( modest or strong ) in plane of these two samples. [ 2 ] In the first type point i.e. GaAs a modest magnetic field is sufficient to invert the initial polarisation splitting. This is due to the smaller D0 distance. In the instance of 2nd type point i.e. AlGaAs a strong magnetic field is required. These are due to S0 and DO. S0 is the distance between the two X provinces and D0 is the distance pushed by the bright province. AlGaAs require stronger field consequence due to Large D0 and S0.In order to analyze the magnetic field consequence for type 2 quantum points we consider an illustration of type 2 quantum point ( InP/GaAs ) . We study the photoluminence of InP/GaAs QD in a strong field of less than 50T.
Figure 2: Graph between the PL and Magnetic field.
We can see the Pl consequence with the additions in the magnetic field. The magneto PL measurings at low excitement powers established that the excitons have a bohr radius of 15nm and adhering energy of 1.5 meV. [ 4 ] The little value for adhering energy of the exitons indicates the set alliance in these QDs.
Influence of magnetic field on 1 dimensions ( quantum wires ) :
Quantum wires are the 1-dimension nano construction. Their breadth and thickness has been confined to nanoscale. The magnetic field is applied on the finite subdivision of quantum wire. The application of magnetic field makes the conductivity set acquire quantized. The alteration in magnetic field even oscillates the quantum wire. The alteration in the magnetic field changes the figure of bomber sets which result in quantisation. The oscillation consequences the Aharanov- Bohm intervention due to inch provinces.
The Aharonov- Bohm consequence provides us the mechanism of tuning consequence by agencies of magnetic field. The magnetic field when applied analogue to the ring of the nanowire, sing the length of the really big than the perimeter. [ 2 ] This parallel field which enters the rings split in two partial moving ridges. These two partial moving ridges propagate along the lower and upper weaponries of the ring. When the same field is subjected perpendicular the nano wire starts hovering. So as the magnetic field increases the wire oscillation besides increases. Then until a impregnation point is reached and the wire stops hovering.
Influence of magnetic field on 2 dimensions ( quantum Wellss ) :
See a 2- dimensional stuff and using the magnetic field. It can be done in two ways using the field normal and parallel to the interface. If we apply a magnetic field perpendicular to the interface of the plane, it quantizes the in-plane cyclotron gesture into set of distinct Landau degrees. This leads to a distinctively 2- dimensional belongings. If the same field is applied parallel to the interface the plane bends the negatron orbits to traverse the interfaces, ensuing in the contemplation in the well and burrowing through the barrier. Hence the parallel magnetic field is used to analyze the burrowing gesture in a ace lattice.
The consequence of magnetic field on the 2 dimensional nanostructures can be explained by utilizing the quantum hall consequence. The Hall Effect can besides be detecting in a nanostructure incorporating 2 DEG. In the experiment the electric field along the x-axis be E x and it can be determine by mensurating the electromotive force along that axis i.e. V x. [ 5 ] When a magnetic initiation is applied in the way perpendicular to the 2DEG the electric resistance becomes a 2d tensor. This allow two electric resistance ‘s to be determined as
I? xx =Ex/J x and I? xy= E y/j x — — – ( 1 )
Ex – the electric field along the x-axis
E y- the electric field green goods due to magnetic field along y-axis
J x- the current denseness along the current flow of current
In the instance of 2 dimensional nano construction there ‘s a different behavior observed than bulk semiconducting material. Although the electric resistance I? xy increases with increasing field, it does so in a measure like mode. In add-on I? xx oscillates between nothing and non nothing values, with zeros happening at field where I? xy forms a tableland. [ 1 ]
The application of magnetic field on the construction signifier bands. These sets are known as Landau degrees. The degeneration of each Landau degrees are given by
J= vitamin E B/h — — — ( 2 )
So as the field increases the degeneration of each degree besides increases. Hence the bearer denseness in the construction the figure of occupied degrees decreases with increasing field. Under the influence of high magnetic the undermentioned relate the conduction and electric resistance constituent
I? xx ~= I? xx/ ( I? xy ) 2 I? xy ~= 1/I? xy= RhB — — — — ( 3 )
The first relationship shows that the zero conduction values obtained when precisely an whole number figure of landau degrees are occupied consequences in a nothing value for I? xx.
The tableland values of I? xy are sample independent and are related to the cardinal changeless H and e. Valuess for I? XY can be measured to really high truth and are now used as the footing for the opposition criterion and besides to cipher the all right construction invariable. [ 1 ]
The parametric quantity J is known as filling factor. The value of J occurs merely for the whole number values. Hence it is known as the whole number quantum hall consequence. However, in sample with really high bearer motilities, tableland in I? xy and minima I? xx are besides observed for fractional values of J, giving rise to the fractional quantum hall consequence. [ 1 ]
By the application of parallel magnetic field for a non magnetic nanostructure we find that, they generate a bantam perpendicular constituent of the field and measured the ensuing hall electromotive forces.
The step hall electric resistance does non increase linearly with magnetic field and besides the hall incline exhibits negative corrections traveling through a local lower limit as the 2-d holes are spin.
A magnetic field analogue to the interface plane bends the negatron orbits to traverse the interface, ensuing in contemplation in the well and burrowing through the barrier. A parallel field is therefore used to analyze the burrowing gesture in a supper lattice.
Figure 3: Quantum Hall Effect
Conduction electron & A ; valency hole in a magnetic field normal to the interface
A magnetic field normal to the interface plane quantizes the in-plane cyclotron gesture into a set of distinct Landau degrees. The conductivity negatron in a quantum good, the gesture in the normal magnetic field is simple. The parabolic energy bomber sets in zero magnetic Fieldss are quantized into sets of Landau degrees with equal spacing. [ 5 ] In the instance of hole in magnetic field normal to the interface, the mini k.p methods help to calculate the Landau degrees and visualising them.
Influence of magnetic field on 3 dimensions ( Bulk semiconducting materials ) :
The influence of magnetic consequence on majority semiconducting material can be explained by halls consequence. In the halls consequence a current flows a long a semiconducting material saloon to give some current denseness. A magnetic field is applied normal to the axis of the saloon, which produces a magnetic force on each traveling charge bearer. This force causes the bearer to debar in the way perpendicular to both the field and the original gesture. It consequences in an electric field along the other axis. This axis is perpendicular to the current and magnetic field. The hall field produce an electrostatic force on the charge bearers opposes the magnetic field. Equilibrium is rapidly reached where the two forces balance to give a zero net force. A halls consequence helps to understand the bearer denseness to be determined every bit good as the bulk bearer type by utilizing the magnetic field consequence. In the instance of majority semiconducting material, the electric resistance due to X and Y increase linearly with increasing magnetic field with the electric resistance due to x axis remains changeless.
Figure 4: Hallway Consequence
We have seen the assorted nano constructions and the magnetic file influence on these constructions. The magnetic field changes the additive polarisation in the quantum points. In some QDs modest magnetic field is require and in some stronger magnetic field is require inverting the additive polarisation. The application of magnetic field oscillates the quantum wire. In the instance of quantum well or two-dimensional construction the electric resistance increases with addition in magnetic field and it besides oscillates. In the instance of majority stuff the magnetic field produces a electromotive force perpendicular to both the magnetic and electric field ( Halls Effect ) .

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