2015-2016

Sardam

ZAGROS ABDULLRAHMAN OMA

2015-2016

QUANTUM DOT

Soran

University

Faculty of Science

Chemistry

Department

Third stage

Introduction

Quantum dot are very tiny particlules on the order of a nanometer in siz, QDs are composed of

hundred to thousands atoms. QD is a semiconductor who excition are confined in all three

spatial dimension. Semiconductors are cornerstone of the electronics industry and make

possible personal computers.

And those semiconductor materials can be made from an element, such as Silicon,Germanium

or a Compound,such as Cds.

QDs can the different of color depending of the size.

QDs special because they are so small 4,000,000 dots in take up 2cm,

QDs formed when the dots is exposed to a pulse of light at the right wavelength and time, the

electron is raised to an excited state, after that the electron back to the ground state, in the

location of those electrons backs drop behind the dots, these dots then have the ability to glow.

Changing these size the emitting color of quantum dots can be tuned, shorter quantum dots

emitting shorter wavelength of light and bigger quantum dots emitting longer wavelength of

light. The energy band gap is correlated with size, as the dimension of particle decrease,

the energy increase.

The height and energy difference between energy levels increase of quantum dot decrease,

smaller Dot equal to the higher Energy those equal to the smaller Wavelength and Blue Color.

History

The early semiconductor work of Bell Labs in 1947 led to a whole revolution in electronics.

The first discovered of Quantum dot in the form of Nanocrystals (Glass Crystals) early 1980 by

Russian Physicist Ekimov.

Application

Solar cells, Biology (biosensors & imaging), Light emitting diodes (LEDs), Quantum computation,

Flat-panel displays, Memory elements, Photodetectors and Lasers….ets

Production

There are several ways to confine excitons in semiconductors resulting in different methods to

produce quantum dot.Quantum dots are grown by advanced epitaxial techniques or by ion

implantation,or in Nano devices made by state of the art lithoraphice techniques,.

i- Colloidal Synthesis:-

Colloidal semiconductor Nano crystal are synthesized from precursor compound dissolved in

solutions , much like traditional chemical processes.

i- Fabrication:-

CMOS technology can be employed to fabricate silicon quantum dots.

Ultra small (L=20 nm, W=20nm) CMOS transistors behave a single elecrone quantum dot, when

operate at cryogenic temperature.

ii- Electrochemical Assembly:-

Highly ordered arrays of quantum dot may also be self assembled by electrochemical

techniques, Atemplate is created by causing an ionic reaction at electrolyte metal interface

Which result in the spontaneous assembly of nanostructures.

Characterization

Quantum dot can be characterized by two techniques:

ii- Optical Characterization

Electron microscopes and atonic force microscopes (AFM) are widely used for the optical

characterization of the size of the qdots. For the cross section investigation of pdote structures,

transmission electron microscopy (TEM) is the moste used

Ii- Electrochemical Characterization:

Qdots can be detected directly or indirectly by oxidatively dissolving the metal ion into aqueous

metal ion and then electrochemically sensing the ions by using stripping voltammetry or

potentiometry or electrochemical impedance spectroscopy (EIS)

Conclusion (Discussion)

Quantum dot can be synthesized to be essentially any size, and therefore, produce

essentially any wavelength of light.

The future looks bright and exiting on all the possible applications of Quantum dot.

Quantum dote is Nano crystal made of semiconductor material that are small enough to

exhibit quantum mechanical properties. There are several ways to confine in

semiconductors resulting in different methods to produce quantum dot.

Quantum dot formed when electron goes up in ground state to existed state after that

this electron goes down to the ground state after extinction of light (energy) so in the

location of electrons drop behind of spot or dot (hole) those hole are Quantum dots.

Reference

http://www.asemblon.com/

http://www.worldenergyoutlook.org/

http://www.springer.com

http://www.Accademy.com