Nano electronics and science unit I introduction, survey of modern electronics

NANO ELECTRONICS AND SCIENCE

Diode as Basic Element of Electronics, Field Effect of Transistors, Heterostructure

transistors, Resonant-Tunneling diodes and transistors Need for New Concepts in

Electronics, From Microelectronics towards Bimolecular Electronics

Electromagnetic Waves and Maxwell’s Equations, Duality of Electron, Schrödinger

Equation, Eigenvalue Problem and Electron in Quantum Well, Electrons in Multiple

Quantum Wells. Super lattices Artificial Atoms: Quantum Dots, Molecules, Energy Level

Splitting, Chemical Bonds,Optical Transitions and Lasers

UNIT III ROLE OF PATTERN FORMATION IN NANOELECTRONICS

High Resolution Lithography, Dip-Pin Lithography, NEMS, Nano-Electromechanical

Systems, Self-Assembly structures – Chemically Directed Self-Assembly,

Surface-Layer Proteins in nanolithography

Quantum Well cascade Lasers and other Quantum-Well Devices, Quantum Wires,

Quantum Dots and Quantum Dot molecules, Quantum Dot Based cellular Automata,

Coulomb Effects, Single Electron Devices Nanoscale sensors and Actuators

Challenges and Potential Applications of Inorganic Hetero structures, Quantum Dots

Embedded in organic Matrix, organic light emitting diodes, Quantum Wire Interconnects,

DNA and Peptides, Fullerenes and carbon nanotubes, Molecular Electronics Materials

and Biomolecules, Future Integrated circuits: Quantum computing

Text Books:

1. C.P. Poole and F.J.Owens, “ Introduction to nanotechnology”,John Wiley &

Sons,2003

2. M.A. Ratner and D.Ratner, “ Nanotechnology ; a gentle introduction to the next big

idea” ,

Prentice Hall,2002

ASME Press

2. S.E.Lyshevski,”Nano-and micro-electrochemical systems fundamentals of nano and

microengineering ,2004.

1. 
   What is lower dimension devices?
   

• 
  The theory of the behavior of electrons in structures of dimensions lower than three is well known. Although true zero, one and two dimensional physical structures are not possible, if one or more dimensions are less than the de Broglie wave length of an electron the structure has the quantum properties of a lower dimension structure.
  

2. 
   Define OLED?
   

OLED technology is used in commercial applications such as displays for mobile phones and portable digital media players, car radios and digital cameras among others. Such portable applications favor the high light output of OLEDs for readability in sunlight and their low power drain. Portable displays are also used intermittently, so the lower lifespan of organic displays is less of an issue. Prototypes have been made of flexible and rollable displays which use OLEDs' unique characteristics. Applications in flexible signs and lighting are also being developed.^[71] Philips Lighting have made OLED lighting samples under the brand name 'Lumiblade' available online.^[72]

3. 
   Explain about the lower dimensions devices?
   

• 
  The theory of the behavior of electrons in structures of dimensions lower than three is well known. Although true zero, one and two dimensional physical structures are not possible, if one or more dimensions are less than the de Broglie wave length of an electron the structure has the quantum properties of a lower dimension structure.
  
• 
  The technology for producing structures with one or more dimension sufficiently small to achieve low-dimension quantum effects (approximately 10 nm) has recently advanced enough to allow fabrication of devices based upon low-dimension quantum effects.
  
• 
  Devices operating on quantum confinement are more efficient in energy so there is less wasted energy to be dissipated as heat.
  
• 
  Quasi-two dimensional devices, such as quantum well semiconductor lasers, are now economically practial, but quasi-one and zero dimensional devices such as quantum wires and quantum dots are not now economically practical, perhaps because of the additional processing required to create wires and dots. IBM, Bellcore and Phillips dropped research and development programs for quantum wires and dots in the mid-1990s.
  
• 
  Electrons can be confined to one semiconductor material by sandwiching the semiconductor material between two layers of higher energy-band gap materials. Such a structure is called a heterojunction.
  
• 
  There are allowed and forbidden energy levels for a electrons in a material. The conductivity of a material is determined by the occupancy of the allowed energy bands. Energy bands which are filled are called valence bands and the ones that are sparcely occupied are called conduction bands. The conductivity of a material is determined by the occupancy of its energy bands.
  
• 
  The availability of electrons to fill the energy bands depends upon the valence electrons of the material, but can be altered by doping, the introduction of chemically-related material into the crustal lattice of the material. Also photo-electric photons can change the occupancy of a material.
  
• 
  The development of Molecular-Beam Epitaxy (MBE) in the laste 1960's made quasi-two dimensional structures feasible. Not only did this allow the creation of ultrathin films but multiple layers of such films. However it was not until 1974 that quantum well devices were produced.
  
• 
  The typical laser energy arrangement involves four states:
  
  1. 
     E₃: The state to which electrons are pumped
     
  2. 
     E₂: The upper state of two states involved in the productions of photons
     
  3. 
     E₁: The lower state to which electrons drop from the upper state after emitting a photon
     
  4. 
     E₀: The ground state to which electrons fall from E₁
     
• 
  The key to the operation of the laser is a population inversion, a higher population in the upper state E₂ than in the lower state E₁. This is achieved by pumping to E₃and the rapid exit of electrons from the lower state E₁.
  
• 
  In conventional lasers the energy states are natural energy level of the lasing material such as ruby crytal or helium=neon gases. In the quantum cascade laser the energy states are determined by the physical characteristics of the quantum wells and can be adjusted to any desired levels. The quantum cascade laser relies upon cascades of 25 quantum well configurations.
  
• 
  Quantum wires and quantum dots may be more efficient and faster than quantum films.
  
• 
  It is much more difficult to fabricate quantum wires than quantum films. One promising technology deposits semiconductor material at the bottom of V-shaped lines, such might be found in a diffraction grating.
  
• 
  Laser wires generate photons through the self annihilation of exciton, pairings of electrons and holes. Conventional lasers, by contrast, emit photons from the annihilation of free electrons and free holes. When the current is increased a conventional laser's emission frequency may derease, whereas for wire or dot lasers the frequencies are stable when current is increased.
  
• 
  Variations in the width of quantum wires may result in their functioning as a chain of quantum dots. This may occur at low temperatures.
  
• 
  Variations in the thickness of quantum films result in clumps that function as quantum dots. This approach offers the possibility of creating arrays of quantum dots.
  
• 
  There is a possibility of using molecules as quantum dots. The problem is creating contacts and linkages.
  

4. 
   Explain the organic lights?
   

From Wikipedia, the free encyclopedia

Demonstration of a flexible OLED device

A green emitting OLED device

An organic light emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes. Generally, at least one of these electrodes is transparent.

OLEDs are used in television set screens, computer monitors, small, portable system screens such as mobile phones and PDAs,watches, advertising, information, and indication. OLEDs are also used in large-area light-emitting elements for general illumination. Due to their low thermal conductivity, they typically emit less light per area than inorganic LEDs.

An OLED display works without a backlight. Thus, it can display deep black levels and can be thinner and lighter than liquid crystal displays. In low ambient light conditions such as dark rooms, an OLED screen can achieve a higher contrast ratio than an LCD—whether the LCD uses either cold cathode fluorescent lamps or the more recently developed LED backlight.

There are two main families of OLEDs: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a Light-emitting Electrochemical Cell or LEC, which has a slightly different mode of operation.

OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes.