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Derive the AC electrical conductivity of metal according to Drude model. Explain the inadequacies of Drude model and write the assumptions made in free electron model.

Ans - AC electrical conductivity of metal according to Drude model, the charge carriers experience a drag coefficient  and under an applied electric field E, this leads to the following differential equation- Here we are considering only the real part. The equation for conduction electrons in this [...]

Explain the variation of conductivity with doping.

Ans. For doped semiconductor, the conductivity can be increased by adding a small amount of another material, called a dopants , in it, For donor type doping, the dopants 'donate' electrons to the semiconductor and make n-type material. For explain, Gr-V phosphorus is used [...]

Explain the density of state at low dimensional structures.

Ans. In a crystalline solid material the energy and the volume density of electronic state change across the energy band In general, the number of energy levels, which correspond to the electronic wave functions in the crystal, in the central region of the band [...]

Draw and explain the schematic diagram of the splitting of energy levels of isolated atoms to energy bands.

Ans. The electronic energy levels in crystalline solids are quite different from that of a single atom. This is because the potential characterization of the crystalline structure is a periodic function in space whose value at any point is the result of contributions of every atom. Although [...]

Explain the basic process of VLS technuque

Ans. Vapour-liquid-solid (VLS) growth technique is a latest process, which is mainly used to grow nanowires/rods/whiskers of various elemental and compound materials. In general, nanowires of semiconducting materials are conveniently grown via the VLS process, where material from the vapour is incorporated via a liquid [...]

Explain the following nanlithographic technique (i)Ball-milling (ii)Chemical bath (iii)Lon beam deposition

Ans. Ball milling -  It is a simple method for nanomaterial preparation, which is based on the mechanical crushing process , Here small balls are allowed to rotate around the inside of a drum and drop with gravity force on to a solid enclosed [...]

Why electrode position process is needed to grow nano – rods/wires • through the alumina nano-pores ?

Ans. To integrate one-dimensional nanomaterial into a device, a fabrication method is uses that enables well-ordered nanomaterials with uniform diameter and length. Template directed growth is a nanomaterials fabrication method that uses a template which has nanopores with uniform diameter and length. Using chemical [...]

Describe briefly the deposition of some nanocrystalline thin film via sol-gel dip-coating/spin-coating/spray-coating techniques.

Ans. Sol-geL method gives very important use in deposition of thin film on various substrates via dip-coating/spin-coating/spraying process. For sol-gel dip-coating process, the· substrate is generally dipped into the sol and taken out to coat it with the required material. Depending on the number [...]

Explain the molecular beam epitaxy technique for the epitaxial growth of material Or Write short note on molecular beam epitaxy.

Ans. Epitaxy is a process of an ordered crystalline growth of materials on a crystalline substrate. It is a kind of interface between a thin film and a substrate. In general, epitaxially grown films are fabricated from gaseous or liquid precursors. The deposited film [...]