PartA

Q.1 Any four of the following:
 

Point defects concentration	B = Defect formation energy
Creep rate	B = Activation energy for creep
Diffusivity	B = Barrier height in motion of diffusing species
Fluidity	B = Activation energy for viscous deformation
Charge carrier density, in an intrinsic semiconductor	B = Band gap/2
Charge carrier density, in an extrinsic semiconductor	B = Separation of impurity levels from band edge

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Q.2

 

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Q.3

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Q.4 Griffith asserted that brittle material such as untempered glass contain numerous elliptical cracks at the surface and in the interior. It can be shown that, under an applied stress £m, the local stress at the tip of such a crack is

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Where £d is the crack length and R is the radius of curvature at the tip. A compressive load closes, not opens, the Griffith flaws and therefore does not cause fracture unless the intrinsic strength of the material is exceeded. But a piece of glass on top of an uneven surface is subjected to alternation compressive and is subjected to alternating compressive and is subjected to alternation compressive and ensile stresses, the latter tending to open the cracks and easily causing fracture due to stress concentration at their tips.

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Q.5

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Resolved shear stress

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¡§Critical resolved shear stress is that magnitude of £F that is great enough to result in slip (along the said slip direction in the said slip plane) by dislocation motion.

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• 8. If an amount dm of the material is deposited, the effective thickness of the quartz plate increase by:

 

 
 
 
 
 
 
 
 
 

Where £l_Q and S are the density and the area of the plate, respectively. The f changes by:



The deposition rate at the position of the quartz plate is thus

• Two-probe technique:

Therefore, the V/I is equal the contact resistance.
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Four probe technique:

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Q.9 RF Sputtering ¡÷ high vacuum (~10^-5 torr base pressure) required

\ Need 4 more components:
 

(1)	Roughing pump
(2)	High vacuum pump
(3)	Pressure gauge for low vacuum + controller
(4)	Pressure gauge for high vacuum + controller

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(1)	(e.g.) Votary vane pump	¡@
(2)	* Diffusion pump or turbomolecular pump	(* not needed)
(3)	(e.g.) Pirmni gauge	(By measuring thermal conductivity of residue gas in he chamber)
(4)	(e.g.) Penning gauge	(By measuring cold cathode discharge current)

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10.

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Ek = x-ray or UV photon energy-work function difference-Eb

\ Ek = constant-Eb

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XPS => elemental composition of sample

• valence states of particular elements (from chemical shifts)
UPS => valence Band (V.B.) structure
• energy level of surface states (if present)
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Non-dispersive energy analyzers,

e.g. retarding field analyzer or time-of-flight analyzer

Dispersive analyzer,

e.g. electrostatic cylindrical mirror

or magnetic double-focusing

or electrostatic hemispherical

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11. Weight of sample as a function of time (isothermal) or temperature (usually rising);
Any three of the following:¡K..(*)
1. Phase transition involving weight change i.e. sublimation or condensation,
2. Decomposition with gaseous products;
3. Oxidation;
4. Carburzing;
5. Defalcation;
6. Combustion.
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Difference in the property being monitored, which is the differential heat inputs to sample and reference which are maintained to have identical temperature (DSC), but is the discrepancy between sample and reference temperatures when both are heated at the same rate (DTA); any 3 of the above (*), plus phase transitions such as melting and solidification, glass transition, crystallization, cross-linking, polymerization, diffusing, all kinds of chemical reaction, ¡K

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Molar fraction of impurities

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Where T is the temperature at which at which fraction a of the material has melted, T0 is the melting point of pure material, D H is the molar heat of fusion, and R is the gas constant.

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Limitations: all impurities concerned must be completely insoluble in solid phase but completely insoluble in the melt.