Question

cells. Si, Ge and O-Sn are approximately 1x 10", - in each of 1 x 10°, 0.46 and 11 x 10-12 m. Rationalize this hcp; (c) trend in values. (c) How does the change in electrical resistivity with temperature vary for a e at 80K typical metal and for a semiconductor? form is 6.9 Distinguish between an intrinsic and extrinsic Suggest, semiconductor, giving examples of materials that mame is fall into these classes, and further classify the types Suggest of extrinsic semiconductors. What structural features military do many semiconductors have in common? 6.10 The metallic, covalent and ionic radii of Al are 143, or the 130 and 54 pm respectively; the value of rion is for a of 6-coordinate ion. (a) How is each of these quantities gest defined? (b) Suggest reasons for the trend in values. of (6.11 With reference to the NaCl, CsCl and TiO, structure line types, explain what is meant by (a) coordination on number, (b) unit cell, (c) ion sharing between unit cells, and (d) determination of the formula of an ionic on salt from the unit cell.

please answer only circled ones with full explanation plz

Answer 1

Page 6 * Distinguish between an intrinsie and extrinsic Semiconducton. Basie of Intrinsie Semiconductor extrinsie semiconducton Dileepence' t. Doping Doping on addition of impurity A small amount of impurity does not take place in limpwory is dopped in a intrinsie Semiconductor pure semiconducion.fo preparing exthinsic Semicondueron. and holes are not equal Density of the number of thee The number of ele elech pon electrons in the conduction and holes are not and holes Iband is equal to the number o holes in the volonce band Electrie a conductivity Electrical Electhical conduchůty is cond Kelivity low is high Dependancyl Electric Conductivity is a Os eleemical lanerion of temperature conductivity alone. Electrical conductivity depend) on temperature as well as on the amount of impurity doping in the pure Semiconducton. Impunity like as Sb, P, In, Bi, Al etc. are dopped with Germanium and silicon athom Example ebystalline form of pule Silico wysiland Gebmanium (Ge). classification of extinsic Semieon auctors Based on the type of impurities added, extninsie Semiconductors aje classified in two types. type semiconducton (Pentavalent atom) op-type semiconducton. Thivauent impurities) N-type semieonduct

Page Common feature Strucal featwe in cu Semiconducton, • Semiconductors wie made up of atoms bonde 40gchien to form a unifor structure. • Each silicon com has four Valancy electron which wte Shared, forming covoulent bonds with the sout Burrounding s aroms, a) who is meant by Coondination mum ben:. 1 In an Jonie metal the coordination nur the cation is equal to the number of anions al in close proximity to it. Nad is a cubie structure and each Sodium Cation is swulounded by four chionine ions on the same plane as wel as one below and one above, so the corondination homben is 6. For escl the sth. is Body centered cubie struct SO Co-ordination numben is 8. The purile sth of TiO2 the co-ondination is (6:3). b) unit celle The simplest beapearing unit in a chystal is called a unit ceu. Each unit cele is defined in terms of lattice points the point in space about which the parrcle are free to vibrare in a ehystal. opposit faces of a unit ceu are paravel. The unit eau of nace consist of Nat cansist of Nat and at ions. For a face site it is shared with a Unit cell. And for an eadge sit ition is a shared by 3 other unit eel, escl, has a cubie unit cello. Тio, ha a etha gonad и it соu и е ғtemium cation have a coordination no ot 6. meaning they are surrounded by an octahedron 24 6 oxygen atem.

page- ction sharing For nad when counting the number otions, 'a connen sithe would be shared by 7 other uniteets. The pefon A conner would by y8 if anion. A similar occurance happens with the face site and the edge sites, for 1 • by oth other anis cen! for ° edge site, it is shouted by 3 othepi unit cell. For es el meceu edge must conne et Baltice poina the presence of co ion at one connen, implies the posence of action at every conner of the cu. The co-opdinges 1/2, V2, 12 dese bibe a lattice point at the eepreb of the cell. For the TiO2 the one connen would be / et anion. d) Determination of topmula of ionie sout from unit cell Nac: face cenethic - cubie. wree with na in all Octaned nal sites. The be are 4 na and quin cach unit cell. Each unit een has a formua units of Nael Sthe esel simple cubie a "with es in au cubie sires. There are 1 cs and 1 ae in each unit cel. fach unit cell has a formula anit of aselsth. Jiez pusile has a primitive tetragonal whit cel. the co-ordination number for tid is 6 4 fono is 3. These are two ti and found in each unit, Each unit een has a formula units of Tio Structure