VALLIAMMAI ENGINEERING COLLEGE

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1 VALLIAMMAI ENGINEERING COLLEGE SRM Naga, Kattankulathu DEPARTMENT OF PHYSICS QUESTION BANK II SEMESTER PH PHYSICS FOR ELECTRONICS ENGINEERING (Common to ECE, EEE, E&I) Regulation 2017 Academic Yea Pepaed by D.M.Anbuchezhiyan, Ms.R.Nithya Balaji, Ms.S.Gandhimathi, Ms.R.Sasieka, Ms.S.Sowmiya, Ms.M.P.Ramya Rajan & D.S.Muugavel,

2 VALLIAMMAI ENGINEERING COLLEGE SRM Naga, Kattankulathu DEPARTMENT OF PHYSICS QUESTION BANK SUBJECT: PH PHYSICS FOR ELECTRONICS ENGINEERING SEM/YEAR: II SEM/AY UNIT I - ELECTRICAL PROPERTIES OF MATERIALS Classical fee electon theoy Expession fo electical conductivity Themal conductivity, expession Wiedemann Fanz law Success and failues electons in metals Paticle in a thee dimensional box degeneate states Femi Diac statistics Density of enegy states Electon in peiodic potential: Bloch thoem metals and insulatos Enegy bands in solids tight binding appoximation Electon effective mass concept of hole. PART - A S.No Questions Level Comp etence 1. What ae the souces of esistance in metals? BTL1 Reme mbe 2. Define dift velocity. How is it diffeent fom themal velocity of an electon? BTL4 Analys e 3. Find the dift velocity of electons coppe wie whose coss sectional aea is 1 mm 2. When the wie caies a cuent of 10 A. Assume that each coppe atom contibutes one electon of the electon gas. Given n = 8.5x10 28 /m Define the tems elaxation time, collision time and mean fee path of an electon. BTL4 Analys e 5. What is meant by a fee electon? BTL1 Reme mbe 6. What ae the meits of classical fee electon theoy of metals? BTL1 Reme mbe 7. Diffeentiate between electical conductivity and themal conductivity. BTL4 Analys e 8. What is meant by degeneate and non-degeneate states? BTL1 Reme mbe 9. Define density of enegy states. BTL4 Analys e 10. Define Femi level and Femi enegy with its impotance. BTL4 Analys e 11. What do you undestand by Femi-Diac statistics? BTL1 Reme mbe 12. The Femi enegy of coppe at 0 K is 7.04 ev. Calculate the Femi enegy at 300 K.

3 13. Calculate the Femi enegy of coppe at 0 K if the concentation of electons is 8.5x10 28 m What is a peiodic potential? BTL1 Reme mbe 15. What ae fobidden bands? BTL1 Analys e 16. Compae fee electon appoximation and tight binding appoximation. BTL4 Analys e 17. What is meant by effective mass appoximation? BTL1 Reme mbe 18. Will the effective mass of the electon be negative? Justify you answe. BTL6 Ceatin g 19. Explain the concept of hole and give its advantages. Undes tand 20. What is the phenomenon that explains the concept of hole? BTL1 Reme mbe Pat-B S.No Questions Level Competence 1. i) Give the postulates of fee electon theoy. Deive an expession fo electical conductivity of a metal by using classical fee electon theoy. (3+7) BTL1 Remembe ii) Calculate the electical and themal conductivities fo a metal with a elaxation time second at 300 K. Also calculate Loentz numbe using the above esult. (Density of electons = 6x10 28 m -3 ). (3) 2. Deduce mathematical expession fo electical conductivity and themal conductivity of a conducting mateial and hence obtain Wiedemann-Fanz law. (13) 3. State and pove Wiedemann-Fanz law. Why does the Loentz numbe detemined expeimentally does not agee with the value calculated fom the classical theoy? (10+3) 4. (i) Deive the one dimensional box and calculate the enegy values and wave function. (10) (ii) An electon is confined to a one dimensional box of side m. Obtain the fist fou Eigen values of the electons. (3) 5. Obtain Eigen values and Eigen functions of an electon enclosed in a 3-D potential box. (13) 6. Deive an expession fo the density of states and based on that calculate the caie concentation in metals. (13) 7. i) Stating with the density of enegy states obtain the expession fo the Femi enegy of an electon at 0 K and hence obtain the expession fo the aveage enegy of an electon. (10) ii) The Femi enegy of silve is 5.51 ev. What is the aveage enegy of a fee electon at 0 K? (3) 8. (i)wite an expession fo the Femi enegy distibution function F (E) and discuss its behaviou with change in tempeatue. Plot F (E) vesus E fo BTL1 Undestand Remembe Undestand Undestand Undestand Undestand Undestand

4 T= 0 K, and T > 0 K. (7) ii) Use the Femi distibution function to obtain the value of F (E) fo the level just 0.01eV above the Femi level at 200 K. (3) iii) Evaluate the Femi function of enegy K B T above the Femi enegy. (3) BTL6 Ceating 9. (i) Define Femi enegy. Obtain a geneal expession fo the Femi enegy of Undestand electons in solids at zeo degee Kelvin. Show that at the same tempeatue, the aveage enegy of the electon is (3/5) th. (10) (ii) The density of silve is 10.5x10 3 kg/m 3. The atomic weight of silve is Each silve atom povides one conduction electon. The conductivity of silve at 20 C is 6.8 x10 7 Ω -1 m -1. Calculate the density of electon and also the mobility of electons in silve. (3) 10. Explain the enegy band theoy of solids. (13) Undestand 11. Wite notes on (i) Enegy levels (7) Undestand (ii) Enegy bands (3) Undestand (iii) Bound and fee electons (3) Undestand 12. i) State and explain Bloch theoem. (7) Undestand (ii) Explain fee electon appoximation and tight binding appoximation with Undestand suitable diagams. (6) 13. (i) Explain the fomation of tight binding appoximation. (6) Undestand (ii) Discuss the concept of holes fomation.(7) Undestand 14. (i) Wite a shot note on effective mass of an electon. (5) Undestand (ii) Deduce an expession fo the effective mass. (4) Undestand (iii) Daw E-K cuve and explain the concept of hole. (4)

5 UNIT II SEMICONDUCTOR PHYSICS Intinsic Semiconductos Enegy band diagam diect and indiect semiconductos Caie concentation in intinsic semiconductos extinsic semiconductos Caie concentation in Ntype & P type semiconductos Caie tanspot: Velocity electic field elations dift and diffusion tanspot Einstein s elation Hall effect and devices Zene and avalanche beakdown in p n junctions Ohmic contacts Tunnel diode Schottky diode MOS capacito Powe tansisto. PART - A S.No Questions Level Compete nce 1. Define semiconducto and mention its popeties. BTL1 Remembe 2. Define the tem mobility of a semiconducto. BTL1 Remembe 3. What ae n-type and p-type semiconductos? Give examples. BTL1 Remembe 4. Why compound semiconductos ae called diect band gap semiconductos? Give its application. 5. What is meant by dono and accepto level? BTL1 Remembe 6. Find the esistance of an intinsic Ge od 1 cm long,1 mm wide, and 0.5mm thick at 300 K. Fo Ge, n i = 2.5 x /m 3, µe= 0.39 m 2 V -1 s -1 and µ h = 0.19 m 2 V -1 s -1 at 300 K. 7. With incease of tempeatue the conductivity of semiconducto inceases while BTL6 Ceating that of metals deceases. Give easons. 8. What is meant by caie tanspot in semiconducto? BTL1 Remembe 9. Diffeentiate between dift and diffusion tanspot. BTL4 Analyse 10. Wite the Einstein elation. Undesta nd 11. What is Hall Voltage? BTL1 Remembe

6 12. The Hall Co-efficient of a specimen of doped silicon is found to be 3.66x10-4 m -3 /C. The esistivity of specimen is 8.93x10-3 Ω m. Find the mobility and density of chage caies. 13. Mention the applications of Hall Effect. BTL1 Remembe 14. What is the beakdown mechanism adopted in zene and avalanche beakdown? BTL1 Remembe 15. Mention some of the diffeence between zene and avalanche beakdown. BTL1 Remembe 16. Mention the uses of Ohmic contact. BTL1 Remembe 17. Distinguish between Ohmic contact and Schottky diode. BTL4 Analyse 18. What is pinciple of opeation in tunnel diode? BTL1 Remembe 19. Name few applications of Schottky diode. BTL1 Remembe 20. Why ae vetical stuctues pefeed fo a powe tansisto? Pat-B S.No Questions Level Competence 1. Deive an expession fo density of electons in the conduction band and Undestand density of holes in the valence band of an intinsic semiconducto. (13) 2. Deive the intinsic caie concentation fo intinsic semiconducto. (13) Undestand 3. Obtain an expession fo the caie concentation of electons in the conduction band of n-type semiconducto. (13) 4. Explain extinsic semiconductos and deive the expession fo caie concentation fo n-type and p-type semiconducto. (13) 5. (i) Deive an expession with necessay theoy fo the concentation of caies in p-type semiconductos. (10) (ii) In a p-type gemanium, n i = 2.1x m -3, density of boon=4.5x10 23 atoms m -3.The electons and hole mobility ae 0.4 and 0.2 m 2 /volt.sec Undestand Undestand Undestand

7 espectively. What is its conductivity befoe and afte the addition of boon atoms? (3) 6. (i) What is caie tanspot? Explain its types. (7) BTL1 Remembe (ii) Deive the expession of velocity electic field elations. (6) Undestand 7. Explain the following (i) Dift tanspot (5) Undestand (ii) Diffusion tanspot (5) Undestand (iii) Einstein elation (3) Undestand 8. (i) State and explain Hall effect (3) BTL1 Remembe (ii) With necessay theoy and diagam, deive the Hall coefficient. (10) Undestand 9. (i) Explain any two Hall devices. (10) Undestand (ii) The Hall co-efficient of cetain silicon was found to be x10-5 m 3 C -1 fom 100 to 400 K. Detemine the natue of the semiconducto. If the conductivity was found to be 200 m -1 Ω -1, calculate the density and mobility of the chage caies. (3) 10. Detail the occuence of zene and avalanche beakdown in p-n junction. BTL1 Remembe (13) 11. (i) Descibe the pinciple, theoy and V-I chaacteistics of Tunnel diode. (10) Undestand (ii) Give its advantages and applications of tunnel diode in engineeing field. (3) 12. (i) With a neat sketch, descibe the pinciple, constuction and woking of a Undestand Schottky diode. (10) (ii) Compae the V-I chaacteistics of Schottky diode. (3) BTL4 Analyse 13. Explain in detail the opeation of MOS capacito unde vaious gate voltages. BTL1 Remembe (13) 14. Explain the fabication of the powe tansisto with applications. (13) Undestand UNIT III MAGNETIC AND DIELECTRIC PROPERTIES OF MATERIALS Magnetism in mateials magnetic field and induction magnetization magnetic pemeability and susceptibility types of magnetic mateials micoscopic classification of magnetic mateials Feomagnetism: oigin and exchange inteaction satuation magnetization and Cuie tempeatue Domain Theoy. Dielectic mateials: Polaization pocesses dielectic loss intenal field Clausius Mosotti elation dielectic beakdown high k dielectics. PART - A S.No Questions Level Competence 1. What is Boh Magneton? Wite its value. BTL1 Remembe 2. A magnetic field of 2000 A/m is applied to a mateial which has a susceptibility of Calculate the (i) Intensity of Magnetisation and (ii) Flux density. 3. Define magnetic susceptibility and pemeability. BTL1 Remembe 4. A magnetic field of 1800 ampee/mete poduces a magnetic flux of 3x10-5 webe in an ion ba of coss sectional aea 0.2 cm 2. Calculate pemeability. 5. What ae diamagnetic mateials? Give some examples. BTL1 Remembe

8 6. What ae paamagnetic mateials? Give some examples. BTL1 Remembe 7. What ae magnetic domains and domain walls? BTL1 Remembe BTL1 Remembe 8. What ae Dielectics? 9. Define electic polaization and electic susceptibility. BTL1 Remembe 10. Define dielectic constant. BTL1 Remembe 11. Define dielectic loss and loss tangent. BTL1 Remembe 12. Define dielectic stength. BTL1 Remembe 13. What ae the equiements of good insulating mateials? BTL1 Remembe 14. Calculate the polaization poduced in a dielectic medium of dielectic constant 6 and it is subjected to an electic field of 100 V/m. Given ε 0 = 8.85 x F/m. 15. What ae the factos affecting dielectic loss? BTL1 Remembe 16. The dielectic constant of a He gas at NTP is Calculate the electonic polaizability of He atoms if the gas contains 2.7 x atoms/m 3 and hence evaluate the adius of the He atoms. Given ε 0 = 8.85 x F/m. 17. What ae the ways in which the dielectic beakdown can be minimised? BTL1 Remembe 18. Calculate the maximum potential gadient to which 0.5mm thick mica sheet can be subjected. The dielectic stength fo mica is 100 x (10 6 V/m). Justify you answe. 19. What is meant by high-k-dielectics? Give examples. BTL1 Remembe 20. List out some of the applications of high k-dielecics. BTL1 Remembe Pat-B Questions Level Competence S.No 1. i) State the oigin of magnetic moment. (3) Undestand ii) How ae magnetic mateials classified based on magnetic moments? Compae thei popeties. Give also thei chaacteistics and examples. (10) 2. i) Explain in detail the diffeent classifications of magnetic mateials. (10) Undestand ii) A given mateial has a susceptibility of 900. Detemine the elative pemeability of the mateial. (3) 3. (i) Explain about the oigin of feomagnetism and exchange inteaction in Undestand

9 feomagnetic mateials. (6) (ii) Discuss about satuation magnetisation and Cuie tempeatue. (7) Undestand 4. Explain feomagnetic domain theoy. Biefly explain diffeent types of enegy involved in domain gowth. (13) 5. Wite in detail the oigin of magnetic domains, domain wall motion and effect of anisotopy in cystallinity on domains. (13) Undestand Undestand 6. (i) Discuss electonic and ionic polaizations with examples in detail. (10) Undestand (ii) A solid contains 5x10 28 identical atoms /m 3, each with a polaizability of 2x10-40 Fm 2. Assuming that intenal field is given by the Loentz elation, calculate the atio of intenal field to the applied field. (ε 0 = 8.85 x F/m). (3) 7. (i) Explain the diffeent types of polaization mechanisms involved in a Undestand dielectic mateial. (10) (ii) Explain its fequency and tempeatue dependence. (3) 8. Wite a note on Undestand (i) Dielectic loss (3) (ii) Clausius-Mosotti elation (5) (iii) Diffeent types of beakdown in a dielectic medium. (5) 9. What is dielectic loss? Deive the expession fo dielectic powe loss. (13) BTL1 Remembe 10. What is meant by local field in a dielectic and how it is calculated fo a cubic stuctue? Deduce the Clausius Mosotti elation. (13) BTL1 Remembe 11. Deive an expession fo intenal field in a cubic stuctue. Deduce the Undestand Clausius Mosotti elation.(13) 12. What ae the diffeent types of dielectic beak down in dielectic medium? Discuss in detail the vaious types of dielectic beakdown.(13) BTL1 Remembe 13. Detail the theoy, popeties and applications of high-k-dielectics with Undestand examples. (13) 14. Explain the theoy of high-k-dielectics and give a bief note on its popeties and applications. (13) BTL1 Remembe

10 UNIT IV OPTICAL PROPERTIES OF MATERIALS Classification of optical mateials caie geneation and ecombination pocesses Absoption emission and scatteing of light in metals, insulatos and Semiconductos (concepts only) photo cuent in a P N diode sola cell photo detectos LED Oganic LED Lase diodes excitons, quantum confined Stak effect quantum dot lase. PART - A Questions Level Competence S.No 1. What ae optical mateials? Give its types. BTL1 Remembe 2. Define caie geneation and ecombination. BTL1 Remembe 3. What ae the types of caie geneation? BTL1 Remembe 4. What is the pinciple used in PIN photodiode? Undestand 5. Give any fou applications of photodiode. BTL1 Remembe 6. Wite the pinciple of opeation in a sola cell. BTL1 Remembe

11 7. List out any fou applications of sola cell. BTL1 Remembe 8. What is meant by photo detecto? BTL1 Remembe 9. Mention the popeties of photo detectos used in fibe-optic BTL1 Remembe communication. 10. What ae the main equiements fo a suitable LED mateial? BTL1 Remembe 11. Why goup III and goup V elements alone should be chosen fo manufactuing LED s? 12. Why the shape of the LED is made as hemispheical? 13. Mention any fou advantages of LED in electonic display BTL1 Remembe 14. What ae the popeties of LED? BTL1 Remembe 15. List out the ecent applications of OLED. BTL1 Remembe 16. What is the pinciple of lase diode? BTL1 Remembe 17. Calculate the long wavelength limit of a extinsic semiconducto if the ionisation enegy is 0.02 ev. 18. What ae excitons? Give its types. BTL1 Remembe 19. What do you undestand by quantum confined stak effect? Undestand 20. What is the pinciple used in quantum dot lase? BTL1 Remembe Pat-B S.No Questions Level Competence 1 (i) Explain the salient featues of optical mateials. (3) Undestand (ii) Explain the diffeent phenomenon that take place as an electomagnetic adiation is incident on a given optical mateial. (10) 2. Descibe the optical absoption in metals, dielectics (insulatos) and Undestand semiconductos. (13) 3. Descibe the pinciple, constuction and woking of a photodiode. (13) Undestand 4. (i) Descibe the constuction and woking of a sola cell. (10) Undestand (ii) Give the advantages, disadvantages of a sola cell. (3) BTL1 Remembe 5. Descibe the constuction and woking of a photodetecto. (13) Undestand 6. Explain the theoy and woking of LED. (13) Undestand 7. Explain how p-n junction diode acts as light emitting diode. (13) Undestand 8. (i) What ae the diffeences between LED and OLED? (7) BTL4 Analyse

12 (ii) Compae photodiode and lase diode. (6) BTL4 Analyse 9. (i) What is meant OLED? (3) BTL1 Remembe (ii) Descibe in detail, the constuction and woking of OLED. (10) Undestand 10. (i) Descibe the pinciple, constuction and woking of a GaAlAs diode lase. Undestand (10) (ii) Calculate the wavelength of emission fom GaAs semiconducto lase whose band gap enegy is 1.44 ev. (Planck s Constant = x Js) and chage of an electon is 1.6 x C). (3) 11. Explain the constuction and woking of a semiconducto diode lase (lase Undestand diode) with diagam. (13) 12. Discuss with theoy, constuction and woking of homojunction and Undestand heteojunction semiconducto lase. (13) 13. Wite shot notes on (i) Excitons (6) (ii) Quantum confined Stak effect. (7) Undestand 14. (i) Explain the phenomenon of quantum Stak effect. (7) Undestand (ii)explain the woking and pinciple of a Quantum dot lase. (6) Undestand UNIT V NANOELECTRONIC DEVICES Intoduction electon density in bulk mateial Size dependence of Femi enegy quantum confinement quantum stuctues Density of states in quantum well, quantum wie and quantum dot stuctues Zene Bloch oscillations esonant tunneling quantum intefeence effects Mesoscopic stuctues: Conductance fluctuations and coheent tanspot Coulomb blockade effects Single electon phenomena and Single electon Tansisto magnetic semiconductos spintonics Cabon nanotubes: Popeties and applications PART - A S.No Questions Level Competence 1. What is meant by bulk mateials? BTL1 Remembe 2. Wite the equation fo an electon density in a conducto at T = 0K. BTL1 Remembe 3. Whethe Femi enegy vaies on mateial s size? If yes o no, justify you BTL6 Ceating statement. 4. What will happen to the band gap when the volume is educed fom that of a BTL5 Evaluate solid to a nano mateial? 5. What is meant by tunnelling? BTL1 Remembe

13 6. What is meant by quantum confinement? BTL1 Remembe 7. What we will obseve when we deceases the size of the paticle to nano size? BTL5 Evaluate 8. What is meant by quantum confined stuctue? BTL1 Remembe 9. Define the tem quantum well, quantum wie and quantum dot. Undestand 10. Wite any two applications of quantum well, quantum wie and quantum dot. BTL1 Remembe 11. In quantum dot, how will be the natue of the mateial and band gap? BTL5 Evaluate 12. What ae Bloch oscillations? BTL1 Remembe 13. What ae Zene-Bloch oscillations? BTL1 Remembe 14. Define esonant tunnelling. Undestand 15. What is meant esonant tunnelling diode? BTL1 Remembe 16. Define mesoscopic. Undestand 17. Define Coulomb blockade effect. Undestand 18. How Coulomb blockade pevent unwanted tunnelling? 19. What is spintonics? BTL1 Remembe 20. What is CNT? BTL1 Remembe Pat-B Questions Level Competence 1. Explain the electon density in bulk mateial and size dependence of Femi enegy. (13) Undestand 2. Explain quantum confinement and quantum stuctues in nano mateials. (13) Undestand 3. Discuss density of states in quantum well, quantum wie and quantum dot. Undestand (13) 4. Wite note a Zene Bloch oscillations, esonant tunnelling and quantum BTL1 Remembe intefeence effect. (13) 5. Explain mesoscopic stuctue of conductance fluctuations and coheent Undestand tanspot. (13) 6. Descibe Coulomb blockade effect and single electon phenomena. (13) Undestand 7. Explain the phenomena of single electon which is used in single electon Undestand

14 tansisto. (13) 8. (i) Descibe the constuction and woking of single electon tansisto. (7) Undestand (ii) Explain Coulomb blockade effect. (6) Undestand 9. What ae magnetic semiconductos? List out the popeties and applications BTL1 Remembe of magnetic semiconductos. (13) 10. Explain the woking of spintonics and its applications. (13) Undestand 11. Discuss on spintonics and also on spin based Field Effect Tansisto. Undestand 12. Wite a shot note on (i) GMR (7) (ii) Spin valve (6) BTL1 Remembe 13. Descibe the cabon nano tubes with thei popeties and applications. (13) Undestand 14. (i) Wite a note on magnetic semiconducto. (6) BTL1 Remembe (ii) Mention the physical popeties and applications of CNT. (7) Undestand