tailieunhanh - Materials Science and Engineering - Electronic and Mechanical Properties of Materials Part 2

Tham khảo tài liệu 'materials science and engineering - electronic and mechanical properties of materials part 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Example Conductivity Engineering Objective increase strength of Cu but keep conductivity high ne 2T e Ơ ----- p m m l VT Scattering length connects scattering time to microstructure l decreases T decreases Ơ decreases lo K------------------------------------ o o o o o o Dislocation o edge o o o o I o o o o o o o o o o . Fitzgerald-1999 21 Example Conductivity Engineering Can increase strength with second phase particles As long as distance between second phase l conductivity marginally effected X Cu microstructure S OR dislocation p . Oj-X L ự L l Material not strengthened conductivity decreases ---------------------------------------------------------- . Dislocation motion inhibited by second phase material strengthened conductivity about the same . Fitzgerald-1999 22 11 Example Conductivity Engineering Scaling of Si CMOS includes conductivity engineering One example as devices shrink. - vertical field increases - T decreases due to increased scattering at SiO2 Si interface - increased doping in channel need for electrostatic integrity ionized impurity scattering - TSiO2 Timpurity if scaling contmues properly 23 12 Experimental Hall Results on Metals HAU. COEFFICIENTS OF SELECTED ELEMEM s IS MODERATE ro HIGH FIELDS Valence 1 metals look like free-electron Drude metals Valence 2 and 3 magnitude and sign suggest problems METAL VALENCE 1 tRniiec Li 1 Na 1 K 1 Rb 1 Gs 1 Cu 1 Ag 1 Au 1 Be Ị Mg -Ị In 3 Al 3 These are roughly the limiting values assumed by as the held becomes very large lot order lo4 G . and the temperature very low. m carefully prepared specimens. The data are quoted in the lorm 1ị II. where II is the density for which the Drude form agrees with the measured - 1 RHec. Evidently the alkali metals obey the Drude result reasonably well the noble metals C u. Ag Au less well and the remaining entries not at ail. . Fitzgerald-1999 25 .