We expressed flux of residual gas molecule 27Imk t Chamber p=106Tor(J≈5×10 cm The source also→flux P For Al at 1000 K, p vap/10-7 Torr (from tigure vap 2rmsourcekgT. m=species to be evaporated, =27 amu for Al Al<2 X 1013 Al/9m2-s just above crucible Therefore heat al to t> 800 C but that's not all Net flow out of crucible -A #/t) Mass flow out of crucible -J A m(mass /t) Note: 3 different temperatures: source=Evaporant>>Substrate chamber=Tresid gas=Rt. System not in thermal equilibrium; only thermal interaction among them is by radiation and/or conduction through solid connects(weak contact). No convection when NK <<1 6.152J3.155J6.152J/3.155J 9 The source also ⇒ flux J = pvap 2πmsourcekBTsource For Al at 1000 K, pvap = 10 -7 Torr (from figure) m = species to be evaporated, = 27 amu for Al JAl ≈ 2 x 1013 Al/cm2-s just above crucible Mass flow out of crucible ~ J Ac m ( mass / t) We expressed flux of residual gas: J ≈ 5 ×1014 molecules cm2 Chamber p = 10 ( s) -6 Torr J = p 2πmkBT Net flow out of crucible ~ J Ac (# / t) Ac Therefore heat Al to T > 800 C but that’s not all… Note: 3 different temperatures: Tsource ≈ Tevaporant >> Tsubstrate > Tchamber = Tresid gas ≈ RT. System not in thermal equilibrium; only thermal interaction among them is by radiation and/or conduction through solid connects (weak contact). No convection when NK << 1