Atomic flux on surface due to residual gas atoms nv 2k T area. t 2k V zm, t Given 10-b Torr of water vapor room temp, find flux latm 10'P p=10°Tor 760t atm kgT(R7)=0.025eV=4×102J P=1.3×10-4 18 3×10kg J=4.8x104atoms/molecules cm sec What is atomic density in I monolayer(MD) of Si? N=5x1022cm3=1.3x1015cm So at 10-6 Torr, 1 ML of residual gas hits surface every 3 seconds Epitaxy requires slow deposition, surface mobility So you must keep pressure low to maintain pure film 6.152J3.155J6.152J/3.155J 5 Atomic flux on surface due to residual gas J atoms area ⋅ t       = nv x 2 = p 2kBT 2kBT πm = p 2πmkBT = J Given 10-6 Torr of water vapor @ room temp, find flux p =10−6Torr × 1atm 760 T × 105Pa atm , kBT RT ( )= 0.025eV = 4 ×10−21 J p =1.3×10−4 N m 2 mH2O = 18 NA = 3×10−26 kg What is atomic density in 1 monolayer (ML) of Si? N = 5 x 1022 cm-3 => 1.3 x 1015 cm-2. So at 10-6 Torr, 1 ML of residual gas hits surface every 3 seconds! Epitaxy requires slow deposition, surface mobility, So you must keep pressure low to maintain pure film J = 4.8 ×1014 atoms/molecules cm2sec     