The NBE feature is attributable to the O 2p valence bandwhich is centered at 3.26 eV. Since the spectral feature ofthe D1 and D2 levels becomes obvious for the oxidative annealed ZnO:N samples at 700 and 800 °C, both deep levelsare probably the intrinsic nature of p-type ZnO:N films. Ingeneral, the DLOS spectrum increases monotonically withincident photon energy, because the amount of photocapacitance transients is proportional to the sum of charge-chargecontribution from optical active deep levels.22 Thus, the D2level is a discrete deep level with an optical threshold at2.14 eV, whereas the D1 level is potentially an efficientgeneration-recombination center with a strong interactionwith both the conduction and the valence bands.20 As theillumination energy is increased above the threshold energyof 1.23 up to 1.77 eV, the steady state photocapacitance decreases correspondingly, indicating that the hole transitionfrom the D1 level to the valence band is the dominant process. Sequentially, the positive photocapacitance transientsobserved at photon energies above 1.77 eV are due to theelectron transition from the D1 level to the conduction band.More importantly, we can also observe an acceptor stateemission at 3.01 eV near the NBE transitions, as typicallyseen for the oxidative annealed ZnO:N sample at 700 °C.This energy level can probably be assigned to N atoms thatreside at O-lattice sites in ZnO, i.e., N acceptors NO. TheNO concentration increases significantly by the oxidative annealing at 700 and 800 °C
The NBE feature is attributable to the O 2p valence band<br>which is centered at 3.26 eV. Since the spectral feature of<br>the D1 and D2 levels becomes obvious for the oxidative annealed ZnO:N samples at 700 and 800 °C, both deep levels<br>are probably the intrinsic nature of p-type ZnO:N films. In<br>general, the DLOS spectrum increases monotonically with<br>incident photon energy, because the amount of photocapacitance transients is proportional to the sum of charge-charge<br>contribution from optical active deep levels.22 Thus, the D2<br>level is a discrete deep level with an optical threshold at<br>2.14 eV, whereas the D1 level is potentially an efficient<br>generation-recombination center with a strong interaction<br>with both the conduction and the valence bands.20 As the<br>illumination energy is increased above the threshold energy<br>of 1.23 up to 1.77 eV, the steady state photocapacitance decreases correspondingly, indicating that the hole transition<br>from the D1 level to the valence band is the dominant process. Sequentially, the positive photocapacitance transients<br>observed at photon energies above 1.77 eV are due to the<br>electron transition from the D1 level to the conduction band.<br>More importantly, we can also observe an acceptor state<br>emission at 3.01 eV near the NBE transitions, as typically<br>seen for the oxidative annealed ZnO:N sample at 700 °C.<br>This energy level can probably be assigned to N atoms that<br>駐留在氧化鋅,即N受體O點陣網站?NO。的<br>在700和800℃顯著NO濃度的增加通過氧化退火
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