Page - 151 - in Photovoltaic Materials and Electronic Devices

Duringtheetching, ITOfilmsarereducedtoIn–ClandIn-(NO3)3 resulting in thechange incrystallinityoffilmsetchedfordifferentperiodsof time. Thestructural parameters such as d spacing, lattice constants, net lattice distortion and grain sizes areestimatedandlisted inTable1 incomparisontodata fromtheJointCommittee onPowderDiffractionStandards (JCPDS)/InternationalCentre forDiffractionData (ICDD)database. The etching process also distorts the ITO structural long-range order, which has an impactontheopto-electronicpropertiesof thefilms. Thegrainsizeoffilmsdid notchangeevenafteretchingfor8min.,particularly for ITOfilmsprocessedinan oxygendeficientenvironment. Duringtheetchingprocess theexcessweaklybound oxygen atoms are removed from the ITO surfaces exposing layers with different grain sizes. The ITO structure distortion due to etching for longer periods of time (8 min) can be seen from the XRD spectra shown in Figure 1. There was however no evidence of ITO film for the results shown in Figure 1A after they were etched for 8 min. There is evidence of decreased crystallinity for the rest of the ITO films (Figure1B,C)as theoxygenatomsarestrippedfromtheIn–OnetworkbytheHCl andHNO3. Table 1. Structural parameters of ITO sputtered films with 0, 0.4 and 1.0 sccm oxygenandetchedat1,3,5and8min. OxygenFlow Rate (sccm) Etching Time(min) DSpacing (222) (Å) LatticeConstant (222) (Å) Net-Lattice Distortion GrainSize (222) (nm) StandardJCPDS for ITO06-0416 – 2.921 10.1180 – – 0 1 2.932 10.1552 –0.0036 16 3 2.934 10.1629 –0.2970 16 5 2.934 10.1629 –0.2885 17 8 – – – – 0.4 1 2.908 10.0731 –0.0075 31 3 2.912 10.0869 –0.0157 25 5 2.914 10.0954 –0.0153 23 8 2.914 10.0954 –0.0169 20 1.0 1 2.917 10.1059 – 13 3 2.913 10.0915 –0.2828 13 5 2.911 10.0845 – 14 8 2.908 10.0764 – 19 3.1.2. AFMAnalysis Figure 2 shows the AFM surface topology of the ITO films deposited under threedifferentoxygenenvironmentsandetchedfor1minand8min. 151