Seite - 149 - in Photovoltaic Materials and Electronic Devices

atroomtemperatureusingJobin-YvonLabRAMHR800RamanSpectrometer(Horiba Scientific, Edison, NJ, USA) with the excitation wavelength of 633 nm and the resolutionisabout~0.1cm´1. Sheetresistanceofthesampleswascharacterizedusing fourpointprobestationconsistingof ITOoptimizedtipswith500microntipradiiset to60gramspressureandanRM3000testunitfromJandelEngineeringLimited,Kings Langley, UK. The optical transmission and thickness of the films was determined usingvariableanglespectroscopicellipsometry(UV-VISV-VASEwithcontrolmodule VB-400, J.A. Woollam Co., Lincoln, NE, USA). Surface roughness was evaluated usingaVeecoDimension3000atomicforcemicroscope(Veeco,OysterCity,NY,USA) operated in tapping mode with Budget Sensors Tap300Al-G cantilevers (Innovative SolutionsBulgariaLtd.,Sofia,Bulgaria). It shouldbenotedthat transmittancedata was measured for ITOon sodalime glass (SLG) substrate and all the rest of the data wasonITOonSi/SiO2 substrate. 2.2. ChemicalShaving:WetEtching In thispresentwork, theoxygen0,0.4and1.0sccmdepositedITOfilmswere used for the etching process for 1, 3, 5 and 8 min, respectively. The annealed ITO/Si samplesareetchedat roomtemperatureusingHCl:HNO3:H2O(1:1:5) combination andtheresistivityandthicknessof thefilmswerecheckedfor1,3,5and8minetched films. For the 0 sccm ITO films, the thickness of the film was changed from 70 to 44 nm for 1 to 5 min etching time. Similarly the 0.4 sccm films thickness changed from 89 to 47 nm and 84 to 22 nm for 1.0 sccm films. The decrement of thickness wasreflected in theresistivityvalues. Thechemical reactionof theHClandHNO3 etchingreactionsareas follows[39]: In2O3` 2HClÑ2InCl`H2O`O2p∆Hq (1) In2O3` 12HNO3Ñ2InpNO3q3` 6NO2` 6H2O (2) 3. Results 3.1. StructuralAnalysis 3.1.1. XRDAnalysis XRDresults for the ITOfilmsdepositedusingdifferentoxygenconcentrations (0 sccm, 0.4 sccm, 1.0 sccm), annealed in air at 300˝C for 30 min and then etched for different times (1,3,5and8min)areshowninFigure1. 149