Sezen, H.

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Hikmet SezenMay 15, 2013Dynamic XPS for Photoinduced Voltage Changes on Semiconducting MaterialsKarlsruheInstitute of Functional Interfaces (IFG)Chemistry Department• Part I(2009-2011):o Introduction X-ray Photoelectron Spectroscopy (XPS)Controlled Surface Charging DC, SQW, Model Photoconductivityo Our Motivationo Results & Discussions np-Si and np-Si/SiOx CdS np-GaNo Conclusions• Part II(2012-): Instrument: Theo TiO2Outline:Ankara/Turkey, Prof. Şefik SüzerKarlsruhe/Germany, Prof. Christof WöllX-ray Photoelectron Spectroscopy:detectorФ work functionKL1L2, L3MValance bandFermi levelVacuum levelX-Rays1s2s2p3s,p,dphotoelectronsBEpe = hυx-ray – KEpeVacuum levelFermi levelSpectrometerSampleФ work functionElectronenergyanalyzervDCReadout:PrincipleThe Survey Spectrum of GaN• Provide Chemical/Elemental Information• Capable to Separate Chemical States of Elements• Highly Surface Sensitive : 1-20 nm• Quantative Analysis: Stoichiometric, Thickness, and Depth Profile ....       X-ray Photo lectron Spectroscopy:violetgreenredflip mirrors980nmNDFchoppershutterlensglass flangeportInstrument (Part I):Cracking HardwareThermofisher - K-AlphaCustomized Sample HolderDC-AC SupplierOptics BoardOptics BoardSpecifications:•Monochromatic Al K-α (1486.68 eV) X-ray source•X-ray spot 400-30 µm•~100 msec snapshot with an 128 channel detector Cracking SoftwareModel:Method:BEpe=hυx-ray - KEpeSample on an 3Dmoveable stage120 110 100 90Binding Energy (eV)SiOx Si+4Si0112 108 104 100 96-20 -10 0 10 200.0A3.0µA6.0µA(+) chargeZPC103.2 eVSi2pSi0Binding Energy(eV)Si+4(-) charge+10 VCurrent Bias Potentials (V)-10 V100 90 80 70Binding Energy (eV)+10V -10VAuIfilx-raysIxray+10V-10V-10V+10VIfilx-raysIxray-10V+10VSiOxSi+ chargeAu4fSi2pControlled Surface Charging (DC):ConductiveDielectricafter bias correction +10V-10VGr.Gr.Ifilx-raysIxraysampleDCX-Rays+ - + - + -+ - + - + e-e-e-gunIfSurfa e Cha ging:100 95 90 85 80 75 70 Au (As Is) Au + RC Au + R20.00 eV19.29 eV19.31 eV20.00 eVAu4fGrounded100 Hz SQWBinding Energy (eV)0.001 Hz SQWControlled Surface Charging (SQW):R CAu-10V+10VX-RayIfilIx-ray95 90 85 80 75Au4fGroundedBinding Energy (eV)100 95 90 85 80 75 70Binding Energy (eV) R CAu-10V+10VX-RayIfilIx-rayIRcharging-10 V+10 Vn-type p-typee - e -e -h +h +h +e -h +hυVBCBEfe-h generationCharge SeparationOur Motivation:EfieldKinetic Energynegativechargepositivechargee -e -h +h +diodePhotoconductivity:σ = neμ Rarrier G ner ti-0.80.00.81.62.43.24.01.1 eV  Conduction Band Valance Band3.4 eVGaN  SiBand Gap(eV)CdS2.4 eVDefectSurfaceMid gapTraps...possible!!!Band Offset Measurement Between n- and p-type doped SiSurface Photov ltage:Results: np-Sip-Si: downward B.B.103 102 101 100 99 98 97n-SiLaser OFFBinding Energy (eV)0.17 eVGold Contactp-SiX-Ray Spotn-Sip-Si0.30 eV0.82 eVCBVB0.29 eV0.83 eVEfn-Sip-Si0.53 eVcalculated “band offset”:N = 2.8 x 1014 cm-3P =4.7 x 1014 cm-3103 102 101 100 99 98 97Laser ONn-Si0.49 eVp-SiSi2pGold Contactp-SiX-Ray SpotLaser Spotn-SiH. Sezen, S. Suzer, J Chem. Phys. 135, 141102(2011)SPV:p- and n-SiSi2pBand-Bending! Band-Flatting! 50 100 150 200 250 300n-Si/SiOxp-Si/SiOxTime (s)50 100 150 200 250 300n-Sip-Si p-SiSiOxthermaln-SiHF cleaned As IsLaser ONLaser ONSi2pLaser ONLaser OFFp-SiSiOx:Band Bending / Inversion of SiOx/p- and n-SiH. Sezen, S. Suzer, J Chem. Phys. 135, 141102(2011)p- and n-Siline scanSurface Band-Bending!SiOx inducedn-typeCBVBEfSiOxbendingSiOx/n-Si+++++++p-typeSiOxbendingSiOx inducedSiOx/p-SiEfVBCBPossible band diagram:Binding Energy Kinetic Energy+++++++H. Sezen, S. Suzer, J Chem .Phys. 135, 141102(2011)C. Munakata, et al. Jp. Appl. Phys. 23, 1451(1984)H. Kobayashi et al. Appl. Phys. Lett. 73 933(1998)Band Bending / Inversion of SiOx/p- and n- SiFurther Band-BendingInversion of Band-Bending112 108 92 881kHz SQW0.001Hz SQWBinding Energy (eV)Grounded-0.19 eV -0.19 eV(c)(b)(a)+10V0-10V0108 104 100 96 92p-Si Laser OFF Laser ON-0.19 eVPhoto-Dynamic XPS with p-Si:115 110 95 90Binding Energy (eV)0.001Hz SQW19.67 eV20.00 eV20.00 eV20.00 eV 20.00 eV1kHz SQWPhoto-Dynamic XPS with SiOx/p-Si:FloodGunX-RaysdetectorSiSiO2e-e-FGfasterslowerH. Sezen, S. Suzer Thin Solid Films 534, 1(2013)Si4+ Si0Si0Si4+silicasilica407 406 405 404407 406 405 404Red LaserGreen LaserViolet LaserCd3d5/2Binding Energy (eV)VioletLaser ONLaser OFFCdSCd3d5/2Binding Energy (eV)+0.2eV CdSBand gap 2.4 eVSPV:FloodGunX-RaydetectorCdSe-e-Gr.n-type shiftGroundedSPV or photoconductivity?416 412 396 392n-type SPV Laser OFF 3.0 OD 2.0 OD 0.3 OD Laser ON104Hz SQW0.001Hz SQWBinding Energy (eV)416 412 396 392n-type SPVn-type SPVphotoconductivityn-type SPV(b)discharging of apositive chargedischarging of anegative chargephotoconductivityphotoconductivity(a)CdSIfilx-raysIxray+10V-10VSQWPhoto-dynamic XPS(SQW):0.5 eV0.6 eV0.5 eV0.0 eVCd3d5/2Cd3d5/2H. Sezen,  S. Suzer Surf. Sci. 604, L59(2010)Resolved differentphenomenaH. Sezen,  S. Suzer Surf. Sci. 604, L59(2010)The electrical parameters of CdS film1200 1000 800 600 400 200 0Ga 2sN1sGa 3s,   3p,   3dO1sGa 2pBinding Energy(eV)Ga LMMp-GaNExperimental Setup:Band gap 3.4 eV GaNBand gap 3.4 eVViolet Laser 3.1 eV1124 1122 1120 1118 1116 1114Binding Energy(eV)-0.39 eV Laser OFF Laser ONp-GaNGa2p3/2n-GaN+0.15 eVGaNH. Sezen, E. Ozbay, O. Aktas, S. Suzer Appl. Phys. Lett. 98, 111901(2011)Static SPV :SPV Mechanisms:H. Sezen, E. Ozbay, O. Aktas, S. Suzer Appl. Phys. Lett. 98, 111901(2011)0 100 200LaserOFFTime(s)LaserONLaserOFF(FG OFF)0 100 2001116.81117.21117.61118.01118.4(b)n-GaNLaserONp-GaN(a)Ga2p3/2 B. E. (eV)(FG ON)LaserOFFGa2p3/2 B. E. (eV)bulksurfaceDynamic SPV Transients:H. Sezen, E. Ozbay, O. Aktas, S. Suzer Appl. Phys. Lett. 98, 111901(2011)slower: accu. e- faster: diss. e-H. Sezen, S. Suzer J. Spectrosc. Dyn. 2, 3(2012)H. Sezen, E. Ozbay, O. Aktas, S. Suzer Appl. Phys. Lett. 98, 111901(2011)1120 1118 1116 1114p-GaNp-type Shiftn-type ShiftBinding Energy (eV) Laser OFF Violet Laser ON Green Laser ON Red Laser ONGa2p3/21120 1118 1116 1114p-GaNp-type Shiftn-type ShiftBinding Energy (eV) Laser OFF Violet Laser ON Green Laser ON Red Laser ONGa2p3/2h+Green or RedLaser BulkEfVBCBSurfacep-GaNh+BulkEfVBCBSurfaceViolet Laserp-GaNe-SPVInversed SPVInversion of  SPVunpublished dataGaN SPV:ConclusionsBEpe=hυx-ray – KEpeBEpe=hυx-ray – KEpe ± e•V ± e•Q/CBEpe=hυx-ray – KEpe ± e•V ± e•Q/C I∆Rph ± e•SPV ....rest of the world:but we:but we:H. Sezen, S. Suzer Thin Solid Films 534, 1(2013)E. Yilmaz, H. Sezen, S. Suzer Angew. Chem. Inter. Ed. 51, 5488(2012). Organic species:Thanks toProf. Şefik Süzer (advisor)  Chem., Bilkent U., TRDr. Gülay Ertaş Chem., Bilkent U., TRProf. Atilla Aydınlı                Phys, Bilkent U., TRProf. Ekmel Özbay Phys, Bilkent U., TRProf. Mehmet Erbudak Phys, ETHZ, CHProf. Oğuz Gülseren Phys, Bilkent U., TRAsst. Prof. Ömer İlday Phys, Bilkent U., TRAsst. Prof. Özgür Aktaş EE Eng., Bilkent U., TRAsst. Prof. Aykutlu Dana    Phys, Bilkent U., TRAsst. Prof. Özgür Birer Chem., Koç U., TRDr. Tim Nunney and crew of the Surface Analysis Department of Thermofisher, UKAcknowledgementHikmet Sezen, Carsten Natzeck, Alexei Nefedov, Christof WöllInstitute of Functional Interfaces (IFG)Chemistry of Oxydic and Organic InterfacesKIT North CampusIFGNOWPart II(2012-):472 464 456r-TiO2(110)Ti2+Ti3+Sputtered  Intensity (a.u.)Binding Energy (eV)AnnealedTi2pTi4+oxidation stateXPS:LEED:R-TiO2(110)surface crystal structure 290 280C1s    Binding Energy (eV)Intensity (a.u.) Before sputtering After sputteringcleanness9 6 3 0 -3 (HeI)Annealing Sputtered AnnealedTi+3 3dO 2p Valence Band    Intensity (a.u.)Binding Energy (eV)TiO2 UPS: defect state3 2 1 0 -1AnnealingTi3+ 3dIntensity (a.u.)    Binding Energy (eV)Sample Preparation:Annealing SputteringcharacterizationTiO2 single crystal:TiO2 Band structure: shallow state4000 3000 2000 100011159403680970Treatments:r-TiO2 powderTs: 300 K0.001 UV atomic hydrogenAbsorbanceWavenumber (cm-1)  D.A. Panayotov, J.T. Yates, Chem. Phys. Lett. 436, 204 (2007) powders:4000 3000 2000 1000 UV atomic hydrogenTreatments:910121013703730 3215372532151205r-TiO2(110)    AbsorbanceWavenumber (cm-1)0.0005Ts: 300 K910single crystal:Thank you for your attention!..

Dynamic XPS for photoinduced voltage changes on semiconducting materials

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Dynamic XPS for photoinduced voltage changes on semiconducting materials

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