MaterialsLetters139(2015)352–354

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MaterialsLetters

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IsoelectronicCdTe-dopedZnOthin lmsgrownbyPLD

E.A.Martín-Tovara,R.Castro-Rodrígueza,A.Iribarrenb,n

ab

DepartamentodeFísicaAplicada,CINVESTAV-IPN,UnidadMérida,97310,Mérida,Yucatán,México

InstitutodeCienciayTecnologíadeMateriales(IMRE),UniversidaddeLaHabana,ZapatayG,Vedado,LaHabana10400,Cuba

articleinfo

Articlehistory:

Received29August2014Accepted13October2014

Availableonline22October2014Keywords:

IsoelectronicdopingZnO

Thin lm

Pulselaserdeposition

abstract

IsoelectronicCdTe-dopedZnOthin lmsweregrownbythepulselaserdeposition(PLD)techniqueusingtargetsofZnOmixedwithCdTe.X-raydiffractionshowsasingle-phasehexagonalofZnOwurtzitestructure.X-rayphotoelectronspectroscopyshowstheformationofZn–Tebonds,whichdemonstratestheoccupationofOvacanciesbyTeatomsintheZnOlattice,althoughCd–TeandTe–Obondswerealsopresent.Elementalanalysisofthe lmsgaveCdconcentrationlowerthan2%intheZnO lm,likelyduetolowCdsolidsolubilityinZnO.Crystallitesize, lmthickness,chemicalconcentrationsandmorphologiccharacteristicsarealsoreported.

&2014ElsevierB.V.Allrightsreserved.

1.Introduction

NowadaystheinterestinZnOremainsduetotheirperspectiveapplicationsin eldsofscienceandtechnologyasoptoelectronics,photovoltaics,sensors,catalysts,piezoelectricity,electro-opticaldevices.Inthesameway,ZnOhasbeenobtainedbyalotofdifferenttechniques[1–5].ZnOhasbeenreportedtohavebandgapenergybetween3.2and3.37eV[6]andalarge60meVexcitonbindingenergy.ItswidebandgapmakesZnOagoodcandidateforUVandbluewavelengthphotonicapplicationsandtheelectricandgas-interactingsurfacepropertiesasagassensoramongotherapplications[7–10],whichhavestimulatedthecontinuityofthestudiesofthismaterialanditsapplications.

NaturallyZnOhasn-typeconductivityduetoOvacanciesandinterstitialZn,althoughZnvacanciesarealsopresent[6].Suchdefectsmakeitdif culttopreparep-typeZnO.Onewayoftryingtopassivatethesedefectsisbyisoelectronicdoping,whichcanbeconsideredasamethodforpassivatingandreducingthedefectconcentration,speci callyvacancies,intheZnOlattice.SeveralelementhavebeenusedforZnOdoping,butfewworkshasbeencarriedoutusingTeatoms[6,11,12].TelluriumandcadmiumatomshavetheadvantagesofbeingisovalentrespectOandZn,respectively.Theycanbeconsideredaspassivatingatomsthatcanalsochangethebandgap[10,13]andtheconductivity[14]inZnO.

TheeffectofCdandTedopingcanconstituteanintermediateorparallelmethodforattainingp-typeZnOusingotherco-dopantelementasnitrogen[11].InthisworkisoelectronicCdandTedopedZnO lmsweregrownbythepulselaserdeposition(PLD)

technique.Structural,morphologicalandchemicalanalysesofthe lmswerecarriedout.

2.Experimental

ZnOthin lmwasdepositedonITO/glasssubstratesusingaNd:YAG-laseroperatingintheQ-switchmodewithenergydensityatthetarget$2J/cm2.Thetargetwasasoliddiskof4.65mmthickand8.05mmdiametermadeupofamixtureofZnOnanoparticles(99.99%Aldrich)withadditionof30wt.%ofCdTe(99.99%Aldrich),whichweremilled,pressedat10Tfor5minandsinteredat6001Cfor2h.The lmsweredepositedatsubstratetemperatureTs¼3001Cinvacuum$1.3Â10À7Paand3000lasershots.ThestructuralpropertiesweredeterminedusingaD5000SiemensX-raydiffractometer.Thethicknessofthe lmswasmeasuredbyaSurfacePro lometerDektak-8,Veeco.Elementalanalysisofthe lmswascarriedoutbyenergydispersivespectroscopy(EDS)withaJEOLJSM7600Fscanningelectronmicroscope.X-rayphoto-electronspectroscopy(XPS)analyseswereperformedinaK-ALPHAThermoScienti cSystem.

3.Resultsanddiscussion

TheCdTe-dopedZnO lmshadthicknessof$112nm,similartothoseofundopedZnO.

Theobserveddiffractionpeaksforboth lmsarewurtziteZnOphase[15],andpreferentialorientationintheplane(002).AllthepeaksareshiftedtotheleftwithrespecttothepositionoftheZnOpowderstandardpattern,whichindicatestensilestress.From(100),(002)and(101)peaks,theaveragegrainsizecalculated

n

Correspondingauthor.

E-mailaddresses:augusto@imre.oc.uh.cu,a_iribarren@yahoo.com(A.Iribarren).

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0167-577X/&2014ElsevierB.V.Allrights

reserved.