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New Jersey Institute of Technology Digital Commons @ NJIT Theses Electronic Theses and Dissertations Spring 5-31-2015 Optical properties of black silicon - an analysis Suramya Sekhri New Jersey Institute of Technology Follow this and additional works at: https://digitalcommons.njit.edu/theses Part of the Materials Science and Engineering Commons Recommended Citation Sekhri, Suramya, "Optical properties of black silicon - an analysis" (2015). Theses. 244. https://digitalcommons.njit.edu/theses/244 This Thesis is brought to you for free and open access by the Electronic Theses and Dissertations at Digital Commons @ NJIT. It has been accepted for inclusion in Theses by an authorized administrator of Digital Commons @ NJIT. For more information, please contact [email protected]. Copyright Warning & Restrictions The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. 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Please Note: The author retains the copyright while the New Jersey Institute of Technology reserves the right to distribute this thesis or dissertation Printing note: If you do not wish to print this page, then select “Pages from: first page # to: last page #” on the print dialog screen The Van Houten library has removed some of the personal information and all signatures from the approval page and biographical sketches of theses and dissertations in order to protect the identity of NJIT graduates and faculty. ABSTRACT O PTICAL PR O PER TIES O FBLACKSILICO N -AN AN ALYSIS by S uramyaSekhri S ilicon isthe preeminent solarcellm aterialof the day becauseitisthe first semiconductorthatw aslearned to comm ercialize and continuesto be the principal semiconductingm aterialusedinphotovoltaictechnology forthem anufactureofsolar cells.S ilicon,anindirectbandgapsemiconductingm aterial,hasareflectanceofabout 30% inthe visiblerange ofw avelengths.S tandardS ilicon solarcellsarenot entirely usefulintheinfraredspectrum region.InordertoenhancetheperformanceofS ilicon solarcells,reflectancelossesmustbem inimizedandabsorptionm ustbem aximized.In thesolarcellindustry,anti-reflection(AR )coatingisusedtosuppressreflectionlosses. AR coatingsarelimited inusebecausethey onlyreducethereflectanceforanarrow rangeofw avelengthsandincidentanglesincetheirfunctionalityisbasedonaquarter- w avelength coating. S urface texturing isa technique,by w hich the reflectivity is reduced.BlackS ilicon isam aterialw ithsurfaceroughnessinthem icron scale. Black S ilicon,when used insteadofCrystalline S ilicon,offersthe possibility to increasethe absorptionoflightinthevisibleandinfraredrangeofw avelengths.BlackS iliconhasa verylow reflectivityinthevisiblerangeofw avelengths.Itexhibitshighabsorptancein thevisibleandinfraredregion. T hem ainobjectiveofthisthesisistostudy thevarious fabrication techniquesused to form Black S ilicon,present a comparative study of structuraldifferencesand analyze itsopticalpropertiesby simulation and compare them w ith the simulated and experimentalopticalpropertiesofBlack S ilicon and CrystallineS ilicon. O PTICAL PR O PER TIES O FBLACKSILICO N -AN AN ALYSIS by S uramyaSekhri A T hesis S ubmittedtotheFacultyof N ew JerseyInstituteofT echnology inP artialFulfillmentoftheR equirementsfortheDegreeof M asterofS cienceinM aterialsScienceandEngineering InterdisciplinaryP rograminM aterialsScienceandEngineering M ay2015 APPRO VAL PAGE O PTICAL PR O PER TIES O FBLACKSILICO N -AN AN ALYSIS S uramyaSekhri Dr.N .M .R avindra,ThesisAdvisor Date P rofessor,DepartmentofP hysics,N JIT Director,InterdisciplinaryP rograminM aterialsScience& Engineering,N JIT Dr.M ichaelJaffe,Comm itteeM ember Date R esearchP rofessor,DepartmentofBiomedicalEngineering,N JIT Dr.HalinaO pyrchal,Comm itteeM ember Date S eniorU niversityL ecturer,DepartmentofP hysics,N JIT M r.B.S .M ani,Comm itteeM ember Date U niversityL ecturer,DepartmentofM echanical& IndustrialEngineering,N JIT Dr.W illisB.Hamm ond,Comm itteeM ember Date CEO ,W .B.Hamm ondAssociates,LL C BIOGR AP HICAL SKETCH Author: S uramyaSekhri Degree: M asterofS cience Date: M ay2015 U ndergraduateandGraduateEducation: M asterofS cienceinM aterialsScienceandEngineering, N ew JerseyInstituteofT echnology,N ewark,N J,U S A,2015 BachelorofS cienceinP hysics, KiroriM alCollege,U niversityofDelhi,Delhi,India,2013 M ajor: M aterialsScienceandEngineering iv T othefivepillarsofmy life:God,my Grandparents,andm y P arents. W ithoutyou,my lifew ouldfallapart. Imightnotknow w herethelife’sroadw illtakem e, butw alkingw ithYou,God,throughthisjourneyhasgivenmestrength. M om,you havegivenmesomuch,thanksforyourfaithinm e, andforteachingm ethatIshouldneversurrender. Daddy,you alwaystoldm eto“ reachforthestars.” IthinkIgotm yfirstone. T hanksforinspiringmeforeverythinginlifeandofcourse,Physics! v ACKN O W L EDGEM EN T S Iw ouldliketoexpressmy deepestappreciationtom y thesisadvisorDr.N .M .R avindra w ho hasthe attitude and substance ofa genius.He continuallyand convincingly conveyed a spiritofadventureinregard to m y thesisand research. W ithout his guidanceandpersistenthelpthisthesiswouldnothavebeenpossible.T hanksforgiving m etheopportunitytobepartoftheBlackS iliconresearch. S pecialthankstoallmy thesiscomm itteemembersDr.M ichaelJaffe,Dr.Halina O pyrchal,M r.B.S .M ani,Dr.W illisB.Hamm ondfortheirvaluabletime andforserving onm y comm ittee. S pecialT hankstoM s.ClarisaGonzalez,AssociateDirectorofGraduateS tudies and M s.L illianQ uiles, AdministrativeAssistantat the GraduateS tudiesO fficefortheir valuableandeffectiveinputsandhelpingm eimprovem y overallthesis. Iam gratefultoallmy researchgroup m embers:S itaL axmi,ChiranjiviL amsal, VishalN akhate,AniketM aske,SarangM uleyw hohavesupportedmethroughoutentire process,bothbykeepingm eharmoniousandhelpingmeputtingpiecestogether. Iamhighlygratifiedbym y Grandparents:M r.M adanL alSekhriandM rs.S udesh S ekhriand parents:M r.Vikram S ekhriand M rs.Anu S ekhrifortheirlimitlessand imm ensesupport,encouragement and blessings.T hank you foralwaysboosting m y m oraleandkeepingfaithinm e.Iappreciatem y sibling:R ohinyaS ekhri’snever-ending beliefinm e and forbeing therethroughthickand thin.M y deepestgratitude tom y vi friendsbackinIndiaforalwayskeepingm y spiritshighandforalltheencouragement andpraise. vii TABLEO FCO N TEN TS Chapter P age 1 INTRO DU CTION ………………………………………………………………………………………………….. 1 2 SILICO N -AN AN ALYSIS……………………………………………………………………………………….. 4 2.1 N aturalAbundance………………………………………………………………………………………. 4 2.1.1 AmorphousSilicon………………………………………………………………………….…. 4 2.1.2 CrystallineS ilicon…… … … … … … … … … … … … … … … … … … … … … … … … … … … … … 6 2.2History………………………………………………………………………………………………………… 6 2.2.1 Firsttimepreparation-1823… … … … … …… … … … … … … … … … … … … … … … … … … 7 2.2.2 CrystallineS ilicon-1854… … … … … … … …… … … … … … … … … … … … … … … ..…… .… 7 2.2.3 T oday’sScenario…………………………………………………………………………………. 7 2.3 O ccurrence………………………………………………………………………………………………….. 8 2.4 P roperties…………………………………………………………………………………………………….. 9 2.4.1 P hysical……………………………………………………………………………………………….. 9 2.4.2 Chemical……………………………………………………………………………………………… 11 2.5Applications……………………………………………………………………………………….………….. 12 2.5.1 Solar…………………………………………………………………………………………….………. 12 2.5.2 Electronics……………………………………………………………………………………….…… 13 2.5.3 S emiconductors…………………………………………………………………………………. 14 2.5.4 Glasses……………………………………………………………………………………………….. 15 2.5.5Ceramics…………………………………………………………………………………………….. 15 2.5.6FiberO ptics……………………………………………………………………………….………. 16 2.5.7P olymers…………………………………………………………………………………………….. 16 viii TABLEO FCO N TEN TS (Continued) Chapter P age 3 BLACKSILICO N …………………………………………………………………………………………………… 19 3.1 BlackS iliconHistory…… … … … … … … … … … … … … … … … … … … … … … … … … … .…… … … … 19 3.2 P roductionP rocesses…………………………………………………………………………………… 20 3.3 M ethodsofFabricatingBlackS ilicon…… … …… … … … … … … … … … … … … … … … … … … . 20 3.3.1 DryEtching………………………………………………………………………………………….. 21 3.3.2 W etchemicaletching…… … … … … … … … … … … … … … … … … … … … … … … … … … … .. 26 3.3.3 T heLaserM ethod………………………………………………………………………………… 33 3.3 S urfaceAnalysis……………………………………………………………………………………………. 36 3.3.1 S cienceofsurfaceroughness…… … … … … … … … … … … … … … … … … … … .…… … … . 36 3.3.2 ComparativestudyofBlackS iliconS EM images-RIE…… … … … … … … … … … 38 3.3.3 ComparativestudyofBlackS iliconS EM images-PIII…… … … … … … … … … … 39 3.3.4 ComparativestudyofBlackS iliconS EM images-BoschR IE……… … … … … . 40 3.3.5ComparativestudyofBlackS iliconS EM images-M ACE…… … …… … … … … . 41 3.3.6ComparativestudyofBlackS iliconS EM images- Femtosecondlaser……………………………………………………………………………….. 43 3.3.7Comparisonofthesurfacesbyallfabricationm ethods…… … … … … … … … … 50 4 O PTICAL PRO PERTIES………………………………………………………………………………………….. 52 4.1 Comparisonofopticalproperties-allmethods…… … … … … … … … … … … … … … … … . 53 4.1.1 R IE-PIII…………………………………………………………………………………………………
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  • Black Silicon Photodetector Breaks the 100% Efficiency Limit 14 August 2020

    Black Silicon Photodetector Breaks the 100% Efficiency Limit 14 August 2020

    Black silicon photodetector breaks the 100% efficiency limit 14 August 2020 The secret behind the breakthrough: Unique nanostructures The external quantum efficiency of a device is 100% when one incoming photon generates one electron to the external circuit. 130% efficiency means that one incoming photon generates approximately 1.3 electrons. The researchers found out that the origin of the exceptionally high external quantum efficiency lies in the charge-carrier multiplication process inside silicon nanostructures that is triggered by high- UV-light triggers electron multiplication in energy photons. The phenomenon has not been nanostructures. Credit: Wisa Förbom observed earlier in actual devices since the presence of electrical and optical losses has reduced the number of collected electrons. Aalto University researchers have developed a "We can collect all multiplicated charge carriers black silicon photodetector that has reached above without a need for separate external biasing as our 130% efficiency. Thus, for the first time, a nanostructured device is free of recombination and photovoltaic device has exceeded the 100% limit, reflection losses," Prof. Savin explains. which has earlier been considered as the theoretical maximum for external quantum In practice, the record efficiency means that the efficiency. performance of any device that is utilizing light detection can be drastically improved. Light "When we saw the results, we could hardly believe detection is already used widely in our everyday our eyes. Straight away we wanted to verify the life, for example, in cars, mobile phones, results by independent measurements," says Prof. smartwatches and medical devices. Hele Savin, head of the Electron Physics research group at Aalto University.