Izinto Ezintsha Eziguqukayo – I-Black Silicon
I-silicon emnyama luhlobo olutsha lwezinto ze-silicon ezineempawu ezibalaseleyo ze-optoelectronic. Eli nqaku lishwankathela umsebenzi wophando kwi-silicon emnyama ngu-Eric Mazur kunye nabanye abaphandi kwiminyaka yakutshanje, lichaza indlela yokulungiselela kunye nokwakheka kwe-silicon emnyama, kunye neempawu zayo ezinje ngokufunxa, ukukhanya, ukukhutshwa kwentsimi, kunye nokuphendula kwe-spectral. Likwabonisa ukusetyenziswa okubalulekileyo kwe-silicon emnyama kwi-infrared detectors, iiseli zelanga, kunye ne-flat-panel displays.
I-crystalline silicon isetyenziswa kakhulu kwishishini le-semiconductor ngenxa yeenzuzo zayo ezifana nokulula kokucocwa, ukulula kokusebenzisa i-doping, kunye nokumelana nobushushu obuphezulu. Nangona kunjalo, ikwanazo neengxaki ezininzi, ezifana nokukhanya okubonakalayo kunye ne-infrared kumphezulu wayo. Ngaphezu koko, ngenxa yesithuba sayo esikhulu sebhendi,i-silicon ekristaleAyikwazi ukufunxa ukukhanya ngamaza okukhanya angaphezu kwe-1100 nm. Xa ubude bokukhanya okukhawulezileyo bungaphezulu kwe-1100 nm, izinga lokufunxa kunye nokuphendula kwezixhobo zokubona i-silicon liyancitshiswa kakhulu. Ezinye izinto ezifana ne-germanium kunye ne-indium gallium arsenide kufuneka zisetyenziswe ukufumanisa la maza okukhanya. Nangona kunjalo, iindleko eziphezulu, iipropati ze-thermodynamic eziphantsi kunye nomgangatho wekristale, kunye nokungahambelani neenkqubo ze-silicon ezivuthiweyo ezikhoyo kunciphisa ukusetyenziswa kwazo kwizixhobo ezisekwe kwi-silicon. Ke ngoko, ukunciphisa ukubonakaliswa kwemiphezulu ye-silicon ekristale kunye nokwandisa uluhlu lwamaza okukhanya olufunyenweyo lwezixhobo zokubona i-silicon kunye ne-silicon ezihambelanayo zihlala zingumxholo oshushu wophando.
Ukunciphisa ukubonakaliswa kwemiphezulu ye-silicon ekristale, kuye kwasetyenziswa iindlela ezininzi zovavanyo kunye neendlela, ezinje nge-photolithography, i-reactive ion etching, kunye ne-electrochemical etching. Ezi ndlela zinokutshintsha, ngandlela ithile, imo yomphezulu kunye ne-near-surface ye-silicon ekristale, ngaloo ndlela zinciphisai-silicon Ukukhanya komphezulu. Kuluhlu lokukhanya okubonakalayo, ukunciphisa ukukhanya kunokunyusa ukufunxa kunye nokuphucula ukusebenza kakuhle kwesixhobo. Nangona kunjalo, kumaza obude obungaphezulu kwe-1100 nm, ukuba akukho manqanaba amandla okufunxa angeniswayo kwisithuba sebhendi yesilicon, ukukhanya okuncitshisiweyo kukhokelela kuphela ekudlulisweni okwandisiweyo, kuba isithuba sebhendi yesilicon ekugqibeleni sithintela ukufunxa kwayo ukukhanya kwe-long-wave length. Ke ngoko, ukwandisa uluhlu lwe-wavelength olunobuthathaka lwezixhobo ezisekwe kwisilicon kunye ne-silicon, kuyimfuneko ukwandisa ukufunxa kwe-photon ngaphakathi kwesithuba sebhendi ngelixa ngaxeshanye kunciphisa ukukhanya komphezulu wesilicon.
Ngasekupheleni kweminyaka yoo-1990, uNjingalwazi uEric Mazur kunye nabanye kwiYunivesithi yaseHarvard bafumana into entsha—i-silicon emnyama—ngexesha lophando lwabo malunga nokusebenzisana kwe-laser ye-femtosecond nezinto, njengoko kubonisiwe kuMfanekiso 1. Ngelixa befunda iimpawu ze-photoelectric ze-silicon emnyama, u-Eric Mazur kunye noogxa bakhe bamangaliswa kukufumanisa ukuba le nto ye-silicon eyakhiwe nge-microelectric ineempawu ezikhethekileyo ze-photoelectric. Ifunxa phantse yonke into ekuluhlu lwe-near-ultraviolet kunye ne-near-infrared (0.25–2.5 μm), ibonisa iimpawu zokukhanya ezibonakalayo nezikufutshane ne-infrared kunye neempawu ezilungileyo zokukhupha intsimi. Oku kufunyaniswa kwabangela uvakalelo kushishino lwe-semiconductor, kunye neemagazini ezinkulu ezikhuphisanayo ukunika ingxelo ngayo. Ngo-1999, iimagazini zeScientific American kunye ne-Discover, ngo-2000 icandelo lesayensi leLos Angeles Times, kunye no-2001 imagazini iNew Scientist zonke zapapasha amanqaku athetha ngokufunyanwa kwe-silicon emnyama kunye nokusetyenziswa kwayo okunokwenzeka, bekholelwa ukuba inexabiso elikhulu elinokubakho kwiindawo ezifana nokubona kude, unxibelelwano lwe-optical, kunye ne-microelectronics.
Okwangoku, uT. Samet waseFransi, uAnoife M. Moloney waseIreland, uZhao Li waseFudan University eTshayina, kunye noMen Haining waseChinese Academy of Sciences bonke benze uphando olunzulu kwi-silicon emnyama kwaye bafumana iziphumo zokuqala. I-SiOnyx, inkampani eseMassachusetts, e-USA, ide yaqokelela i-$11 yezigidi kwimali-mboleko ukuze isebenze njengeqonga lophuhliso lwetekhnoloji kwezinye iinkampani, kwaye iqalile ukuvelisa iimveliso ze-silicon wafers ezimnyama ezisekwe kwi-sensor, ilungiselela ukusebenzisa iimveliso ezigqityiweyo kwiinkqubo ze-infrared imaging zesizukulwana esilandelayo. UStephen Saylor, i-CEO ye-SiOnyx, uthe iingenelo eziphantsi kunye novakalelo oluphezulu lwetekhnoloji ye-silicon emnyama ngokuqinisekileyo ziya kutsala ingqalelo yeenkampani ezigxile kuphando nakwiimarike zemifanekiso yezonyango. Kwixesha elizayo, inokungena kwimarike yeekhamera zedijithali kunye neekhamera zekhamera ezixabisa izigidigidi zeerandi. I-SiOnyx ikwavavanya iipropati ze-photovoltaic ze-silicon emnyama, kwaye kunokwenzeka kakhulu ukubaisilicon emnyamaiza kusetyenziswa kwiiseli zelanga kwixesha elizayo. 1. Inkqubo yokwenziwa kweBlack Silicon
1.1 Inkqubo yoLungiselelo
Ii-wafer ze-silicon ezinekristale enye zicocwa ngokulandelelana nge-trichloroethylene, i-acetone, kunye ne-methanol, emva koko zibekwe kwinqanaba lethagethi elinokushukunyiswa elinemilinganiselo emithathu kwigumbi lokufunxa. Uxinzelelo olusisiseko lwegumbi lokufunxa lungaphantsi kwe-1.3 × 10⁻² Pa. Igesi esebenzayo ingaba yi-SF₆, Cl₂, N₂, umoya, H₂S, H₂, SiH₄, njl., ngoxinzelelo olusebenzayo lwe-6.7 × 10⁴ Pa. Okanye, indawo yokufunxa ingasetyenziswa, okanye ii-elemental powders ze-S, Se, okanye Te zinokugqunywa kumphezulu we-silicon kwi-vacuum. Inqanaba lethagethi lingantywiliselwa emanzini. Iipulse zeFemtosecond (800 nm, 100 fs, 500 μJ, 1 kHz) eziveliswa yi-Ti:sapphire laser regenerative amplifier zijoliswa yilensi kwaye zikhanyiselwe ngokuthe nkqo kumphezulu wesilicon (amandla okukhupha ilaser alawulwa yi-attenuator, equlathe ipleyiti yesiqingatha-wamaza kunye ne-polarizer). Ngokuhambisa inqanaba lokujolisa ukuze kuskenwe umphezulu wesilicon nge-laser spot, izinto zesilicon emnyama ezinommandla omkhulu zinokufunyanwa. Ukutshintsha umgama phakathi kwelensi kunye ne-silicon wafer kunokulungisa ubungakanani bendawo yokukhanya ekhanyiselwe kumphezulu wesilicon, ngaloo ndlela kutshintsha i-laser fluence; xa ubungakanani bendawo buhlala buhleli, ukutshintsha isantya sokuhamba kwesigaba sokujolisa kunokulungisa inani leepulse ezikhanyiselwe kumphezulu weyunithi yomphezulu wesilicon. Igesi esebenzayo ichaphazela kakhulu imo yesakhiwo se-silicon surface. Xa igesi esebenzayo ihlala ihleli, ukutshintsha i-laser fluence kunye nenani leepulse ezifunyenweyo kwindawo nganye yeyunithi kunokulawula ukuphakama, umlinganiselo wombono, kunye nesithuba sezakhiwo ezincinci.
1.2 Iimpawu zeMicroskopu
Emva kokukhanyiswa yilaser ye-femtosecond, umphezulu we-silicon ecwebezelayo ekuqaleni ubonisa uluhlu lwezakhiwo ezincinci ze-conical ezicwangciswe rhoqo. Iincopho ze-cone zikwindawo efanayo nomphezulu we-silicon ojikelezileyo ongakhanyiswanga. Imilo yesakhiwo se-conical inxulumene negesi esebenzayo, njengoko kubonisiwe kuMfanekiso 2, apho izakhiwo ze-conical eziboniswe kwi-(a), (b), kunye (c) zenziwe kwi-SF₆, S, kunye ne-N₂ atmospheres, ngokwahlukeneyo. Nangona kunjalo, ulwalathiso lweencopho ze-cone aluxhomekekanga kwigesi kwaye luhlala lukhomba kwicala le-laser incidence, aluchaphazeleki ngumxhuzulane, kwaye aluxhomekekanga kuhlobo lwe-doping, i-resistivity, kunye ne-crystal orientation ye-crystalline silicon; iziseko ze-cone azilingani, kunye ne-axis yazo emfutshane ehambelana nolwalathiso lwe-laser polarization. Izakhiwo ze-conical ezenziwe emoyeni zezona zirhabaxa, kwaye ubuso bazo bugqunywe zi-nanostructures ze-dendritic ezincinci ze-10–100 nm.
Okukhona i-laser fluence iphezulu kwaye inani lee-pulses liphezulu, kokukhona ziphakama kwaye zibanzi izakhiwo ze-conical. Kwi-SF6 gas, ukuphakama u-h kunye nesithuba u-d sezakhiwo ze-conical zinobudlelwane obungelulo ulayini, obunokubonakaliswa malunga ne-h∝dp, apho u-p=2.4±0.1; zombini ukuphakama u-h kunye nesithuba u-d zinyuka kakhulu ngokunyuka kwe-laser fluence. Xa i-fluence inyuka ukusuka kwi-5 kJ/m² ukuya kwi-10 kJ/m², isithuba u-d sinyuka ngamaxesha ama-3, kwaye xa sidibene nobudlelwane phakathi kuka-h no-d, ukuphakama u-h kuyanda ngamaxesha ali-12.
Emva kokufakelwa kobushushu obuphezulu (1200 K, iiyure ezi-3) kwi-vacuum, izakhiwo ze-conical zeisilicon emnyamaakutshintshanga kakhulu, kodwa izakhiwo ze-dendritic ze-10-100 nm kumphezulu zinciphile kakhulu. I-ion channeling spectroscopy ibonise ukuba ukuphazamiseka kumphezulu we-conical kuye kwehla emva kokufakelwa, kodwa uninzi lwezakhiwo eziphazamisekileyo azitshintshanga phantsi kwezi meko zokufakelwa.
1.3 Indlela Yokwenziwa
Okwangoku, indlela yokwakheka kwe-silicon emnyama ayicaci. Nangona kunjalo, u-Eric Mazur nabanye bacinga ukuba, ngokusekelwe kutshintsho kwimo yesakhiwo se-silicon kumphezulu kunye nomoya osebenzayo, phantsi kokukhuthazwa kwe-high-intensity femtosecond lasers, kukho impendulo yekhemikhali phakathi kwegesi kunye nomphezulu we-crystalline silicon, okuvumela ukuba umphezulu we-silicon ukrolwe ziigesi ezithile, zenze ii-cones ezibukhali. U-Eric Mazur nabanye banxulumanise iindlela zomzimba nezekhemikhali zokwakheka kwesakhiwo se-silicon kumphezulu: ukunyibilika kunye nokususwa kwe-substrate ye-silicon okubangelwa zii-laser pulses eziphezulu; ukukrolwa kwe-substrate ye-silicon yi-ions ezisebenzayo kunye namaqhekeza aveliswa yi-laser field enamandla; kunye nokuphinda kusetyenziswe inxalenye ekhutshiweyo ye-substrate silicon.
Izakhiwo zekhoni kumphezulu wesilicon zenziwe ngokuzenzekelayo, kwaye uluhlu oluqhelekileyo lunokwenziwa ngaphandle kwemaski. U-MY Shen nabanye bancamathisele i-2 μm thick transmission electron microscope copper mesh kumphezulu wesilicon njengemaski, baze bakhanyisa i-silicon wafer kwigesi ye-SF6 nge-femtosecond laser. Bafumene uluhlu olucwangciswe rhoqo lwezakhiwo zekhoni kumphezulu wesilicon, oluhambelana nepateni yemaski (jonga uMfanekiso 4). Ubungakanani bomngxuma wemaski buchaphazela kakhulu ulungiselelo lwezakhiwo zekhoni. Ukusasazwa kwe-incident laser yi-mask apertures kubangela ukusasazwa okungalinganiyo kwamandla e-laser kumphezulu wesilicon, okubangela ukusasazwa kobushushu obuqhelekileyo kumphezulu wesilicon. Oku ekugqibeleni kunyanzela uluhlu lwesakhiwo somphezulu wesilicon ukuba lube luqhelekileyo.