Izinto Ezintsha Eziguqukayo - I-Black Silicon
I-silicon emnyama uhlobo olusha lwezinto ze-silicon ezinezakhiwo ezinhle kakhulu ze-optoelectronic. Lesi sihloko sifingqa umsebenzi wocwaningo nge-silicon emnyama ka-Eric Mazur nabanye abacwaningi eminyakeni yamuva nje, sichaza indlela yokulungiselela nokwakheka kwe-silicon emnyama, kanye nezakhiwo zayo ezifana nokumuncwa, ukukhanya, ukukhishwa kwensimu, kanye nokusabela kwe-spectral. Siphinde siveze ukusetshenziswa okubalulekile kwe-silicon emnyama kuma-detector e-infrared, amaseli elanga, kanye nezibonisi zephaneli ezisicaba.
I-crystalline silicon isetshenziswa kabanzi embonini ye-semiconductor ngenxa yezinzuzo zayo njengokulula kokuhlanzwa, ukulula kokusebenzisa izidakamizwa, kanye nokumelana nokushisa okuphezulu. Kodwa-ke, inezinkinga eziningi, njengokukhanya okuphezulu okubonakalayo kanye nokukhanya kwe-infrared ebusweni bayo. Ngaphezu kwalokho, ngenxa yegebe elikhulu lebhendi,i-silicon ekristaliayikwazi ukumunca ukukhanya ngamaza amakhulu kune-1100 nm. Uma ubude bokukhanya kwesigameko bungaphezu kwe-1100 nm, izinga lokumunca kanye nokuphendula kwezitholi ze-silicon liyancipha kakhulu. Ezinye izinto ezifana ne-germanium kanye ne-indium gallium arsenide kumele zisetshenziswe ukuthola lawa maza. Kodwa-ke, izindleko eziphakeme, izakhiwo eziphansi ze-thermodynamic kanye nekhwalithi yekristalu, kanye nokungahambelani nezinqubo ze-silicon ezivuthiwe ezikhona kunciphisa ukusetshenziswa kwazo kumadivayisi asekelwe ku-silicon. Ngakho-ke, ukunciphisa ukubonakaliswa kwezindawo ze-silicon ezikristalu kanye nokwandisa ububanzi bobude bokubona be-photodetectors ezisekelwe ku-silicon kanye ne-silicon kusalokhu kuyisihloko socwaningo esishisayo.
Ukuze kuncishiswe ukubonakaliswa kwezindawo ze-silicon ezikristalu, kuye kwasetshenziswa izindlela eziningi zokuhlola namasu, njenge-photolithography, i-reactive ion etching, kanye ne-electrochemical etching. Lawa masu angashintsha, ngezinga elithile, isimo sobuso kanye nesimo esiseduze kwe-silicon ekristalu, ngaleyo ndlela kuncishiswei-silicon Ukubonakaliswa kobuso. Ebangeni lokukhanya okubonakalayo, ukunciphisa ukubonakaliswa kungandisa ukumuncwa futhi kuthuthukise ukusebenza kahle kwedivayisi. Kodwa-ke, kuma-wavelength angaphezu kuka-1100 nm, uma kungekho amazinga wamandla okumuncwa afakwa ku-silicon band gap, ukubonakaliswa okuncishisiwe kuholela ekudlulisweni okwandisiwe kuphela, ngoba i-band gap ye-silicon ekugcineni inciphisa ukumuncwa kwayo kokukhanya okude. Ngakho-ke, ukuze kwandiswe ububanzi bobude bokukhanya obubucayi bamadivayisi asekelwe ku-silicon nahambisana ne-silicon, kuyadingeka ukwandisa ukumuncwa kwe-photon ngaphakathi kwe-band gap ngenkathi ngesikhathi esifanayo kunciphisa ukubonakaliswa kobuso be-silicon.
Ngasekupheleni kweminyaka yama-1990, uSolwazi Eric Mazur nabanye eHarvard University bathola into entsha—i-silicon emnyama—ngesikhathi socwaningo lwabo mayelana nokusebenzisana kwama-laser e-femtosecond nezinto, njengoba kuboniswe kuMfanekiso 1. Ngesikhathi befunda izakhiwo ze-photoelectric ze-silicon emnyama, u-Eric Mazur kanye nozakwabo bamangala ukuthola ukuthi le nto ye-silicon eyakhiwe nge-microstructure inezakhiwo ze-photoelectric ezihlukile. Imunca cishe konke ukukhanya ebangeni le-near-ultraviolet kanye ne-near-infrared (0.25–2.5 μm), ikhombisa izici zokukhanya ezibonakalayo neziseduze ne-infrared kanye nezakhiwo ezinhle zokukhishwa kwensimu. Lokhu kutholwa kwabangela umuzwa embonini ye-semiconductor, omagazini abakhulu bephikisana ukubika ngakho. Ngo-1999, omagazini be-Scientific American kanye ne-Discover, ngo-2000 isigaba sesayensi se-Los Angeles Times, kanye nomagazini i-New Scientist ngo-2001 bonke bashicilela izihloko ezikhuluma ngokutholakala kwe-silicon emnyama kanye nezinhlelo zayo ezingaba khona, bekholelwa ukuthi inenani elikhulu elingaba khona emikhakheni efana nokuzwa okukude, ukuxhumana kwe-optical, kanye ne-microelectronics.
Njengamanje, u-T. Samet waseFrance, u-Anoife M. Moloney wase-Ireland, u-Zhao Li waseFudan University eShayina, kanye no-Men Haining wase-Chinese Academy of Sciences bonke benze ucwaningo olunzulu nge-silicon emnyama futhi bathole imiphumela yokuqala. I-SiOnyx, inkampani eseMassachusetts, e-USA, isize yaqoqa imali eyizigidi eziyi-11 zamaRandi emalini yokuqalisa ukuze isebenze njengeplatifomu yokuthuthukisa ubuchwepheshe kwezinye izinkampani, futhi isiqalile ukukhiqizwa kwezentengiselwano kwama-wafer e-silicon amnyama asekelwe ezinzwa, ilungiselela ukusebenzisa imikhiqizo eqediwe ezinhlelweni zezithombe ze-infrared zesizukulwane esilandelayo. UStephen Saylor, i-CEO ye-SiOnyx, uthe izinzuzo eziphansi kanye nokuzwela okuphezulu kobuchwepheshe be-silicon emnyama zizodonsela ukunaka kwezinkampani ezigxile ocwaningweni nasezimakethe zezithombe zezokwelapha. Esikhathini esizayo, ingangena ngisho emakethe yekhamera yedijithali kanye nekhamera yekhamera ebiza izigidigidi zamaRandi. I-SiOnyx nayo okwamanje izama izakhiwo ze-photovoltaic ze-silicon emnyama, futhi kungenzeka kakhulu ukuthii-silicon emnyamaizosetshenziswa kumaseli elanga esikhathini esizayo. 1. Inqubo Yokwakheka kwe-Black Silicon
1.1 Inqubo Yokulungiselela
Ama-wafer e-silicon e-single-crystal ahlanzwa ngokulandelana nge-trichlorethylene, i-acetone, ne-methanol, bese ebekwa esigabeni sethagethi esinyakaziswayo esinezilinganiso ezintathu ekamelweni le-vacuum. Ingcindezi eyisisekelo yegumbi le-vacuum ingaphansi kuka-1.3 × 10⁻² Pa. Igesi esebenzayo ingaba yi-SF₆, Cl₂, N₂, umoya, H₂S, H₂, SiH₄, njll., ngengcindezi yokusebenza engu-6.7 × 10⁴ Pa. Ngaphandle kwalokho, indawo ye-vacuum ingasetshenziswa, noma izimpushana ze-elemental ze-S, Se, noma i-Te zingambozwa ebusweni be-silicon ku-vacuum. Isigaba sethagethi singacwiliswa emanzini. Ama-pulse e-Femtosecond (800 nm, 100 fs, 500 μJ, 1 kHz) akhiqizwa yi-Ti:sapphire laser regenerative amplifier agxilwe ilensi futhi akhanyiswe ngokuqondile phezu kobuso be-silicon (amandla okukhipha i-laser alawulwa yi-attenuator, equkethe ipuleti le-half-wave kanye ne-polarizer). Ngokuhambisa isigaba sokuqondiwe ukuze kuskenwe ubuso be-silicon nge-laser spot, kungatholakala izinto ze-silicon emnyama endaweni enkulu. Ukushintsha ibanga phakathi kwelensi ne-silicon wafer kungalungisa usayizi wendawo yokukhanya ekhanyiswe phezu kobuso be-silicon, ngaleyo ndlela kushintshe ukukhanya kwe-laser; lapho usayizi wendawo uhlala njalo, ukushintsha isivinini sokuhamba kwesigaba sokuqondiwe kungalungisa inani lama-pulse akhanyiswe endaweni yeyunithi yobuso be-silicon. Igesi esebenzayo ithinta kakhulu ukuma kwesakhiwo se-silicon surface. Lapho igesi esebenzayo ihlala njalo, ukushintsha ukukhanya kwe-laser kanye nenani lama-pulse atholakele endaweni ngayinye kungalawula ukuphakama, isilinganiso sesici, kanye nesikhala sezakhiwo ezincane.
1.2 Izici ze-Microscopic
Ngemva kokushiswa ngemisebe ye-laser ye-femtosecond, ubuso be-silicon obubushelelezi bokuqala bubonisa uhla lwezakhiwo ezincane ezi-conical ezihlelwe njalo. Iziqongo ze-cone zisendizeni efanayo nobuso be-silicon obungashiswanga ngemisebe obuzungezile. Ukuma kwesakhiwo se-conical kuhlobene negesi esebenzayo, njengoba kuboniswe ku-Figure 2, lapho izakhiwo ze-conical eziboniswe ku-(a), (b), kanye no-(c) zakhiwe emoyeni we-SF₆, S, kanye ne-N₂, ngokulandelana. Kodwa-ke, isiqondiso seziqongo ze-cone asincikile kugesi futhi sihlala sikhomba isiqondiso se-laser, asithinteki amandla adonsela phansi, futhi futhi asincikile kuhlobo lwe-doping, i-resistivity, kanye nokuqondiswa kwe-crystal kwe-silicon ye-crystalline; izisekelo ze-cone azilingani, kanti i-axis yazo emfushane ihambisana nesiqondiso se-laser polarization. Izakhiwo ze-conical ezakhiwe emoyeni zinzima kakhulu, futhi ubuso bazo bumbozwe yi-nanostructures ze-dendritic ezincane kakhulu ezingama-10–100 nm.
Uma ukukhanya kwe-laser kuphakeme futhi inani lama-pulse likhulu, izakhiwo ezi-conical ziba zinde futhi zibanzi. Kugesi we-SF6, ukuphakama kwe-h kanye nesikhala se-d sezakhiwo ezi-conical kunobudlelwano obungewona umugqa, obungachazwa cishe njenge-h∝dp, lapho i-p=2.4±0.1; kokubili ukuphakama kwe-h kanye nesikhala se-d kuyanda kakhulu ngokukhanya kwe-laser okwandayo. Lapho ukukhanya kukhuphuka kusuka ku-5 kJ/m² kuya ku-10 kJ/m², isikhala se-d sikhuphuka izikhathi ezi-3, futhi kuhlanganiswe nobudlelwano phakathi kwe-h no-d, ukuphakama kwe-h kuyanda izikhathi eziyi-12.
Ngemva kokufakwa kwe-anneal okushisa okuphezulu (1200 K, amahora ama-3) endaweni evalekile, izakhiwo ezi-conical zei-silicon emnyamaakushintshanga kakhulu, kodwa izakhiwo ezincane ze-dendritic ezingama-10-100 nm ebusweni zancipha kakhulu. I-ion channeling spectroscopy ibonise ukuthi ukuphazamiseka ebusweni obuyindilinga kwehla ngemva kokufakelwa, kodwa iningi lezakhiwo eziphazamisekile alishintshanga ngaphansi kwalezi zimo zokufakelwa.
1.3 Indlela Yokwakheka
Okwamanje, indlela yokwakheka kwe-silicon emnyama ayicaci. Kodwa-ke, u-Eric Mazur nabanye bacabanga, ngokusekelwe ekushintsheni kwesimo sesakhiwo se-silicon surface kanye nomoya osebenzayo, ukuthi ngaphansi kokukhuthazwa kwama-laser e-femtosecond anamandla aphezulu, kukhona ukusabela kwamakhemikhali phakathi kwegesi kanye nobuso be-silicon obucwebezelayo, okuvumela ukuthi ubuso be-silicon buqoshwe ngamagesi athile, kwakhiwe ama-cone abukhali. U-Eric Mazur nabanye babhekisela ezindleleni zomzimba nezamakhemikhali zokwakheka kwesakhiwo se-silicon surface microstructure ku: ukuncibilika kanye nokususwa kwe-substrate ye-silicon okubangelwa ama-pulse e-laser acwebezelayo aphezulu; ukuqoshwa kwe-substrate ye-silicon ngama-ion asebenzayo kanye nezinhlayiya ezikhiqizwa yinsimu ye-laser enamandla; kanye nokuvuselelwa kwengxenye ekhishwe ye-substrate ye-silicon.
Izakhiwo eziyindilinga ebusweni be-silicon zakhiwe ngokuzenzekelayo, futhi i-array engajwayelekile ingakhiwa ngaphandle kwe-mask. U-MY Shen nabanye banamathisele i-mesh yethusi ye-transmission electron microscope engu-2 μm ubukhulu ebusweni be-silicon njenge-mask, base bekhanyisa i-silicon wafer kugesi ye-SF6 nge-laser ye-femtosecond. Bathole i-array ehlelwe njalo yezakhiwo eziyindilinga ebusweni be-silicon, ehambisana nephethini ye-mask (bheka Umfanekiso 4). Usayizi we-aperture we-mask uthinta kakhulu ukuhlelwa kwezakhiwo eziyindilinga. Ukuphazamiseka kwe-laser ye-incident yi-mask apertures kubangela ukusatshalaliswa kwamandla e-laser okungalingani ebusweni be-silicon, okuholela ekusabalalisweni kwezinga lokushisa ngezikhathi ezithile ebusweni be-silicon. Lokhu ekugcineni kuphoqa i-array yesakhiwo se-silicon surface ukuba ibe ejwayelekile.