Zinthu Zatsopano Zosintha - Silicon Yakuda
Silikoni wakuda ndi mtundu watsopano wa zinthu za silikoni zomwe zili ndi mphamvu zabwino kwambiri zamagetsi. Nkhaniyi ikufotokoza mwachidule ntchito yofufuza za silikoni wakuda yochitidwa ndi Eric Mazur ndi ofufuza ena m'zaka zaposachedwa, ikufotokoza mwatsatanetsatane njira yokonzekera ndi kupanga silikoni wakuda, komanso makhalidwe ake monga kuyamwa, kuwala, kutulutsa kwa nthaka, ndi kuyankhidwa kwa spectral. Ikufotokozanso za ntchito zofunika kwambiri za silikoni wakuda mu zozindikira za infrared, maselo a dzuwa, ndi zowonetsera za flat-panels.
Silikoni yoyera imagwiritsidwa ntchito kwambiri mumakampani opanga ma semiconductor chifukwa cha zabwino zake monga kuyeretsa kosavuta, kugwiritsa ntchito mankhwala osokoneza bongo, komanso kukana kutentha kwambiri. Komabe, ilinso ndi zovuta zambiri, monga kuwunikira kwakukulu kwa kuwala kowoneka ndi kwa infrared pamwamba pake. Kuphatikiza apo, chifukwa cha kusiyana kwakukulu kwa band,silikoni ya kristaloSizingayamwitse kuwala ndi mafunde opitilira 1100 nm. Pamene mafunde a kuwala kochitika ali oposa 1100 nm, kuchuluka kwa kuyamwa ndi kuyankha kwa zozindikira za silicon kumachepa kwambiri. Zipangizo zina monga germanium ndi indium gallium arsenide ziyenera kugwiritsidwa ntchito kuzindikira mafunde awa. Komabe, mtengo wokwera, makhalidwe oipa a thermodynamic ndi khalidwe la kristalo, komanso kusagwirizana ndi njira za silicon zokhwima zomwe zilipo zimachepetsa kugwiritsa ntchito kwawo muzipangizo zochokera ku silicon. Chifukwa chake, kuchepetsa kuwunikira kwa malo a silicon opangidwa ndi kristalo ndikuwonjezera kuchuluka kwa mafunde ozindikira a zozindikira zochokera ku silicon ndi silicon zomwe zimagwirizana ndi silicon kumakhalabe nkhani yofufuza kwambiri.
Pofuna kuchepetsa kuwunikira kwa malo a silicon opangidwa ndi kristalo, njira zambiri zoyesera ndi njira zagwiritsidwa ntchito, monga photolithography, reactive ion etching, ndi electrochemical etching. Njirazi, mpaka pamlingo wina, zitha kusintha mawonekedwe a silicon yopangidwa ndi kristalo pamwamba ndi pafupi ndi pamwamba, motero zimachepetsasilikoni Kuwunikira pamwamba. Mu kuwala kooneka, kuchepetsa kuwunikira kumatha kuwonjezera kuyamwa ndikuwongolera magwiridwe antchito a chipangizocho. Komabe, pa mafunde opitilira 1100 nm, ngati palibe mphamvu yoyamwa yomwe imalowetsedwa mu silicon band gap, kuwunikira kochepa kumangopangitsa kuti pakhale kufalikira kwakukulu, chifukwa silicon band gap pamapeto pake imachepetsa kuyamwa kwake kwa kuwala kwa kutalika kwa mafunde. Chifukwa chake, kuti muwonjezere kuchuluka kwa mafunde a zida zozikidwa pa silicon komanso zogwirizana ndi silicon, ndikofunikira kuwonjezera kuyamwa kwa photon mkati mwa band gap pomwe nthawi yomweyo kuchepetsa kuyamwa kwa silicon pamwamba.
Kumapeto kwa zaka za m'ma 1990, Pulofesa Eric Mazur ndi ena ku Harvard University adapeza chinthu chatsopano—silicon wakuda—pa kafukufuku wawo wokhudza momwe ma laser a femtosecond amagwirira ntchito ndi zinthu, monga momwe zasonyezedwera pa Chithunzi 1. Pamene ankaphunzira za mphamvu zamagetsi za silicon wakuda, Eric Mazur ndi anzake adadabwa kupeza kuti silicon yopangidwa ndi microstructure iyi ili ndi mphamvu zapadera zamagetsi zamagetsi. Imayamwa pafupifupi kuwala konse komwe kuli pafupi ndi ultraviolet ndi pafupi ndi infrared (0.25–2.5 μm), kuwonetsa mawonekedwe abwino kwambiri a kuwala kowoneka bwino komanso pafupi ndi infrared komanso mphamvu zabwino zotulutsa mpweya m'munda. Kupeza kumeneku kunayambitsa chidwi mumakampani opanga ma semiconductor, ndipo magazini akuluakulu adapikisana kuti alembe za izi. Mu 1999, magazini a Scientific American ndi Discover, mu 2000 gawo la sayansi la Los Angeles Times, ndipo mu 2001 magazini ya New Scientist onse adasindikiza nkhani zokhudzana ndi kupezeka kwa silicon wakuda ndi ntchito zake zomwe zingatheke, pokhulupirira kuti ili ndi phindu lalikulu m'magawo monga kuzindikira kutali, kulumikizana kwa optical, ndi ma microelectronics.
Pakadali pano, T. Samet wochokera ku France, Anoife M. Moloney wochokera ku Ireland, Zhao Li wochokera ku Fudan University ku China, ndi Men Haining wochokera ku Chinese Academy of Sciences onse achita kafukufuku wambiri pa silicon yakuda ndipo apeza zotsatira zoyambirira. SiOnyx, kampani ku Massachusetts, USA, yasonkhanitsa ndalama zokwana $11 miliyoni kuti ikhale nsanja yopangira ukadaulo kwa makampani ena, ndipo yayamba kupanga ma wafer akuda a silicon okhala ndi masensa, akukonzekera kugwiritsa ntchito zinthu zomalizidwa mumakina ojambulira a infrared a m'badwo wotsatira. Stephen Saylor, CEO wa SiOnyx, adati mtengo wotsika komanso ubwino wokwera wa ukadaulo wakuda wa silicon udzakopa chidwi cha makampani omwe amayang'ana kwambiri kafukufuku ndi misika yojambulira zamankhwala. M'tsogolomu, ikhoza kulowa mumsika wa makamera a digito ndi makamera a camcorder okwana mabiliyoni ambiri. SiOnyx pakadali pano ikuyesanso mphamvu za photovoltaic za silicon yakuda, ndipo ndizotheka kwambiri kutisilikoni wakudaidzagwiritsidwa ntchito m'maselo a dzuwa mtsogolo. 1. Njira Yopangira Silicon Yakuda
1.1 Njira Yokonzekera
Ma wafer a silicon okhala ndi kristalo imodzi amatsukidwa motsatizana ndi trichloroethylene, acetone, ndi methanol, kenako amaikidwa pa gawo la chandamale chosunthika m'chipinda chopanda vacuum. Kupanikizika kwapansi kwa chipinda chopanda vacuum ndi kochepera 1.3 × 10⁻² Pa. Mpweya wogwira ntchito ukhoza kukhala SF₆, Cl₂, N₂, mpweya, H₂S, H₂, SiH₄, ndi zina zotero, ndi kuthamanga kwa ntchito kwa 6.7 × 10⁴ Pa. Kapenanso, malo osungira vacuum angagwiritsidwe ntchito, kapena ufa wa S, Se, kapena Te ukhoza kuphimbidwa pamwamba pa silicon mu vacuum. Gawo lofunikira likhozanso kumizidwa m'madzi. Ma pulse a Femtosecond (800 nm, 100 fs, 500 μJ, 1 kHz) opangidwa ndi amplifier yobwezeretsa laser ya Ti:sapphire amayang'aniridwa ndi lenzi ndipo amawalitsidwa mozungulira pamwamba pa silicon (mphamvu yotulutsa laser imayendetsedwa ndi attenuator, yomwe imakhala ndi mbale ya theka la mafunde ndi polarizer). Mwa kusuntha gawo la chandamale kuti mufufuze pamwamba pa silicon ndi malo a laser, zinthu zakuda za silicon zazikulu zitha kupezeka. Kusintha mtunda pakati pa lenzi ndi silicon wafer kumatha kusintha kukula kwa malo owala omwe amawalitsidwa pamwamba pa silicon, potero kusintha kuwala kwa laser; pamene kukula kwa malo kuli kokhazikika, kusintha liwiro loyenda la gawo la chandamale kumatha kusintha kuchuluka kwa ma pulse omwe amawalitsidwa pamalo a unit of silicon surface. Mpweya wogwira ntchito umakhudza kwambiri mawonekedwe a microstructure ya pamwamba pa silicon. Mpweya wogwira ntchito ukakhala wokhazikika, kusintha kuwala kwa laser ndi kuchuluka kwa ma pulse omwe amalandiridwa pa unit area kumatha kuwongolera kutalika, chiŵerengero cha mbali, ndi mtunda wa ma microstructures.
1.2 Makhalidwe a Microscopic
Pambuyo pa kuwala kwa laser ya femtosecond, pamwamba pa silicon yosalala yoyambirira imakhala ndi mapangidwe ang'onoang'ono a conical omwe amakonzedwa nthawi zonse. Ma cone top ali pamtunda womwewo ndi pamwamba pa silicon yosawala. Mawonekedwe a conical structure akugwirizana ndi mpweya wogwira ntchito, monga momwe zasonyezedwera pa Chithunzi 2, pomwe conical structures zomwe zawonetsedwa mu (a), (b), ndi (c) zimapangidwa mumlengalenga wa SF₆, S, ndi N₂, motsatana. Komabe, njira ya cone tops siili yodalira mpweya ndipo nthawi zonse imaloza ku mbali ya laser, osakhudzidwa ndi mphamvu yokoka, komanso yodalira mtundu wa doping, resistivity, ndi crystalline direction ya crystalline silicon; ma cone bases ndi asymmetrical, ndi short axis yawo yofanana ndi njira ya laser polarization. Ma conical structures opangidwa mumlengalenga ndi owopsa kwambiri, ndipo pamwamba pawo pali ma dendritic nanostructures abwino kwambiri a 10–100 nm.
Kuchuluka kwa kuwala kwa laser komanso kuchuluka kwa ma pulses, kumakhala kutalika komanso kukulirapo kwa kapangidwe ka conical. Mu mpweya wa SF6, kutalika kwa h ndi mtunda wa d wa kapangidwe ka conical kumakhala ndi ubale wosalunjika, womwe ungatchulidwe ngati h∝dp, pomwe p=2.4±0.1; kutalika konse kwa h ndi mtunda wa d kumawonjezeka kwambiri ndi kuwonjezeka kwa kuwala kwa laser. Pamene kuwala kumawonjezeka kuchokera pa 5 kJ/m² kufika pa 10 kJ/m², mtunda wa d umawonjezeka ndi nthawi zitatu, ndipo kuphatikiza ndi ubale wa h ndi d, kutalika kwa h kumawonjezeka ndi nthawi 12.
Pambuyo pa kutentha kwambiri (1200 K, maola atatu) mu vacuum, mapangidwe a conical asilikoni wakudasizinasinthe kwambiri, koma mapangidwe a 10–100 nm dendritic pamwamba adachepa kwambiri. Ma ion channeling spectroscopy adawonetsa kuti vuto lomwe lili pamwamba pa conical linachepa pambuyo pa annealing, koma ambiri mwa mapangidwe osasinthika sanasinthe pansi pa mikhalidwe iyi ya annealing.
1.3 Njira Yopangira Zinthu
Pakadali pano, njira yopangira silicon yakuda siikudziwika bwino. Komabe, Eric Mazur ndi anzake adaganiza, kutengera kusintha kwa mawonekedwe a kapangidwe ka silicon pamwamba ndi mlengalenga wogwirira ntchito, kuti pansi pa kusonkhezeredwa kwa ma laser amphamvu kwambiri a femtosecond, pali kusintha kwa mankhwala pakati pa mpweya ndi pamwamba pa silicon, zomwe zimapangitsa kuti pamwamba pa silicon pakhale kujambulidwa ndi mpweya winawake, ndikupanga ma cones akuthwa. Eric Mazur ndi anzake adati njira zakuthupi ndi zamakemikolo zopangira kapangidwe ka silicon pamwamba ndi izi: kusungunuka ndi kuchotsedwa kwa substrate ya silicon komwe kumachitika chifukwa cha ma pulse a laser amphamvu; kuchotsedwa kwa substrate ya silicon ndi ma ions ndi tinthu tomwe timapangidwa ndi mphamvu ya laser; ndi kubwezeretsedwanso kwa gawo lochotsedwa la substrate ya silicon.
Mapangidwe a conical pamwamba pa silicon amapangidwa mwangozi, ndipo gulu lofanana ndi lokhazikika lingapangidwe popanda chigoba. MY Shen ndi anzake adalumikiza mesh ya copper ya maikulosikopu ya maikulosikopu ya 2 μm yokhuthala pamwamba pa silicon ngati chigoba, kenako adayatsa silicon wafer mu mpweya wa SF6 ndi laser ya femtosecond. Adapeza gulu lokonzedwa bwino la ma conical pamwamba pa silicon, mogwirizana ndi mawonekedwe a chigoba (onani Chithunzi 4). Kukula kwa chigoba kumakhudza kwambiri kapangidwe ka ma conical. Kufalikira kwa laser yochitika ndi ma aperture a chigoba kumayambitsa kugawa kosafanana kwa mphamvu ya laser pamwamba pa silicon, zomwe zimapangitsa kuti kutentha kugawike nthawi ndi nthawi pamwamba pa silicon. Izi pamapeto pake zimapangitsa kuti gulu la ma silicon pamwamba likhale lokhazikika.