ISSN: 2354-0575
ANH HU^dNG CUA N H I $ T DQ VA CACBON DEN HINH THAI CAU TRUC
\ DAY NANO S n . I C DlTOC HINH THANH BANG PHUONG PHAP BOC BAY NHIET Nguyin Thi Thiiy' ^, Nguyin Hokng Tu4n', Nguyen Duy Hilng^
Nguyin Dii-c Chiln'-^, Nguyin Hfru Lam'-^
1 Viin Vdt ly ky thugt, Trudng Dgi hgc Bdch khoa Hd Ndi 2 Tnrang Dgi hgc Supham Ky thuat Hung Yin 3 Vien Tiin tien ve Khoa hoc vd Cdng nghi. Tnrang Dgi hge Bdch khoa Hd Ndi Tom tat:
Trong bdi bdo ndy, chung tdi dd tdng hap thdnh eong ddy nano Si trin de Si(l 11) bdng phuong phdp bdc bay nhiet tir ngudn ran sii dung xuc tdc Au (dp ddy 1-10 nm) vdi ngudn vat lieu khdc nhau tir bgt Si vd hdn hop (Si+C). Hinh thdi vd cdu triic vi md ciia ddy nano Si duoc nghiin ciru boi kinh hien vi dien tii quit (FESEM), tinh ehdt quang cua ddy Si duoe nghien ciru hang phuang phdp dophP quang huynh quang. Cdc ddy nano phdt trien ddng deu, ddi ca micromet vd cd dudng kinh nhd trong khodng 10-30 nm Tit khoa: day nano Si. xue tdc, hoc bay nhiit.
Gioi thieu
Silic la vat lieu truyen thong da dugc nghien ciiu va ling dung trong hau het cac linh kien dien tii va quang dien tu. Gan day, khi phat hien nhirng uu diem Yuot trgi ve tinh chat co, tinh chat nhiet, tinh chat dien va quang cua cau triic silic mpt chieu (day nano Si) so voi vat lieu dang khoi [1,2], day nano Si da thu hilt nhieu su quan tam cua cac nha khoa hgc. Hien nay tren the gioi, day nano Si da dugc che tao bai cac nhom nghien ciiu vai nhiiu phuang phap khac nhau nhu boc bay nhiet [3], hoc bay dung xung laser (PLD) [4], \kng dong hoa hoc tir pha hoi (CVD) [5].
Trong nghien cim nay, chung toi sii dung phuang phap b i c bay nhiet tao day nano Si vai cac nguon vat lieu bay hai ban dku khac nhau, g i m bgt h6n hgp (Si:C) vai ty le thay d6i va bgt Si khong chira C. Dong then, su anh huong ciia nguon vat lieu, cac thong s6 cong nghe trong qua trinh chi tao len cau tnic va tiah chat quang ciia day nano Si da dugc nghien ciiu.
Thuc nghiem
Day nano Si dugc che tao bang phuang phap b6c bay nhiet a nhiet do cao trong 16 thach anh. D i u tien, d i Si{l 11) kich thuac (2x2) cm dugc lam sach be mat bang phuang phap hoa hgc sir dung cac hoa chat nhu con, aceton, axit HF 1%. D i sau do dugc nia bang nuoc khii ion va lam kho trong moi truong khi nita. Tiep theo, mgt lop mong vang (Au) voi do day n-ong khoang tir 1-10 nm dugc phii len b i mat de Si bang phucmg phap b6c bay bSng chiiin dien tir de lam xiic tac trong qua trinh hinh thanh day nano Si. Cac de Si nay sau do dugc chuyin nhanh vao buong dung mlu ciia he b6c bay nhiet (la ong thiiy tinh thach anh - quarzl chiu nhiet dg cao) d i thuc hien qua trinh hinh thanh day nano Si.
Hinh I. Hi Id ngang ehi tgo ddy nano Si bang ky thugt boc bay nhiet trin he CVD Nguon vat lieu bay hai dang bgt dugc dat trong coc dung vat lieu biing oxit nhom chinh tam 16 - noi CO nhiet do dugc xac dinh chinh xac bing cap nhiet. Nhiet do ctia he bfic bay nhiet c6 thi xac dmh thong qua phuong phap sii dung cap nhiet loai K va he hien thi. Toe do nang nhiet, thai gian nang nhiet dugc dieu khien thong qua bg diiu khiin nhi?t do Buong phan ling duoc hiit chan khong so cip bang ragt he bcrm chan khong co hoc. Khi At tinh khiet (99,9%) dugc dua vao buong phan ling vai luu lugng duac giii on dinh khoang 500 seem (Hinh la).
Hinh la. He dien tu (trdi) vd bd &
(phdi) khiin khi GFC
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Nhiet dp trong 16 dugc nang len 1100 - 1200''C vai t6c do la 10°C/min va dugc duy tri trong su6t qua trinh phan ling tao day Si (Hinh 2).
t ( ^
t(pbut) Hinh 2. Quy trinh nang nhipt trong qud trinh che
tgo ddy nano Si
Ket thuc qua trinh hinh thanh day, he hoc bay nhiet dugc Iam ngugi tu nhien trong moi truong khi tra. Mau dugc dua ra ngoai de phan tich khi nhiet do dat toi nhi?t do phong. Sau qua trinh, hinh thai va cau tnic cua day nano dugc phan tich biing hiin vi dien hi quet FESEM (Hitachi S4800 tai phong thi nghiem kinh hien vi dien tii - Vien Ve sinh Dich te Trung uang v^ ph6ng thi nghiem trgng diem thugc Vien Khoa hgc Vat lieu). Tinh chat quang ciia day dugc nghien ciiu bang pho quang huynh quang (PL) (cac phep do pho huynh quang dugc tien hanh tai phong thi nghiem Cooperman Vien Khoa hgc Vat lieu vai he do sii dung nguon laser kich thich He- C d ) .
Ket quS v^ thao luan
Su hinh thanh day Si dugc biet theo ca che hcfi-long-ran (VLS), Theo do, a nhiet do cao cac hat hgp kim xitc tac (Au-Si) nong chay, cac nguyen hi Si khi dugc cung c i p vao duoi dang pha hai se lang dgng va khueeh tan vao hat xuc tac (Au-Si) Khi dat toi trang thai qua bao hoa tir nhihig gigt hgp kim (Au-Si) se hinh thanh nen day Si. Kich thuoc cua hat xuc tac se anh huang tai dudng kinh ciia day Si thu nhSn dugc.
Truac hit, chung toi nghien ciiu v i su anh huong ciia vi tri dat mau so vdi coc dung vat lieu trong qua trinh hinh thanh day Si. Hinh 1 the hien anh SEM ciia cac mau co chiia day Si dugc hinh thanh trong dieu kien mang Au xuc tac day 1 nm, nhiit do trong qua trinh phan ling la 1100°C, bgt nguyen lieu la h6n hgp vdi ty le Si:C (4:1), thoi gian phan ung la 90 phiit vai luu lugng khi Ar la 500 seem. Khoang each giua de Si vdi h6n hgp bgt ngu6n la 3; 4, 5; 6 va 7,5 cm (tuong ung cac hinh 3.a. 3 . b , 3 . c v a 3 . d ) ,
Khoa h9C & Cong ngh? - So 4/2014 Journal of Science and Technology
Hinh 3. Ddy nano Si hinh thdnh tren diSi(lll)phu idp xuc tdc Au ddy I nm vdi khodng each tir de tai cdc dung bdt vgt hiu Si:C la 3 em (a), 4,5 em (b), 6
em (e) vd 7,5 em (d)
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Trong ca bon trudng hgp tren, day Si deu dugc hinh thanh nhung phan bo kich thudc khac nhau: day nho kich thudc nho hon 10 nm va cac day Idn hem khoang 30 nm. Su hinh thanh hai loai cau triic day nhu tren co lien quan den su hinh thanh cac hat Au dong vai tro chat xuc tac trong qua trinh phan img.
Co the thay hat xiic tac co anh hudng Idn den qua trinh hinh thanh day Si. Cac nghien ciiu ve su hinh thanh hat An a nhiet do cao cho thay sir ton tai cua hai cau tnic: eac hat nho va cac hat idn hon do su lien ket tu cac hat nho han tao thanh. Cac ket qua chup anh FESEM khac cho thay day nano Si co kich thuoc kha dai (hang chuc micromet) va co cac hat Au d phia dau cua day Si.
Idp xiic tdc Au ddy I nm dgt di sdt ngudn vgt liiu vai ty Ip hdn hgp bpt vdt lieu ban ddu Si.Cld 4:1 (a), tylp2.1 (b) vd bdt Si khdng chira C (c) tgi IIOO^C
D i khao sat anh hudng cua ngu6n v^t li?u tdi su hinh thanh cua day nano Si, chiing toi tiin hanh tao day Si tren d i S i ( l l l ) phii 1 nm Au, sir dung h6n hgp bgt Si'C co ty le 4:1 (Hmh 4.a) va ty le 2:1 (Hinh 4.b) (vdi tdng k h i i lugng 0,1253g) va bgt Si khong chiia C (c) trong ciing dieu kiSn nhiet do che tao d 1100°C va dugc dat sat nguin vat lieu. Quan sat anh FESEM (Hmh 4), cho fliiy day nano Si deu hinh thanh c6 dudng kinh day kha nho (nhd hem 30 nm). Tuy nhien, day nano Si hinh thanh trong trudng hgp bgt Si khdng chiia C co mat do thap han nhieu so vdi cac trudng hgp con lai.
Nhu vay, co the thay C dong vai trd la chit hoat hoa, day nhanh qua trinh boc bay cua bgt Si, hinh thanh day nano.
Hinh 4. Ddy nano Si hinh t/idnh tren di Si(lll) phu
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Hinh 5. Ddy nano Si hinh thdnh tren di Si(IIl) phii Idp xiic tdc Au ddy 10 nm dgt de sdt ngudn vgt lieu voi ty le hdn hgp bpt vdt lieu ban dau Si:Cld 4:1 (a)
vd bpt Si khdng chua C (b) tgi llOO^C Hinh 5 la anh FESEM chup b i mat mlu chua day nano Si hinh thanh tren d i Si( 111), b i day Idp Au xuc tac tuong ling la 10 nm vdi cac nguin vat li^u la hon hgp Si:C (4:l=0,1250g) (Hinh 5.a) va bgt Si khong cbda C (Hinh 5.b). K i t qua cho thiy day nano Si mgt phan hinh thanh tren d i Si sir dung bgt h6n h c ^ chiia C. Phin ciu tnic co kich
Journal of Science and Technology
thudc Idn - 100 nm, theo chiing toi cd thi hoac la cau tnic day SiO^ hoac day Si do su hinh th^nh cau tnic cac hat Au co kich thude kha Idn khi bi day Idp Au dugc phii len di Si day 10 nm tdng hgp d nhi?t do cao. Qua trinh il d nhiet dg cao HOO^C se chuyen ciu tnic mang Au thanh cac hat c6 kich thudc khong ddng diu, din din su hinh thanh cac cau true neu tren.
ISSN: 2354-0575 Hinh 6 la phd huynh quang cua day nano Si dugc kich thich bdi budc song 442 nm vdi cac ngudn vat lieu khac nhau. Tren anh pho PL xuat hien hai dinh rat manh 405 nm va 510 nm thugc viing anh sang mau xanh, nguon goc ciia hai dinh phat xa da duac giai thich la do cac tam sai hong d Idp vo SiOj, hoac d be mat Idp tiep xiic giua loi Si vdi lap vo SiO, nhu cac niit khuyet oxy gay ra [4-7]. Dinh phat xa trong vung anh sang do -750 nm, nguon goc ciia dinh phat xa nay thudng dugc giai thich la do s\r tai hgp cua cap dien tu -16 trong trong loi nano tinh the ciia day nano Si che tao dugc.
Kit luan
Chung tdi da khao sat su hinh thanh day nano Si bang phucmg phap boc bay nhiet vdi cac dieu kien cong nghe chS tao khac nhau, Su anh hudng ciia nguon vat lieu, nhiet do va khoang each giiia de Si va nguon dung vat lieu trong qua trinh hinh thanh day nano Si da duoc nghien ciru. Pho huynh quang cua mau cho thay c6 su phat xa cua loi Si trong cau tnic day Si dugc boc Idp oxit silic trong qua trinh hinh thanh cau tnic.
Biifes6ng(nm)
•')
Hinh 6. Phd huynh quang cua ddy nano Si a nhiet do phdng vai cdc ngudn vgl lieu bpt khdc nhau: bpt Si khdng chira C (a) vd hdn hgp Si:C (b) tdng hap
a llOO^C Tki ligu tham khao
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[2]. Minsung Jeon and Koichi Kamisako, Materials Letters, 63, 777 (2009).
[3]. V. Schmidt,J. VWittemann, andU. Gosele, "Growth, thermodynamics, and electrical properties of silicon nanowires.. "Chemical reviews, vol. 110, no. 1, pp. 361-88, Jan. 2010.
[4]. X. J. Wang, B. Dong, and Z Zhou, "Preparation and phololumineseence of high density SiOx
nanowires with Fe304 nanopariieles catalyst," Matenals Letters, vol. 63, no. 13-14, pp 1149- 1152, May 2009.
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[5] D . L i a n d R K i m , "Thermal conductivity of individual silicon nanowires," vol S3, no. 14, pp.
2934-2936, 2003.
[6]. J. Qi, J. M. White, A. M Belcher, and Y. Masumoto, "Optical spectroscopy of silicon nanowires."
Chemical Physics Letters, vol. 372, no. 5-6, pp. 763-766, May 2003.
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EFFECTS OF TEMPERATURE AND CARBON TO THE MORPHOLOGY STRUCTURE OF SILICON NANOWIRES PREPARED BY USING METHOD OF THERMAL EVAPORATION Abstract:
Silicon nanowires were sucessfully prepared on silicon wafer, Si (III), by means of chemical vapor deposition with gold catalysts having thickness 1-10 nm by using powdery mixters of (Si+C) in different weight ratio) Morphological microstructure of Si nanowires is were studied by Filed emission scanning eleclmn microscopy (FESEM); Optical properties of Si nanowires were investigated by measurement of the fluorescence spectrum FESEM studies revealed that the obtained silicon nanowires are characteristics of
smaller diameter of about 10-30 nm and leghth in several micron Keywords: Si nanowires, catalytic, thermal evaporation.
Ngiroi phan bien: PGS.TS. Tran Trung
