TAP CHi KHOA H p c & C 6 N C NGHf CAC TRU'dNG DAI HQC K t T H U A T • S 6 90 - 2012
C H ^ T ^ O DAY NANO SILIC B A N G PHlTONG PHAP B6C BAY N H I | ; T SILICON NANOWIRES FABRICATION BY THERMAL EVAPORATION METHOD Nguyen Thf Thuy'\ Phgm Viit V&n',HoAng QuangSm^, VirtmgXuSitAnh',
Nguyen HoAng Tudn', Nguyin D&c Chiin', Nguyin Hitu LAn^*
'Tru&ng Dgi hgc Bdch khoa Hd N^i
^Tru&ng Dgi hgc Sur phgm kp thu^t Himg YSn Nhin ngiy 17 tiling 7 nim 2011; Chip nh^n ding ngiy 08 tiling 8 nam 2012
T6M TAT
Diy nano Silic (Si) vdi kich thudv vi hlnh thii khic nhau dlroc chi t^o thinh dng trin di 51(111} bing phirong phip bic bay nhlit tir bit SI theo ca chi VLS (rin-ldr^-khl). Trong qui trinh thirc nghi$m, ming mdng vdng (Au) phii trin <Si SI bing phuvng phip bic bay tiing chOm diin A>
dl^rc sir dvng Iim xiic tic trong qui trinh mpc diy nano Si. Kit qui chyp inh bing Mnh hiin vi diin tir quit phit xa tru-dmg (FESEM) cho thiy diy nano Si dlAw; chi t^o c6 chiiu did khi ASn, dUtJng klnh trung binh vii c/jyc nanomet. Hlnh thii vi kich ihuirc cia diy SI phy thuic vio bi diy ICrp kim top/
xic tic vi aiu kiin chi t^o.
A B S T R A C T
Silicon nanowires (SiNWs) with different diameters and morphc^o^es grown on Si(111}
substrate by thermal evaporation method following the vapor-liquid- solkl (VLS) mechanism. SI powder played as a solid source for the formation of the SiNWs. in our experiment, a gold thin film grown on the SI surfaces by electi-on beam evaporation, was used as catalyst to grow SiNWs. TTie tSameter md morphology of SiNWs were characterized by field emission scorning electron mKroscopo (FBSEM). It was shown that the average size of nanowires is about tens of nanometer. The size and morphology of SiNWs were shown depending on the catalyst layer thiclmess and Rowing conc£tion.
1. G l d l THI$U
Silic la vit lieu bin dan dupc sii dung pho bien trong cdng nghe vi dien ti>, diing de che tao cac linh ki§n di$n tii nhu: diode, transistor... Silic dupc ling dyng nhieu trong y hpc, quin su vi cdng nghiip. Die biet, m$t dang cau triic ciia Si l i diy nano Si (ciu tnic mdt chieu) cd kich thudc dudng kinh nhd cd nanomet. Khi kich thudc dudng kinh ciia day nano du nhd keo theo hi^u img giam giii lupng tii trong ciu tnic, tinh chat ciia diy nano Si sS hoin toin khic so vdi tinh chat ciia bin dSn khii thdng tiiudng [l]-[3]. Cic tinh chit di|n vi tinh chat quan^ ciia diy nano Si dupc cic nhi khoa hpc cho rang cd su "noi trOi" [4]-[6] vi cd tilm nang ling dpng trong tiremg lai, dip ung nhu ciu ciia con ngudi nhu: giim kich thudc linh kien, ting tic dp xiV ly vi nang cao hi|u suit ciia cac thiit b) dien tir [7]-[10].
Chinh vi v$y, trong nhung nam gan day cic nha khoa hpc da tip tnmg nghi€n ciiru chl t^o cau true day nano Si vdi nhiiu phuong phap khic nhau nhu: epita^Q', b6c bay chiim di|n tii.
ho trp tir nguin laser, ling dpng hda hpc tu pha hoi (CVD). Day nano Si dupc chl t^o bing nhiing phuong p h ^ neu tr£n diu dua tren co chl hoi - long - lin (VLS) [6]-[ 12].
Phin trSm nguyen tit SI Hinh I. Gidn dS pha cua hgp kim Au-Si, nhi$t d0 ndng chdy cia hop kim tgi diim ciing tinh th^p han nhiiu so vdt nhi^t dd ndng chdy cOa kim loai vdng vd silic.
Tren giin do pha ciia hpp kim Au-Si (hinh I), nhiet d$ ndng chay ciia vang (Au) vi
TAP CHi KHOA Hpc & C6NG NGH? CAC TRU'dNG DAI HpC K* THUAT # S 6 90 - 2012 ciia silic (Si) tuong ling la 1064 "C va 1414 "C
[13]. Tuy nhien khi chung hinh thanh hpp kim (Au-Si), d diim cung tinh (eutectic) thi nhipt dp ndng chiy cua hpp kim Au-Si rit thap vio khoing - 360 °C. Nhi|t dp nay thap hon nhieu nhi|t dp ndng chiy cCia timg vit lieu rieng re va diy chinh la co sd cho qui trinh hinh thinh diy nano Si dien ra [I4],[15].
liong nghicn ciiu niy, chung tdi thuc hien chl tao day nano Si tr€n dl Si( 111) li mit tinh till dl hinh thinh diy Si hon so vdi cic mit tinh till khac nhu Si(lOO), Si(l 10) [16]. Phuong phE^ si^ dvng l i bic bay nhiet trong mdi trudng hon hpp khi (90% Ar + 10% Hi), sii dung chan khong t h ^ vdi nguon rin li bpt Si:C, Cic thong s6 tiong qui trirdi chl t90 diy nano Si nhu: nhiet dp, Ap suit, luu lupng khi, vi tri, thdi gian mpc diy... cd the dupc diiu khien d€ dang va chinh xic.
2. THV'C NGHIEM
Chiing tdi tiln hanh lam s^h dl Si( 111) b ^ phuong phap xit ly hda hpc. Sii dung nude khu ion vi cac dimg dich aceton, ethanol dl loai bd cac t ^ ban trSn be mat dl Si. Sau do, Idp oxit silic hinh thinh tu nhien tren be mit de Si(lll) bi loai bd bing dung dich axit HF pha loang ~l-2%. Khi dl Si khdng cdn dinh udt nude chung td Idp dxit da b) lo^i bd hoin toan.
Hep theo, ie Si dupc dua nhanh vao buing chiia mau ciia h^ bic bay bing chiim dien tit vi dupc bom hiit chan khdng den ^ suit ~-5xlO'^
mbar. Muc £ch ciia qua trinh niy la tao ming mdng Au cd dp sach cao tren dl Si de lam xiic tic cho qua trinh t^o day Si. Trong qua trinh che t£LO mang mdng Au, dl giii mau ludn ludn quay dl dim bio ming Au hmh thanh dong diu tren toin bl mit dl Si. Bl diy mang Au dupc xic dnh tiidng qua he do be day ming ( F l ^ cua may trSn ca sd he vi can tinh till th^ch anh (QCM).
Sau khi ming Au da dupc hlnh thanh tren dl Si, man dupc chuyen nhanh vio buing phin ling ciia he boc bay nhipt. Buing phin img dupc hut chan khdng so c ^ bing mpt he bom chan khdng co hpc. Mpt ddng khi tra (Ar) dupc (bra vio buong phin ling do duy tri ap suit ~ 10"' mbar. Sau dd, mau dupc ning nhiet vi ii d nhiet dp 1100 "C trong thdi gian 15 phiit dl khio sat su hinh thanh h^t hpp kim xiic tic tren bl mit ciia dl Si(IlI). Trong qua trinh thuc
nghiem, thuyin chua bpt vit lieu (Si.C) dupc d$t tai tim cua Id nhiet, Thuyen chira de Si(lll) dupc dit t?u vi tri each thuyin, bpt Si khoing 5-7 cm (dim bio t^ do vung nhiet dp v ^ on djnh va dong diu). M§u dupc dat nghieng mpt gdc ~30° so vdi mat phang ngang de dim bio qui trinh hinh thanh day nano Si la toi uu. De hinh thanh day nano Si, nhiet dp t^
viing chua bdt Si vi dl Si(t 11) dupc thiit lip d 1100 "C. Khi dd cac nguySn tii Si dupc van chuyin tdi bl mit dl Si(lll) nhdhSn hpp khi mang (Ar/H:) vdi luu lupng khi 160 seem, thdi gian 60 phiit. Kit thuc qui trinh hinh thanh day, he boc bay nhiet dupc Iim ngudi tu nhien trong mdi trudng khi tra.
Sau khi diy nano Si dupc hinh thanh tren dl Si(l 11), chiing tdi sii dyng kinh hiin vi dien tii qu^ phit xa trudng (FESEM) dl khao sit cau true, kich thudc va hinh thai ciia day.
BSn c^nh dd, nhiing nghien ciru vl su hinh thanh h^t hpp kim xiic tic Au-Si tren de Si(l 11) ciing dupc khio sat va phan tich.
3. KtT QUA VA T H A O LUAN Tnrdc hit, chiing tdi khao sat su hinh thinh hat hpp kim xitc tic Au-Si tren bl mat de Si(lll) da dupc lam s^ch. Ming mdng Au dupc chl t ^ bing phuong phap boc bay chiim dien tii vdi bl diy tii 0,5 nm den 4 nm va dupc u trong mdi trudng khi tra d nhiet dp I I00°C, thdi gian 15 phiit. Khi dd qui tiinh hinh thinh cic h^it hpp kim cd kich tiiudc cd nanomet se xiyra,
Hinh 2.(a-c) l i anh SEM ciia be mat dl Si(lll) chiia ming mdng Au vdi cic bl diy tuong ling 0,5 nm (a), 1 nm (b) vi 4 nm (c) sau khi u nhiet. Dli vdi mSu cd mang Au day 0,5 va I nm, kich thudc trung binh ciia h^t hpp kim xiic tic dirpc do vio khoang ~50 nm vi khi ding diu. Trong khi dd, mang Au cd be diy 4 nm cho cic hat hpp kim cd kich thudc Idn hon vi till hipn su khdng dong diu vl phan bl kich thudc. Vipc hinh thanh cic hat xiic tic cd kich thudc Idn vi khdng ding deu dupc ly giii bdi hai nguyin nhin: Thu nhat, vi|c tu dam ciia cac h^t kich thudc nhd hon khi nhiet dp ii Idn. Thii hai do inh hudi^ bdi bl ds^ mang xiic tic Au tr€n dl Si(Ill). ^£ing Au cang day, kich thudc h^t hpp kim xiic tic sau qua trinh li s€ cing Idn.
TAP cut KHOA UpC & CdNG NGHf CAC TRU'ONG DAI HpC K^ THUAT • S6 90-2012
Hinh 2 Anh ShJit c uu man^An in'n ilv Si(! 11) u nhu'-nr l/nir'C ironrjht'n i;i.in 1'^ phiil
Hinh3.AnhSEMciiaddynanoSltrinaiSt(m)vdibiddytndngAu0.5(a), I (b}.2(c)vd4nm(d).
Sau khi h^t hpp kim xiic tic (Au-Si) dupc hudi thinh tren bl mit dl Si(lll), budc tiep theo la tien hanh mpc day nano Si bing phuong p h ^ boc bay nhiet tu nguin v$t lieu bdt Si:C. Trong hau hit cic nghiSn cuu dil tao ve day nano Si bing phuong phip bic bay nhiet di dupc cdng bl, day nano Si dupc mpc tiiep co chl hoi-ldng-rin (VLS).
TrSn hlnh 3 l i inh SEM chup bl ni$t mSu cd chiia day nano Si hinh thinh trfin Ah Si{l 11)
vdi be day Idp vang xiic tic tuong ling la 0,5 (a), 1(b), 2 (c) va 4 nm (d). Kit qui cho tiiiy khi bl day mang Au cdn mdng (cd 0,5-1 nm), diy nano Si hinh thanh khi dong diu, day khi dii (cd micromet) va c6 kich diu6c dudng kinh tiung binh nim trong khoing 30-50 nm. Khi ming Au diy hem (tiudng hpp 2 nm vi 4 nm), diiing tdi quan sit dupc s\i phan b6 khdi%
dong deu ve kich thudc dfiy Si. Cac di^ cd kich tiiudc nhd ~ 30 nm nam dan xen vdi cac diy cd kich thudc Idn hon (80-90 nm). Vi|c
TAP CH! KHOA Hpc & C6NG NGH? CAC TRU'DNG DAI HOC KV THUAT • S 6 90 - 2012 hinh thanh cic cau triic day nano Si khdng ding
deu vl kich thudc the hien su phan b l khdng ding deu vl kich thudc vi mit dp cac h^t kim
loai xuc tic hpp kim (Au-Si) da trinh bay d tren
m'K^
I ciia ddy nano Si trSn di Si(lll) vdi cdu triic dang bach tudc trudc (a) vd sau khi loai bd xHc tdc kim loai (b). Di Si duoc phit mang vdng ddy I nm
Mdt kit qui khi thti vi mi chiing tdi nh^n duoc kht thay doi diiu kien cdng nghp chl t^o la viec nhin dupc ciu tnic diy nano cd hinh dpng bpch tupc. Kit qui niy li hoin toin phii hpp vdi nghien cuu trudc dd ve vipc su dung Ga lam xiic tic dl hinh thinh day Si02 [17]
Hnh 4 thi hien cic ciu tnic d^ng bach tupc cua day nano Si trudc (a) vi sau khi lo^i bd hpt xiic tac kim loai vang (b). D I Si(lll) trong trudng hpp nay dupc phii Idp xiic tic ving diy 1 nm.
Viec loai bd hoin toin hat xiic tic bang hda chit dio t h ^ day nano Si dang bach tupc cd co che phat trien t^i dinh (tip-growth), theo do cac bpt xuc ^ ludn dupc wy len phia dau diy Si.
Kit qui ciia su hinh thinh diy nano Si dang bpch tu$c cd thi dupc giii thich thdng qua su hinh thanh cua cic hat xiic tic tiong qui trinh ning vaii nhiet.
R5 ring, dieu kien cdng nghe cd inh hudng Idn tdi su hinh thinh cua diy nano Si.
Trong tiudng hpp ning nhi^t true tilp 16n 1100 C, qui trinh hinh thinh day nano Si ngay khi nhi^ dp niy Aigc xic 1 ^ se dan tdi xu hudng ket tu nhau ciia cac h^t xuc tic cd kich tiiudc nhd. Cic day nano Si dupc hinh thinh kem theo qua trinh day cic h^t xiic tic len phia dau day nano Si, Khi dd cic h^t xiic tic se kit tu vio
TAI LI|;U THAM KHAO
1. Zheng v., Rivas C , Lake R., IEEE Transactions, Vol. 52,1097-1103 (2005).
nhau. Do dd, ta thay dudng nhu cac day nano Si dupc hinh thiinh tii mpt h^t xiic tic co kich thudc Idn cd hinh dang gilng bach tupc. Khac vdi diiu kien chan khdng t h ^ vi dupc u nhiet qua viing nhiet dp tnmg gian (~600 "C), cac hat hpp kim (Au-Si) rieng re co kich thudc nhd se dupc hinh thanh on $nh vi la ca sd de hinh thanh day nano Si rieng biet.
KfiTLUAN
Chiing tdi da khio sit su hinh thanh hat hpp kim xiic tic (Au-Si) trgn de Si(lll), qua do da chl tao thinh cdng day nano Si vdi kich tiiudc vi hinh thii ciia diy nano Si khac nhau.
Su khic nhau niy lien quan din d i u kien cdng ngh$ che tao: bl day Idp xac tic, diiu kien nang vi u nhi^t . Die biet, chiing tdi da chl tao thinh cdng day nano Si hinh thii gilng bach tupc vdi mit dp diy khi Idn. Cic kit qui nghien ciiu niy la tiln dl cho vi@c vmg dung day nano Si trong cic Imh vuc ciia cupc song.
Ldt cim on
Cic tac gii xin cim on su ho tip vl kinh phi tii de tii cua Qui phit trien khoa hpc va cdng nghe quoc gia NAFOSTED, ma so 103.02.99.09.
TAP CHl Kl IOA HQC 4 C6NG NGHf CAC THtrONG B/^ HQC Kj THDiT * S6 90 - 2012 2, F. Sacconi, M. P. Persson, M. Povolotskyi, L, Latessa, A. Pecchia, A. Gagliardi, A.
Balint, T. Fraunheim, A. Di Carlo, J Comput Electron, Vol. 6, 329-333 (2007).
3 Huang J M, Weng C. C, Chang M. T, Inter. Jour. ofThential Sciences, Vol. 49, 1095- 1102(2010).
4. 0. Demlchel, F. Oehler, V. Calvo, P. Noe, N. Pauc, P. Gentile, P. Ferret, T. Baron, N.
Magnea, Physica E, Vol. 41, 963-965 (2009).
5. Shi F., Lin J , Huang Y., Zhang J., Tang C , Materials Chemistry and Physics, Vol. 118, 125-128 (2009).
6. Fukata N , Oshima T., Okada N., Kizuka T., Tsurui T., Ito S , Murakami K., Physica B, 864-867 (2006).
7. Tian B., Zheng X., Kempa J. T, Fang Y., Yu N., Yu G., Huang J., Lieber M. C, Nature, Vol.449, 885-889(2007).
8. Wan Y., Sha J., Chen B., Fang Y , Wang Z., Wang Y, Recent Patents on Nanotechnology, Vol. 3, 1-9 (2009).
9. Demami F , Ni L , Rogel R., Salaun C. A, Pichon L , Procedia Engineering, Vol. 5, 351- 354 (2010).
10. Zhang J. O, Zhang L., Huang J. M, Heniy Luo H. Z, Ignatius Tay K. G, Andy Lim J. E, Kang G. T, Chen Y, Sensors and Actuators B, Vol. 146, 138-144 (2010).
11. Schmidt V., Wittemann V. J, Gosele U, Chemical Reviews, Vol. 110, 361-388 (2010).
12. Wang N., Cai Y,, Zhang Q. R, Materials Science & Engineering R, Vol. 60, 1-51 (2008).
13. Jin-Shyong Lin, Chien-Chon Chen, Eric Wei-Guang Diau, Tzeng-Feng Liu, Journal of Materials processing technology. Vol. 206,425-430 (2008).
14. S Sharma, T. L Kamins, R. S Williams, Jour. Appl. Phys, Vol. 80, 1225-1229 (2005).
15. Lin S. J, Chen C. C, Guang Diau W. E, Liu F. T, Journal of Materials Processing Technology, Vol. 206,425-430 (2008).
16. E. I. Givargizor, Journal of Ciystal Growth, Vol. 31,20-30 (1975).
17. Zheng Wei Pan, Zu Rong Dai, Chris Ma, and Zhong L. Wang, J. Am. Chem. Soc., Vol 124 (8),1817-1822 (2002).
Sia chi liSn h$: Nguyen Him Ltal - Tel: (04)3868.2540, Email: [email protected] Vien V8t ly Ky thuat - Tniing Bai hpc Bach khoa Ha Npi
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