Chế tạo và nghiên cứu màng SnO2 và SnO2 pha tạp : Đề tài NCKH. QT.03.08

DAI HOC QUOC GIA HA NOI TRUONG DAI H O C K H O A H O C Tl/NHIEN TEN DE TAI: CHE TAG VA NGHIEN CUU MANG SnOi VA Sn02 PHA TAP MA SO: QT 03 - 08 CHU TRI DE TAI: TS LE THI THANH BINH CAC CAN BO THAM GIA: ThS LE DUY KHANH CN NGUYEN THANH BINH BAI HOC QUOC GIA HA N y i TRUNG TAM THONG TIN THU VIEN 01 / 54-f- HA NOI - 2004 QT03-08 BAO CAO TOM T A T Che tao va nghien curu mang Sn02 va SnOj pha tap Ma so Chu tri de tai: Cac can bo tham gia: QT-03~08 TS Le Thi Thanh Binh Ths Le Duy Khanh CN Nguy6n Thanh Binh L Muc tieu va noi dung l.L Muc tieu - Che tao mang Sn02, Sn02: F, SnOs: Sb bang phuang phap phun tinh dien Khao sat tfnh chat quang, huynh quang va dien cua cac mang Trong qua trinh trien khai nghien cim ket hop dao tao sinh vien dai hoc va hoc vien cao hoc L2.Noi dung - Tao duac cac mang Sn02, Sn02: F, Sn02: Sb vai cac nong tap khae Khao sat su phu thuoc tfnh chat vat ly ciia mang vao di^u kien tao mSu - Khao sat sir phu thuoc tfnh chat huynh quang va kfch thfch huynh quang vao nhiet do Ket qua chinh 01 luan van thac si 02 khoa luan tot nghiep Dai hoc 02 bao cao khoa hoc Tinh hinh kinh phi de tai - Kinh phf duac cap: Kinh phf duac cap den 12 - 2003 da toan xong: 10.000.000 VND 10.000.000 VND Khoa quan ly (Ky va ghi ro ho ten) Chu tri de tai (Ky va ghi ro ho ten) 07nA^ TS Nguyin The Binh TS Le Thi Thanh Binh chu tri de tai PHO HlEU TRJONG T3 xyia/w cJl(a,'fUy BRIEF REPORT OF PROJECT The preparation of Sn02 and doping SnOj films and the research on their properties The code number: The coordinator: The participants of the project: QT - 03 - 08 Dr Le Thi Thanh Binh MSc Le Duy Khanh BSc Nguyen Thanh Binh Purpose and contents of the work l.L Purpose - To prepare the Sn02, Sn02: F and Sn02: Sb films by BSD To research on the optical, photoluminescence and electrical properties of the received films - To train master and bachelor students 1.2 Contents - The preparation Sn02, Sn02: F and Sn02: Sb films with different doping concentration - The research on the effect of deposition condition on physical properties of Sn02 films - The research on the temperature dependence of the films photoluminescence and excitation photoluminescence Main results - 01 master thesis 02 bachelor thesis 02 scientific reports Phan chfnh bao cao MUC LUC Bao cao torn tit Brief report of project Muc luc Mddau Noi dung chfnh PhSn Tdng quan ve tinh hinh nghien ciiu vat lieu SnOs Phfe2, Ky thuat thue nghiem Phan Ket qua nghien cuu Ket luan Tai lieu tham khao 6 11 29 30 MO DAU Sn02 la ban din viing cam rpng, chuyen miic thang (Ey= 3,6 eV tai T = 300 K) Mang SnOj suot va dan dien tot duac six dung rpng rai nhieu linh vuc nhu pin mat trdi, cac linh kien quang dien tir, man hinh tinh the long, sensor nhay khf Mang Sn02 duac che tao bang nhieu phuang phap nhu: phun dung dich, phun tinh dien, boc bay chan khong, lang dong hoa hoc tir pha hai Cac nghien ciiu ca ban ve Sn02 va cac nghien ciiu ling dung Sn02 cac llnh vuc cong nghe khae da duac nhieu nha nghien ciiu quan tam M6i mot cong nghe che tao mang, m5i mot phuang phap pha tap vao mang Sn02 diu tao duac mot loai san pham Sn02 vai cac tfnh cha't vat ly mong muon Tren ca sa thiet bi san co a bo mon, chiing toi da trien khai de tai che tao mang Sn02 va Sn02: F, Sn02: Sb bang phuang phap phun tinh dien, vai muc dfch nghien ciiu anh huang cua che tao mang len cac tfnh cha't vat ly nhu tfnh chat hap thu, tfnh cha't huynh quang va tfnh chat dien ciia mang NOI DUNG CHINH PHAN T N G Q U A N \ i TINH HINH NGHIEN CtTU VAT LIEU SnOj 1.1 Cau true tinh the cua Sn02 [1, 2, 3] SnOa la ban dan loai n, thuoc nhom A^^B'^\ co ca'u triic tii giac (rutile) vcd cac hang so mang a = 4,734 A, c = 3,185, ti so ^ = 0,673 A va tham so noi u = 0.307 Trong m6i o mang co chiia nguyen tir: nguyen tu Sn va nguyen tirOnhutr^n hinh Vi trf cac nguyen tir duac tfnh tir ti so c/a va tham so noi u Cac ion Sn^"" nam a cac vi trf (0 0) va (1/2 1/2 1/2) va duac bao quanh bai khoi bat dien xien ciia cac ion O^' nam a cac vi trf ± (u u 0) va ± (1/2+u 1/2-u 1/2) M6i ion Sn'*"' lien ket vdi ion O^', hai ion a khoang each d^ =^ua va bon ion a khoang each d^ =[2(l/2-w)' +(c/2i3)j ~a M6i ion O^' chi co ion Sn"^^ bao quanh gan nhat Hinh Mo hinh ca'u triic tinh the Sn02 Trong cac nghien ciiu ve tfnh cha't tinh the cua Sn02, tir X-ray gia tri hang so mang nhan duac co the thay doi chut ft pha tap vao Dieu thucmg duac giai thfch bai kha nang dien ke cua cac ion tap chat mang tinh the Trong nhirng nam gan day, ngoai xu huong tao cac mang Sn02 suot va CO dan dien cao, cac nha khoa hoc dang tfch cue tao vat lieu Sn02 co ca'u triic nano vai muc dfch nghien ciiu khai thac cac tfnh cha't dieu ki ciia loai vat lieu phuc vu cho cong nghe linh kien nano [4, 5, 6] 1.2 Tinh chat hap thu cua Sn02 Vat lieu Sn02 hap thu manh a mien tir ngoai, ba hap thu a lan can eV thucmg quan sat duac rat r5 cac truyen qua va hap thu ciia cac mang Sn02 Mang Sn02 cho anh sang vung kha kien truyen qua rat tot Do truyen qua ciia mang Sn02 phu thuoc ra't nhieu vao phuang phap che tao, day cua mang va loai tap cha't cung nhu n6ng tap chat dua vao mang Bang phuang phap CVD cac tac gia [7] da tao dugc mang Sn02 vai truyen qua 45% - 99% mien kha kien va tfnh duac gia tri E^, = eV tir hap thu Bang phuang phap Sol-Gel cac tac gia [8] da khao sat truyen qua ciia cac mang theo so 16p tao nen mang Do truyen qua trung binh cua cac mang vao ca 80% Cac tap cha't Sb va F thuang duac sir dung de nang cao dan dien cho cac mang Sn02 Tuy nhien nong tap cha't cang tang thi truyen qua cang giam va chi dat khoang 42% den 64% a bu6c song 800 nm [9,10] Su phu thuoc cua truyen qua vao nhiet de cung duac cac tac gia [9] quan tam, ho da chi neu cimg nong Sb, nhiet de cang cao thi truyen qua cang giam nhung dp dan dien lai cang tang Doi v6i m6i phuang phap che tao mang thi co the tim duac mot che dp toi uu de cac mang Sn02 thoa man duac ca hai yeu cau la truyen qua cao va dp dan dien lan 1.3 Tinh chat huynh quang Cac nghien ciiu huynh quang ciia Sn02 khong nhieu vi Sn02 khong phai la vat lieu phat quang manh nhiet dp phong, huynh quang cua cac mang Sn02 CO cac dinh 393 nm, 439 nm, 486 nm, 496 nm [11] va 500 nm [6] Ta't ca cac dinh deu co nguon goc tir sai hong VQ , mot loai sai hong luon ton tai mang, duac hinh qua trinh tao mang Dinh huynh quang a 3,14 eV (394,8 nm) khong thay doi theo nhiet dp [12] duac giai thfch bang anh huang ciia cac yeu to sai hong mang nhu V^,, Vg^ hoac anh huang ciia kfch thuac nano cac hat tinh the mang Trong mot nghien cuu khae [13], huynh quang cua Sn02 tren de InSb a 10 K thay ddi vi trf dinh tir 2.8 eV den 3,3 eV dp day mang thay doi tir 1750 A den 1990 A, ket qua dupe giai thich tren qui luat giam nang luang viing cam hien tuong giam cac sai hong mang d6 day mang tang len Cac tac gia [14] da nghien ciru tfnh chat huynh quang a nhiet dp K ciia cac mang Sn02 che tao bang phuang phap CVD Cac ket qua nghien ciiu cho tha'y cucfng dp va vi tri cac dinh 3,38 eV, 3,33 eV, 3,1 eV va 2,4 eV thay doi theo nhiet dp de Theo cac tac gia nguyen nhan hinh dai 2,4 eV la su ton tai cac niit khuyet oxy, dai 3,1 eV lien quan den sai hong mang Cucmg dp cac dinh 3,33 eV va 3,38 eV giam manh nhiet dp de tang tir 425 "C len 500 "C Ca che huynh quang ling vdi dinh 3,33 eV la chuyen dai dien tir tir viing dan den acceptor va ling vai dinh 3,38 eV la chuyen dai cap donor - acceptor 1.4 Tinh chat dien Sn02 la vat lieu co tfnh dan dien tot, dupe ling dung rat nhieu vao viec che tao cac dien cue Khi pha tap Sb hoac F vao thi tfnh cha't dien ciia mang Sn02: Sb va Sn02: F thay doi va phu thuoc ra't nhieu vao cac cong nghe tao mang, nong dp tap cha't dua vao, che dp tao mang Dp day mang tang len thi dien tra ciia mang giam va dat den mot gia tri gi6i han Dien tra ciia mang giam theo nong dp tap Sb va dat mot gia tri cue tieu Khi nhiet dp de qua trinh tao mang thay doi thi dien tra ciia mang ciing thay doi Ham so bieu di6n sir phu thuoc ciia dien tra vao nhiet dp de se qua mot gia tri cue tieu PHAN KY THUAT THlTC NGHIEM 2.1 Tao mang b^ng phuang phap phun tinh dien Cac mang Sn02 va Sn02: F, Sn02: Sb dupe che tao bang phuang phap phun tinh dien, sa d6 he phun tinh dien dupe mo phong tren hinh Nguon dot ^ ^ ^ ^ ^ ^ De Kim phun u > Dung dich tao miu 19 kV Van dieu chinh Hinh Sa he phun tinh dien Dung dich diing de tao mang dupe dua vao xylanh, qua ong truyen den dau kim phun Kim phun lam bang thep khong gi, dupe noi vdi cue duang (+) ciia ngu6n cao ap 18 kV Diem co dien the bang ciia nguon cao ap (v6 may) dupe noi vai be mat cua nguon nhiet dupe lam bang thep khong gi Tren be mat CO gan mot he thong ga mSu de giu cac de lamen qua trinh phun mang De dupe dot nong bang mot nguon nhiet dien Nhiet dp ciia ngu6n dupe giu on dinh bang bp khong che nhiet dp Khi nhiet dp de dat tai gia tri dinh truac va dupe giiJ on dinh, nguon cao the se dupe bat len Duoi tac dung cua dien truong sinh bai nguon 18 kV, dung dich dupe phun len de lamen da duac dot nong Khoang each giua de va dau kim phun co the dieu chinh de chpn dupe che toi iru cho viec tao mang Dung dich diing de phun dupe tao tir cac hoa chat SnCU SH^O va NH4F vai cac dung moi la tuyet doi, a xit HCl va nuac ca't Diing SnCl4 5H2O hoa H2O va c6n co cho them HCl se tao dupe dung dich khong tap de phun mang Sn02 Muon co mang Sn02: Sb, can phai tao them dung dich tir SbCl^ hoa tan Trpn deu dung dich tren theo ty le DAI HOC QUOC GIA HA NOI TRirc3NG DAI HOC KHOA HOC Tl/NHIEN *+* LE DUY KHANH NGHIEN Ctru TINH CHAT CUA MANG BAN DAN Sn02 Chuyen nganh: Vat ly Ban dlin va Dien moi Ma so 1.02.12 LUAN VAN THAC SI KHOA HOC NGirdl HUCING DAN KHOA HOC TS Le Thi Thanh Binh HA NOI -2004 DAI HOC OLOC GIA HA NOI TRLONG DAI HOC KHOA HOC TUNHIEN KHOA VAT LY Ho Xuan Huong CHE TAO VA NGHIEN ClTU MANG SnO, VA SnO,:F BANG PHUONG PHAP PHUN TINH DIEN KHOA LUAN TOT NGHIEP HE DAI HOC CHINH QUY Nganh: Khoa hpc Vat heu Can bo huang dan: TS LE THI THANH BINH Can bo phan bien; PCS TS LE HONG HA HA NO! -2004 « DAI HOC QUOC GIA HA NOI TRC5NG DAI HOC KHOA HOC TUNHIEN KHOA VAT LY *-Jằ*J^WI-irf 1- ã j l-SI f>J w ằãô Pham Van Hoan NGHIEN c t r u TINH CHAT DIEN VA QUANG CUA MANG Sn02 VA Sn02:Sb CHE TAO BANG PHUONG PHAP PHUN TINH DIEN KHOA LUAN TOT NGHIEP HE DAI HOC CHINH QUY Nganh: Khoa hoc Vat lieu Can bo huong din: TS Le Thi Thanh Binh Ha noi - 2004 Association of Asia Pacific Physical Societies (AAPPS) •Ministry of Science and Teciinology (MOST) Vietnamese Academy of Science and Technology (VAST) Vietnam Physical Society (VPS) [DQ[DQ)Q°2[D(D^ w w u m T f T w ^ *ui'ji»iwpifpi'ijw» i'yi'>l m < i » y i ,-•-iip^iWTniiiiiwmyiLiMiitffi^Kiti • t^w^sv»wi\m%* ijwwir* ^r-im •, J "-ptjij^jW'gHw^wg'i'Wtfi i Hanoi, %tnam, October 25^1,2004 'X^- -I^ ft£ i T****## ^-t^iu f Mcifft; j"»KJ*t-J v>t/yfcy^nC€ ty AJ ITv^) The effect of deposition conditions on physical properties of SnOi: Sb films received by ESD Le Duy Khanh*, Le Thi Thanh Binh, Nguyen Ngoc Long Nguyen Thanh Binh Faculty of Physics, Ha noi University of Science, 334 NguyenTrai Str., Thanh Xuan, Ha Noi, Viet Nam Abstract: The Sn02:Sb films was received by electrostatic spray deposition All the films were deposited on glass substrate at the optimized temperature of 410 °C The films are polycrystalline in nature with tetragonal crystal structure Electrical and optical properties of the films have been studied as fiinctions of antimony doping concentration and deposition time The Sb doping concentration was varied in the range of 04-9% The deposition time was varied fi-om to 20 The resistivity of the films was found to decrease fi-om 10 Qcm for the film deposited in to IQcm for the film deposited in 14 The resistivity of the films achieved minimum value Qcm for lat.% of Sb doping The average transmittance in the visible range was found to be 85% and 25% for undoped and doped films respectively The emission and excitation spectra of the films were investigated in the temperature range of 14H-320 K The dominant emissions are situated at 370 nm, 394 nm, 450 nm and 540 nm It was found that these peaks are due to the concentration of oxygen vacancies and are related to structural defect The excitation spectra for 370 nm and 390 nm emission peaks behaved similarly There are two peaks 320 nm and 334 nm in these excitation spectra They are due to band to acceptor and the surface absorption in the films respectively • Email: ichanhld@vnu.edu.vn 223 nt i'suy n A » I A rAi^ir n^ PHYSICS CONFERENCE (9*** APPC) Hanoi, Vietnam - October 25-31, 2004 Conference Venue: Ho Chi Minh Museum, Naoc Ha Str All-Optical Poling of Dye Molecules in Polymer Films 2D and 3D Characterization Nguyen Thi Kim Ngan and Michel Dumont 212 Investigation of Magnetic and Optical Properties of Zni.,Co,0 Powder Prepared by SolGel Process Nguyen Thi Thue Hien, Nguyen Hanh, Huynh Dang Chinh, Le Thi Quy, Le Van Vu, and Ngo Xuan Dai 213 Structure and Optical Properties of ZnO Films Prepared by RF Magnetron Sputtering Method Nguyen Thi Thuy Lieu, Nguyen Xuan Nghia, Nguyen Phuong Thai, Ta Dinh Canh, Nguyen Duy Phuong 214 Synthesis and Characterization of Nano-TiO: Powder Pham Thi Minh Chau and Ung Thi Dieu Thuy 215 Study of Random Lasers from Some Luminophors Tran Thi Kim Chi, Vuong Duong Nguyen, Nguyen Quang Liem and Do Xuan Thanh 216 Characterization of OSL from Natural Quartz Using The CVV - OSL and LM - OSL Techniques Tran Ngoc, Nguyen Manh Son, Vu Xuan Quang 217 Preparation and Optical Properties of Y.-xEr.TizOT Thin Films Used Sol Gel Method Tran Thu Huong, Tran Kim Anh and Le Quoc Minh 218 Visible Photoluminescence from Silicon Nanocrystais in Plannar Microcavities V.V Thu, P.T Huy, and N.D Chien 219 Spectroscopic and Optical Characterization of Erbium-Activated Silica-Alumina Glasses N.V Long, N.D Chien, D.T.X Thao, V.T Lam, P.T Nga, P.N Thang 220 Synthesis of ZnO Nanostructures by a Simple Thermal Evaporation Method Ngac An Bang, Nguyen Ngoc Long, Le Hong Ha, Trinh Thi Loan 221 Anatase Titanium Dioxide: Nanopowders and Doping Transparence Thin Films Cao Xuan Thang, Trinh Ngoc Ha, Pham Thu Nga, Pham Van Thiem, Ngo Ngoc Toan, Nguyen The Khoi, Pham Nam Thang 222 The Effect of Deposition Conditions on Physical Properties of SflOitSb Films Received by ESD Le Duy Khanh, Le Thi Thanh Binh, Nguyen Ngoc Long, Nguyen Thanh Binh 223 Fabrication and Characterization of Sputtered undoped and Cobalt-doped Zinc Oxide Thin Films Ta Dinh Canh, Nguyen Ngoc Long, Nguyen Duy Phuong, Pham Nguyen Hai, Dam Hieu Chi, Ngo Thu Huong, Nguyen Thi Thuy Lieu, Nguyen Xuan Thai and Nguyen Xuan Nghia 224 Importance of Chromophore Environment on the Propagation of Laser Light in Polymer Matrices Tran Hong Nhung, Michael Canva, Helene Goudket, EaKim Buntha, Vu Thi Thuy Duong 225 Tunable Diode Laser based on the External Cavity Applied to Research Aerosol Size of the Wavelength Tran Thi Phuc, Pham Vu Thinh 226 Hanoi, Vietnam - October 25-31 2004 THE EFFECT OF DEPOSITION CONDITIONS ON PHYSICAL PROPERTIES OF SnOz: Sb FILMS RECEIVED BY ESD Le Duy Khanh\ Le Thi Thanh Binh, Nguyen Ngoc Long, Nguyen ThanhBinh^ Faculty of Physics, Hanoi University of Science, Vietnam National University 334 Nguyen Trai str, Thanh Xuan district, Hanoi, Vietnam ABSTRACT: The SnO:: Sb films were received by electrostatic spray deposition (ESD) method Optical properties of the films have been studied as a function offilm thickness The emission and excitation spectra of thefilmswere investigated in the temperature range of 14 K ^ 320 K INTRODUCTION Tin dioxide (SnOj), an n - type semiconductor with a wide band gap (Eg = 3.6 eV at 300 K), is well known for its potential applications in gas sensors, transparent conducting electrodes The studies of the optical properties of undoped and doped Sn02 are very important for device application This paper reports the effect of film thickness on optical properties of SnOi: Sb films received by ESD EXPERIMENTS The SnO?: Sb films were deposited on glass substrates at the optimized temperature of 410 °C The Sb doping concentration was varied in the range of -^ at.% The deposition time was varied from to 20 The absoiption and transmission spectra were recorded by an UV VIS spectrophotometer UV 3101 PC The photoluminescence (PL) and photoluminescence excitation spectra were recorded by spectrofiuometer FL3-22 DISCUSSION The transmittance spectra as the functions of the wavelength in the range 200 - 800 nm for SnOi: Sb films show that the transmittance (T) of the films is remarkably decreased with increasing films thickness Fig shows the transmittance of the Sn02: Sb films at 500 nm and 800 nm as a function of films thickness The transmittance dependence on films thickness obeys the Bouger - Lambert law: T = exp(-arf) 2000 3OO0 Thickness d (nm) Fig I Transmittance dependence on thickness of the SnO:: Sb films k = 500 nm 2-A = 800 nm It was found from these curves that absorption coefficient a = 7.37-10^(c/n'')and a = 6.93 • 10^ ( c w ' ' ) at wavelength 500 nm and 800 nm, respectively Fig shows the absorption spectra of SnO:: Sb films All these curves have a peak in the ultraviolet range The nature of these peaks can be attributed to the surface absorption because the energy of absorption peaks is always higher than that of band gap Eg of Sn02: Sb films The more detail investigation of this absorption peaks is shown in Fig It was found that the peak position E^b depends on thickness d of films In order to try to observe the influence of the film thickness on the optical absorption, we have compared the curve Eab(d) with :4752nm :2397nm Wavelength (nm) Fig Absorption spectra of SnO:: Sb films 'Email: khanhld@vnu.edu.vn; nguyenbinhfg)vnu.edu.vn The Ninth Asia Pacific Physics Conference (9'^ APPC) the curve Ey(d) The values of Eg were determined from absorption spectra a{hv) investigation samples, thea{hy) curve followed the relation: For all a(/7l/)=^(/3V-£j'2 44- The band gap obtained from the plot of (ahv) vs hv for the films with at.% doping Sb varies from 3.49 eV to 3.76 eV As the Sn02: Sb film thickness increases, the band gap energy of the films decreases due to a decrease of the strain effect [1] As can be seen from Fig 3, the position of the absorption peaks shifts to the lower energy side with increasing film thickness in the same way as band gap energy does This means that the thickness affects not only the band gap of the film, but also the film absorption A similar behavior was observed by H L Ma et al [2] Since the PL excitation can be used as a method to determine absorption characteristics of the material, the PL and PL excitation spectra of the film were investigated in the temperature range from 14 K to 300 K Fig shows the typical excitation and emission spectra of SnO:: Sb at.% films with thickness of 2397 nm The PL spectra present four bands at 370 nm (3.35 eV), 394 nm (3.14 eV), 450 nm (2.76 eV) and 540 nm (2.3 eV) All the emission maxima are lower than the band gap of the SnO:: Sb films According to [3], the origin of luminescence 393 nm and 450 nm can be assigned to the recombination of electrons in singly occupied oxygen vacancies with photoexcited holes in the valence band The peak at 540 nm due to 42- V ^'^^^^——_ h m' ^ 38- c ^ V 36- ~'~'~' • J.4- • • 2000 Thickness d (nm) Fig The thickness film dependence of the band gap energy (a) and the absorption peak energy (b) of SnO:: Sb films 540 0x10' 140 K 230 K 320 K 300 350 400 450 500 550 Wavelength (nm) Fig a- PL excitation spectra of SnO:: Sbfilm b- PL spectra of SnO:: Sbfilm oxygen vacancies and the peak at 370 nm are related to the impurity [4] The excitation spectra for the emission peak ^em ~ 370 nm show two maxima at 320 nm (3.87 eV) and 334 nm (3.71 eV) These energies are higher than band gap Ej, = 3.56 eV, so they also can be attributed to the surface absorption These results suggest that the states near the surface of the film play an important role in the luminescence CONCLUSIONS The SnO:: Sb films were prepared by ESD method The absorption coefficient in SnO^: Sb exceeds 10"* cm"' in the visible and infrared regions The band gap energy of the films and the energy of the surface absorption peak decreases with increasing film thickness The surface absorption of the film plays an important role in the luminescence ACKNOWLEDGEMENT This work was supported by project QT 08 03 REFERENCES [1] 12] [3] 14] T W Kim etai, J Phys Chem Sol 6^ (2002) 881 - 885 H L Ma^/a/ App! Surf Sci 191 (2002)313-318 F Gu et at., Chem Phys Lett 372 (2003) 451 - 454 J Jeong et al Sol Stat Comm 127 (2003) 595 - 597 i misLii I November 27-28, 2004 Hanoi, Vietnam •" ri i -t^^^/ i IEEE COMMUNICATIONS SOCIETY ^ / '""^ ^lEEE EB m a Raiiki fieeiranics assaclaUan M Vtahiam (REVl REV04 SESSIONS Session Number Title SESSION WIRELESS COMMUNICATIONS 25- 1-79 SESSION CODING 80- r 124 SESSION ANTENNA AND PROPAGATION 125- - 182 SESSION NETWORK AND OPTICAL COMMUNICATIONS 183- -219 SESSION ELECTRONIC DESIGN 220- -250 SESSION IMAGE AND AUDIO PROCESSING 251 295 SESSION CONTROL 296- -322 SESSION 8A ELECTRONIC MATERIAL 323- -360 SESSION 8B ELECTRONIC MATERIAL 361- -409 Page Electrical and Optical properties of Electrostatic Spray Deposition SnO:: Sb thin films L.D.Khanh, L.T.T.Binh, N.T.Binh and N.N.Long Faculty of Physics, Hanoi University of Science, Vietnam National University 334 Nguyen trai, Thanh Xuan, Hanoi, Vietnam Abstract: Electrical and Optical properties of the Electrostatic Spray Deposition (EDS) antimony (Sb) doped tin dioxide {Sn02) thin films, prepared from SnCl4.5H20 and SbCl3 are presented The doping concentration was varied from - at % of Sb The transmittance and absorption spectra were recorded in the wavelength from 300 nm to 800 nm The band gap energy calculated from optical absorption spectra was 3.8 eV The grain size around 0.3 - 0.4 ^m was found from SEM picture The resistivity p measured by four - point probe method Introduction Tin dioxide SnO? is an n type semiconductor with a wide band gap {E^= 3.6 eV at 300 K) [2] These films can have excellent photoelectric properties Pure and doped Sn02 thin film deposited on glass substrates are used on glass windows for energy conservation and as electrodes in thin film photovoltaic solar cells Due to their technological importance, many researchers have reported the growth techniques properties of Sn02 films In this paper we report a investigation of structural, electrical and optical properties of antimony doped tin dioxide films prepare by the Electrostatic Spray Deposition technique Experiments The films of Sn02 and Sn02: Sb were deposited by Electrostatic Spray Deposition (EDS) technique The schematic of the experiment set up used in the study is shown in Fig.l A high DC the voltage (around 19 KV) was applied between the substrate plate and the capillary stainless steel nozzle The distance from the nozzle to the substrate was kept at cm The DC voltage applied between the nozzle and plate generates a spray and the electrostatic force makes it move towards the heated substrate, which is put on the electrical conductive plate Heater " ^ ^" "^ ^ " -" Substrate Cylinder Nozzle- Solution u IQlcV _ Silicone tube h ControUed valve Figure Schematic diagram of the ESD setup Substrates were glass plates of 22 x 22 X 0.1 mm in size The substrate temperature was kept at 410^ C The spraying solution of 0.25M/1 stannic chloride (SnCL, 5H2O) was dissolved in a mixed solvent consisting of double distilled water and hydrochloric acid (HCl) To achieve Sb doping, antimony tri-chloride (SbCU) was dissolved in isopropyi alcohol and added to the precursor solution The doping ratio for the films was Sb/SnOj = ^ at % The structure and lattice parameters of thin films were analyzed by the SIMENS D5005 diffractometer The surface morphology and thickness were measured by the Scanning Electron Microscope JEOL 5410VL The optical transmittance spectra were recorded by the specu-ophotometer UV-VIS-3101 The sheet resistivity of the SnOz films was measured by using four-point probes method Page 391 I Results and discussion 3.L Structural properties yMJ-HN-SEMGNS O5C05 - Mau Sn03 - 7phm Td = 41 OC -^/^wvyw, -\^4v^^f^;^ • * I ' ' * ' f ' • ' • • — ' ' • • Figure X - Ray diffraction pattern of Sn02 film deposited at 410'^ C The X-ray diffraction measurements of sprayed Sn02 films showed that all of the films were polycrystalline in nature Fig.2 shows a typical X-ray diffraction pattern of SnO: film From the values of inter-planar spacing d measured on XRD pattern, the lattice parameters were calculated It is found that for Sn02 films a = 4.703 i and c = 3.169 A Figure SEM image of surface of SnOj: Sb (2 at %) films at T = 410'' C a - Surface sectional view b- Cross - sectional view Fig.3a shows the scanning electron micrograph of the SnO:: Sb film The average grain size of all doped films are around 0.3 - 0.4 |am No systematic change in grain size with doping concentration has been observed From the cross-section image of this film it is evident that the thickness of the film is about ^m (Fig.3b) 3.2 Optical properties The optical transmittance of the films with different doping concentration was recorded at the room temperature The transmittance spectra were investigated in the range of wavelength from 300 nm to 800 nm The transmittance coefficient decreases from 85 % to 35 % when the doping increases The color of the films varied from grayish white for undoped Sn02 to blackish blue beyond at.% Sb (Fig 4, ) Page 392 •' I • I » I • I • T ^ 300 350 400 450 500 550 600 650 700 750 800 850 500 600 700 Buac song (nm) Wavelength (nm) Figure Transmittance spectrum of SnO^ at 410" C - 15 Figure Transmittance spectrum of SnO, at 7% T = 410" C - 15 22 20-1 18 16-1 14 12^ 10 864 2-1 kv (eV) Figure 5a TTie photon energy dependence of (ah vf for SnO, (T=410"C-15min)film " 0.0 0.5 — ^ 1.0 1.5 /iv(eV) 2.0 2.5 3.0 3.5 4.0 4.5 ^'S"'" ^^ ' ^ ^ P^°T, "''^'^'^ dependence of {all vf for SnO, ^^^^^^ C-7 mm) film The typical plot of the {ahvf versus photon energy hv'xs shown in Fig.5(a, b) As it can be seen from these figures, the absorption edge the plot {ah v)" versus hv is a straight line, at which means that the absorption coefficient a of the films obeys the relation: ahv^A(hv£g)''^(I) where £g is the energy band gap, A '\s ^ parameter independent of h v Such as behaviour indicates that optical transitions in the SnO^: Sb films are direct 3.3 Electrical properties The Van der Pauw technique was used to measure the surface resistivity of the film [4] The deposition time (/) dependence of resistivity for the SnOi Sb films is illustrated in Fig.6 It can be seen that as / increases from to 15 min, the resistivity decreases from 10.5 Qcm to Qcm As t further increases, an opposite behavior occurs When the deposition time increases, the thickness of the film increases and subsequently the substitutional doping increases, resulting in an increase of the carrier concentration and so the resistivity reduces When the film was kept at high temperature for a long Page 393 deposition time for / > 15 min, SnO in the film wiil be more decomposed to SnO:, so the concentration of oxygen vacancy will be reduced, that increases the resistivity of the films 16 14 ? 6- 12-1 c ^ 1o^ E I '^ S >, •| S 4-1 £ - 2-1 5- I ' T ' r"^ r- 10 12 16 18 20 22 Time (min) Figure Sheet resistance of SnO,: Sb thm film as a function of the deposition time — I • 1 ' 1— Sb conccntratiun (ar.%) Figure Sheet resistance of Sn02: Sb thin t~ilm as a function of the Sb concentration The variation in resistivity of the film with Sb concentration is plotted in Fig.7 The variation in the sheet resistance of tin oxide thin films with antimony doping can be explained on the basis of the presence of Sb in two oxidation states, namely Sb^*" and Sb^"^ The possible mechanism may be as follow When SnO: is doped with Sb, a part of the lattice Sn^"^ atoms are replayed by Sb^"" ions resulting in the generation of conduction electrons and thus reducing the sheet resistance It is why a continuous decreases of sheet resistance is observed until Sb concentration < at % Beyond I at % of Sb concentration, the sheet resistance is observed to increase again (Fig 7) This because beyond I at % of Sb doping, a part of the Sb^* ions reduces to the Sb"**" state resulting in the formation of acceptor sites and concomitant loss of carriers The reduction of Sb^^ to Sb"^* has been verified by Kojima et aj [5] by an estimation of the lattice parameter of the doped Sn02 films As the ionic radius of Sn"** is less than that of Sb"^*, an increases in the lattice parameter of Sn02 phase is observed beyond at % of Sb doping This reduction of Sb^"*" to Sb^^can be the reason of the increase in sheet resistance above an optimum level of Sb doping [6,7] Conclusion Polycrystalline SnO: and SnO:: Sb films have been prepared by Electrostatic Spray Deposition technique From X - ray analysis the lattice parameters of the Sn02 films were calculated a = 4.703 A and c = 3.169/f The average grain size of all doped films around 0.3 |am The energy gap £g of the SnO: film is 3.8 eV and of SnO:: Sb film is 3.5 eV The curves of the resistivity dependence on the deposition time and the doping concentration for SnO:: Sb films were investigated Acknowledgment The authors would like to thank Dr Le Van Vu for X-ray measurements and for taking the SEN4 micrographs Reference [11 Xiaotao Hao et al, Applied Surface Science 189 (2002) 157-161 [2] J.Q.Hu et at, J Phys Chem B 2002 106, 3823-3826 [3] Le Duy KJianh, Le Thi Thanh Binh, Nguyen Thanh Binh, Nguyen Ngoc Long, to be published in the Proceedings of the 3''' National Conference on Optic & Spectroscopy (Nha Trang, August 11 -15/2002) [4] Electrical Properties of Materials, L Solymarand D Walsh, sixth Edition, Oxford University Press 1988 Page 394 [5] M Kojima, H Kato M Gatto Phil Mag B 68, 215 (1993) [6] E Elangovan, K Ramamurthi, Cryst Res Technol 38, No 9, 779 - 784 (2003 j [7] C Terrier J.P Chatelon J.A.Roger, Thin Solid Films 295 (1997) 95 - 100 Page 395