BO GIAO DUG VA OAO TAO DAI HOC QUOC GIA HA N O I TRLTCJNG DAI HOC KHOA HOC TlTNHIEN -oOo- Le Thi Thanh Birth Che tao va nghien cihi mot so tinh chat cua cac mang mong ban dSn dung dich ran A B Chuyen nganh: Vat ly Dien tijf J LUAN AN PHO TIEN SI KHOA HOC TOAN - LY NGUdl HU^6NG DAN KHOA HOC l.GSPTSLeKhacBinh PGS PTS Nguyen Ngoc Long O C r O N ' - '-:••:)'• MAf.OI; HA NOI -1996 MUC LUC Mord^u Chirang CAC HOP CHAT BAN DAN ZnS, CdS vA CAC DUNG DICH RAN BAN DAN Zn,Cd,.,S 1.1 Cft'u true dnh thi cua ZnS va CdS 5 1.1.1 CS^u tnic mang lap phuong gia kem 1.1.2 C^u tnic mang luc gidc Wurtzite 1.1.3 Mang tinh the ZnS va CdS 1.2 Ca'u tnic vising nSng lupng cua ZnS va CdS 10 1.2.1 Ca'u tnic viing nang lupng ciia mang I^p phuong 1.2.2 Ca'u true virng nang lupng cua mang luc giac Wurtzite 1.2.3 Viing nang lupng cua ZnS va CdS 1.3 Tinh ch^t h^p thu ciia ban dSn 1.3.1 Khai niem chung 1.3.2 Ha'p thu chuyin ddi thang 1.3.3 Ha'p thu chuyin ddi nghieng 1.4 Cac cach^'phat huynh quang ban dan 1.4.1 1.4.2 1.4.3 1.4.4 1.4.5 1.4.6 Khai niem chung Mo hinh tpa dp cau hinh Tai hop viing - viing Tai hop buc xa qua cac trang thai exciton Chuyin ddi vung - tap ch^t Chuyin ddi done - axepto 1.5 Mdt s6 phuong phap ch^'tao tinh thi va mang dung dich thi 1.5.1 Cdc phuong phap klo dan tinh the 1.5.2 Cac phuong phap che tao mang dung dich ran 10 12 13 15 15 17 18 20 20 21 25 28 33 35 37 37 38 1.6 T6ng quan v^ dung dich ran Zn^^Cdi.j^S 39 1.7 K6t luan 41 Chirang KY THUAT THl/C NGHIEM 43 2.1 He tao mang 43 2.1.1 L6 2.1.2 Bpgamau 2.1.3 He thdng vdi phun, nen 44 44 45 2.2 Ha bdc bay chan kh6ng 45 2.2.1 Bom chan khdng 2.2.2 Buong hoc bay 2.2.3 Ngudn bdc bay 2.2.4 D^bdc bay 45 45 47 47 2.3 H e phd huynh quang va phd truyen qua 47 2.3.1 H e phd huynh quang 2.3.2 H e ph6 truyen qua 2.3.3 Cac phep khac 47 50 51 2.4 K ^ luan Chuong3 CHE TAO VA NGHIEN 51 CLTU CAU TRUC CUA M A N G Zn^Cd,.,S 53 3.1 Tao mang Zn^^Cdj.^S bang phuong phap phun dung dich len de'ndng 53 3.2 Anh hudng cua nhiet dd d^d^n ch^t lupng m^ng 55 3.3 Ch^d6 u mang 60 3.4 Che^dOphatap 61 3.4.1 Phuong phap nhiing mang vao dung dich mudi tapcha'trdi ii d nhiet dp cao 61 3.4.2 Phuong phap hda dung dich mudi tap chat cung vao dung dich phun nen 63 3.5 Tao dien cue sudt Sn02 va l^m dien cue ohmic len mang Zn^^Cdi.^^S 66 3.6 Che'tao mau Zn^Cd^.^S bang phuong phap diing Id vi song 68 3.7 Ph6 nhilu xa tia X ciia mtlng Zn^Cdi.,S 70 3.8 Anh bfe mat cac mang Zn^Cd^^^S chup bang kinh hiln vi dien tu 73 3.9 K a luan 75 Chirang TINH CHAT QUANG vA HUYNH QUANG CUA M A N G Zn.Cdi KHONG PHA TAP ,S 78 4.1 Tfnh cha't quang cua mang Zn^Cd].xS 78 4.1.1 Ph6 hSp thu cua mang Zn.Cdi.^S 4.1.2 X^c dinh d6 r6ng viing ca'm cua cac mang Zn^^Cdi.^S 4.2 Huynh quang ciia cdc mang Zn^Cdi.^S khdng pha tap 78 80 82 4.2.1 Dang phd huynh quang 4.2.2 Su phu thudc ciia dinh ph6 huynh quang theo phan x 4.2.3 Pho huynh quang phan giai thai gian, su phu thupc ciia huynh quang v^o cudng dd kich thich Thdi gian sdng huynh quang 4.2.4 Anh hudng ciia che'dd li nhiet len huynh quang ciia mang Zn^Cdj.^S 4.2.5 Su phu thudc nhiet dd cua ph6 huynh quang cua cac mang Zn^Cdj.^S 83 86 87 91 92 4.2.6 Co che' biic xa cap dono - axepto phd huynh quang cua mang Zn^Cdi.^S khdng pha tap 4.2.7 Hien tupng quang hda ciia mang Zn^Cd,,^S 4.3 K^ luan 94 99 105 Chirang HUYNH QUANG CUA CAC M A N G ZnxCd,.xS PHA TAP Cu VA Mn 106 5.1 Phd huynh quang ciia m ^ g Zn^Cdi^^S : Cu 5.1.1 Dang huynh quang Anh hudng cua sir pha lap ddng len huynh quang 5.1.2 Ph6 huynh quang cua mang Zn^Cdj ^SiCu vdi cac thdng sd phan x khac = 5.1.3 Ph6 huynh quang cua mang Zn^^Cdi.^S : Cu kich thfch lien tuc vdi cac cudng dp khac va a cac nhiel khac 5.1.4 Ca che' biic xa ciia dai sdng dai phd huynh quang cua mang Zn^Cd,.^S:Cu 5.1.5 Tach ph6 huynh quang 5.2 Phd huynh quang ciia mang Zn^Cdi^^S : Mn 5.2.1 Dang phd huynh quang Anh hudng ciia su pha tap len ph6 huynh quang 5.2.2 Pho huynh quang ciia mang Zn^Cdi.^S : Mn vdi cac thong sd phan x khac 5.2.3 Sir phu ihupc cudng dp kich thfch va nhiet dp cua 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giua cac nguyen tit trong hai loai mang tinh the bang nhau Lien ket hda hpc ciia cac nguyen tut trong hai loai mang tinh the cung nhu nhau Chi cd su khac nhau cua trudng tinh the va vhng Brillouin gay ra su khac biet trong the nang tac dung len dien tu Bang phuang phap... mot khoang thanh phan nao dd Gidi ban cua khoang nay dupe xac dinh bang phuang phap tao tinh the va phu thupc vao ndng dp tap chat Trong mien chuyen tiep tii mang nay sang mang khac thi mang tinh the dung dich ran cd the d dang hdn hop hai pha hoac cau tnic hdn don vdi cac gia tri sai hong Idn Tac gia [14] nghien cuti su chuyin pha trong he Zn^Cd^.^S da chi ra rang str chuyen pha trong mang tinh the... Hang so mang Hop chat Lap phuong gid kem a (A ) ZnS ZnS CdS CdS 5,4145 5,832 Luc giac Wurtzite a(A°) c(A°) 3,8230 6,2565 4,1348 6,7490 Bang I Cac thong sd mang cua ZnS va CdS [10] 1.1.3,3 ZnjCdi_j^ Trong dung dich ran, su xuat hien sai hong mang cd the la do sir thay the mot loai nguyen tu nay bang mot loai nguyen tuf khac Neu hai chat ban dau cd cau tnic khac nhau thi cd su chuyen cau tnic tiif trang... hinh 8 la sa dd viing nang lupng cua ZnS va CdS dudi dang tinh the lap phuang Khe nang lupng giua cac diem ddi xiing trong viing nang lupng ciia 14 ZnS va CdS cd the tham khao trong [14] Khdi lupng hieu dung cua dien tu d Ian can day viing din va cua Id trong d lan can dinh vung hda tri ciia tinh thi ZnS va CdS theo tinh toan ly thuyet va thuc nghiem cd the tham khao trong [6] 1.3 Tinh chat hap thu ciia... lupng tap chit dupe chuyin ddn viing din hoac dien tu tir viing hda tri dupe chuyen len miic nang lupng tap chat 3 - Hip thu bdi cac hat tai dien tu do xay ra khi cac hat tai nay chuyen dpng dudi tac dung ciia dien trudng sdng anh sang 4- Hip thu bdi dao dpng mang xiy ra khi anh sang tuang tac vdi dao dpng mang lam thay ddi sd phonon quang hpc 5 - Hip thu exciton xay ra ddng thai vdi su hinh thanh... C —> DA: Tai hop dien tuf tu do - axepto sau; D —> A: Tai hpp cap dono - axepto 1.4.2 Mo hinh toa do cau hinh De giai thfch cac qua trinh huynh quang cd su tham gia cua cac tam sau, ngudi ta thudng su dung md hinh tpa dp cau hinh trong dd cd tinh den su tuang tie manh 21 vdi nhieu phonon Cac ca sd tinh toan ly thuyet mat dp trang thai, xac suit chuyen doi dien tii, tiet dien hip thu, phan bd nang lupng... = E^ - SJiv, (12) hv.i, = E, + S,hv, (13) trong dd hv^ va hv la nang lupng phonon d trang thai kich thfch va trang thai co ban Sa va Se la so phonon trung binh phat ra trong khi hap thu va birc xa Sir dung md hinh tpa dp ciu hinh, nguyen tic Frank - Condon va mot sd gia thiet gan diing, cd the tfnh dupe pho huynh quang cd dang Gauss, bieu diln bdi ham [6]: I(hv)-I,exp (hv-bvj2a^ (14) vdi IQ = — j =... dinh dai pho ling vdi nang luong hv^; a - thiet dien hip thu Dai luong a !i6n he vdfi binh phucmg ban do rong dai pho W qua cong thiii W^ = o^81n2 23 (15) Mdt trong nhung ket qua quan trpng ciia vi6c ap dung md hinh tpa dp ciu hinh la tinh dupe su phu thupc cua ban dp rpng dai phd vao nhiet dp |6J: trong do: W(o) - ban dp rpng tai T = 0 K Ve - tan sd dao dpng mang Ct 1 f\\ trrt Vv n\^rtno i i i i L i... nghia la a nhiet dd cao, W(T) thay ddi tuyen ii'nh theo T Mo hinh tpa dp ciu hinh dac biet thfch hpp dl giai thich cac tfnh chit ciia cac tam tap sau cd miic dp dinh xir cao Md hinh nay cung da dupe irng dung de mo ti cac tam tap chit kem dinh xii: ban trong mdt loat cac chit ban din nhu ZnS, CdS, Gap, GaAs Cac ket qui cho thiy phan idn cac dai phd deu cd ban dp rdng phu thudc vao nhiet dp nhu c6ng thiie... nhan xet, de giai thich sir phu thupc vao nhiet dp thi cong thiic hv 1n O day B la hang sd tim dupe bang each ngoai suy cac gia tri d nhiet dp cao khi T->0K Ddi vdi cac tam rit ndng, ngudi ta thudng su dung md hinh do neKapB de xudng, trong do true tiep khio sat tuang tic giufa cac trang thai di6n tu ciia tam tap chit va trang thai dao ddng phonon ciia mang tinh the ca sd Tuy nhien ket qui nhan dupe ... din D l nhan dupe mang dung dich ran ban dan thi vat lieu bdc bay cd thi chinh la dung dich ran hoac cac hpp chit ban din phan cua dung dich Su bdc bay vat lieu xay dudi tic dung ciia nhiet dp Nhiet... dd mang dung dich ran ban din Thanh phan cua mang d l dang thay ddi va dupe xac dinh bdi tuong quan giiia cac phan hpp chit tdn tai dung dich Khf nen dung d l tao ap suit d diu vdi phun dung dich... 1.6, Tdng quan ve dung dich ran Zn^Cd^xS Nhfeu tic gia tren the gidi da quan tim d6*n viec ch^ tao, nghien ciiu va ling 39 dung dung dich ran ban din ZnxCdi.^S Dl nhan dupe dung dich rin ban