35 5 214 5 CHINESE JOURNAL OF LUMINESCENCE Vol. 35 No. 5 May 214 1-732 214 5-526-5 Ⅱ-Ⅵ ZnO /ZnMgO * 3615 Zn 1 - x Mg x O x =. 4 ~. 6 c ZnO /ZnMgO Ⅱ-Ⅵ X X MgZnO ZnO Ⅱ-Ⅵ O484. 4 A DOI 1. 3788 /fgxb214355. 526 Phase Segregation of ZnO / ZnMgO Superlattice Affected by Ⅱ-Ⅵ Ratio WANG Hao ZHAN Hua-han * CHEN Xiao-hang ZHOU Ying-hui WANG Hui-qiong KANG Jun-yong Department of Physics Xiamen University Xiamen 3615 China * Corresponding Author E-mail huahan@ xmu. edu. cn Abstract ZnMgO alloy allows for tunable optoelectronic devices. However the compositional range between ZnO and MgO is interrupted by a crystalline miscibility gap where the wurtzite crystal structure of ZnO is structurally incompatible with the rocksalt structure of MgO. In this article ten periods of ZnO / ZnMgO superlattice were produced by plasma-assistant molecular beam epitaxy on c- plane sapphire substrate with different oxygen condition. It is found that the sample grown at lower oxygen flow and radio-frenquency RF plasma power tends to form rocksalt phase. With the increase of oxygen flow and RF plasma power wurtzite phase tends to dominate and phase segregation is enhanced. The phase transform affected by the oxygen atoms density is reasoned by the formation enthalpies of ZnO and MgO. Key words MgZnO ZnO superlattice Ⅱ-Ⅵ ratio phase segregation 1 GaN ZnO ZnO MgO ZnO 3. 37 ev ZnO 214-1-7 214-1-27 617684
5 Ⅱ-Ⅵ ZnO /ZnMgO 527 AFM MgO ZnO Varian Cary 3 - Mg. 4 ~. 6 2 ~ 8 nm ZnMgO PHI PHI 5C ESCA System MgO ZnO X XPS 45% 1 C 1s 284. 6 ev ZnMgO Fujita 2-3 c a MgO /ZnO ZnMgO Ⅱ-Ⅵ 1 AFM 1 a ZnMgO 1 1 b 4 2 ZnMgO 5 2 ZnO /ZnMgO 6 ZnO Ⅱ-Ⅵ Zn 1 O 3 2 1 2 Omicron PA-MBE c 1 Mg ZnO /ZnMgO c 3 RMS:.34 nm MBE 1 h.2.4.6 1 min 滋 m 4 Mg 45 1 nm ZnO /ZnMgO Mg 66% ZnO 3 nm ZnMgO 9 nm O Ⅱ-Ⅵ 1 O 1 1-3 Pa O 2 W 2 O 2 1-3 Pa O 25 W Philips Panalytical X'pert Pro X XRD X Cu Kα Fig. 1 4 kv 3 ma 3 2 XRD 2 1 (a) 1..8.6.4.2.8 1. (b) 2.17 1..8.6.4 RMS:1.89 nm.2.2.4.6.8 1. 滋 m nm 12. 1 a 2 b AFM Morphology of sample 1 a and sample 2 b scanned by AFM
528 35 2 Wurzite phase ZnMgO(1) Rock salt phase Sample 1 ZnO(1) Sample 2 3 31 32 33 34 35 36 37 38 39 4 2 兹 / ( ) ZnMgO(111) MgO(111) Al 2O 3(11) 1 2 XRD θ-2θ Fig. 2 XRD θ-2θ spectra of sample 1 and sample 2 1 Al 2 O 3 2 41. 6 1 θ-2θ Al 2 O 3 11 1 9 8 Sample 1 7 36. 9 MgO 111 2 6 Sample 2 5 34. 9 ZnMgO 1 4 36. 8 ZnMgO 111 36. 9 2 3 4 5 6 7 8 MgO 111 1 b 3 2 ZnMgO 姿 /nm 1 2 2 ~ 8 nm Fig. 3 Transmission spectra of sample 1 and sample 2 from MgO 111 36. 9 RS-ZnMgO 111 2 Zn Mg 1 Boutwell 4 ZnMgO 1 ZnMgO 111 2 Mg Zn 1 Zn Mg 1 ZnMgO 2 ZnO ZnO 1% 1 2 143 nm 174 nm 3 2 38 nm ZnO 2 nm MgO 7. 8 ev MgO 2 nm XRD 1 2 Mg Transmission/% 2 to 8 nm X 4 1 2 XPS ZnMgO 5. 85 ev Mg 5. 2 ev Mg I Mg2 p /F Mg2 p X Mg = 1 Zn I Mg2 p /F Mg2p + I Zn2 p 3 /F Zn2 p 3 ZnMgO I XPS F F Mg2p =. 7 F Zn2 p 3 =5. 3 7 Auger Scan 3. 21 1 MgO 111 2 1 Mg 56. 2% 2 Mg 64. 6% ZnO ZnMgO 1 27 nm O XRD
5 Ⅱ-Ⅵ ZnO /ZnMgO 529 O O Zn Mg ZnO 1 7. 8 ev ZnO MgO 2 2. 7 ev ZnO - 348 kj / 1 mol 4 MgO - 61 kj /mol 4 1 Mg 2p MgO ZnO O 1 Zn Mg O Mg Mg Zn O ZnO O O 1s Dutta 8 Zn ZnO Mg- XPS 4 Zn Zn i 1 Zn 2p 3 /2 1 22 ev ZnO ZnO n Zn 2p 3 /2 7. 8 Mg Zn -Zn i Mg-s O-p Zns p O 1s Zn 2p 3 /2 Mg 2p ev 2 Zn 2p 3 /2 2. 7 ev 1 4 Mg-s O-p Zn-s 4 1 p 6 6 2 Zn 1 XPS Liu 9 ZnMgO Zn XPS 1. 1 19 cm - 3 Zn 2p 3 /2 Zn Zn i ZnO XRD 1 XPS (a) (b) 1-Zn 2p 3/2 1-Mg 2p 124 126 128 13 132 134 136 138 5 52 54 56 58 6 62 64 (c) (d) 2-Zn 2p 3/2 2-Mg 2p Fig. 4 12 122 124 126 128 13 132 46 48 5 52 54 56 58 6 4 1 a b 2 c d Zn Mg XPS Zn 2p 3 /2 spectra of sample 1 a and sample 2 c Mg 2p spectra of sample 1 b and sample 2 d.
53 35 1 Zn Zn Mg Mg ZnMg 1 XRD ZnO MgO Zn O 4 ZnO /ZnMgO c ZnMgO ZnO /ZnMgO ZnMgO Ⅱ-Ⅵ ZnMgO 1 Koike K Hama K Nakashima I et al. Molecular beam epitaxial growth of wide bandgap ZnMgO alloy films on 111 oriented Si substrate toward UV-detector applications J. J. Cryst. Growth 25 278 1-4 288-292. 2 Fujita S Tanaka H Fujita S. MBE growth of wide band gap wurtzite MgZnO quasi-alloys with MgO /ZnO superlattices for deep ultraviolet optical functions J. J. Cryst. Growth 25 278 1-4 264-267. 3 Tanaka H Fujita S Fujita S. Fabrication of wide-band-gap Mg x Zn 1 - x O quasi-ternary alloys by molecular-beam epitaxy J. Appl. Phys. Lett. 25 86 19 192911-1-3. 4 Boutwell R C Wei M Schoenfeld W V. The effect of oxygen flow rate and radio frequency plasma power on cubic ZnMgO ultraviolet sensors grown by plasma-enhanced molecular beam epitaxy J. Appl. Phys. Lett. 213 13 3 31114-1-3. 5 Han S Shao Y K Lu Y M et al. Effect of oxygen pressure on preferred deposition orientations and optical properties of cubic MgZnO thin films on amorphous quartz substrate J. J. Alloys Compd. 213 559 29-213. 6 Jiang B Zhang C Jin C et al. Kinetic-dynamic properties of different monomers and two-dimensional homoepitaxy growth on the Zn-polar 1 ZnO surface J. Cryst. Growth Des. 212 12 6 285-2855. 7 Wagner C Muilenberg G. Handbook of X-ray Photoelectron Spectroscopy M. Eden Prairie Perkin Elmer 1979 188. 8 Dutta R Mandal N. Mg doping in wurtzite ZnO coupled with native point defects A mechanism for enhanced n-type conductivity and photoluminescence J. Appl. Phys. Lett. 212 11 4 4216-1-3. 9 Liu J Shan C Wang S et al. Degenerated MgZnO films obtained by excessive zinc J. J. Cryst. Growth 212 347 1 95-98. 1988-211 ZnO E-mail 7596993@ qq. com 1969-1998 E-mail huahan@ xmu. edu. cn